Influence of combined resistance training and healthy diet on muscle ...

J Appl Physiol 119: 918–925, 2015. First published September 3, 2015; doi:10.1152/japplphysiol.00066.2015.

Influence of combined resistance training and healthy diet on muscle mass in healthy elderly women: a randomized controlled trial Emelie Strandberg,1 Peter Edholm,1 Elodie Ponsot,1 Britta Wåhlin-Larsson,1 Erik Hellmén,1 Andreas Nilsson,1 Peter Engfeldt,1 Tommy Cederholm,2 Ulf Risérus,2 and Fawzi Kadi1 1

School of Health and Medical Science, Örebro University, Örebro, Sweden; and 2Department of Public Health and Caring Science, Clinical Nutrition and Metabolism, Uppsala University, Uppsala, Sweden Submitted 23 January 2015; accepted in final form 20 August 2015

Strandberg E, Edholm P, Ponsot E, Wa˚hlin-Larsson B, Hellmén E, Nilsson A, Engfeldt P, Cederholm T, Risérus U, Kadi F. Influence of combined resistance training and healthy diet on muscle mass in healthy elderly women: a randomized controlled trial. J Appl Physiol 119: 918 –925, 2015. First published September 3, 2015; doi:10.1152/japplphysiol.00066.2015.—The delivery of efficient nonpharmacological treatment to prevent the loss of muscle mass in older adults is a major challenge, and information on the combined effects of training and diet is particularly important. Here we aimed to evaluate the effects of 24 wk of resistance training combined with a healthy dietary approach (n-6/n-3 ratio ⬍ 2) in a population of healthy and physically active older women (65-70 years). The three-armed randomized controlled trial included a resistance training ⫹ healthy diet group (RT-HD), a resistance training group (RT), and controls (CON). All subjects included in the study were physically active and had low levels of serum inflammatory markers. In accordance with the dietary goals, the n-6/n-3 ratio dietary intake significantly decreased only in RT-HD by 42%. An increase in 1 repetition maximum in leg extension occurred in RT (⫹20.4%) and RT-HD (⫹20.8%), but not in CON. Interestingly, leg lean mass significantly increased only in RT-HD (⫹1.8%). While there were no changes in serum C-reactive protein and IL-6 levels, a significant decrease in serum level of the pro-inflammatory precursor arachidonic acid (⫺5.3 ⫾ 9.4%) together with an increase in serum n-3 docosahexaenoic acid (⫹8.3%) occurred only in RT-HD. Altogether, this study demonstrates that the effects of resistance training on muscle mass in healthy older adults can be optimized by the adoption of a healthy diet. aging; C-reactive protein; exercise; fatty acids; inflammation; skeletal muscle BETWEEN 2000 AND 2050,

the proportion of the world’s population over 60 years of age is projected to double from about 11 to 22%, increasing from 605 million to 2 billion (66). In parallel, despite the fact that the risk of having a disability accelerates after the age of 80, the current and future older population may spend more years healthy and disability-free than past populations aged 65 and older (33, 34). These demographic changes imply that research aiming to improve health in the older population should focus on subjects with deteriorated health as well as healthy older adults. Aging is accompanied with a progressive decline in skeletal muscle mass leading to sarcopenia. The loss of muscle mass occurs together with a decline in muscle strength and power (19), especially in lower limb muscles (36). Low-grade chronic systemic inflammation, which is defined as a minor elevation in the baseline levels of acute-phase proteins and cytokines

Address for reprint requests and other correspondence: F. Kadi, School of Health and Medical Sciences, Örebro Univ., Örebro, Sweden (e-mail: [email protected]). 918

(10), is currently considered as an important factor contributing to the age-related functional decline. In this respect, C-reactive protein (CRP), one of the most frequently used markers of systemic inflammation, has been shown to be elevated in older adults (15). Elevated concentrations of CRP have been found to be associated to many age-related adverse changes (7, 39), and even older adults with CRP levels ⱖ 1.2 mg/l have a moderately increased risk of developing disease (45), highlighting the role of low-grade systemic inflammation in the age-related functional decline. Although elevations in systemic markers of inflammation have not been reported in all studies (4), the reduction in muscle mass and strength has been found to be associated with increases in systemic markers of inflammation in older adults (51). It has also been shown that the systemic inflammation can blunt the postprandial muscle protein synthesis in aged rats (1). Interestingly, the administration of anti-inflammatory drugs can restore muscle protein synthesis in old rats (46). Additionally, it has been shown that a treatment with anti-inflammatory drugs together with resistance training has beneficial effects on muscle volume and strength (57). Though an anti-inflammatory medication might prove beneficial, daily administration of anti-inflammatory drugs is currently not feasible, indicating the need to develop efficient nonpharmacological approaches to maintain muscle function in healthy older adults. Resistance training is currently considered as the most efficient nonpharmacological strategy to counteract the age-related loss of muscle mass in older adults (41). However, several studies included physically inactive participants as well as older adults with chronic diseases or frail people. In healthy old men and women, resistance training-induced increases in muscle mass have been reported in some (2, 22, 30) but not in all studies (27, 60). Moreover, gains in muscle mass have been reported in older men but not in women (20). There are also discrepancies among studies addressing the efficiency of longterm resistance training in reducing the systemic inflammatory level. Resistance training-induced reductions in systemic markers of inflammation have been reported in older and middle-aged inactive individuals with risk factors for chronic diseases and relatively elevated baseline serum inflammatory markers in some (42) but not in all studies (9). The ability of dietary approaches to reduce systemic inflammation has also been considered. The polyunsaturated omega-3 (n-3) fatty acids have been suggested to have anti-inflammatory properties (14), as a significant decrease in the level of the pro-inflammatory precursor arachidonic acid (AA) has been reported in healthy middle-aged subjects supplemented with the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (16, 26). It has been shown that higher concentrations

8750-7587/15 Copyright © 2015 the American Physiological Society

http://www.jappl.org

Aging, Skeletal Muscle, Diet, and Exercise

of AA are associated with smaller muscle size (44), and AA has been shown to be an important signaling event in the induction of muscle protein degradation through an increased expression and activity of the ubiquitin-proteasome pathway (65). On the contrary, n-3 fatty acids have been shown to inhibit protein degradation (62) and reduce the normal decline in muscle mass and function in older adults (55). Furthermore, supplementation with n-3 fatty acids increases muscle protein synthesis above basal, postabsorptive values in older adults (54). Altogether, alterations in serum levels of n-3 fatty acids might have a direct action on muscle mass in older adults. To our knowledge, there is no data on the effects of resistance training combined with a whole diet approach aiming to modify the n-6/n-3 ratio on muscle mass in healthy, physically active older women. By using a three-armed randomized controlled trial, the objective of this investigation was to evaluate the effects of 6 mo of resistance training combined with a healthy diet on skeletal muscle mass and strength as well as systemic markers of inflammation in a population of healthy, physically active older women. MATERIALS AND METHODS

Study design. A three-armed randomized controlled trial was performed. Randomization was done by block design to ensure equal numbers of older women assigned to a control group (CON; 68 ⫾ 1 yr), a resistance training group (RT; 68 ⫾ 2 yr) and a resistance training plus healthy diet group (RT-HD; 67 ⫾ 1 yr). To ensure that the comparison groups were as similar as possible with regard to baseline inflammatory level, the randomization was stratified by serum CRP level. All subjects were informed about the nature and possible risks of the experimental procedures before written, informed consent was obtained. The study was conducted in accordance with the policy statement set forth in the Declaration of Helsinki and approved by the regional ethical review board of Uppsala. Subjects. Elderly women were recruited through an advertisement in a local newspaper. A medical history and electrocardiograms were assessed by a physician. Exclusion criteria were 1) living in a nursing home; 2) self-reported inability to walk; 3) cardiovascular, pulmonary, metabolic, rheumatologic, and psychiatric disease; 4) musculoskeletal problems; 5) use of medication; 6) a food allergy; and 7) unexplained weight loss, defined as unintended loss ⱖ 5% body wt over the preceding 6 –12 mo. To be included in the study, older women had to be aged between 65 and 70 years, with a BMI ⬍ 30,

•

919

Strandberg E et al.

fasting glucose ⬍ 6 mmol/l, fasting cholesterol ⬍ 8 mmol/l, systolic blood pressure ⬍ 140 mmHg, and diastolic blood pressure ⬍ 90. Additionally, subjects had to be recreationally physically active. The subjects physical activity behaviors were assessed by a previously validated questionnaire (EPAQ2) (63). All subjects included in the study participated in various recreational physical activities, such as walking, Nordic walking, jogging, cycling, swimming, and skiing; none of the subjects had previously participated in structured resistance training. In total, 122 volunteers were screened and the 63 older women who remained after applying inclusion and exclusion criteria were considered eligible for the randomized controlled trial (RCT). After the 63 women were randomized into three groups, a total of eight subjects withdrew from the study (3 from CON, 4 from RT, and 1 from RT-HD) and did so for reasons not related to the intervention (Fig. 1). The CON group was asked to maintain their normal activities of daily living. Resistance training intervention. Supervised progressive resistance training was performed twice a week during 24 wk. Subjects performed three sets per exercise with 2 min of rest between sets and 3 min of rest between exercises. The initial workload corresponded to 50% of 1 repetition maximum (1 RM) during the first 2 wk where the subjects performed 12–15 repetitions per set. A workload of 75– 85% 1 RM (8 –12 reps/set) was set for the rest of the intervention. Training load was adjusted throughout the intervention. The following exercises were performed: squat, leg extension, leg press, seated row, and pull down. Additionally, 5 min of core stability exercises and seven squat jumps were included. Training sessions ended with 5 min of stretching exercises. Diet and dietary assessment. The subjects in the RT-HD group attended a dietary consultation and were given a diet plan. Details of the prescribed diet are summarized in Table 1. Briefly, 44 E% of carbohydrates (fiber intake ⬎25 g/day), 36 E% of fat (mainly monounsaturated and polyunsaturated fatty acids), and 20 E% of protein with the following major adjustment: the n-6/n-3 ratio ⬍2. In accordance with these general dietary goals, several numbered menus were proposed to the participants. The subjects were trained to prepare their meals according to the recommendations provided by a nutritionist. The daily calorie requirements for each participant in RT-HD were calculated based on predicted basal metabolic rate (BMR) by the Harris-Benedict equation (50) and estimated physical activity level. The dietary intake was adjusted in 200 kcal increments to match individual energy requirements. Subjects in CON and RT were instructed to maintain their habitual dietary intake throughout the study. The dietary intake was monitored by using a food record over a period of 6 days at baseline, week 12, and week 24. The subjects were instructed by a nutritionist on how to record their daily food intake by

122 Subjects screened Excluded n=59. (Not meeting inclusion criteria) 63 Randomized

RT n=21

CON n=21

18 assessed at 24 weeks

RT-HD n=21

Withdrew: n=4

Withdrew: n=3


Fig. 1. Organization chart of participant flow throughout the study.

Withdrew: n=1


J Appl Physiol • doi:10.1152/japplphysiol.00066.2015 • www.jappl.org

920


Table 1. Nutrient goals and prescribed key foods for the dietary intervention Dietary Intake

Nutrient goals Carbohydrate, E% Fiber, g/day Protein, E% Total fat, E% Saturated fat, E% Unsaturated fat n-6/n-3 ratio Prescribed foods Cereal products Vegetables/fruits/berries Fish and seafood Dietary fats Meat products Dairy products Soft drinks/juice

ⱖ2/3 of total fat

44 ⬎25 20 36 ⬍10 ⬍2

High whole-grain (rye, oat, barley) ⱖ600 g/day ⱖ500 g/wk Rape seed oil, olive oil, nuts and seeds Lean meat ⱕ0.5 l/day (low fat) Be avoided/⬍1.5 dl juice/day

E%, energy percent.

using a portion size guide developed by the Swedish National Food Agency (31). The dietary analysis program Dietist XP (Kost och Näringsdata) was used. 1 Repetition maximum. Maximum strength was assessed by using the 1 RM test. During a familiarization session, the proper lifting technique was practiced and maximum strength was estimated by using a multiple repetition test procedure. The 1 RM was determined for each exercise during the second visit. Following a warm-up period, the load was set at 90 –95% of the estimated 1 RM and increased with ⬃2.5–5% after each successful lift until failure. A 3-min resting period was allowed between consecutive attempts, and the 1 RM was obtained within five attempts. Maximal isometric quadriceps strength. Maximal isometric quadriceps strength was measured in subjects seated on an adjustable chair with a 90° angle of hip and knee joints and with restraining straps crossing the torso and tested leg. The force sensor (K. TOYO 333A) was attached above the malleoli at one third of the distance between the lateral femoral epicondyle and lateral malleolus. Subjects were instructed to exert maximal force as quickly as possible and to maintain this force for 3–5 s. Verbal encouragements were provided. All measurements were performed on the dominant leg, and each subject performed three extensions at maximal voluntary effort separated by a rest period of 2.5 min. Monitoring of physical activity. Recreational physical activity was assessed by accelerometry (Actigraph model GT3x, Pensacola, FL) at baseline, week 12, and week 24. This assessment was performed to monitor physical activity level outside the intervention. The accelerometer was worn with an elastic belt on the right hip for 6 consecutive days. Participants were informed to wear the monitor all waking hours except for bathing or swimming. The monitors were initialized and downloaded by using the manufacturer software ActiLife 6. Nonewear time was defined as periods of at least 60 consecutive min of zero values. The total number of counts per minutes per day (cnts·min⫺1·day⫺1) and the average number of minutes spent in moderate-to-vigorous physical activity (MVPA) per day were derived. MVPA was defined as all activities with an intensity ⱖ760 cnts/min, a threshold frequently previously used in older women (38). The resistance training sessions for the RT and RT-HD groups at week 12 and week 24 were excluded from the analysis. Dual X-ray absorptiometry and anthropometric measurement. Regional body composition was estimated by using dual X-ray absorptiometry (DXA; LUNAR Prodigy, GE Medical systems) performed in the fasted state. The system software (Hologic Apex version 2.3) provided the mass of fat-free soft tissue, fat, and bone mineral density for the lower limb, defined as the region extending from the inferior

•

Strandberg E et al.

border of the ischial tuberosity to the distal tip of the toes. Body weight and height were measured to the nearest 0.1 kg and 0.1 cm, respectively, by using standardized equipment and procedures. Blood samples. Blood samples were obtained between 7.00 and 9.00 AM after an overnight fast. The participants were asked to avoid smoking and alcohol and not to engage in any strenuous physical activity 24 h before the blood sample. Blood was collected by venipuncture from an anticubital vein, centrifuged at 4,000 rpm for 10 min and stored in ⫺80°C. Determination of CRP and IL-6 levels. CRP level was measured by using a high-sensitivity C-reactive protein (Hs-CRP) kit by a fully automated immunoturbidimetric assay (Advia 1800, Chemistry System, Siemens, Germany). Commercially available enzyme linked immunosorbent assay kit was used (Quantikine HS, R&D Systems) for the assessment of IL-6 levels. All samples were run in duplicates and the average of two values was used for data analysis. Determination of serum ␣-linolenic acid (18:3 n-3), EPA (20:5 n-3), DHA (22:6 n-3), linoleic acid (18:2 n-6), and arachidonic acid (20:4 n-6). Briefly, serum lipids were extracted with chloroform and phospholipids were separated from other lipids by thin-layer chromatography and transmethylated with methanol and sulfuric acid (8). The percentage composition of methylated fatty acids was determined by gas chromatography (GC) with flame ionization detection. GC used for the analysis consisted of 30-m capillary column coated with Thermo TR-FAME (Thermo Electron) and Agilent Technologies system (GC 6890N, Autosampler 7683, and Agilent ChemStation). The temperature used was between 150 and 260°C. The fatty acids were identified by comparing the retention time of each peak with the methyl ester standard (Nu Check Prep, Elysian, MN). Statistical analysis. All variables were tested for normality by using the Shapiro-Wilk normality test and skewed data were log transformed. One-way ANOVA was used to examine between-group differences at baseline. The effects of the RCT were analyzed by using two-way repeated measure ANOVA (time and group) followed by the Holm-Sidak post hoc procedure. An ANCOVA was performed to control for possible confounding effects of total energy intake or relative protein intake on changes in muscle mass. With an alpha level set at 0.05, the power of statistical tests ranged between 0.80 and 0.90. With a required minimum of 15 subjects in each group, 21 subjects per group were included to allow for a 20 –25% drop out rate. P ⱕ 0.05 were considered significant. Statistical analyses were performed using SPSS version 20.0 (SPSS, Chicago, IL). RESULTS

At baseline there were no significant differences between groups with regard to age, BMI, leg lean mass, leg fat mass, leg bone mineral density (BMD), strength, CRP, IL-6 (Table 2). There were no significant alterations in BMI by the end of the 24-wk intervention in any of the groups. Training attendance for the participants was 87 ⫾ 8% (39 ⫾ 4 sessions, 1.77 ⫾ 0.15 sessions/wk) and 91 ⫾ 6% (41 ⫾ 3 sessions, 1.81 ⫾ 0.13 sessions/wk) in the RT and RT-HD groups, respectively. The assessment of physical activity level at baseline revealed that all participants met the physical activity recommendation of accumulating 30 min or more of moderate-to-vigorous physical activity per day on 5 or more days/wk (23). We also found that the level of physical activity was similar between the groups at baseline (Table 2) and that there were no significant changes in the activity level over the 24-wk intervention period (Table 2), the latter indicating that participants did not modify their physical activity behaviors during the study.



•

921

Strandberg E et al.

Table 2. Body composition, physical activity level, serum inflammatory markers and muscle strength at baseline and by the end of the study CON

RT

RT-HD

Variable

PRE, n ⫽ 21

POST, n ⫽ 18

PRE, n ⫽ 21

POST, n ⫽ 17

PRE, n ⫽ 21

POST, n ⫽ 20

Height, cm Body mass, kg BMI, kg/m2 1 RM leg extension CRP, mg/l IL-6, pg/l Leg lean mass, kg Leg fat mass, kg Leg BMD, g/cm2 PA, cnts·min⫺1·day⫺1

165 ⫾ 4.6 67.1 ⫾ 8.2 24.5 ⫾ 2.8 49.7 ⫾ 9.6 1.29 ⫾ 0.93 1.85 ⫾ 1.77 12.61 ⫾ 1.66 8.34 ⫾ 1.94 1.15 ⫾ 0.11 278 ⫾ 151

– 67.7 ⫾ 8.6 24.8 ⫾ 2.9 49.8 ⫾ 10.3 1.30 ⫾ 0.87 1.86 ⫾ 1.92 12.41 ⫾ 1.67 8.55 ⫾ 1.81 1.16 ⫾ 0.11 327 ⫾ 178

163 ⫾ 5.3 65.2 ⫾ 8.0 24.5 ⫾ 2.8 49.2 ⫾ 10.2 1.25 ⫾ 0.78 1.29 ⫾ 0.92 12.78 ⫾ 1.28 8.53 ⫾ 1.85 1.13 ⫾ 0.08 268 ⫾ 62

– 65.8 ⫾ 8.2 24.6 ⫾ 2.9 59.0 ⫾ 10.3* 1.33 ⫾ 0.76 1.27 ⫾ 1.05 12.82 ⫾ 1.43 8.72 ⫾ 1.99 1.12 ⫾ 0.08 257 ⫾ 49

165 ⫾ 5.3 65.9 ⫾ 11.0 24.3 ⫾ 3.9 49.5 ⫾ 6.3 1.35 ⫾ 0.89 1.22 ⫾ 0.90 12.50 ⫾ 1.58 9.17 ⫾ 3.43 1.14 ⫾ 0.10 337 ⫾ 127

– 65.7 ⫾ 10.9 24.4 ⫾ 4.6 60.0 ⫾ 7.1* 1.46 ⫾ 1.06 1.44 ⫾ 1.12 12.71 ⫾ 1.53* 8.99 ⫾ 3.18 1.15 ⫾ 0.09 329 ⫾ 174

All values are given as means ⫾ SD. *P ⱕ 0.05. CON, control group; RT, resistance training group; RT-HD, resistance training ⫹ healthy diet group; CRP, C-reactive protein; BMI, body mass index; RM, repetition maximum; BMD, bone mineral density; PA, physical activity.

The assessment of the dietary intake showed no significant differences in macronutrients intake between the three groups at baseline and revealed that participants in CON and RT did not alter their nutritional habits throughout the study period (Table 3). In accordance with the dietary goals, dietary n-3 polyunsaturated fatty acids (PUFA) increased as expected, and consequently the n-6/n-3 ratio dietary intake significantly decreased only in RT-HD by 42% (from 3.1 ⫾ 1.3 to 1.8 ⫾ 0.6, P ⬍ 0.05). Stratification by CRP ensured equal baseline inflammatory status in the three groups (Table 2). The baseline levels of both CRP and IL-6 in this population of healthy older women were low and were not altered in response to the intervention. The analysis of blood samples showed that there was a significant increase in n-3 DHA serum level (⫹8.3%) in RT-HD only, which further confirms dietary compliance. There were no significant changes in serum fatty acids ␣-linolenic acid, EPA and linoleic acid in any of the groups in response to the intervention (Table 4). Interestingly, despite the low inflammatory level of participants, there was a significant decrease in the pro-inflammatory precursor AA in RT-HD only (⫺5.3 ⫾ 9.4%, P ⬍ 0.05) (Table 4). The training volume in leg extension exercise was similar for both training groups (1,183 ⫾ 219 kg/session in RT and 1,186 ⫾ 143 kg/session in RT-HD, P ⫽ 0.962). By the end of the intervention period, there was a significant increase in 1 RM in leg extension in both RT and RT-HD (Fig. 2A). Maximal isometric quadriceps strength also increased significantly (P ⬍ 0.05) in both RT (19.0 ⫾ 3.4%) and RT-HD (15.3

⫾ 3.5%). On the contrary, CON did not change their 1 RM in leg extension over the course of the 24-wk period (⫺1.9 ⫾ 6.4%, P ⫽ 0.278) (Fig. 2A). Leg lean mass, fat mass, and BMD evaluated by using DXA revealed no significant differences between the three groups at baseline (Table 2). However, there was a significant increase in leg lean mass in response to the 24-wk intervention only in RT-HD (time ⫻ group effect, P ⫽ 0.027) (Fig. 2B). ANCOVA was used to control for possible confounding effects of total energy intake and absolute or relative protein intake on changes in muscle mass. We found that these covariates had no significant effects on changes seen by the end of the intervention. DISCUSSION

The present study provides information on the combined effects of exercise and dietary interventions in a group of recreationally active older women homogenous with respect to age and with no chronic diseases. The main findings of the present study were that resistance training improves muscle strength in healthy and recreationally active older women and that gains in skeletal muscle mass occur only when resistance training is combined with a healthy diet. In our study, the design of the diet was based on a whole dietary approach with no use of dietary supplements or pharmacological agents. The prescribed diet was in line with the current dietary guidelines in Europe and the United States, i.e., a healthy diet rich in wholegrain products, vegetables, fruits, fish, and polyunsaturated fats from vegetable oils and nuts,

Table 3. Daily dietary intake at baseline and by the end of the study CON, n ⫽ 16

RT, n ⫽ 14

RT-HD, n ⫽ 20

Variable

PRE

POST

PRE

POST

PRE

POST

Energy, kcal Carbohydrates, E% Protein, E% Fat, E% SFA, E% MUFA, E% PUFA, E% Ratio, n-6/n-3

1,669 ⫾ 435 45.0 ⫾ 7.9 17.0 ⫾ 3.3 35.4 ⫾ 5.5 13.7 ⫾ 2.6 12.9 ⫾ 2.4 5.6 ⫾ 1.8 3.1 ⫾ 0.8

1,569 ⫾ 397 43.4 ⫾ 7.3 18.5 ⫾ 4.1 35.2 ⫾ 4.8 14.5 ⫾ 3.1 12.6 ⫾ 2.3 5.2 ⫾ 2.0 3.1 ⫾ 1.1

1,667 ⫾ 338 46.8 ⫾ 5.2 16.3 ⫾ 2.0 34.1 ⫾ 4.0 13.4 ⫾ 2.5 12.2 ⫾ 1.6 5.3 ⫾ 1.6 3.2 ⫾ 1.0

1,715 ⫾ 432 43.2 ⫾ 5.9 17.2 ⫾ 2.1 35.9 ⫾ 5.9 14.3 ⫾ 3.4 12.6 ⫾ 2.3 5.8 ⫾ 1.8 3.4 ⫾ 1.4

1,583 ⫾ 443 45.9 ⫾ 7.1 16.8 ⫾ 1.7 33.6 ⫾ 5.7 13.7 ⫾ 3.2 11.9 ⫾ 2.2 5.1 ⫾ 1.3 3.1 ⫾ 1.3

1,769 ⫾ 272 42.8 ⫾ 3.3 19.9 ⫾ 2.4 36.3 ⫾ 3.2 9.7 ⫾ 1.5* 14.4 ⫾ 1.6* 9.0 ⫾ 2.1* 1.8 ⫾ 0.6*

All values are given as means ⫾ SD. *Indicates significant changes compared with PRE, P ⱕ 0.05. SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids. J Appl Physiol • doi:10.1152/japplphysiol.00066.2015 • www.jappl.org

922


•

Strandberg E et al.

Table 4. Fatty acid composition in phospholipids at baseline and by the end of the study CON, n ⫽ 14 Variable

18:3 20:5 22:6 18:2 20:4

n-3, n-3, n-3, n-6, n-6,

% % % % %

RT, n ⫽ 17

RT-HD, n ⫽ 19

PRE

POST

PRE

POST

PRE

POST

0.27 ⫾ 0.10 2.30 ⫾ 0.79 5.80 ⫾ 1.16 19.81 ⫾ 2.05 8.91 ⫾ 1.77

0.29 ⫾ 0.06 2.37 ⫾ 0.62 6.10 ⫾ 1.30 19.66 ⫾ 2.52 8.57 ⫾ 1.73

0.29 ⫾ 0.06 2.77 ⫾ 0.97 5.73 ⫾ 0.91 20.84 ⫾ 1.23 8.18 ⫾ 1.30

0.29 ⫾ 0.07 2.70 ⫾ 0.75 5.58 ⫾ 0.88 20.55 ⫾ 1.67 8.30 ⫾ 1.17

0.28 ⫾ 0.06 2.34 ⫾ 0.73 5.19 ⫾ 0.88 20.32 ⫾ 1.80 9.03 ⫾ 0.90

0.33 ⫾ 0.10 2.53 ⫾ 0.82 5.62 ⫾ 0.95* 20.89 ⫾ 2.17 8.54 ⫾ 1.18*

All values are given as means ⫾ SD. *Indicates significant changes compared with PRE, P ⱕ 0.05. Variable 18:3 n-3, ␣-linolenic acid; 20:5 n-3, eicosapentaenoic acid; 22:6 n-3, docosahexaenoic acid; 18:2 n-6, linoleic acid; 20:4 n-6: aracidonic acid.

tion (i.e., metabolic syndrome or Type 2 diabetes) (6). Moreover, it was recently shown that compared with a diet with low intake in n-6 PUFA and high in saturated fatty acids, a diet with high intake in n-6 PUFA induced an increase in total muscle mass without changes in serum inflammatory levels (48). Alternatively, changes in baseline serum CRP levels occur only under the influence of the cumulative effects of exercise and dietary changes over the course of many years, and not after shorter-term interventions. This possibility is consistent with the hypothesis that physical exercise acts predominantly by reducing body fat. This is supported by the

Changes in 1RM Leg Extension (%)

A

25

*

*

20

CON RT RT-HD

15

10

5

0

-5

B Changes in Leg Lean Mass (%)

with very low amounts of red meat and saturated fats. In accordance with the dietary goals, a decrease in the n-6/n-3 ratio dietary intake occurred only in RT-HD, and an increase in serum n-3 DHA further confirmed dietary compliance. The fact that resistance training improves muscle strength in both RT and RT-HD is in accordance with several studies in both healthy and frail older adults (40). However, our findings show that resistance training alone did not lead to significant improvements in leg lean mass in a population of healthy and physically active older women. Likewise, previous reports failed to show any significant improvements in muscle mass in older men and women (27, 60), and one report demonstrated significant resistance training-induced improvements in muscle mass in older men but not in women (20). As indicated earlier, the time spent in moderate-to-vigorous physical activity by the participants in this study was in line with the recommendations for physical activity in both young and older adults (23, 35) and higher than what has been reported in previous studies assessing physical activity behaviors in older women (38). In this respect, improvements of muscle mass are more frequently reported in physically inactive older (53) and old/frail subjects with risk factors for chronic diseases (5). Even in frail older people, it has recently been demonstrated that a dietary protein supplementation is required to increase muscle mass (56). A previous study demonstrated that administration of overthe-counter dosages of nonsteroidal anti-inflammatory drugs combined with a resistance training program appeared to enhance muscle hypertrophy and strength gains compared with resistance training alone in older adults (57). The significant improvements in leg lean mass in our healthy, physically active older women occurred only when resistance training was combined with the healthy diet. In this population of healthy and physically active older women, baseline serum CRP and IL-6 levels were low and the diet-induced improvement of muscle mass was not accompanied by changes in serum levels of these markers. Several previous investigations exploring the effects of whole diet (58), supplementation with fish oil (43), or resistance training alone (9) did not report changes in systemic inflammatory markers. Reductions in serum CRP and IL-6 levels were generally reported in response to resistance training in older adults with low physical activity levels (42) and were accompanied by a decrease in fat mass in some (13) but not all studies (37). It has also been shown that supplementation with the n-3 ␣-linolenic acid reduces IL-6 levels in older men but not in women (11) and that even increased n-6 PUFA intake is not associated to elevated systemic inflammation (21). In feeding trials, even a dramatic (⬎3-fold) increase in the n-6/ n-3 PUFA ratio does not increase signs of inflammation or oxidative stress in subjects with low-grade systemic inflamma-

3

*

2

1

0

-1

-2

-3

Fig. 2. Relative changes in 1 RM leg extension strength (A) and leg lean mass (B) in older women following 24-weeks intervention. *Indicates significant changes, P ⱕ 0.05.



association between weight loss and reductions in CRP levels (52). The increase in muscle mass, which occurred only in RTHD, was accompanied by a diet-induced reduction of AA and an increase in DHA. Decreased AA might have a positive effect on muscle mass, as it has been shown that higher concentrations of AA are associated with smaller muscle size (44). Additionally, AA has been shown to be an important signaling event in the induction of muscle protein degradation through an increased expression and activity of the ubiquitinproteasome pathway (65). Additionally, the diet-induced increase in serum n-3 DHA might have contributed to the increase in muscle mass as n-3 fatty acids have been shown to inhibit protein degradation (62), enhance muscle protein synthesis (54), and reduce the normal decline in muscle mass and function in older adults (55). Despite the fact that leg lean mass increased significantly in RT-HD, there were no significant differences in the magnitude of the improvement in leg extension strength between RT and RT-HD. This implies that significant changes in muscle strength can be achieved without significant changes in muscle mass in older women, highlighting the role of neuromuscular adaptations (i.e., motor unit recruitment) in strength improvements in older adults. It can thus be hypothesized that the 1.8% improvement in leg lean mass in RT-HD does not necessarily translate into superior effects on muscle strength in healthy and physically active older women. In older women, previous studies showed significant increases in muscle strength with no significant increases in skeletal muscle mass after resistance training (20, 27, 60), and in studies reporting increases in skeletal muscle mass in healthy older adults, the magnitude of changes generally ranges between 2 and 6% (2, 18, 22, 24, 30, 49, 53, 59). Sillanpaa et al. (2009) reported a 2% increase in lean leg mass following 21 wk of resistance training in older women aged between 39 and 64 yeas (53). Leenders et al. (2013) also reported a 2.9% increase in leg lean mass in healthy older women following 6 mo of resistance training (30). A 2.1% increase in fat-free mass was reported after 6 mo of resistance training in participants who underwent a period of 8 mo of detraining prior to the start of the intervention (49). Differences in the physical activity level of participants prior to the intervention and individual differences in the response to exercise might explain the differences between the studies. In general, the low magnitude of training-induced changes in muscle mass in older women can also be explained by a reduction of the anabolic response to exercise in older individuals (28). The 24-wk dietary intervention was self-administrated and based on dietary counselling. This dietary design is less rigorous than controlled nutrient diets. However, the strategy used in our study allows reducing the participant burden given that one of the major challenges in any long-term dietary study is the retention of eligible study members for the duration of the intervention. To improve participant compliance, several menus were designed according to the general dietary goals. Food records performed at the start, in the middle, and at the end of the intervention indicated high compliance. Furthermore, the increase in the n-3 fatty acid DHA serum level, which occurred only in RT-HD, further points to a high level of compliance. By the end of the intervention, there was a nonsignificant mean difference of 186 kcal/day in RT-HD. This slight difference in total energy intake and in absolute or

•

Strandberg E et al.

923

relative protein intake had no significant influence on changes in muscle mass. Noteworthily, previous studies showed that protein intakes of 0.9 g·kg⫺1·day⫺1 or 1.2 g·kg⫺1·day⫺1 combined with resistance training gave similar effects on muscle mass in older adults, indicating that increases in protein intake in subjects with already adequate protein intake would not further enhance the effects of the intervention (25). Participants included in our study had a baseline protein intake of ⬃1 g·kg⫺1·day⫺1, which is considered an adequate intake for older women (3, 12, 47). In the present study, body composition was assessed by using DXA, which is less accurate than other tools such as computed tomography (CT) or magnetic resonance imaging (MRI). DXA has previously been considered to be a reasonable alternative to CT and MRI for estimating regional and total body composition (29), and by using DXA the amount of radiation is far less than other methods. Furthermore, it has been demonstrated that the use of DXA for the regional analysis of the limb area is particularly accurate compared with DXA measurement of the trunk area (64). Additionally, previous studies have evaluated body composition by using DXA, CT, and MRI and showed good between-method agreement in the determination of muscle size (17, 32, 61). Our findings suggest that the practice of resistance training together with the adoption of a healthy diet by a population of healthy and physically active older women with no risk factors for chronic diseases and low serum levels of inflammatory markers can optimize the resistance training-induced gains in muscle mass. To reduce the prevalence of sarcopenia and to delay the age-related functional decline, it is important to evaluate the myogenic potential of nonpharmacological interventions before the occurrence of different comorbidities leading to muscle weakness. In this study, although moderate, the intervention-induced changes in muscle mass can be considered to be promising as they can be implemented in healthy active older women and can delay the impact of aging on the muscular system. It can also be hypothesized that the same intervention would induce more benefits at the level of muscle mass in inactive older women with poor health status. Further research is needed to understand the molecular mechanisms underlying changes in muscle mass in response to combined resistance training and a healthy diet. In conclusion, an intervention based on resistance training combined with a healthy diet can optimize the resistance training-induced increases in skeletal muscle mass in healthy and physically active older women. Increases in muscle mass were not accompanied by a reduction of serum CRP or IL-6 but were associated with a diet-induced reduction in serum AA and an increase in serum DHA. This information is important for refining cointerventions compatible with long-term lifestyle changes aiming to improve muscle mass in older women in order to delay the occurrence of sarcopenia. ACKNOWLEDGMENTS We thank the participants as well as Rolf Pettersson, Per Odenkrans, Adrian Hosford-Donovan, Sara Mijwel, Sofia Nilsson, Jenny Ewen, and Siv Tengblad for their help during the study. GRANTS Support for this study was provided by Swedish National Center for Research in Sports Grants P2012/0102 and P2014-0117.


924


DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author(s). AUTHOR CONTRIBUTIONS E.S., P. Edholm, E.P., B.W.-L., A.N., P. Engfeldt, T.C., U.R., and F.K. performed experiments; E.S., E.H., and F.K. analyzed data; E.S. and F.K. interpreted results of experiments; E.S. prepared figures; E.S. and F.K. drafted manuscript; E.S. and F.K. edited and revised manuscript; E.S., P. Edholm, E.P., B.W.-L., E.H., A.N., P. Engfeldt, T.C., U.R., and F.K. approved final version of manuscript; F.K. conception and design of research. REFERENCES 1. Balage M, Averous J, Remond D, Bos C, Pujos-Guillot E, Papet I, Mosoni L, Combaret L, Dardevet D. Presence of low-grade inflammation impaired postprandial stimulation of muscle protein synthesis in old rats. J Nutr Biochem 21: 325–331, 2010. 2. Bamman MM, Hill VJ, Adams GR, Haddad F, Wetzstein CJ, Gower BA, Ahmed A, Hunter GR. Gender differences in resistance-traininginduced myofiber hypertrophy among older adults. J Gerontol A Biol Sci Med Sci 58: 108 –116, 2003. 3. Bauer J, Biolo G, Cederholm T, Cesari M, Cruz-Jentoft AJ, Morley JE, Phillips S, Sieber C, Stehle P, Teta D, Visvanathan R, Volpi E, Boirie Y. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc 14: 542–559, 2013. 4. Beharka AA, Meydani M, Wu D, Leka LS, Meydani A, Meydani SN. Interleukin-6 production does not increase with age. J Gerontol A Biol Sci Med Sci 56: B81–B88, 2001. 5. Binder EF, Yarasheski KE, Steger-May K, Sinacore DR, Brown M, Schechtman KB, Holloszy JO. Effects of progressive resistance training on body composition in frail older adults: results of a randomized, controlled trial. J Gerontol A Biol Sci Med Sci 60: 1425–1431, 2005. 6. Bjermo H, Iggman D, Kullberg J, Dahlman I, Johansson L, Persson L, Berglund J, Pulkki K, Basu S, Uusitupa M, Rudling M, Arner P, Cederholm T, Ahlstrom H, Riserus U. Effects of n-6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: a randomized controlled trial. Am J Clin Nutr 95: 1003–1012, 2012. 7. Blake GJ, Ridker PM. C-reactive protein, subclinical atherosclerosis, and risk of cardiovascular events. Arterioscler Thromb Vasc Biol 22: 1512– 1513, 2002. 8. Boberg M, Croon LB, Gustafsson IB, Vessby B. Platelet fatty acid composition in relation to fatty acid composition in plasma and to serum lipoprotein lipids in healthy subjects with special reference to the linoleic acid pathway. Clin Sci (Lond) 68: 581–587, 1985. 9. Bruunsgaard H, Bjerregaard E, Schroll M, Pedersen BK. Muscle strength after resistance training is inversely correlated with baseline levels of soluble tumor necrosis factor receptors in the oldest old. J Am Geriatr Soc 52: 237–241, 2004. 10. Bruunsgaard H, Pedersen BK. Age-related inflammatory cytokines and disease. Immunol Allergy Clin North Am 23: 15–39, 2003. 11. Cornish SM, Chilibeck PD. Alpha-linolenic acid supplementation and resistance training in older adults. Appl Physiol Nutr Metab 34: 49 –59, 2009. 12. Deutz NE, Bauer JM, Barazzoni R, Biolo G, Boirie Y, Bosy-Westphal A, Cederholm T, Cruz-Jentoft A, Krznaric Z, Nair KS, Singer P, Teta D, Tipton K, Calder PC. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr 33: 929 –936, 2014. 13. Donges CE, Duffield R, Drinkwater EJ. Effects of resistance or aerobic exercise training on interleukin-6, C-reactive protein, and body composition. Med Sci Sports Exerc 42: 304 –313, 2010. 14. Ferrucci L, Cherubini A, Bandinelli S, Bartali B, Corsi A, Lauretani F, Martin A, Andres-Lacueva C, Senin U, Guralnik JM. Relationship of plasma polyunsaturated fatty acids to circulating inflammatory markers. J Clin Endocrinol Metab 91: 439 –446, 2006. 15. Ferrucci L, Corsi A, Lauretani F, Bandinelli S, Bartali B, Taub DD, Guralnik JM, Longo DL. The origins of age-related proinflammatory state. Blood 105: 2294 –2299, 2005. 16. Fisher M, Levine PH, Weiner BH, Johnson MH, Doyle EM, Ellis PA, Hoogasian JJ. Dietary n-3 fatty acid supplementation reduces superoxide production and chemiluminescence in a monocyte-enriched preparation of leukocytes. Am J Clin Nutr 51: 804 –808, 1990.

•

Strandberg E et al.

17. Fuller NJ, Hardingham CR, Graves M, Screaton N, Dixon AK, Ward LC, Elia M. Assessment of limb muscle and adipose tissue by dual-energy X-ray absorptiometry using magnetic resonance imaging for comparison. Int J Obes Relat Metab Disord 23: 1295–1302, 1999. 18. Geirsdottir OG, Arnarson A, Briem K, Ramel A, Jonsson PV, Thorsdottir I. Effect of 12-week resistance exercise program on body composition, muscle strength, physical function, and glucose metabolism in healthy, insulin-resistant, and diabetic elderly Icelanders. J Gerontol A Biol Sci Med Sci 67: 1259 –1265, 2012. 19. Goodpaster BH, Park SW, Harris TB, Kritchevsky SB, Nevitt M, Schwartz AV, Simonsick EM, Tylavsky FA, Visser M, Newman AB. The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study. J Gerontol A Biol Sci Med Sci 61: 1059 –1064, 2006. 20. Hanson ED, Srivatsan SR, Agrawal S, Menon KS, Delmonico MJ, Wang MQ, Hurley BF. Effects of strength training on physical function: influence of power, strength, and body composition. J Strength Cond Res 23: 2627–2637, 2009. 21. Harris WS, Mozaffarian D, Rimm E, Kris-Etherton P, Rudel LL, Appel LJ, Engler MM, Engler MB, Sacks F. Omega-6 fatty acids and risk for cardiovascular disease: a science advisory from the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation 119: 902–907, 2009. 22. Hartman MJ, Fields DA, Byrne NM, Hunter GR. Resistance training improves metabolic economy during functional tasks in older adults. J Strength Cond Res 21: 91–95, 2007. 23. Haskell WL, Lee IM, Pate RR, Powell KE, Blair SN, Franklin BA, Macera CA, Heath GW, Thompson PD, Bauman A. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 39: 1423–1434, 2007. 24. Hunter GR, Wetzstein CJ, McLafferty CL Jr. Zuckerman PA, Landers KA, and Bamman MM. High-resistance versus variable-resistance training in older adults. Med Sci Sports Exerc 33: 1759 –1764, 2001. 25. Iglay HB, Thyfault JP, Apolzan JW, Campbell WW. Resistance training and dietary protein: effects on glucose tolerance and contents of skeletal muscle insulin signaling proteins in older persons. Am J Clin Nutr 85: 1005–1013, 2007. 26. Kelley DS, Taylor PC, Nelson GJ, Schmidt PC, Ferretti A, Erickson KL, Yu R, Chandra RK, Mackey BE. Docosahexaenoic acid ingestion inhibits natural killer cell activity and production of inflammatory mediators in young healthy men. Lipids 34: 317–324, 1999. 27. Kosek DJ, Kim JS, Petrella JK, Cross JM, Bamman MM. Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults. J Appl Physiol (1985) 101: 531–544, 2006. 28. Kumar V, Selby A, Rankin D, Patel R, Atherton P, Hildebrandt W, Williams J, Smith K, Seynnes O, Hiscock N, Rennie MJ. Age-related differences in the dose-response relationship of muscle protein synthesis to resistance exercise in young and old men. J Physiol 587: 211–217, 2009. 29. Lee RC, Wang ZM, Heymsfield SB. Skeletal muscle mass and aging: regional and whole-body measurement methods. Can J Appl Physiol 26: 102–122, 2001. 30. Leenders M, Verdijk LB, van der Hoeven L, van Kranenburg J, Nilwik R, van Loon LJ. Elderly men and women benefit equally from prolonged resistance-type exercise training. J Gerontol A Biol Sci Med Sci 68: 769 –779, 2013. 31. Livsmedelsverket. Portionsguide. Ljungby, Sweden: JOMA Grafisk Produktion, 2009. 32. Maden-Wilkinson TM, Degens H, Jones DA, McPhee JS. Comparison of MRI and DXA to measure muscle size and age-related atrophy in thigh muscles. J Musculoskelet Neuronal Interact 13: 320 –328, 2013. 33. Manton KG, Gu X, Lamb VL. Change in chronic disability from 1982 to 2004/2005 as measured by long-term changes in function and health in the US elderly population. Proc Natl Acad Sci U S A 103: 18374 –18379, 2006. 34. Manton KG, Gu XL, Lamb VL. Long-term trends in life expectancy and active life expectancy in the United States. Popul Dev Rev 32: 81–105, 2006. 35. Nelson ME, Rejeski WJ, Blair SN, Duncan PW, Judge JO, King AC, Macera CA, Castaneda-Sceppa C. Physical activity and public health in older adults: recommendation from the American College of Sports



36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

Medicine and the American Heart Association. Med Sci Sports Exerc 39: 1435–1445, 2007. Newman AB, Kupelian V, Visser M, Simonsick E, Goodpaster B, Nevitt M, Kritchevsky SB, Tylavsky FA, Rubin SM, Harris TB, Health ABCSI. Sarcopenia: alternative definitions and associations with lower extremity function. J Am Geriatr Soc 51: 1602–1609, 2003. Olson TP, Dengel DR, Leon AS, Schmitz KH. Changes in inflammatory biomarkers following one-year of moderate resistance training in overweight women. Int J Obes (Lond) 31: 996 –1003, 2007. Orsini N, Bellocco R, Bottai M, Hagstromer M, Sjostrom M, Pagano M, Wolk A. Profile of physical activity behaviors among Swedish women aged 56 –75 years. Scand J Med Sci Sports 18: 95–101, 2008. Pearson TA, Mensah GA, Alexander RW, Anderson JL, Cannon RO 3rd, Criqui M, Fadl YY, Fortmann SP, Hong Y, Myers GL, Rifai N, Smith SC Jr, Taubert K, Tracy RP, Vinicor F, Centers for Disease Control and Prevention, and the American Heart Association. Markers of inflammation and cardiovascular disease: application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation 107: 499 –511, 2003. Peterson MD, Rhea MR, Sen A, Gordon PM. Resistance exercise for muscular strength in older adults: a meta-analysis. Ageing Res Rev 9: 226 –237, 2010. Peterson MD, Sen A, Gordon PM. Influence of resistance exercise on lean body mass in aging adults: a meta-analysis. Med Sci Sports Exerc 43: 249 –258, 2011. Phillips MD, Patrizi RM, Cheek DJ, Wooten JS, Barbee JJ, Mitchell JB. Resistance training reduces subclinical inflammation in obese, postmenopausal women. Med Sci Sports Exerc 44: 2099 –2110, 2012. Pot GK, Brouwer IA, Enneman A, Rijkers GT, Kampman E, Geelen A. No effect of fish oil supplementation on serum inflammatory markers and their interrelationships: a randomized controlled trial in healthy, middle-aged individuals. Eur J Clin Nutr 63: 1353–1359, 2009. Reinders I, Song X, Visser M, Eiriksdottir G, Gudnason V, Sigurdsson S, Aspelund T, Siggeirsdottir K, Brouwer IA, Harris TB, Murphy RA. Plasma phospholipid PUFAs are associated with greater muscle and knee extension strength but not with changes in muscle parameters in older adults. J Nutr 145: 105–112, 2015. Ridker PM. High-sensitivity C-reactive protein: potential adjunct for global risk assessment in the primary prevention of cardiovascular disease. Circulation 103: 1813–1818, 2001. Rieu I, Magne H, Savary-Auzeloux I, Averous J, Bos C, Peyron MA, Combaret L, Dardevet D. Reduction of low grade inflammation restores blunting of postprandial muscle anabolism and limits sarcopenia in old rats. J Physiol 587: 5483–5492, 2009. Rizzoli R, Stevenson JC, Bauer JM, van Loon LJ, Walrand S, Kanis JA, Cooper C, Brandi ML, Diez-Perez A, Reginster JY, Force ET. The role of dietary protein and vitamin D in maintaining musculoskeletal health in postmenopausal women: a consensus statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO). Maturitas 79: 122–132, 2014. Rosqvist F, Iggman D, Kullberg J, Cedernaes J, Johansson HE, Larsson A, Johansson L, Ahlstrom H, Arner P, Dahlman I, Riserus U. Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans. Diabetes 63: 2356 – 2368, 2014. Roth SM, Ivey FM, Martel GF, Lemmer JT, Hurlbut DE, Siegel EL, Metter EJ, Fleg JL, Fozard JL, Kostek MC, Wernick DM, Hurley BF. Muscle size responses to strength training in young and older men and women. J Am Geriatr Soc 49: 1428 –1433, 2001. Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 40: 168 –182, 1984.

•

Strandberg E et al.

925

51. Schaap LA, Pluijm SM, Deeg DJ, Visser M. Inflammatory markers and loss of muscle mass (sarcopenia) and strength. Am J Med 119: 526 e529 – e517, 2006. 52. Selvin E, Paynter NP, Erlinger TP. The effect of weight loss on C-reactive protein: a systematic review. Arch Intern Med 167: 31–39, 2007. 53. Sillanpaa E, Laaksonen DE, Hakkinen A, Karavirta L, Jensen B, Kraemer WJ, Nyman K, Hakkinen K. Body composition, fitness, and metabolic health during strength and endurance training and their combination in middle-aged and older women. Eur J Appl Physiol 106: 285–296, 2009. 54. Smith GI, Atherton P, Reeds DN, Mohammed BS, Rankin D, Rennie MJ, Mittendorfer B. Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial. Am J Clin Nutr 93: 402–412, 2011. 55. Smith GI, Julliand S, Reeds DN, Sinacore DR, Klein S, Mittendorfer B. Fish oil-derived n-3 PUFA therapy increases muscle mass and function in healthy older adults. Am J Clin Nutr 2015. 56. Tieland M, Dirks ML, van der Zwaluw N, Verdijk LB, van de Rest O, de Groot LC, van Loon LJ. Protein supplementation increases muscle mass gain during prolonged resistance-type exercise training in frail elderly people: a randomized, double-blind, placebo-controlled trial. J Am Med Dir Assoc 13: 713–719, 2012. 57. Trappe TA, Carroll CC, Dickinson JM, LeMoine JK, Haus JM, Sullivan BE, Lee JD, Jemiolo B, Weinheimer EM, Hollon CJ. Influence of acetaminophen and ibuprofen on skeletal muscle adaptations to resistance exercise in older adults. Am J Physiol Regul Integr Comp Physiol 300: R655–R662, 2011. 58. Uusitupa M, Hermansen K, Savolainen MJ, Schwab U, Kolehmainen M, Brader L, Mortensen LS, Cloetens L, Johansson-Persson A, Onning G, Landin-Olsson M, Herzig KH, Hukkanen J, Rosqvist F, Iggman D, Paananen J, Pulkki KJ, Siloaho M, Dragsted L, Barri T, Overvad K, Bach Knudsen KE, Hedemann MS, Arner P, Dahlman I, Borge GI, Baardseth P, Ulven SM, Gunnarsdottir I, Jonsdottir S, Thorsdottir I, Oresic M, Poutanen KS, Riserus U, Akesson B. Effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile and inflammation markers in metabolic syndrome – a randomized study (SYSDIET). J Intern Med 274: 52–66, 2013. 59. Verdijk LB, van Loon L, Meijer K, Savelberg HH. One-repetition maximum strength test represents a valid means to assess leg strength in vivo in humans. J Sports Sci 27: 59 –68, 2009. 60. Vincent KR, Braith RW, Feldman RA, Magyari PM, Cutler RB, Persin SA, Lennon SL, Gabr AH, Lowenthal DT. Resistance exercise and physical performance in adults aged 60 to 83. J Am Geriatr Soc 50: 1100 –1107, 2002. 61. Visser M, Fuerst T, Lang T, Salamone L, Harris TB. Validity of fan-beam dual-energy X-ray absorptiometry for measuring fat-free mass and leg muscle mass. Health, Aging, and Body Composition Study–DualEnergy X-ray Absorptiometry and Body Composition Working Group. J Appl Physiol (1985) 87: 1513–1520, 1999. 62. Wang Y, Lin QW, Zheng PP, Zhang JS, Huang FR. DHA inhibits protein degradation more efficiently than EPA by regulating the PPARgamma/NFkappaB pathway in C2C12 myotubes. Biomed Res Int 2013: 318981, 2013. 63. Wareham NJ, Jakes RW, Rennie KL, Mitchell J, Hennings S, Day NE. Validity and repeatability of the EPIC-Norfolk Physical Activity Questionnaire. Int J Epidemiol 31: 168 –174, 2002. 64. Wells JC, Fewtrell MS. Measuring body composition. Arch Dis Child 91: 612–617, 2006. 65. Whitehouse AS, Khal J, Tisdale MJ. Induction of protein catabolism in myotubes by 15(S)-hydroxyeicosatetraenoic acid through increased expression of the ubiquitin-proteasome pathway. Br J Cancer 89: 737–745, 2003. 66. World Health Organization. Aging and Life Course (Online). http:// www.who.int/ageing/about/facts/en/ [14 Sept. 2014].
