Effect of eight weeks of strength training on fatigue ... - IOS Press

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Isokinetics and Exercise Science 17 (2009) 101–106 DOI 10.3233/IES-2009-0340 IOS Press

Original Article

Effect of eight weeks of strength training on fatigue resistance in men and women Emanuel Péricles Salvadora,b,e,∗ , Raphael Mendes Ritti Dias c , André Luiz Demantova Gurjãoa,e , Ademar Avelara,e , Luiz Gustavo Pintod and Edilson Serpeloni Cyrino a,e a

Group of Study and Research in Metabolism, Nutrition and Exercise, Gepemene, Brazil São Paulo Support Foundation for Research, FAPESP, Brazil c School of Physical Education, University of Pernambuco, UPE, Brazil d School of Physical Education and Sports, University of S a˜ o Paulo, Brazil e Physical Education and Sport Center, Londrina State University, UEL, Brazil b

Abstract. The purpose of the present study was to compare the effects of eight weeks of strength training on fatigue resistance in men and women. Thirty-three men and twenty-three women performed eight weeks of strength training in three weekly sessions. Subjects performed four sets using 80% of 1-RM tests on bench press, squat and arm curl. Fatigue index (FI) was used for analysis of decline in motor performance along the sets. The sum of the number of repetitions accomplished in the four sets in each exercise was used to indicate the fatigue resistance. Anova or Ancova two-way (time x gender) was employed for statistical analysis (P < 0.05). Eight weeks of strength training increased significantly 1-RM strength, fatigue resistance and total number of repetitions in both genders. FI decreased significantly in both genders after training (men = 50% vs. women = Time x gender interaction was observed in the total number of repetitions in squat (P = 0.04) and arm curl exercises, regarding gains to women (P = 0.01). In conclusion, eight weeks of ST improved strength, FR, FI and total number of repetitions performed. However, women obtained greater adaptations than men. Keywords: Weight exercises, resistance training, multiple sets, fatigue, gender

1. Introduction Strength training (ST) is considered a useful method to increase strength, power and resistance to fatigue (FR). Among those adaptations, FR can be defined as the capacity to resist fatigue in conditions of prolonged period of strength use [4]. Fatigue resistance is demanded in countless sporting modalities, as well as in common daily activities. ∗ Address for correspondence: E.P. Salvador, Grupo de Estudo e Pesquisa em Metabolismo, Nutriça˜ o e Exerc´ıcio, Centro de Educaça˜ o F´ısica e Esporte, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, km 380, Campus Universitário, CEP 86051-990, Londrina, PR, Brasil. E-mail: [email protected].

It is known that the capacity to resist fatigue is modulated by a series of intrinsic (age, sex, motivation, previous experience and training level) and extrinsic (volume, intensity, contraction types and exercises) factors [12]. Regarding the intrinsic factors, sex is one of the most studied. The literature suggests that women present larger FR in comparison with men in different contraction types, speed, position, age groups and exercises performed [2,5–7,10,16]. However there is lack of information about the posttraining gender variation in FR. Once ST programs are prescribed according to the specific characteristics of subjects, possible gender differences in adaptation to ST must be considered to maximize training adaptations. Thus, attendance studies with interventions can contribute to the knowledge regarding gender effect of

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E.P. Salvador et al. / Effect of eight weeks of strength training on fatigue resistance in men and women

training. Therefore, the purpose of the present study was to compare the effects of eight weeks of ST on FR in men and women

2. Method 2.1. Subjects Thirty-three men (21.8 ± 2.9 years, 70.5 ± 9.4 kg and 175.4 ± 6.7 cm height) and 23 women (20.9 ± 2.1 years, 58.3 ± 6.3 kg and 163.3 ± 6.5 cm) participated voluntarily in this study. As inclusion criteria, participants should not have taken part in any physical exercise programs during the previous six months of the study. All subjects signed a consent term. This study was approved by the Ethics Committee in Research of the Londrina State University. 2.2. Muscle strength Subjects were tested before and after eight weeks of strength training on bench press, squat and arm curl exercises, respectively. Each of the three exercises was preceded by warm up series (6 to 10 repetitions) with approximately 50% of the load to be used in the first attempt in the 1-RM test. The test started two minutes after warming up. Subjects were asked to complete two repetitions. The load was gradually increased until the subject could lift the resistance once but not twice. This load was therefore defined as 1-RM [3]. Rest interval between exercises was 3–5 min. For all exercises, the form and the technique of execution were standardized and continually monitored. Besides, the subjects accomplished the tests in the same period of the day and were absent from the physical exercises practice during the period of the tests. The registered load was the highest obtained between the different sessions of the tests. All subjects were submitted to four sessions of 1-RM tests to become familiarized to strength tests. 2.3. Fatigue resistance FR test was performed 2–3 days after the 1-RM tests. The exercises and order of exercises used for FR test were the same as in 1-RM test. Test protocol consisted of the execution of four series in each exercise with 80% of 1-RM value, until voluntary exhaustion. The subjects were asked to execute the maximum number of repetitions in each set. Rest

interval between sets was 2 min while 3–5 min was allowed between exercises. The three exercises were preceded by warm-up series, with the same equipment used in the test. Six to 10 repetitions were performed with approximately 40% of 1-RM for each exercise. The index of decline strength between the first and the fourth set of each exercise was used as fatigue index (FI) as proposed by Sforzo and Touey [19]: FI=[(S(1st.series – S(4th.series) )/S(1st.series) ] * 100% – FI = Fatigue Index – S = Strength (load lifted up X number of repetitions executed during the series).

2.4. Training protocol The ST program lasted 8 weeks with 3 weekly sessions in alternate days. For all subjects, the frequency of training sessions was higher than 80% (19 to 24 sessions). The training program consisted of 10 exercises executed as follows: bench press, leg press at 45 ◦ , lat pull downs, knee extension, shoulder press, knee flexion, triceps press down, calf extension on leg press, arm curl and crunches. All exercises were executed in 3 sets of 8–12 RM, except for calf extension exercises (three sets of 15–20 RM) and crunches (three sets of 50 repetitions with body weight). The rest interval between sets and exercises was 1–2 min. For all exercises, the load was periodically readjusted using the weight test by maximum repetitions as proposed by Rodrigues and Rocha [17].

2.5. Statistical analysis Normality and homoscedasticity were checked by Shapiro Wilk’s and Levene test, respectively. The effect of the training program on the strength and FR were analyzed by two-way ANOVA for repeated measures (gender x time). For the variables in which there were differences between groups at baseline, ANCOVA twoway was used (gender x time), using the baseline values as a covariate. For all ANOVA and ANCOVA analyses that presented significant F value (P 0.05), the Tukey’s post hoc test was used to track the differences. All values are presented in mean ± SD.


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Table 1 1-RM test (kg) in baseline and after eight weeks of strength training in Bench Press, Squat and Arm Curl in men and women

Bench Press Baseline Post-training ∆% Squat Baseline Post-training ∆% Arm Curl Baseline Post-training ∆% Total Baseline Post-training ∆%

Men (n = 33)

Women (n = 23)

62.4 ± 14.8 68.4 ± 13.6* + 9.6

31.9 ± 5.9 36.7 ± 5.6* + 15.0

124.0 ± 24.8 137.7 ± 24.5* + 11.0

71.1 ± 13.6 80.2 ± 14.0* + 12.8

40.0 ± 7.4 44.8 ± 7.4* + 12.0

22.8 ± 4.0 26.9 ± 3.5* + 18.0

226.4 ± 43.3 250.9 ± 40.3* + 10.8

125.7 ± 21.3 140.7 ± 20.4* + 11.9

Effects ANCOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time

F

P

86.6 10.4 1.2

0.01 0.01 0.28

85.0 6.4 3.6

0.01 < 0.01 0.07

47.3 8.6 0.2

< 0.01 < 0.01 0.62

123.8 11.1 2.9

< 0.01 < 0.01 0.09

*P < 0.05 vs. baseline. Table 2 Fatigue index in baseline and after weight training of strength training in Bench Press, Squat and Arm Curl in men and women

Bench Press Baseline Post-training ∆% Squat Baseline Post-training ∆% Arm Curl Baseline Post-training ∆% Mean Baseline Post-training ∆%

Men (n = 33)

Women (n = 23)

75.6 ± 10.0 56.7 ± 7.7* − 25.0

61.6 ± 18.5 39.2 ± 8.4* − 36.4

59.9 ± 16.9 46.6 ± 13.6* − 22.2

64.3 ± 14.2 45.3 ± 11.4* −29.6

65.1 ± 11.3 56.7 ± 11.8* − 12.9

48.3 ± 25.2 37.1 ± 10.9* − 23.2

66.8 ± 8.1 55.3 ± 7.7* − 17.3

58.1 ± 11.4 40.5 ± 5.5* − 31.3

Effects ANCOVA Time Gender Gender X Time ANOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time

F

P

94.3 47.9 0.8

< 0.01 < 0.01 0.41

35.9 0.4 0.7

< 0.01 0.58 0.30

12.2 29.3 0.3

< 0.01 < 0.01 0.62

117.1 31.5 2.0

< 0.01 < 0.01 0.17

*P < 0.05 vs. baseline.

3. Results Eight weeks of ST increased strength significantly in both genders (Table 1). The values of intraclass coefficient correlation for the 1-RM tests at baseline ranged from 0.97–0.99 indicating a high reliability of the strength measurements. Before starting the program, women presented 51%, 57% and 57% of the men’s muscular strength in BP, SQ and AC exercises, respectively. After eight weeks these values increased to 54%, 58% and 60%. Time x gender interaction was nonsignificant for any of the tested exercises, indi-

cating a uniform gender-independent improvement of maximum strength in men and women. The FI decreased significantly in both genders for all exercises (Table 2) following the training program. Again, no time x gender was apparent. There was a significant increase in total number of repetitions after the ST in both genders (Table 3). At baseline women presented better performance in BP and AC exercises (+11% and +16%, respectively) and a lesser performance in the SQ exercise (−24%) compared to men. Following training, the women presented better performance than men in BP, SQ and AC exercises (+13%, +1% and +27%, respectively). There was time x gen-

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E.P. Salvador et al. / Effect of eight weeks of strength training on fatigue resistance in men and women Table 3 Total number of repetitions in the four series with 80% of 1-RM in baseline and after eight weeks of strength training in Bench Press, Squat and Arm Curl in men and women

Bench Press Baseline Post-training ∆% Squat Baseline Post-training ∆% Arm Curl Baseline Post-training ∆% Total Baseline Post-training ∆%

Men (n = 33)

Women (n = 23)

18.3 ± 5.3 27.2 ± 6.2* + 48.6

20.5 ± 6.4 31.2 ± 5.6* + 52.2

22.3 ± 7.9 30.0 ± 6.5* + 34.5

16.9 ± 6.2 30.3 ± 7.0* + 79.3

22.1 ± 5.2 23.9 ± 5.8 + 8.1

26.3 ± 5.5 32.6 ± 8.1* + 23.9

63.8 ± 10.5 81.3 ± 13.1* + 27.4

63.7 ± 12.1 94.0 ± 11.5* + 47.6

Effects ANOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time ANCOVA Time Gender Gender X Time ANOVA Time Gender Gender X Time

F

P

87.3 6.5 0.7

< 0.01 0.01 0.43

62.9 0.1 4.6

< 0.01 0.80 0.04

12.4 15.8 6.6

< 0.01 < 0.01 0.01

129.6 6.7 9.2

< 0.01 0.01 < 0.01

*P < 0.05 vs. baseline.

der interaction in the total number of repetitions in SQ (P < 0.02 and F = 4.6), AC (P < 0.01 and F = 6.6) and in the total number of repetitions of the three exercises. A more detailed gender-related performance analysis during the 4 sets is presented in Fig. 1. Except for the AC in men, there was significant improvement in the number of repetitions performed at each set of the three exercises after the training period (P < 0.01). Although the ST program increased the number of repetitions in the all sets of the three exercises, the decrease in performance between sets was not different after eight weeks of ST (P < 0.01). At baseline and post-training, women performed more repetitions than men in the first, second and third sets in BP (P < 0.01). At baseline and post-training, women performed more repetitions than men in the four sets of AC (P < 0.01). In SQ at baseline, men accomplished more repetitions in first and second sets (P < 0.01). In the post-training period those differences were not apparent.

4. Discussion Several studies investigated FR gender variations in isometric, isokinetic and isoinertial contractions. However, to our knowledge, no other previous study investigated the effect of ST program in the fatigue resistance using isoinertial measurements. Most of the cross-sectional studies indicate that women have greater capacity to resist fatigue than men [2,5–7,10,16]. However, the mechanisms under-

lying the differences between genders are not fully understood. It has been hypothesized that histological, cytological and neural differences may account for these differences. Previous studies indicated that women have a greater proportion of type I muscle fibers [20] and greater amount of muscular creatine content [14]. Other studies demonstrated that men presented greater motor unit activation frequency along the contraction [15,16] that could lead to faster fatigue. Therefore, responses to training programs may be gender-dependent. The results of the present study show that eight weeks of ST promoted increase in 1-RM strength and decrease of FI in both groups. These improvements have been previously shown in men and women [1,8,9]. However, studies comparing gender responses to ST are limited, indicating greater alteration in the total number of repetitions in women. In this study we did not analyze the mechanisms that underlie these responses. However, differences between genders in the neural and morphologic adaptations to the ST program have been previously indicated. For example, Lemmer et al. [11] reported that nine weeks of unilateral ST in men and women induced an increase in the strength of the contralateral limb only in women, indicating differentiated neural responses between genders. Regarding the morphologic alterations, Martel et al. [13] have demonstrated an exclusive increase in the proportion of type I fibers with concomitant reduction of type IIx fibers in women after nine weeks of ST . Another important finding of the present study refers to the decrease in performance during the sets in the


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Fig. 1. Number of repetitions performed in four sets in Bench Press, Squat and Arm Curl exercises by men (quadrates) and women (circles) in baseline (white points) and after eight weeks of strength training (black points). a < set 1, b < set2, c < set 3, * vs. baseline (P < 0.01).

three exercises. In baseline and post training, there was a significant decline in the number of repetitions along sets for both groups. Thus, the accomplishment of multiple sets of ST with 80% of 1-RM does not enable the maintenance of the number of repetitions along sets. Similar results were observed by Salvador et al. [18], using multiple sets, also verified significant decline in the number of repetitions accomplished along the sets. It seems that the prescription based in percentage of 1-RM is limited in multiple sets of exercises using intensity with 80% of 1-RM. One limitation of the present study is the absence of a control group. However, the objective of the present study was to compare the adaptations after ST between men and women, and not to analyze the efficacy of ST

to increase strength and FR. Another limitation of the present study was the inclusion of squat in tests protocols and leg press 45 ◦ in training program. Leg pess 45◦ was not used in tests because the weight capacity of our equipment was limited to 250 kg. On the other hand, the adaptations occurred in this exercise provide important indication regarding the transfer of strength gains suggesting that the increase in the initial period in novice trainers is not specific for the exercise. The results of the present study have an important practical application. Since gender-related responses due to same ST program are different, ST prescription for improvement of FR for men and women should be structured accordingly in order to optimize training adaptations.

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In conclusion, eight weeks of ST improved strength and the total number of repetitions with concomitant decrease in FI, in both genders. Women presented greater adaptation in the total number of repetitions in the SQ, AC exercises and total number of repetitions added to the three exercises.

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