Individualized 12-Week Exercise Training Programs Enhance Aerobic ...

CLINICAL FEATURES

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Individualized 12-Week Exercise Training Programs Enhance Aerobic Capacity of Cancer Survivors Riggs J. Klika, PhD; Kathleen E. Callahan, LOSW; Scott N. Drum, PhD

Abstract: Changes in aerobic capacity were evaluated after 12 weeks of training among a motivated heterogeneous group of cancer survivors (N = 54 [41 women and 13 men]), living at moderate altitude. Changes in power at lactate threshold (PTlact), peak power (Ppeak), and peak oxygen uptake (VO2 peak) were evaluated in this group (average age, 53.8 ± 10.8 years) that completed a minimum of 12 weeks of an individualized exercise program (on average 5 days•week-1 for 47.5 ± 17.2 min•session-1). Daily exercise duration was based on the goals and functional capacity of each individual. Training intensity for each subject was based on heart rate (HR) value at lactate threshold (Tlact) obtained during a symptom-limited cardiopulmonary exercise test. Intensity was categorized into 5 ranges: recovery (60%–80% HR Tlact); endurance (80%–100% HR Tlact); threshold (100%–105% HR Tlact); intervals (105%–115% HR Tlact); and maximal eﬀorts (≥ 115% HR Tlact). Overall compliance with the exercise prescription was ~72% and subjects reported exercising within the 5 training ranges, 12.1%, 63.9%, 18.6%, 4.2%, and 1.2% of the time, respectively. After training, PTlact increased 9.5% (121.8 ± 43.5 vs 133.2 ± 34.1 W; P < 0.05), Ppeak increased 12.6% (175.5 ± 55.6 vs 195.6 ± 54.2 W; P < 0.05) and VO2 peak increased 11.4% (33.4 ± 12.5 vs 37.2 ± 10.4 mL•kg-1•min-1; P < 0.05). The results of this research indicate that: 1) cardiopulmonary exercise testing with lactate threshold determination was safe and eﬀective in the evaluation and exercise prescription phase for a group of cancer survivors and 2) a training program based on 2 higher intensity workouts per week can elicit significant changes in aerobic capacity of a diverse group of cancer survivors. Keywords: aerobic capacity; VO2; peak; training; cancer Riggs J. Klika, PhD 1 Kathleen E. Callahan, LOSW 1 Scott N. Drum, PhD 2 1 Cancer Survivor Center for Health and Wellbeing, Aspen, CO; 2Western State College of Colorado and Gunnison Valley Hospital, Gunnison, CO

Correspondence: Riggs Klika, PhD, 1450 Crystal Lake Rd., Aspen, CO 81611. Tel: 970-920-5836 Fax: 970-925-9543 E-mail: [email protected]

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Introduction The role of exercise in rehabilitation programs for cancer survivors is becoming increasingly significant as the number of cancer patients surviving > 5 years increases.1 As cancer survivors report physical performance and participation limitations 1.4 to 1.8 times greater than individuals with no cancer history,2 an important component of physical well-being could be addressed with a safe and efficacious physical rehabilitation program addressing deficits contributing to these limitations. Cardiorespiratory (CR) fitness is closely related to limits in functional capacity, and low levels of CR fitness have been associated with a markedly increased risk of premature death from all causes, whereas increased CR fitness is associated with a reduction in death from all causes.3 Additionally, there is strong agreement that higher CR fitness and fitness in general is associated with higher quality of life;4–8 there is a growing body of evidence suggesting that higher levels of physical activity and the associated increases in CR fitness may decrease the recurrence of cancer.9–11 Although there are few randomized controlled studies addressing physical fitness and survival, it is plausible that increased physical activity during and after treatment (depending on the general health of the cancer survivor) will lead to increased physical fitness which in turn may limit restrictions in physical participation, ultimately leading to decreased comorbidities and possibly extending survival. Cancer survivors tend to decrease their physical activity levels after their diagnosis,9,12,13 and a burgeoning area of rehabilitation is directed specifically at the cancer survivor population to increase accumulated minutes of intermittent or continuous exercise, both during and after treatment. Although there are a number of health-related variables that must be considered when providing therapeutic exercise for this population, it is relatively clear that on average cancer survivors can and do respond to exercise training similarly to noncancer patients, both during and after cancer treatment has ended.14–18 What is less clear is the magnitude of the changes, the course of these changes over time, and the exercise load requierd to elicit physiologic adaptations.

© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, October 2009, No. 3, Volume 37 041509e

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Aerobic Capacity of Cancer Survivors

Every cancer patient/survivor is unique in their response to cancer treatment (radiation, chemotherapy, and/or surgery); thus, it seems prudent to create individualized rehabilitation programs to address the myriad of factors affecting participation and compliancy. In order to create individualized rehabilitation programs for the cancer survivor, the use of symptom-limited cardiopulmonary exercise testing (CPET) has been shown to be effective and safe in assessing physical function and exercise limitations.7,19–22 Exercise professionals use CPET for the cancer population to: 1) quantify the functional status of the individual; 2) identify underlying comorbid conditions that may preclude exercise (eg, pulmonary fibrosis, cardiomyopathy, hypertension); and 3) develop an appropriate exercise prescription to assist the patient in coping with and/ or recovering from cancer and its treatment.8,22–24 However, it is the use of data obtained from the CPET and subsequent exercise prescription that requires further elucidation. Intensity of exercise is routinely determined based on physiological markers measured during CPET such as maximal heart rate (HR), ventilatory threshold (V-slope method), and HR and/or power at lactate threshold (PTlact). We have previously demonstrated the efficacy of using lactate threshold measures in the establishment of training intensity that increased fitness in both healthy middle-aged adults (average age, 46.5 ± 10 years) and a single cancer survivor (age, 56 years).25,26 Lactate threshold testing is highly reproducible, can be measured with a submaximal protocol, and increases the precision of the training prescription. Therefore, the purpose of this study is to: 1) assess the utility of CPET and lactate threshold determination in a cancer survivor group with a variety of cancers; 2) create individualized exercise training programs for each survivor based on HR at Tlact; 3) quantify the work done for each survivor during a given period; and 4) quantify the changes in aerobic and work capacity following 12 weeks of training.

Materials and Methods Subjects Fifty-four cancer survivors, including women (n = 41) and men (n = 13) of varying cancer type, stage, and treatment (Table 1) with a combined mean age of 53.8 ± 10.8 years (range, 23–79 years) underwent symptom-limited CPET with lactate measures between 2006 and 2009. Subjects were chosen from 162 cancer patients who had enrolled in fitness training during and after cancer treatment at the Cancer Survivor

Table 1. Cancer Survivor Characteristics (N = 54) Value

%

Age (y) Mean ± SD

53.8 ± 10.8

Range

23–79

Sex Male

13

24

Female

41

76

Active men

11

85

Active women

29

71

Breast

26

48.1

Prostate

4

7.4

Ovarian

4

7.4

Non hodgkin lymphoma

3

5.6

Thyroid

3

5.6

Hodgkin lymphoma

2

3.7

Brain

2

3.7

Basal cell carcinoma

1

1.9

Lung

1

1.9

Malignant fibrous histiosarcoma

1

1.9

Chronic lymphocytic leukemia

1

1.9

Anal

1

1.9

Lipo sarcoma

1

1.9

Testicular

1

1.9

Mantle cell lymphoma

1

1.9

Colon

1

1.9

Squamous cell esophageal

1

1.9

Chemotherapy

5

9.3

Chemotherapy plus radiation

3

5.6

Chemotherapy plus surgery

15

27.8

Chemotherapy plus radiation plus surgery

11

20.4

Radiation

3

5.6

Radiation plus surgery

6

11.1

Surgery

10

18.5

Autologous stem cell transplantation plus radiation

1

1.9

Alkylate

22

40.7

Antimetabolite

9

16.7

Antineoplastic

17

31.5

Activity status at time of first assessment

Cancer type

Treatment

Chemotherapy drugs

© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, October 2009, No. 3, Volume 37

(Continued)

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Table 1. (Continued) Value

%

Antidepressant

4

7.4

Estrogen antagonist

5

9.3

Cytokines

1

1.9

Immunopotentiating

1

1.9

Antitumor antibiotic

2

3.7

Synthetic steroid

2

3.7

Taxane

8

14.8

1

14

25.9

II

18

33.3

III

6

11.1

IV

5

9.3

Not definable

11

20.4

Cancer stage

Time of testing From initial diagnosis to 6 months after diagnosis

6

11.1

Between 6–12 months after diagnosis

10

18.5


7

13.0


5

9.3


7

13.0


9

16.7

36 months and after

10

18.5

Values are counts and percentage of total sample (N = 54).

Center for Health and Wellbeing (CSCHW) in Aspen, CO. Subjects enrolling at the center tend to be highly motivated, well educated, and from all levels of socioeconomic status. For the purpose of this study, only cancer survivors who had finished primary treatments (chemotherapy, radiation, and/or surgery) and who participated in at least 3 months of training were included. Excluded study participants were tested at the center, but were assessed during their cancer treatment, did not complete the minimum training period of 3 months, or did not reschedule a follow-up CPET.

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an altitude of 2400 m, and all subjects were residents of the area (range, 1800–2400 m). Measures were made in the order reported below for both pre- and post-12 weeks of training.

Activity Status Activity status (yes/no) was gathered from the cancer and general medical history and defined as meeting or not meeting the 1995 American College of Sports Medicine (ACSM)/Centers for Disease Control and Prevention (CDC) guidelines for physical activity at the time they presented.27 Activity status is presented in Table 1, with 74% of the participants indicating that they were meeting ACSM/CDC guidelines before entering the program.

Body Composition Height and weight were recorded and body mass index calculated. Body composition was estimated with skinfold measures using a Harpenden skinfold caliper at 7 sites.28 Ageand sex-specific equations were used to calculate percentage of fat.29,30 The same technician made pre- and post-treatment measures and has a reported technical error of measurement between 0.12 and 0.60 mm.

Pulmonary Function Testing (PFT) Subjects completed PFT on a calibrated Vmax Encore metabolic analyzer (Cardinal Health, Anaheim, CA) to determine forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC ratio. Calibration for PFT and metabolic measures were made prior to each test using 3-L syringe calibration and known gases according to manufactures instructions. Standards for FVC, FEV1, and FEV1/FVC ratio were determined using equations of Morris.31 Pulmonary function testing was measured to ascertain if errant radiation treatment may have caused pulmonary fibrosis and affected lung volumes and possibly caused a decrease in pulmonary ventilation. This test aids in the differential diagnosis of fatigue in cancer patients and possible exercise limitations.32

Methods

Measurement of Tlact

The study protocol was approved by the Cancer Survivor Center’s Institutional Review Board, and all participants provided written informed assent to participate in the project. Additionally, all cancer survivors provided signed physician (either oncologist or primary care) assent to participate in testing and subsequent fitness training. Testing took place at

Forty-seven subjects completed a continuous 3-minute stage incremental exercise test on an Excalibur Sport cycle ergometer (Lode, Groningen, The Netherlands). The incremental protocol began at 50 W, followed by 25-W increments every 3 minutes thereafter until threshold was obtained.33 Each subject was instructed to maintain a cadence of their choice between 80 and


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100 rev⋅min−1 and at the end of every stage, power, HR, blood lactate (mmol⋅L−1), and rating of perceived exertion (RPE) using modified Borg scale of 1 to 1034 were recorded. Oxygen saturation (Sport Stat [Nonin Medical, Inc., Plymouth, MN] digital oxygen saturation meter) was measured on the index finger, and blood pressure was measured manually (Omron sphygmomanometer [Omron Healthcare, Inc., Bannockburn, IL]) and recorded within each stage. Blood samples were obtained via piercing of the ring (third) fingertip and collected in a 32-μL capillary tube to ensure equivalent blood volumes (∼16–20 μL). The samples were then analyzed with an Accusport (Sports Resource Group, Hawthorne, NY) lactate analyzer. The Accusport lactate analyzer has good reliability35–37 and has been reported to give slightly elevated blood lactate concentrations at simulated altitude.37 The subjects continued with the protocol until they reached a workload in which lactate concentration increased 1 mmol⋅L−1 over baseline, followed by a subsequent increase in lactate ⱖ 1 mmol⋅L−1. After the preceding increases in blood lactate were observed, resistance was decreased to 50 W for an 8-minute recovery period. Maximal oxygen consumption was measured immediately following the recovery. The blood lactate threshold was determined by graphing the lactate versus power relationship, which allowed for determination of power and heart rate at which blood lactate increased 1 mmol⋅L−1 above baseline, as described by Coyle et al.38 Seven subjects who were not comfortable with cycle ergometry or requested to be tested while walking were evaluated using a calibrated mechanized treadmill with a modified Naughton protocol3 and 3-minute stages. Threshold and maximal workloads were converted to wattage based on speed, grade, and the subject’s weight to have comparable workloads among the entire sample.3

Measurement of Peak Oxygen Consumption (VO2 peak) Peak oxygen consumption was measured using a calibrated Vmax Encore metabolic analyzer. The initial workload and/ or speed and grade for this procedure were equivalent to the last workload attained during the Tlact assessment. Workloads were then increased in 25-W increments every minute on the cycle ergometer while grade on the treadmill was increased 2.5% per stage using constant velocity. Peak oxygen uptake was recorded when the subject reached volitional exhaustion or when there was a decrease or plateau in oxygen consumption

with increasing workload and a respiratory exchange ratio (R) ⬎ 1.1. Peak oxygen consumption was expressed relative to body weight, and peak power (Ppeak) was recorded as the highest workload that was maintained for a minimum of 20 seconds. Oxygen saturation and maximal blood pressure were recorded upon the immediate completion of the test. Standard placement 12-lead electrocardiography (ECG) was used to monitor cardiac function during testing. Criteria for terminating the test prior to volitional exhaustion and ECG criterion were based on ACSM and American College of Cardiology Association standards.3

Exercise Programming Each subject was prescribed exercise based on individual goals (eg, participation in activities of daily living, weight management, general physical fitness, increasing performance capacity, increasing balance, feeling less fatigued, etc.), but was constructed on and utilizing a polarized training concept of 2 hard/higher intensity exercise sessions, with 3 less intense (eg, 10 minutes warm-up, 10 minutes cool down, and 20 minutes with HR in the endurance range) sessions⋅week−1, as outlined by Seiler and Kjerland.39 Intensity of exercise was based on individual HR at Tlact and was categorized into 1 of 5 categories: recovery (60%–80% HR Tlact), endurance (80%–100% HR Tlact), threshold (100%–105% HR Tlact), interval (105%–115% HR Tlact), and maximal effort (⬎ 115% HR Tlact). The 2 hard/higher-intensity sessions were at or above threshold and the remaining sessions were prescribed below HR at Tlcat. Training ranges calculated as a percent of HR at Tlact and corresponding rating of perceived exertion (RPE) based on a modified Borg scale of 1 to 10 are presented in Table 2.

Table 2. Training Ranges and Corresponding Rating of Perceived Exertion. Percent of HR Tlacta

RPEb

Recovery

60–80

1–2 Easy

Endurance

80–100

3–5 Moderate

Threshold

100–105

6–7 Hard

Intervals

105–115

8–9 Very hard

Maximal efforts

115-maximal heart rate

9–10 Maximal

a

Calculated based on heart rate at lactate threshold (see text for Tlact determination point). b Based on modified Borg scale.


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Duration for each session was dependent on activity status prior to diagnosis. For those classified as nonactive prior to diagnosis, minimum exercise duration was 10 min⋅session−1 and increased toward 30-min⋅session−1 under supervision of a cancer exercise specialist for the first 30 days of activity. These subjects then participated in unsupervised conditioning for the remaining 8 weeks. For those meeting the physical activity criterion, duration was based on goals, health status, severity of cancer, and agreement in what the individual believed they could do. Duration for active individuals typically varied between 30- and 60-min⋅session−1 and was self-reported, unsupervised exercise. All aerobic sessions consisted of a warm-up period (∼8–10 minutes) and similar cool-down period and a time period within a specific HR range. For example, a threshold (higher intensity) workout included a warm-up and cool-down period followed by 2 × 10 minutes at Tlact HR with 10 minutes of recovery between each interval. Therefore, while this exercise session might rank high on overall RPE, only 20 minutes of the 50-minute session was at or above threshold. Hard/higher intensity exercise sessions at HR Tlact consisted of varying combinations of 2 to 4 intervals between 8 and 20 minutes in duration. For those individuals who could work above the threshold range, maximal effort sessions consisted of 2 to 10 intervals of 15 to 120 seconds, followed by appropriate rest periods typically at a work-to-rest ratio of 1 to 3. Fourteen subjects (mostly those diagnosed with breast cancer) participated in resistance training and aerobic conditioning during the 12-week period. These individuals were prescribed aerobic conditioning guidelines similar to those presented above in addition to 2 or 3 sessions⋅week−1 of resistance training specific to their needs and limitations. Each resistance training session was supervised by a cancer exercise specialist and consisted of a combination of body weight, free weights (dumbbell), cable resistance machines, balance board work, and core (abdominal and lower back) exercises. During the training phase, subjects had weekly contact (in person, by phone and/or by email) with an exercise physiologist or cancer exercise specialist/certified cancer exercise trainer who adjusted the program according to client feedback. Typically, duration of activity was altered upward/ downward based on feedback, while intensity remained constant throughout the training period. All subjects were given a set of precautions for participation in exercise training40 and instructed to contact staff or their primary care physician

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with any health issues during the training period. Because routine blood work was not available after treatment had ended, reductions in volume and intensity of exercise were immediately advised, and the client was instructed to consult with their primary care physician or oncologist if feeling abnormally fatigued and/or exhibiting signs and symptoms of other illness.

Daily Log and Exercise Load Each client kept a daily log of exercise, including average heart rate (HRave), duration (minutes), type of activity, and RPE based on a modified Borg scale of 1 to 1034 for each exercise session. Heart rate was recorded using Polar (Polar Electro Inc., Lake Success, NY), SUUNTO (Suunto America, Ogden, UT), or CycleOps (Saris Cycling Group, Madison, WI) heart rate monitors (client chosen) and participant HR data files were sent (via email on a weekly or bimonthly basis) and analyzed by staff members. When HR files were not available (ie, clients did not wear HR monitor), exercise intensity was classified using reported RPE. Exercise load was calculated by multiplying exercise session duration by RPE made 30 minutes postexercise according to the procedures of Foster et al.41

Statistical Analysis Pre- and post-training physical and physiological data for women and men were analyzed separately and together but not by cancer type due to low cancer-specific group numbers. Pre- and post-training comparisons were made using dependent t-tests. Alpha level was set at P ⱕ 0.05 for all analyses.

Results All subjects completed 2 CPET tests without ECG abnormalities that resulted in premature termination of any test. Heart rate and blood pressure responses to CPET were normal on all tests. Two subjects experienced asymptomatic ECG abnormalities (PVCs) during testing and were referred for follow-up with their physicians. One subject experienced significant low blood oxygen saturation at maximal effort and was administered supplemental oxygen after testing. Pulmonary function testing was conducted on all clients before training, and all but one client had FVC, FEV1 and FEV1/FVC values within normal limits. The single male subject (Hodgkin lymphoma and autologous stem cell transplant) with abnormally low FEV1/FVC chose to remain in the study to increase respiratory capacity.


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Because pre-training assessment varied from time of diagnosis, peak values for power and aerobic capacity are presented. All subjects post-training were able to reach at least one criterion for achieving VO2 max according to ACSM standards.3 Rate of perceived exertion was used effectively as 90% of the entire sample reported reaching Tlact between an RPE of 5 and 7 of 10, with 6 reaching the highest correlation with Tlact (r = 0.71). During the 12 weeks, 3240 exercise sessions were prescribed (54 subjects⋅5 d⋅week−1⋅12 weeks). Exercise data was obtained on 2332 sessions (72%) and this was assumed to be compliancy to the prescription. Because of reporting and recall limitations, more exercise sessions may have been completed but data were not available to confirm this. Subjects reported participating in walking, running, hiking, cycling, Nordic and alpine skiing, swimming, yoga, resistance training, and pilates. Heart rate data was available on 1865 sessions and were analyzed with appropriate HR monitor manufacturer’s software. Time within each training range (recovery, endurance, threshold, interval, and maximal effort) was calculated from each HR data file. Time within each training range for the remaining 467 sessions was based on reported RPE. For these exercise sessions, it was assumed that there was a combined

warm-up and cool-down period of 15 minutes, which was categorized in the recovery range and the remaining time classified into the training range that corresponded to the reported RPE. Percent time spent and average session length for each training range is presented in Figure 1. Exercise duration for the combined sample for all sessions ranged from 10 to 300 minutes with an average of 47.5 ± 17.2 min⋅session−1. One individual completed a 5-hour bicycle ride (300 minutes) that was not included in the reported means for exercise duration. Average exercise duration tended to be longer for higher intensity exercise sessions. Training data by sex is presented in Table 3. Women reported less time spent above HR Tlact than men and virtually no time near or at maximal HR. Duration of exercise per session was relatively similar among women and men. Average load (RPE⋅duration) was 302 ± 106 (range 10–2400), which corresponds to approximately 60 minutes of exercise at an RPE level of 5 out of 10. When cancer survivors performed higher intensity workouts (eg, threshold and above), the overall duration of the workout was longer versus the easier exercise sessions (eg, recovery and endurance sessions), although in comparison with the total duration of the higher intensity workouts only a small percentage of time was spent within the threshold or

Figure 1. Time in each intensity and average duration per session. Percentage of time in range Average session length

90.0 63.9 80.0

60

70.0 50 60.0 40

50.0

30

40.0 30.0

18.6

20

Time (min)

Percentage (%) of total training time

70

20.0

12.1 10

10.0

4.2 1.2 0

0.0 Recovery

Endurance

Threshold

Intervals

Maximal Efforts

Target Training Range


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Table 3. Training Data Percent of Total Training Time in Range

Average Duration of Session (min)

Women

Men

Combined

Women

Men

Combined

Recovery

13.5

8.1

12.1

45.0

24.0

40.2

Endurance

64.0

61.3

63.9

50.5

59.0

52.2

Threshold

17.5

22.3

18.6

60.0

62.0

60.5

Intervals

4.1

4.9

4.2

68.9

65.1

68.3

Maximal efforts

0.1

1.5

1.2

68.0

68.0

68.0

greater target HR range. In summary, total workout duration and percent of time spent within the target HR zone for recovery, endurance, threshold, interval, and maximal work sessions were 40.0 ± 21 minutes and 100%, 52.8 ± 17 minutes and 100%, 62.4 ± 11 minutes and 18.6%, 68.1 ± 6 minutes and 4.2%, and 68.0 ± 8 minutes and 1.2%, respectively. Differences in physical and selected physiological variables for women and men are presented in Tables 4 and 5, respectively. On average, women lost 2.1 kg of body weight, had a decreased percentage of fat 1.7% and had a decreased BMI of 1.8 points. There were no changes in body weight or composition following training for men. For the combined sample, there were significant increases in fitness from pre- to postexercise training, respectively, as measured by an 11.4% increase in VO2 peak (33.4 ± 12.5 vs 37.2 ± 10.4 mL⋅kg−1⋅min−1; P ⬍ 0.05), which was confirmed by changes in Ppeak of 12.6% (175.5 ± 55.6 W vs 195.6 ± 54.2 W; P ⬍ 0.05). Additionally,

power at lactate threshold from pre- to postexercise training, respectively, increased 9.5% (121.8 ± 43.5 W to 133.2 ± 34.1 W; P ⬍ 0.05) for the entire sample. Female cancer survivors had greater percent increases than males in all physiological variables; PTlact (10.2 vs 7.5%); Ppeak (14.7 vs 6.0%); and VO2 peak (14% vs 5%).

Discussion The purpose of this study was to evaluate the effectiveness of a cancer survivor exercise rehabilitation program that included pre- and post-training CPET, individualized exercise prescription based on a percentage of lactate threshold, training at moderate altitude, and monitoring of exercise load. The cancer survivor group was very diverse (17 types of cancer) and had completed cancer treatment prior to entering the study. The results demonstrated that prescribing a general aerobic exercise program based on a “polarized training” concept

Table 4. Physical and Physiologic Characteristics of Males Variable

Males (n = 13) Before training

Age

After Training

Mean

SD

Min

Max

Mean

SD

Min

Max

P value

52.1

10.4

37.9

72

52.2

10.4

38

72

0.1497

Height (m)

1.8

0.1

1.7

1.9

1.8

0.1

1.7

1.9

0.3044

Weight (kg)

80.5

10.3

66.8

102

79.9

1.1

66.8

100.2

0.412

Body mass index (kg⋅m−2)

25.7

2.8

22.7

30.5

25.6

2.8

22.7

29.9

0.4983

Percent fat (%)

18.8

5.3

11.5

28.9

17.9

5.2

10.5

27.9

0.054

Sig

VO2 peak (mL⋅kg−1⋅min−1)

42.8

12.2

27.8

58

45

10.5

30

63.4

0.0249

*

VO2 peak (L⋅min−1)

3.3

0.7

2.6

4.5

3.5

0.7

2.7

4.8

0.0182

*

Ppeak (W)

254.3

58.6

175

300

269.4

55.6

200

375

0.0015

*

PTlact (W)

157.4

40.2

115

200

169.2

35.2

115

225

0.0016

*

Heart rate max (beat⋅min−1)

168.5

24.5

134

210

167

23.8

134

205

0.4408

Significance level set at P ⬍ 0.05. Abbreviations: Ppeak, peak power; SD, standard deviation; PTlact, power at lactate threshold; VO2 peak; peak oxygen uptake.

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Table 5. Physical and Physiologic Characteristics of Females Females (n = 41)

Variable

Before Training

After Training

Mean

SD

Min

Max

Mean

SD

Min

Max

P value

Age

54.2

11.2

23.0

79.0

54.2

11.2

23.0

79.0

0.1589

Height (m)

1.7

0.1

1.5

1.8

1.7

0.1

1.5

1.8

0.0661

Weight (kg)

68.1

18.5

41.4

119.2

66.0

16.2

41.4

110.2

0.0432

*

Body Mass Index (kg⋅m )

26.0

6.0

18.0

48.7

24.2

5.9

17.8

47.7

0.0025

*

Percent fat (%)

26.0

8.2

13.5

50.0

24.3

7.0

12.7

50.0

0.0162

*

30.5

13.2

17.9

52.5

34.8

10.3

19.4

56.4

0.0009

*

−2

VO2 peak (mL⋅kg−1⋅min−1) −1

Sig

VO2 peak L⋅min )

2.0

0.5

0.9

3.1

2.3

0.5

1.0

3.4

0.0229

*

Peak power (Ppeak) (W)

150.6

52.3

100.0

225.0

172.2

52.3

125.0

275.0

0.0000

*

Power Tlact (W)

110.5

45.2

75.0

150.0

121.8

33.8

75.0

175.0

0.0000

*

Heart rate max (beat⋅min−1)

160.2

15.2

120.0

195.0

157.4

19.8

121.0

202.0

0.0025

*

Significance level set at P ⬍ 0.05. Abbreviations: SD, standard deviation; VO2 max, maximal oxygen consumption, PTlact, power at lactate threshold.

that includes 2 higher intensity sessions (ⱖ Tlact) a week and 3 additional sessions considered of a lesser intensity (⬍ Tlact) resulted in significant changes in aerobic fitness. To increase the precision of exercise intensity prescription, HR Tlact was used both as an objective marker of fitness status and as a guideline for exercise prescription. Cancer survivors at low altitude (∼1500 m) have been shown to have similar lactate profiles compared with individuals at sea level and similar responses to noncancer individuals.16 At this altitude (2400 m), cancer survivors tend to have similar lactate responses compared with healthy age-matched adults (unpublished observations). In this cancer survivor cohort, women experienced greater changes in fitness (delta scores) than men. This appeared to be related to the high general fitness of the men, who tended to have greater VO2 peak values prior to training. Additionally, the aerobic capacity of this sample was substantially higher than other clinical investigations6,16,20,21,42 and similar to those reported by Schumacher et al18 and de Backer et al.19 This may be attributed to the chronic adaptations of residents living at altitude, and the extremely active lifestyle of residents of this region (Aspen, CO), as 74% of the sample was somewhat active prior to starting this fitness program. The adherence rate for the program was high, and given the delimitations of the study, the attrition rate was not applicable. Only survivors completing 12 weeks of training were included for analysis. Adherence to our program was a result of setting reasonable goals for cancer survivors, weekly

client contact, exercise program review and adjustment with a cancer exercise specialist, and the knowledge of a pending follow-up assessment. Exercise prescription for cancer survivors at CSCHW is consistent with ACSM’s general guidelines of exercise prescription and with the American Cancer Society’s recommendations of 30 to 60 minutes of exercise at least 5 d⋅week−1. Our prescription differs only in exercise intensity (ⱖ Tlact 1–2 × week or ⬎ 6 METS) versus moderate-to-vigorous intensity recommendations most days of the week, which typically suggests a workload between 3 and 6 METS.3,43,44 Because our cancer survivor group had a tendency to be relatively active, we observed that exercise intensity should be individualized based on their physiologic response to graded exercise testing rather than an absolute number, such as suggested by general ACSM guidelines. While our CS population appeared relatively select, it should be noted that they are not athletes in training. The group ranged from housewives, businessmen and women, contractors, lawyers, and retirees among others. To participate in physical activities typical of this region (hiking, cycling, Nordic and alpine skiing), exercise intensity at 3 to 6 METS was deemed to be too low to elicit significant changes in aerobic capacity and could possibly limit activity. Lastly, results from this study confirm that cancer survivors exhibit similar magnitudes and rates of training adaptations to healthy adults as long as there are no pathologies to the heart and lungs following cancer treatment.16 This is in agreement with others who used similar approaches to successfully train


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cancer survivors following chemotherapy/stem cell transplant by using lactate values determined during CPET to successfully increase fitness.14,18,19 In our sample, even the 5 individuals with metastatic disease had improvements in fitness on a similar magnitude to the rest of the sample. Further research should address the benefits of exercise training for those with advanced metastatic disease.

Implications for Cancer Survivors This study adds to the body of evidence that CPET is a safe and effective method to evaluate functional capacity in cancer survivors and that the measurement of lactate threshold may aid in establishing individualized exercise training intensities for this population. Rehabilitation/fitness programs for CS based on Tlact may allow for a more precise measure of intensity and may give the exercise/health professional more confidence/success in prescribing safe individualized aerobic exercise plans. An aerobic training program based on 2 harder/high-intensity (“polarized training”) exercise sessions per week along with 3 low-intensity (⬍ Tlact) workouts per week of approximately 50 to 60 minutes duration was sufficient to increase maximal and submaximal work capacity in a group of cancer survivors living at moderate altitude.

Acknowledgments The authors wish to acknowledge Cardinal Health who provided metabolic testing equipment for this study.

Conflict of Interest Statement Riggs J. Klika, PhD, and Kathleen E. Callahan, LOSW disclose conflicts of interest with Cancer Survivor Center for Health and Wellbeing. Scott N. Drum, PhD discloses no conflicts of interest.

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