Abstract
Objectives
Given apparent consumer interest in calorie counting and arguably inadequate understanding of the differential effects of exercise modality despite equivalent caloric expenditure, we sought to quantify and compare the acute physiological responses within and between a BODYPUMP™ (BP) group-fitness class and steady-state cycling (CARDIO), matched for caloric cost (iso-caloric) and time (iso-time).
Design
Acute cross-over study design.
Methods
Twelve healthy recreationally active females (30.1 ± 5.8 years [mean ± SD]) completed cardiorespiratory fitness and strength tests. Subsequently, BP and CARDIO were performed on separate days in randomized order, during which heart rate was monitored continuously, and rating of perceived exertion solicited. Blood samples were collected immediately pre- and post-trial and at 45 min post-trial for determination of human growth hormone (HGH), interleukin 6 (IL-6), and cortisol. Lactate (BL) was determined from capillary blood. All outcome measures were analyzed for within-, and between-trial differences.
Results
HGH, IL-6 and BL were significantly elevated immediately post-trial for both BP and cycling; the elevation for HGH and BL was significantly greater for BP than CARDIO. IL6 remained elevated at 45 min post-trial for both exercise modes, but there was no significant between trial difference. Mean heart rate for both trials was 68% of individually determined maximum heart rate, and predicted VO2 during BP was 14.9 ± 5.2 ml kg min, or 46.7 ± 19.4%VO2peak. Mean load self-selected by participants during BP ranged from 21 ± 7%1RM to 32 ± 9%1RM across four exercises.
Conclusions
These results indicate that BP provided some more potent acute physiological effects than iso-caloric and iso-time steady-state cycling.
Keywords
1. Introduction
There is ostensibly a widespread focus amongst consumers of exercise products on the measurement of energy cost in the form of calories expended, via processes such as indirect calorimetry from heart rate.
1
It is reasonably conjectured that such an arbitrary focus on caloric cost of exercise might preclude a more nuanced understanding of the residual physiological effects of an exercise session. Resistance training, for example, may utilise similar total energy per session to lower intensity cardiovascular training, but result in different chronic adaptations.Some exercise modalities are a potent stimulus for hormone and lactate secretion, with the response magnitude dependent on the exercise characteristics (mode, duration, and intensity) and population characteristics.
2
For example, blood lactate accumulates during higher intensity exercises and is associated with the release of human growth hormone (HGH). HGH stimulates protein synthesis in addition to increasing bone mineralization, lipolysis, liver gluconeogenesis and immune function.3
Additionally, the pleiotropic cytokine/myokine Interleukin-6 (IL-6) modulates downstream inflammatory responses and is associated with activation of AMP-activated protein kinase, amongst other effects.4
To date, the focus on these processes have been during cardiovascular exercise or high-load resistance training, and it is known that IL-6 release is responsive to weight bearing exercise of sufficient intensity and/or longer exercise sessions.4
Also elevated acutely resultant from various exercise modalities, cortisol is associated with anabolic and lipolytic processes,5
hence of interest in terms of potential positive health responses.Les Mills BODYPUMP™ (BP) is 60-min full body low-load, high repetition resistance training group exercise class, in which the participants use a bar and self-selected weights. According to Les Mills International, globally there are over 17,000 Bodypump licenses operational, and that approximately 80% of all participants are female. Instructors provide cues about technique and recommended loads throughout the class. Set repetitions are performed according to movements pre-choreographed to music. Past research has described the typical energy expenditure
6
, 7
of a class as well as various beneficial adaptations8
, 9
of BP. But previous studies investigating the effects of BP have been limited owing to various methodological issues such as the use of novice participants,8
, 9
, 10
no direct comparison to other iso-caloric exercise modalities, and lack of descriptive details quantifying acute BP session characteristics relative to maximum capacity.11
Additionally, no other study has detailed acute hormonal responses to BP in women accounting for menstrual phase.Therefore the primary aim of this study was to quantify and compare the acute (within, and immediately post session) hormonal, physiological and perceptive responses of a Les Mills BP class to a calorie- and time-matched steady-state cycling session in a cohort of BP familiar female participants. These acute responses provide insight into some mechanisms underpinning how different exercise modalities might result in longer-term adaptations for health benefit beyond calorie expenditure. Specifically, we compared the within, and between-condition dynamics of human growth hormone (HGH), interleukin 6 (IL-6), cortisol, and lactate. We also sought to determine the 45-min post session hormonal and physiological responses. A further aim was to quantify the load participants utilized during BP in order to better understand and describe the self-selected loads typically utilized in an actual class, relative to quantified maxima.
2. Methods
Twelve healthy women (age 30.1 ± 5.8 years, mass 74.0 ± 10.8 kg, stature 168 ± 5.4 cm, and BMI 26.1 ± 4.2 kg/m2 [mean ± SD]) who were not on oral contraceptives volunteered to participate in this research. All participants were regular BP attendees (by self-assessment had participated in BP about once a week or more on a regular basis over at least six months), and were recruited from advertisements placed in an exercise facility. All signed informed consents resultant from institutional ethical approval (AUTEC 16/401) prior to commencing the study.
All participants completed four trial sessions. The first session was a virtual BP class, as one group, to familiarize the participants with the class and procedures as well as to collect heart rate (HR) and perceptive data. Participants were then required to visit the testing venue three more times (Monday, Wednesday and Friday) in one week over the next four weeks, scheduled at exactly the same time of day per participant to account for diurnal variation in physiological and hormonal status. Additionally, given the known fluctuations in key hormonal measures and performance across a normal menstrual cycle, participants were required to attend testing sessions as close to the proliferative phase of the uterine cycle as possible immediately after their monthly menstruation ceased. This was self-reported, but verified
12
via the determination of circulating progesterone and luteinizing hormone levels across both testing occasions in that week. This criterion necessitated multiple testing occasions across several weeks. The second session was dedicated to strength and aerobic fitness testing. The third and fourth sessions were randomly ordered as another virtual BP class in a small group, and a steady-state stationary cycling session, during both of which blood was collected immediately prior to the trials, immediately post-exercise (Post0) and 45 min post completion (Post45) of the trials. Participants were asked to attend trial sessions with as practically as possible identical activity, exercise, sleep, and nutrition patterns for the 48 preceding hours.During the group BP, heart rate (HR) was collected continuously throughout the class using the Polarflow H7 system (Polar, Finland). The average HR overall for the class excluding the cool-down was used for caloric expenditure estimation and subsequent matching for the cardiovascular session (CARDIO). After each track, participants were requested to record the load they used for the track and their rating of perceived exertion (RPE) using a modified Borg scale of 1–10. Additionally, at the end of the session, they were required to provide an overall session RPE (1–10), and enjoyment rating on a scale utilizing Likert style questions, from −3 (hated it) to 3 (loved it).
For the baseline fitness testing on Monday, mass and stature were recorded using a scale (Tanita, Japan) and stadiometer (Seca, Germany) respectively. Self-assessed day of menstrual phase was requested and recorded. Following a brief standardised warm-up with a self-selected load, each participant performed, in order, the squat, bench press, deadlift and modified bent-over-row tests (detailed below) with a two-minute rest between each test. These exercises were chosen in order to determine relative loads used by participants for four of the major movements in BP. Participants were instructed to perform movements using the technique they would normally use for the respective movement in class and all movements were performed at a self-selected pace. A New Zealand Registered Exercise Professional supervised the procedures. For each exercise, the load was increased until the participant reported volitional failure or their technique deviated unsatisfactorily from instructed, within the range of 3 and 15 repetitions, and a standardized equation
11
was then applied to estimate 1RM.For the squat, participants were instructed to unrack the 10 kg barbell from the portable standing rack, adopt their habitual class stance and descend until knee angle was approximately 90°. For the bench press, using a customised 3 kg BP bar plus loaded plates and 20 cm high step, participants lay supine with hands positioned on the bar just outside shoulder width. From a starting position of extended elbows (the bar was handed to them), participants lowered the bar to a level where the elbows were no lower than bench height such that the elbows were at approximately 90°. For the deadlift, most participants were not habituated with standard deadlift from floor technique, as it is not used commonly during BP. Hence, we utilised a modified deadlift technique where the loaded bar (as used in bench press) was handed to the participant such that the repetition started from a standing position. Feet were hip-distance apart, knees slightly bent and the grip was approximately or slightly greater than hip width. The bar was lowered only to the knees after which the participant came up to a fully extended position. For the bent-over-row, the loaded bar was handed to the participant such that the repetition started from a standing position. To replicate the process in a typical BP class, bent-over-rows were performed in sets of three before rising to a fully extended position, repeated consecutively. Feet were hip-width apart, knees slightly bent and grip on the bar was at hip distance. The range of the bar during the row was from knee height until the bar touched the naval.
To determine VO2peak, participants performed an incremental graded exercise test on a cycle ergometer (Monark 824E, Sweden). After a two-minute warm-up (0.5 kilopon [kp]), load was increased by 0.5 kp every two minutes, at a self-selected cadence between 65–80 rpm. The test was terminated upon the point of volitional fatigue or when a cadence of 55 rpm could not be maintained. Gas analysis was carried out using a breath-by-breath ergospirometer (Metalyzer 3B system; CORTEX, Leipzig, Germany), which was calibrated immediately before each test. The VO2peak was determined as the highest VO2 averaged over 15 s. The mean HR during the last 15 s of each two-minute stage and the RPE at the end of each stage were also recorded.
On arrival to the both ensuing trials, pre-exercise blood samples were obtained via venipuncture by a certified phlebotomist from an antecubital vein and collected into K+ tubes. Serum was then isolated by centrifugation (1500 rpm at 4 °C for 10-min) and frozen at −20 °C until analyses using specific assays on a Roche Modular E170. Assessed were serum human growth hormone (HGH), interleukin-6 (IL-6), cortisol, progesterone, and luteinizing hormone. Additionally, whole capillary blood was taken via fingertip puncture (Safe-T-Pro Plus, Mannheim, Germany) for determination of blood lactate (BL, mmol L−1) using a portable lactate analyser (Lactate Pro, Arkray, Japan). Blood collection was repeated immediately after, and 45 min post-exercise.
For the BP trial, groups of 2–5 participants completed a virtual BP class. Blood lactate was recorded once during the class, immediately after the fourth track. RPE after each track, session RPE and enjoyment were recorded as described above. Repetitions per track (full range + partial range) were: Squat 93 + 72; Bench press 70 + 80; Deadlift 48 + 44, and; Row 48 + 44.
For the CARDIO trial, participants cycled on a non-instrumented indoor stationary cycle (Body Bike International, Frederikshavn, Denmark) with a weighted flywheel mechanically linked to the pedals. After a two-minute warm-up, participants were required to maintain a pre-determined individualised HR for 55 min such that it would be iso-caloric and iso-time to the BP class. The target HR was the individual’s average HR over the BP class (excluding the cool down) measured during the first session. The trial ended with a three-minute cool-down. Participants were instructed to manipulate a combination of cadence and load to maintain target HR. Participants observed their own HR on a projected screen and were asked to maintain their target ±4 BPM during the main cycling phase. RPE was recorded every ten minutes during the session and an overall session RPE and enjoyment rating were provided post-exercise as in BP. Participants were allowed to listen to their own choice of music for the duration of the session.
Prediction of aerobic energy expenditure (EE) in kilocalories (kcal) was estimated for both BP and CARDIO. The linear relationship between HR and sub-maximal VO2 during the incremental graded exercise test for each individual was determined and the equation was subsequently used to estimate each participant’s mean VO2 (L min). Given consumption of one litre of oxygen is equivalent to expending 5.024 kcal, the estimated EE during the 60 min BP class was determined.
Descriptive data are presented as mean ± SD. Data was checked for normality and distribution. SPSS software (version 22, SPSS Inc, Chicago, IL) was used to determine differences within and between BP and CARDIO (α= 0.05). Paired sample t-tests were used to investigate within-trial effects on variables for each exercise type independently. A 2-way ANOVA with type of exercise and time as within-subject effect was conducted to determine the difference in physiological and hormonal outcome measures between the different exercise modalities (BP and CARDIO). The significance level was set to p < 0.05.
3. Results
The mean VO2peak of participants was 33.0 ± 6.4 ml/kg/min, and the average maximum HR during VO2peak testing was 177 ± 9 BPM. Predicted VO2 during the BP class was 14.9 ± 5.2 ml/kg/min, or 46.7 ± 19.4%VO2peak. Table 1 compares HR, EE and perceptive data during BP and CARDIO as well as BP load. RPE per track was 7 ± 1.2 for squat, 8 ± 1.4 for bench press, 7 ± 1.1 for deadlift, and 7 ± 1.6 for row.
Table 1Comparison of physiological and subjective parameters during BODYPUMP™ and CARDIO.
| Parameter | BODYPUMP™ | CARDIO |
|---|---|---|
| Mean ± SD (range) | Mean ± SD (range) | |
| Heart Rate (BPM) | 123 ± 21 (96–163) | 122 ± 20 (93–156) |
| Heart Rate as % maximum | 68 ± 10 (53–84) | 68 ± 9 (51–76) |
| Energy Expenditure (kcal) | 334 ± 127 (202–540) | 336 ± 140 (188–615) |
| Session Rate of Perceived Exertion | 7 ± 1.0 | 4 ± 1.5 |
| Subjective enjoyment | 1.7 ± 0.6 | −0.6 ± 1.2 |
| Average 1 repetition maximum squat (kgs) | 78 ± 19 (42–110) | |
| Average squat track load as % 1 repetition maximum | 25 ± 8 (13–38) | |
| Average 1 repetition maximum bench press (kgs) | 41 ± 5 (31–47) | |
| Average bench press track load as % 1 repetition maximum | 30 ± 8 (18–42) | |
| Average 1 repetition maximum deadlift (kgs) | 74 ± 12 (52–99) | |
| Average deadlift (back track) load as % 1 repetition maximum | 21 ± 7 (12–39) | |
| Average 1 repetition maximum bent-over row (kgs) | 48 ± 8 (39–64) | |
| Average bent-over-row load as % 1 repetition maximum | 32 ± 9 (17–38) |
Strength testing was carried out between self-reported days 3 and 9 post menstruation cessation (6 ± 2.2 days). There were no between-trial differences in luteinizing hormone and progesterone levels immediately prior to BP (6.04 ± 2.00 iu/L and 0.57 ± 0.43 nmol/L respectively) and CARDIO (6.43 ± 3.02 iu/L and 1.02 ± 2.11 nmol/L respectively, p > 0.05).
Table 2 presents within-trial and between-trial differences in human growth hormone, cortisol, Interleukin-6, and blood lactate for BODYPUMP™ and CARDIO. There were no baseline differences between BP and CARDIO. HGH levels increased after both BP (p = 0.005) and CARDIO (p = 0.019). These increases were significantly greater in BP than CARDIO at Post0, but not at Post45. IL-6 significantly increased in both BP (p = 0.002) and CARDIO (p = 0.030), and remained elevated above baseline at Post45 in both conditions but the between trial difference was not statistically significant. BL significantly increased in both BP (p = 0.001) and CARDIO (p = 0.035). These increases were significantly greater in BP than CARDIO at Post0, but not at Post45. BL was 5.11 ± 3.09 mmol/L immediately after the back track during the BP class. There were no significant within-trial changes in cortisol levels in either of the exercise trials.
Table 2Within-trial and between-trial differences in human growth hormone, cortisol, interleukin-6, and blood lactate for BODYPUMP™ and CARDIO.
| BODYPUMP™ | CARDIO | Between-trial difference p value | |
|---|---|---|---|
| Human growth hormone (pg/ml) | |||
| Immediately pre-trial | 558 ± 474 | 599 ± 754 | |
| Immediately post-trial | 3698 ± 1255 | 2368 ± 1163 | 0.016 |
| 45 min post-trial | 1149 ± 902 | 1149 ± 1266 | 0.945 |
| Cortisol (nmol/L) | |||
| Immediately pre-trial | 302 ± 107 | 265 ± 107 | |
| Immediately post-trial | 321 ± 92 | 294 ± 149 | 0.873 |
| 45 min post-trial | 275 ± 94 | 269 ± 125 | 0.578 |
| Interleukin-6 (pg/ml) | |||
| Immediately pre-trial | 3.54 ± 0.67 | 3.84 ± 0.76 | |
| Immediately post-trial | 4.88 ± 0.91 | 4.71 ± 1.03 | 0.288 |
| 45 min post-trial | 4.47 ± 0.76 | 5.01 ± 0.97 | 0.424 |
| Blood lactate (mmol/L) | |||
| Immediately pre-trial | 2.2 ± 0.9 | 1.8 ± 0.6 | |
| Immediately post-trial | 5.8 ± 3.0 | 3.2 ± 1.6 | 0.024 |
| 45 min post-trial | 2.5 ± 1.5 | 2.5 ± 1.2 | 0.371 |
Values are represented as mean ± SD.
a Significant within-trial difference from immediately pre-trial (p < 0.05).
b Significant between-trial difference (p < 0.05).
4. Discussion
To our knowledge, this is the first study to objectively compare the acute physiological and hormonal responses between a high repetition resistance session, and an iso-caloric, iso-time steady-state cardiovascular session, in female participants familiar with BP, not on oral contraceptives, and accounting for menstrual cycle. It is also the first study to provide detailed descriptive data of relative loads utilized during the squat, chest and back tracks during BP.
13
, 14
The main findings of this study indicate that differences in the immediate acute HGH and BL responses exist between exercise modes, in this cohort, despite matching them a-priori for caloric cost and exercise duration.HGH levels increased immediately post-exercise following both exercise sessions, but with a significantly greater increase after BP than CARDIO, indicative of potential positive physiological adaptations over a longer term beyond the apparent consumer focus on utilising caloric expenditure from commercially available activity trackers as a key metric for determining the effectiveness of an exercise session. High load, low repetition training has been reported as a pre-requisite to inducing significant HGH release,
15
but our findings suggest that low load, high repetition training also elicits such an effect. We also observed increased circulating IL-6 levels after PUMP and CARDIO at both time-points, but the difference between trials was not significant. It is interesting that we did not observe a significant increase within BP for cortisol, concomitant with HGH and IL-6 elevations, although it is possible that diurnal variation was more influential for cortisol than HGH or IL-6.4
The greater BL resultant from BP compared to CARDIO is also indicative of its relatively greater metabolic demand. We found BL mid-class (immediately post back-track) was 5.11 ± 3.09 mmol/L. Oliveira et al.,
10
observed BL after the squat track of 4.00 ± 1.45 mmol/L, significantly greater than after the back track (2.70 ± 0.98 mM). Oliveira et al.10
suggested that in their study, the increase in BL during the class was positively related to the muscle mass used in the track and the intensity of the track. Greco et al.,8
also reported BL post BP, noting values of 4.7–5.0 mmol/L immediately post class. In the present study, BL levels increased more after BP than CARDIO, which is likely due to the repetitive bursts of higher-effort, fatiguing exercise during tracks, interspersed with inter-track rest periods as opposed to steady state exercise, and also relatively grater muscle mass utilized compared to cycling.This is the first study to quantify the intensity of the squat, chest and back track during BP in terms of actual loads used as percentage of predicted-1RM. Average loads self-selected by participants during class, represented as a percentage of predicted one repetition maximum were 25 ± 8% for the squat, 30 ± 8% for the bench press, 21 ± 7% for the deadlift, and 32 ± 9% for the bent-over-row. A previous study on healthy untrained young adult females indicated that the average load used for squatting was 10% 1RM (in that paper, data was not detailed as %1RM for the chest and back tracks).
10
The relatively greater loads in our findings are most probably owing to the relatively greater training experience of our cohort. That is, it could be reasonably conjectured that participants with more training experience of BP would self-select loads greater than those of BP naïve. Arguably, our findings are therefore of greater relevance to habitual attendees of such classes rather than to novice participants naïve to such stimuli, and might better represent typically encountered self-selected loads by regular BP attendees. It is possible though those differences may be explained by specific choreography of the class.There is recent conjecture that strength gains may result from much lighter loads than previously considered the minimum requisite.
16
, 17
The minimum effective load must be considered in the context of the broader exercise prescription. One study9
reported no increase in 1RM in the squat and bench press after 12 weeks of regular BP attendance among overweight/obese adults. The authors suggested that this was because self-selected loads during the squat and chest tracks (12% and 16% 1RM respectively) were not sufficiently high, and muscular fatigue did not occur. This is not surprising given the cohort was new to resistance training and naïve to BP. Prior training studies have reported significant strength gains resultant from several weeks of BP.13
, 18
Although participant self-selected loads are not typically quantified in detail relative to known maximum capacity in published research, it is conceivable that chosen loads beyond ∼12–16% 1RM are needed, and with some progression, to increase strength.17
, 19
, 20
Our findings were that participants chose approximately 20–30% of their predicted 1RM. Although these loads are not traditionally considered ‘heavy’, they could result in significant strength gains if utilized with the requisite consistency. This aspect would warrant closer attention in future studies investigating training effects of BP.HR data in both the present study (68 ± 10%HRmax) and in that by Berthiaume et al.,
6
(60 ± 8%HRmax) indicated that for adult females, BP is a moderate intensity workout, and should result in improved cardiovascular fitness if performed consistently over a period of time.21
As per HR, VO2 data was fairly similar between the study by Berthiaume et al. and ours. In their study, females worked at 14.3 ± 1.3 ml/kg/min (28.0 ± 2.8%VO2peak) during BP while in the present study, the estimated virtual BP VO2 was 14.9 ± 5.2 ml/kg/min (46.7 ± 19.4%VO2peak).5. Conclusion
Calories matter, but so does the acute effect of an exercise session on a suite of hormonal and physiological responses that are known to have positive downstream effects on desirable adaptations such as fat metabolism and protein synthesis, both influential on body re-composition effects. Calorie counters may be too blunt a tool to provide adequate insight into chronic adaptations beyond arbitrary caloric expenditure accumulation. The findings of this study have provided more detailed quantification of the characteristics, relative to actual measured maximum capacities, of a BP class, and show that it has some more potent acute physiological effects than time- and calorie-matched steady-state cardiovascular exercise.
Practical implications
- •Simple caloric expenditure might misrepresent the full effects of an exercise session to consumers.
- •Lighter load group-exercise resistance training elicits physiological responses indicative of potential positive health effects over a training period if performed with the requisite frequency.
- •Participants self-selected loads of approximately 20–30% of their predicted maximum during a BP class.
Acknowledgements
This work was supported in the form of reimbursement for research expenses by Les Mills International Ltd.
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Article info
Publication history
Published online: February 23, 2018
Accepted:
February 17,
2018
Received in revised form:
December 19,
2017
Received:
October 4,
2017
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© 2018 Sports Medicine Australia. Published by Elsevier Ltd.
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