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Unobtrusive technology is enabling us to more accurately gauge the physical effects of group exercise classes.

Research paper: SenseWear Armbands Differentiate Contribution of Select Group Exercise Programs to Daily Activity Requirements
Research team: Aimee L Harvey, Mark R McKean PhD, Brendan J Burkett PhD
Published: Journal of Fitness Research, Issue 3.1, 2014
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Introduction: Fitness centres provide an opportunity for increased activity through group exercise, with 81 per cent of fitness businesses within Australia offering group exercise classes. Les Mills International is the world’s largest provider of pre-choreographed group exercise classes and delivers more than three million workouts weekly in 14,000 fitness facilities across 80 countries. However, there is little empirical evidence of the contribution of group exercise programs towards daily physical activity.

Emerging technologies such as the BodyMedia SenseWear MF-SW Armband (SWA), which measures physical activity and movement data from a tri-axial accelerometer along with physiological sensors (skin temperature and galvanic skin response) have improved sensitivity for detecting subtle changes in energy expenditure, particularly for complex movements. The small, relatively unobtrusive size may provide a more realistic measure of group exercise class activity.

This study used SenseWear Armbands to differentiate and quantify physical activity in different group exercise classes towards ACSM (American College of Sports Medicine) guidelines on daily activity. This new knowledge will be beneficial to public health professionals, fitness professionals and allied health professionals who recommend group exercise programs. It will also allow group exercise participants to specifically choose a class related to their fitness goals and daily activity requirements.

Methods: Using a crossover design, 13 males and 17 females completed four group exercise classes; BODYPUMP™ (release #82), BODYCOMBAT™ (release #52), BODYBALANCE™ (release #57) and BODYATTACK™ (release #77) in a randomised order over seven days. Participants were experienced in, or instructors for, Les Mills International group exercise programs, and had no existing medical conditions or injuries. All sessions were at similar times of day with a minimum of 24 hours rest between each class in the same air-conditioned group exercise studio. Participants followed similar dietary patterns before participating in each class. Instructors were Les Mills International certified and instructed classes as per the defined choreography. Participants wore a Polar RS400 heart rate monitor (Polar Electro Oy, Kempele, Finland) and a BodyMedia SenseWear MF-SW Armband (SWA) (BodyMedia, Philadelphia, PA). Participants also completed a six-question post-participation survey regarding the four group exercise classes and their perceived benefits.

The 30-second article

  • Emerging technologies have improved the ability to more accurately gauge energy expenditure
  • For this study, 30 individuals participated in four different Les Mills pre-choreographed group exercise classes
  • BODYATTACK™ and BODYCOMBAT™ classes produced the highest mean values for heart rate, step count, METS (energy cost), total energy expenditure and RPE
  • Participating in a combination of these classes can enable individuals to meet ACSM’s minimum daily activity guidelines.

Results: Key results are shown in Table 1.

Discussion: The ACSM recommends that most adults engage in moderate intensity cardiorespiratory exercise for at least 30 minutes a day on at least five days a week or vigorous intensity cardiorespiratory exercise for at least 20 minutes a day on at least three days a week. A combination of moderate and vigorous intensity exercise on three to five days a week is recommended for most adults to achieve and maintain health and fitness benefits.

BODYATTACK™ and BODYCOMBAT™ classes produced the highest mean values for heart rate, step count, METS (metabolic equivalents), total energy expenditure and RPE (rate of perceived exertion), and were the only two classes to record effort at above 9.0 METS for short periods of time. The average METS for the entire class fell into the vigorous category of 6.0-9.0. Both genders achieved over 5,000 steps during BODYCOMBAT™ and BODYATTACK™. Average step count per minute for BODYATTACK™ was 103.7 for males and 100.3 for females. BODYCOMBAT™ resulted in 101.4 steps per minute for males and 93.9 steps for females.

Male and female participants found participating in BODYATTACKTM and BODYCOMBAT™ enjoyable, and believed it would help them achieve better coordination and aerobic fitness. In terms of marketing, BODYATTACK™ is described as ‘a high intensity sports-inspired cardiovascular workout’ and BODYCOMBAT™ as ‘high intensity martial arts-inspired cardio’. The measured subjective and objective data support these profiles. Public perception and medical, exercise, and allied health professional recommendations of these classes for co-ordination and aerobic fitness, as well as contributing to reduced body fat, are accurate.

Average METS for both BODYPUMPTM and BODYBALANCETM was in the moderate category. BODYPUMPTM recorded slightly higher average METS than BODYBALANCETM (4.9 as opposed to 3.7 for males, and 4.3 as opposed to 3.2 for females.) When compared, METS for BODYBALANCETM were 24.7 per cent lower than BODYPUMPTM for males and 26.8 per cent lower for females. This is supported by the survey results where both genders reported the BODYPUMPTM class to be more difficult than the BODYBALANCETM by equal amounts of 1.2 out of 5. When completed two to three times per week, both BODYPUMPTM and BODYBALANCETM also meet ACSM guidelines for resistance, flexibility and neuromotor exercise as both programs contain a range of exercises for all the major muscle groups as well as training balance, agility, coordination, gait and flexibility.

Conclusions: SenseWear Armbands appear to be a valid tool to differentiate responses between different group fitness classes, with data matching participant feedback regarding level of difficulty and complexity. Results showed all classes placed into either vigorous or moderate exercise intensity categories, according to average METS. Based on the results of this study, if participants perform three cardiovascular classes (BODYCOMBAT™ or BODYATTACK™), along with two BODYPUMP™ and one BODYBALANCE™ class each week, they will meet all minimum daily activity guidelines made by the ACSM for maintaining cardiorespiratory, musculoskeletal and neuromuscular fitness.

Fitness Research is a partnership between Australian Fitness Network, the University of the Sunshine Coast and the Australian Institute of Fitness. Its mission is to improve the health of Australians through an improved body of fitness knowledge. Access current and back issues of the Journal of Fitness Research at

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