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| Dec 02, 2014
By: Martin Sénéchal, Ph.D., CEP
Exercise is a cornerstone in the management and the prevention of obesity-related chronic conditions. National and international agencies are recommending a minimum of 150 minutes per week of endurance exercise at moderate intensity in conjunction with at least two days of strengthening activity. However, the public generally only remembers the endurance part of this recommendation.
Based on some changes that occur through the lifespan, there is a rationale for emphasizing strength training in individuals. For example, between 20 to 70 years of age, a natural loss in about 40 percent of muscle mass, called “sarcopenia” occurs. In adults, strength training is a rational strategy to attenuate the effect of muscle mass loss. However, it is unknown if older adults can actually increase muscle mass with resistance exercise training. Nevertheless, besides “sarcopenia,” aging is also associated with a decline in muscle strength commonly called “dynapenia.” Interestingly, the rate of loss of muscle strength with aging is much steeper compared to that for muscle mass decline. In other words, individuals lose more muscle strength than muscle mass for a given time period. Therefore, strength exercises should be emphasized to prevent decreases in muscle strength rather than targeting the muscle mass.
The good news is that when sedentary people begin strength training, they obtain fast improvements in muscle strength— within six weeks! In addition, gain in muscle strength can be as high as more than 100 percent, and this occurs in all age groups. Fast improvement in muscle strength is more likely to help people maintaining adherence to exercise training, which is a real challenge in the field of clinical exercise. Specifically with older adults, increasing overall muscle strength will help to achieve activities of daily living such as climbing stairs, and carrying objects (e.g., grocery bags), thereby helping them to be more independent. Finally, being stronger has been associated with a better quality of life and health outcomes.
In this paper recently published in MSSE, we investigated 7,226 men from the Aerobics Center Longitudinal Study first to determine whether low muscle strength was associated with an increased risk of having the metabolic syndrome (cluster of risk factors) and second, to quantify the level (threshold) of muscle strength associated with the metabolic syndrome. In our study, we found that low muscle strength, defined as < 20 percentile of combined 1RM (from bench and leg press) scaled to body weight (per kg body weight), was associated with having metabolic syndrome, especially in young men.
Our result confirms previous work on the topic. However, limitations of previous research were the presence of confounding effects of fitness or adiposity, which were controlled in our study. In addition, our study adds to the literature by proposing thresholds of muscle strength associated with the metabolic syndrome. This point is a stepping-stone for professionals working in the field of exercise. First, the study gave thresholds of relative muscle strength based on two widely used exercises (bench and leg press). Second, these thresholds help them design exercise programs that aim to improve health outcomes. Third, as muscle strength is a modifiable risk factor, our result reinforces the message that people should perform strength training as a part of their exercise regimen to help enhancing metabolic risk factors. Therefore, this study provides evidence for exercise professionals in their day-to-day practice. The next steps are to investigate these thresholds with a prospective study and look at potential mechanisms (biological markers) that could explain why muscle strength is associated with metabolic syndrome.
Martin Sénéchal, Ph.D., CEP, is associate postdoctoral fellow at The Manitoba Institute of Child Health, University of Manitoba, faculty of medicine, department of pediatrics and child health in Winnipeg, Manitoba, Canada. His research focuses on cardiometabolic risk factors, chronic disease and exercise. More specifically, he is interested in the metabolic response to resistance training and the predictors associated with exercise-responders.
This commentary presents Dr. Sénéchal’s views on the topic of a research article which he and his colleagues had published in the August 2014 issue of Medicine Science in Sports & Exercise® (MSSE).
Viewpoints presented on the ACSM blog reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.