Tuesday, January 27, 2009
Some of the people that made the study possible: (from left-right) Yours Truly, Kathleen McMillan, Jennifer Kuk, Shelley Atkinson, and Lance Davidson.
A new study from our lab, published yesterday in Archives of Internal Medicine, suggests that the combination of resistance and aerobic exercise provides the optimal strategy for improving functional capacity as well as insulin resistance (a precursor to type-2 diabetes).
As individuals age, they tend to store more body fat, particularly in the abdomen - where it is believed to pose the greatest threat to metabolic health. Advanced age also tends to bring about the loss of muscle, known as sarcopenia, which is strongly associated with a reduction in physical ability to perform tasks of daily living (climbing stairs, carrying groceries, etc.). The combination of these two bodily changes - increased fat and reduced muscle mass - is referred to as 'sarcopenic obesity' - a major risk for disease and disability among the older demographic.
Although diets may be effective in reducing the adiposity among obese older adults, they also have the unfortunate consequence of further exacerbating sarcopenia, and thus increasing risk of disability. Exercise, on the other hand, has the capacity to reduce adiposity, as well as maintain or even increase muscle mass. However, not all modalities of exercise have the same effect.
Thus, our lab conducted a 6-month randomized-controlled trial in a group of over 130 dedicated older adults (aged 60-80 years) from Kingston, Ontario. Participants in the study were randomly assigned to 1 of 4 possible groups: 1) no-exercise control, 2) resistance exercise (60 minutes/week of weight-training), 3) aerobic exercise (150 minutes/week of treadmill walking), and 4) resistance and aerobic exercise combined (90 minutes/week of treadmill walking plus 60 minutes/week of weight-training). Importantly, every exercise session was performed under direct supervision in our lab.
While those in the aerobic group showed reductions in fat mass and those in the resistance group showed increased muscle mass compared to control, it was the combination of both modalities that provided the optimal solution – leading to both a reduction in total and abdominal fat (not different from aerobic group) as well as an increase in muscle mass (not different from resistance group).
Importantly, these improvements in body composition were mirrored by a 43% improvement in insulin resistance, as measured by the euglycemic-hyperinsulinemic clamp, in addition to improvements on all tests of physical function.
That older adults should regularly participate in both aerobic and resistance exercise has previously been advocated by a number of associations, including the American College of Sports Medicine and the American Heart Association. However, our study is the first to provide evidence for such a recommendation.
Having been a member of the research team that ran this study, along with colleague, friend, and primary author of the study, Dr. Lance Davidson (now a post-doctoral fellow at Columbia) – I can assure you that this study which took 5 years of Dr. Davidson’s life, was no small feat.
I will spare you the details of the 5:00am clamp studies carried out by Lance, the countless 7am Sundays at the hospital MRI, the daily exercise supervision from 7am-7pm (yes, weekends too), the hundreds of maximal exercise tests on Monday nights, and all the other work that went into the study. Such is the life of those of us involved in intervention trials. But in the end, we hope that the important health messages derived from the hard work makes it all worthwhile.
As a final thought, I would like to sincerely congratulate Lance Davidson on this great achievement, who worked tirelessly on the project while juggling his growing family, and many other commitments. It all worked out in the end buddy! I wish you, Aimee and the girls all the best.
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