Exercise Snacks

Unlike junk food, these snacks are healthful

Tiny bursts of strenuous exercise yield big benefits

Martin Gibala and colleagues at McMaster University in Ontario have investigated the effects of brief, high-intensity exercise periods to improve cardiorespiratory fitness. A recent study featured 'exercise snacks' of stair-climbing. Twelve, sedentary, apparently healthy young adults participated in a study that compared the effects of three repetitions of 'all-out' climbing on a three-flight stairwell (60 steps) for 20 seconds. A rest period of 1-4 hours separated the three exercise bouts. Participants repeated the stair climbing protocol three times per week. Twelve non-trained persons comprised the control group. After six weeks, the training group increased maximum oxygen uptake from that at baseline by 5 percent, while that of the control group diminished slightly. Maximum cycling power output of the training group increased by 12 percent, while that of the control group deceased marginally. People who work in low- or high-rise office buildings could easily adopt this protocol with minimal time commitment. What’s keeping you from giving this a try?

Sprint interval training involves brief bursts of high-intensity physical exertion interspersed with short recovery periods in a single exercise session. Researchers in British Columbia recently conducted a pilot study to determine if more widely spaced (from 1-4 hours) brief periods of high-intensity exercise over the course of a day would lead to improvements in peak oxygen intake and power comparable to those of sprint interval training.

Healthy, inactive young adults participated in a randomized controlled study that compared sprint interval training to short sprint training on stationary exercise bicycles. The protocol called for one sprint interval session per day and three per week and three sprint interval sessions per day per day and three per week. All sprint periods lasted 20 seconds; both exercise regimens lasted for a total of 10 minutes each week over six weeks. Absolute peak oxygen consumption increased by 6 and 4 percent for sprint interval training and short sprint training, respectively, with no significant difference between them. Power, measured by the time required to bike 6 miles as fast as possible improved by 13 and 9 percent for sprint interval training and short sprint training, respectively, again with no significant difference between them. Participants reported enjoying both types of training. Well-spaced short bursts of strenuous exertion over a day appeared to produce similar improvements in cardio-respiratory fitness compared to sprint interval training.

Breaking up long periods of sitting predicts improved markers of metabolic health. Given that many Americans avoid extended periods of physical activity, might brief periods of strenuous physical activity also improve metabolic markers? Researchers in British Columbia conducted a follow-up cross-over study with 11 overweight women. In phase 1, participants sat quietly for 9 hours moving only to eat and visit the bathroom. In phase 2, participants sat quietly for one hour then engaged in eight 15-30 seconds of rapid stair climbing every 60 minutes in between more periods of quiet sitting. Each participant completed both phases in a random order. In both phases, participants ate small (530 calorie), high-glycemic index meals at times 0, 3 hours, and 6 hours. Compared to the prolonged sitting condition, the stair-climbing condition led to significantly reduced post-meal total insulin and non-esterified fatty acids but not total glucose or triglyceride. Thus, breaking up extended periods of sitting with brief, strenuous periods of exercise might help overweight people avoid insulin resistance and type 2 diabetes.

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