Sunday, June 7, 2009

10+ 10+ 10 = 30 min or 30 min at a time? Accumulated versus continuous exercise for health benefits


Introduction to the debate – short bout or long drawn exercise:

Current physical activity guidelines endorse the notion that the recommended amount of daily physical activity can be accumulated in short bouts performed over the course of a day. Metabolic impacts of exercises are specific; so training impacts are also specific which vary with duration & intensity & fuel ingestion.

Aerobic exercise is low to medium output held for an extended period. Anaerobic or supra-aerobic exercise is high output, but short in duration. Dr Alsears (USA) recommends supra-aerobic exercise than to aerobic exercise for following training benefits:

1. Lose pounds of belly fat
2. Build functional new muscle
3. Reverse heart disease
4. Build energy reserves available on demand
5. Strengthen immune system
6. Reverse many of the changes of aging.

Dr Alsears of USA calls his program PACE® program. The following prototype is similar to PACE program:

1. Instead of a slow, steady pace on a bicycle or treadmill, try going 80% of your maximum for 2 minutes.
2. Rest for 1 minute
3. Go at 90% for another two minutes
4. Rest for 1 minute
5. Go at 100% for 1 minute
6. Recover

This program is an example of an intermittent training program. Intermittent training is aimed at anaerobic system developments especially for speed, which rarely induces aerobic training benefits of fat reduction. However, note that this program also claims to reduce body fat. Reduction of undue fat is associated with reduction of numerous biological & organic risks pertaining to fat accumulation.

We want to emphasize that, the metabolic switchover to aerobic exercises occurs between 2-3 minutes & efficient fuel utilizations in terms of FFA & TG occurs much later as carbohydrate has to go through the metabolic mill i.e. the TCA cycle fragments of carbohydrate must be present to start the lipid oxidation.

The confusion & the question:

First impression about short duration exercises is in the line of interval training not continuous training. It is taught to us that continuous training is the aerobic training & interval training is more anaerobic training. So how it is possible to get benefits of short bouts of similar to long drawn exercises. “Is there some logic behind it?” this question itched my mind long. As low duration exercises are directly related to a high patient compliance. When I read cumulative effects of short duration exercises is as good as a long drawn exercise I was encouraged to write this article.

The research article by Murphy et al (sports medicine; 2009):

The evidence on the claim that efficacy of accumulated exercises to that of continuous exercise is similar is limited. Murphy & colleagues reviewed (16 studies with before & after evaluation are included) to compare the effects of similar amounts of exercise performed in either one continuous or two or more accumulated bouts on a range of health outcomes. The important points to note are as follows:

A. Review of Long term studies reveals:

1. Impact on cardiovascular fitness: most studies reported no difference in the alterations between accumulated and continuous patterns of exercise.
2. Impact on normalization of BP: there appear to be no differences between accumulated and continuous exercise in the magnitude of this effect.
3. Impact on adiposity, blood lipids and psychological well-being: there is insufficient evidence to determine whether accumulated exercise is as effective as the more traditional continuous approach.

B. Review of Short-term studies reveals:

Murphy & colleagues also studied 7 short-term studies with before & after evaluations. Most of the studies considered the plasma TG response to a meal following either accumulated short or continuous bouts of exercise. Short term studies also suggest that accumulated exercise may be as effective at reducing postprandial lipaemia.

These researchers find a scope for further research to determine if even shorter bouts of accumulated exercise (<10 minutes) confer a health benefit and whether an accumulated approach to physical activity increases adherence among the sedentary population at whom this pattern of exercise is targeted.

Reference:

Murphy MH et al; Sports Med. 2009;39(1):29-43. doi: 10.2165/00007256-200939010-00003.


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