Intermittent aerobic training - part 1 - Tech Brief

American Fitness, March-April, 2002 by Scott Roberts

Aerobic exercise is an important component in the development and maintenance of fitness. Aerobic fitness reduces body fat and disease risk and promotes weight loss. However, there is controversy regarding the "optimal exercise" technique. In the past, most individuals have been taught to exercise aerobically at the constant percentage of their heart rate reserve (HRR) or maximal oxygen uptake (V[O.sub.2]max). However, recent research suggests that intermittent training (IT) may offer some advantages when compared to continuous training (CT) exercise. IT features short bouts of either aerobic or anaerobic exercise interspersed with short periods of rest. The exercise and rest periods may be as short as 30 seconds or as long as six minutes. IT should not be confused with the traditional technique of interval training because interval training often emphasizes high-intensity anaerobic activity, whereas intermittent training is primarily designed for the general public and may be aerobic, anaerobic or unspecified.

Summary of Intermittent Training Research

A recent study conducted by Harold Mayer and colleagues at the Lifestyle Center of America in Sulphur, Oklahoma, compared the effects of intermittent and continuous aerobic exercise among the elderly (1). Factors studied included fitness, weight loss, body composition and thyroid status. The CT group exercised at their target heart rate (THR) for the prescribed time while the IT group alternated between aerobic exercise (until they reached 5 bpm above their THR) and active rest (until their heart rate fell to 5 bpm below their THR). Active rest refers to slow continuous movement (rating of perceived exertion 1 of 10 on the Borg scale) using the same muscle groups as involved in the preceding aerobic activity. THR for both exercise groups was initially set at 40 percent of the V[O.sub.2]max heart rate reserve (HRR). Training intensity increased 5 percent each week to a maximum of 85 percent V[O.sub.2]max HRR.

In Mayer's study, significant reductions occurred in both body fat percentage and weight for the IT group (-1.56 percent and -2.42 kg), but not for the CT group (-0.11 percent and -0.88 kg) or control group ( 0.93 perfect and 1.58 kg). The IT and the CT groups significantly improved their mean cardiorespiratory function as measured by V[O.sub.2]max ( 3.28 ml/kg/min and 2.99 ml/kg/min), respectively, compared to the control group ( 0.22 ml/kg/min). The findings in this study confirm the observations of other research using intermittent training techniques.

A recent study by Mark Ohlsen and Scott Roberts at Central Washington University investigated the effects of CT versus IT on aerobic capacity, body composition and blood lactate response in sedentary college-aged females (2). Using a similar training regime as outlined in the Mayer study, Ohlsen and Roberts found that following an eight week training program, both the CT and IT groups had significant reductions in body weight and fat percentage, increase time to fatigue and increased V[O.sub.2]max. However, the IT group had significantly lower blood lactate responses for each workload throughout the final max test, while no improvements were seen in the CT group. Thus, the IT group demonstrated greater improvement in their anaerobic thresholds compared to the CT group. This improvement allows the subjects to work at a higher percentage of the V[O.sub.2]max compared to the CT group. The work of Roberts and Ohlsen is supported by research conducted by L. Brockman and colleagues in which they found post exercise metabolism improved more with intermittent aerobic exercise then continuous aerobic exercise (3). Any mode of exercise that elevates post exercise metabolism more than another form is desirable for enhancing weight loss.

Results

The results suggest that when comparing intermittent training aerobic exercise (IT) to continuous training aerobic exercise (CT), IT exercise elicits similar improvements of fitness for sedentary individuals, results in greater reductions in body fat percentage, weight and lactate levels during exercise, that are not present with CT exercise. Next issue's column will focus on the specifics of how to plan and implement IT programs.

Scott Roberts, Ph.D., FACSM, FAACVPR, is an assistant professor in the Department of Physical Education and Exercise Physiology at California State University, Chico His primary area of expertise is Clinical Exercise Physiology He has authored and co-authored ten fitness and exercise books and over a hundred articles and chapters in books Roberts has contributed three chapters to Fitness: Theory & Practice textbook, authored two home study courses and contributed numerous articles to American Fitness magazine.

References

(1.) Brockman, L., Berg, K., & Latin, R. (1993). "Oxygen uptake during recovery from intense intermittent running and prolonged walking." Journal of Sports Medicine and Physical Fitness, 33 (4), 330-336.

(2.) Mayer, H.C., DeRose, D.J., Charles-Marcel, Z.L., Sergev, O., Roberts, S.O. & Nethery, V.M. (2001). "Aerobic Intermittent Training: Effects on Fitness, Body Composition and the Thyroid." (in review)