VARYING WORK TO REST RATIOS PRODUCES DIFFERENT METABOLIC RESPONSES
Gosselin, L. E., Kozlowksi, K. F., Bevinney-Boymel, L., & Hambridge, K. (2010). Metabolic and cardiovascular response of different high intensity aerobic interval exercise protocols. Presentation 1028 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.
This study evaluated metabolic and cardiovascular responses during four different high-intensity aerobic interval training protocols with similar total work output. Young physically active Ss (N = 8) participated in five different bouts of exercise over three weeks, where VO2 and heart rate were continuously monitored. Protocol one consisted of 20 minutes of continuous exercise at ~70% of VO2max. Protocols 2, 3, 4, and 5 were interval-based with a work:active-rest ratio (in seconds) of 30-30, 60-30, 90-30, and 60-60 respectively. Each interval protocol was at a workload corresponding to 90% VO2max as determined by a maximal graded exercise test. Active rest was carried out at a workload corresponding to ~35-40% VO2max. The 30-30 protocol included 20 intervals (10 minutes of activity); the 60-30 and 60-60 protocols had 10 intervals (10 minutes of activity); and the 90:30 protocol had seven intervals (10.5 minutes of activity). The total treatment times (including active rest) were as follows: 20 minutes for the 60-60 and 30-30 protocols, 15 minutes for the 60-30 protocol, and 14 minutes for the 90-30 protocol.
The 90-30 seconds high-intensity protocol resulted in the highest VO2, heart rate, rating of perceived exertion, and blood lactate whereas the 30:30 protocol resulted in the lowest of these parameters (all differences were significant). The total caloric energy expenditure was lowest in the 90-30 and 60-30 protocols (~150 kcal), whereas the other three protocols averaged ~200 kcal. The immediate post-exercise blood pressure was similar across all protocols.
Implication. Varying the work-to-rest ratio affects the metabolic responses in high-intensity training. High-intensity training performed at 90% of VO2max is physiologically feasible and may be used as an alternative approach to training middle-aged individuals, but with less time commitment. The higher energy expenditure in the shorter work:rest ratios explains why such training produces faster and greater training effects than longer work periods.
In sports where high numbers of repetitions are desirable, any variation away from one repetitious work to rest ratio, will alter the metabolic (energy) responses causing an athlete's brain to attempt to code different response patterns. That will not result in the best training effect for a particular restricted competition performance if the training aimed at replicating competitive factors.
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