While significant improvements in endurance performance (and corresponding physiological markers such as VO2max, oxidative muscle enzyme activity,performance to exhaustion) are evident following an endurance training program (long, slow distance) in sedentary and recreationally active groups, additional increases in time spent on the bike (hours of training, volume of training) does not enhance either endurance performance or these associated physiological variables. For the already trained athlete, further improvements in performance can be achieved only through high-intensity interval training (HIT).
HOW MUCH TIME IS INVOLVED?
Amazingly, HIT requires only a few weeks to hone that performance edge. One study indicated that as few as four sessions were needed to measure a benefit, while another measured an increase in peak work outputs of 4 to 5 % and simulated 40 km time trial results of 3 to 3.5% after 6 sessions. And these improvements were independent of a change in VO2max.
HOW MANY INTERVALS PER SESSION?
One suggestion was to apply 15% of weekly training miles to HIT. These miles were divided into 6 separate sessions of six to eight 5 min repetitions at 80% of peak power output followed by 60 second rest intervals. Another used twenty 60 second intervals with a 120 second rest. And a third incorporated repeated supramaximal sprinting into the training program with equally good results.
HOW HARD SHOULD I PUSH?
Your personal maximum power output is the ideal for interval intensity and 60% of your personal time to exhaustion is a good interval duration. This combination significantly improved 40-km time trial performance. If you don't know your personal maximum power output, VO2max can be substituted for intensity of effort.
AND A TAPER IS THE KEY TO SUCCESS
HIT should be the final step in your training program with 4 to 6 interval sessions over 2 weeks. Although relatively short, it does have one risk - overtraining fatigue. To get maximum benefit, HIT must be combined with a tapering of your training program. There is suggestive evidence that a slow taper may have an edge, but this is controversial. What is clear is that a 50% single-step reduction in HIT led to an approximately 6% improvement in simulated 100 km time-trial performances after 2 weeks.
Most coaches have interpreted a taper as a decrease in training volume (time) rather than the intensity of each interval session. But a recent study has challenged that perception. In that study, two groups cut their training time by 50 %. One maintained a steady program at 68% VO2max while the other did sprints keyed to their lactate threshold and averaged 83% VO2max. At 21 days there was no difference in performance measures.