Interval Training and 40k TT
If you read my tweets at www.twitter.com/jfriel or in the right hand column on my blog home page you'll notice that I do a lot of intervals. What you're seeing there is similar to what I have many of the athletes I coach do in their training. This form of training has been around for a long time but was first mentioned and studied in the scientific literature in the late 1950s. Since then there have been many studies on the benefit of interval training. Most of these studies compared well-conditioned subjects doing high-intensity intervals with control athletes who trained with steady-state workouts only. This somewhat biased the results since several other studies have shown that for well-trained athletes high intensity training is more effective than simply training with high volume at a lower intensity. And you simply can't do the same amount of high-intensity training in a steady, non-interval workout. Intervals win hands down. So given the choice, if you want to improve your performance in endurance sport, intervals are the way to go.
I recently went back through my archives looking for what the research may say about the best way to train for a 40k time trial in cycling. A couple of the athletes I coach are focused on such events this season. I found four studies which suggested that with only 4 weeks of training race times for such a TT could improve 2% to 4%. So if you do a 40k in 60 minutes such an improvement would knock off 1 minute and 12 seconds to 2 minutes and 24 seconds. That's a lot of time reduction in a very short time frame.
Three of these studies (1,2,3) had similar workout protocols with 2 sessions a week with 6-8 intervals in a session and each interval lasting 5 minutes with 1 minute recoveries (this short recovery time is critical to the results you get--don't lengthen it). The power for these intervals was 80% of power at VO2max. If you find your average power from a 6-minute time trial using a power meter you can assume that is your power at VO2max and be pretty accurate. So if that power was 300 watts you'd do these intervals at 240 watts (6-8 x 5 minutes at 240 watts with 1 minute recoveries). That's probably just about your functional threshold power (the power you can hold for 1 hour). Basically that means you'd be doing intervals at about your 40k TT race power. Strange how that specificity thing works, isn't it?
The final study (4) I looked at used a much higher intensity, however. In this study highly trained cyclists and triathletes did intervals once a week for 4 weeks. Each of these sessions involved doing 8 intervals at power at VO2max with each interval lasting for 60% of the time the subjects could maintain power at VO2max. The recovery after each was twice as long as the work interval. So, let's go back to our example athlete from above. If when doing an all-out effort he could hold 300 watts for 6 minutes here's how his workout would look: 8 x 3 minutes and 36 seconds at 300 watts with 7 minutes and 12 seconds of recovery after each. That would be done once each week. That's a killer session so once a week is plenty.
It is possible, however, to combine these two workouts in a week. I often have riders do the first workout with 5 intervals early in the week and the second workout also with 5 intervals later in the week. In fact, if you track my workouts through Twitter you'll find I'm doing something similar to that right now (when travel allows). Most athletes would need 48 to 72 hours to recover from each of these before going hard again.
Just a side note here... Without a power meter you're just guessing as to what the intensity you should be using is for such workouts. A heart rate monitor doesn't improve that guesswork by much. Power meters are a necessity for such precise interval workouts.
1. Kubukeli ZN, TD Noakes, SC Dennis. 2002. Training techniques to improve endurance exercise performances. Sports Med 32(8): 489-509.
2. Lindsay FH, JA Hawley, KH Myburgh, et al. 1996. Improved athletic performance in highly trained cyclists aftyer interval training. Med Sci Sports Exerc 28: 1427-1434.
3. Weston AR, KH Myburgh, FH Lindsay, et al. 1997. Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists. Eur J Appl Physiol 75(1): 7-13.
4. Laursen PB, CM Shing, JM Peake, JS Coombes, DG Jenkins. 2002. Interval training program optimization in highly trained endurance cyclists. Med Sci Sports Exerc 34(11): 1801-1807.