Fight or Flight Fitness

—–

A 4 minute workout can improve your aerobic fitness to the level normally associated with 60 minutes per day (5-6 days a week). And you will also improve your anaerobic fitness which the traditional 60 minutes of moderate work (70% of Vo2 max) will not.

Would you be interested in cutting your workout time – but getting the same or even better results? But I will warn you during those 4 minutes you will suffer, and it will seem a lot longer than 4 minutes.

Previously, I outlined an effective interval training regimen that centered around 30 seconds of near all out work (be it running sprints, bike, etc) followed by a 4 minute rest period. You repeat this 4-6 times, the problem some people would find is those ‘wasted’ 4 minute rest intervals. If you want to have even a more efficient work out session you can turn to Tabata intervals.

Tabata intervals:

Tabata intervals consist of 20 seconds of all out sprints (170% of Vo2 max) followed by 10 seconds of rest/recovery. You repeat this for 7-8 sets. The total time taken to complete this workout is only 4 minutes. Simple, short and sweet. You can run these sprints (I suggest slight uphill slopes), you can do stairs, bike, rowing, etc.

Peak Performance has a very good article on Tabata intervals (and other intervals), giving details about the science.

The first study consisted of two training protocols using a cycle ergometer. The first protocol used a constant workload of 70% of VO2max for one hour (traditional aerobic training), 5 days a week. After 6 weeks the VO2max had increased from 53ml/kg/min to 58ml/kg/min, but there was no significant change in anaerobic capacity.

The second protocol worked on high-intensity intervals of 20 seconds work, 10 seconds rest. The work rate was at 170% of VO2max and 7-8 sets were done each day for 5 days a week. In the second protocol VO2max increased by 7ml/kg/min (ie more than steady state) and anaerobic capacity improved by 28%. When you look at the total time spent in training for the two sets of subjects, the first protocol involved 30 hours training, while the second involved only 2 hours!

Tabata then compared this highly effective interval workout with a protocol using 4-5 repetitions of a 30-second workout at 200% of VO2max and 2-minute rest intervals. He looked at both the accumulated oxygen deficits of the two protocols and the peak oxygen uptakes during the last 10 seconds of each interval. It was clear that the 20:10 seconds work:rest ratio taxed the anaerobic and aerobic systems maximally. The advantage of 20:10 Tabata intervals is that they are very effective and do not take a long time at all. The disadvantage is that they are very hard work and it takes a highly motivated athlete to work at the high levels of intensity required!

So now you have another arsenal in your interval training regimen. You can pick the short Tabata intervals (20 sec. work, 10 sec. rest) or the more traditional 30 sec. work, 4 min. rest. In reality a wide variety of intervals session with different work to rest ratio will work. The trick might be to mix them up so you do not become so bored. The downside of high intensity interval sessions is they require high motivation. Therefore, you might want to mix them up with more traditional relatively easy endurance sessions (think long easy run or bike).

But if you want to make the most of your time (or do not have a lot of time to spare) give Tabata intervals a try.

——

Alan Couzens over at endurance corner writes a very good piece (click here for the full article) about the overall importance of including sprint intervals in your training even if your overall goal is an ultra endurance even like an Ironman.

He gets into the detailed physiology as you can see from this passage:

In the figure above (adapted from this study), the x axis represents intensity (%VO2max), the y axis represents aerobic adaptation in the form of cytochrome c concentration (nmole/gm). As you can see, slow twitch fibers were maximally (aerobically) trained at an intensity of ~83% of VO2max (approximately equal to the anaerobic or ‘functional’ threshold. FOG fibers were maximally trained at anywhere from 83-116% of VO2max, while FG fibers weren’t significantly trained until the workload exceeded 100% of VO2max, and weren’t maximally trained until the workload reached 116% of VO2max.

But beyond just the interval work he also discusses the importance of long slow stuff (which I have mentioned previously but haven`t gone into the details).

An additional study that has particular relevance to the optimal duration/intensity combination for slow twitch fibers was that of Harms and Hickson (1983). In this study, the researchers found a near linear relationship between duration of work and adaptation of slow twitch fibers. In other words, providing a minimal intensity of training was maintained (60%VO2max), doubling training volume elicited performance improvements of 40-100%. When we compare to the improvements in Dudley’s study, it becomes clear that in the case of slow twitch fibers duration and frequency trump intensity.

Therefore, you can see the benefits of both sprint intervals and long slow endurance stuff that could even include long serious walks.

Now what does he actually prescribe for sprint intervals (for your base training):

Essen (1978) found that providing the length of the training interval was kept short (15-30s), exercise performed in excess of VO2max elicited glycogen depletion patterns and lactate levels much more in accordance with tempo or threshold training, i.e. 2-4mmol/L lactate even when continued for 30-60 minutes (i.e. 30-60 repetitions). These intervals do not provide the same level of stress on the central systems as long intervals, therefore long intervals or time trials are indicated for a short period of time prior to competition to truly peak an athlete, however, in terms of maximizing peripheral adaptations in FG fibers, 30-60 reps of 15-30s with a 15s-1min rest period is optimal.

This at least give you some of the physiology behind interval training and some guidelines (30-60 reps is a lot so I would say gradually build up to this level), with the additional reminder of also including some low intensity endurance work.