Thoughts on high intensity interval training (HIIT)

[Shared from Matt Metzgar’s blog]

Following up on the last post, I think there are many ways to get the benefits of sprinting.  I thought it was interesting that in the video associated with the last post, Mercola stated that he only did Sprint 8 once per week instead of the recommended 3 times per week.

Along those same lines, Clarence Bass recently wrote about interval training.  He writes:

“My concern, however, is that three hard interval sessions a week is too much for most people to sustain; they’ll do it—even enjoy it—under supervision (as in the Little study), but they’re not likely to keep doing it on their own. Hard training every workout is asking for trouble; it is neither fun nor productive. My own experience is that one or at most two hard interval workouts a week is all I can tolerate effectively, especially in the context of a balanced program of strength and aerobic training.”

Clarence has been doing intervals for decades, and I put a lot of stock into what he has to say.

My own experience mirrors this point of view.  When I’ve tried to do the full Sprint 8 programs 3 times per week, I can do it for a month or so, but then I burn out.  Conversely, I can do hard intervals once a week and continue month after month.

So we know sprinting once a week is sustainable, but what are the other options?  Chris over at Conditioning Research (who by the way just released a new book titled Hillfit) pointed to a study the other month about a minimalist sprinting routine.

Here is an interesting part of the study:

“Several recent studies have suggested that high-intensity interval training (HIT), a training model involving a series of 30-second ‘all-out’ cycling sprints (i.e. Wingate sprints) with 4 minutes of rest/recovery between each bout, may provide a time-efficient strategy for inducing adaptations that are similar to traditional cardiorespiratory training (Gibala et al. 2006; Burgomaster et al. 2005; Burgomaster et al. 2008; Rakobowchuk et al. 2008; Burgomaster et al. 2007; Trilk et al. 2010).

Furthermore, we have recently demonstrated the beneficial effects of HIT on insulin sensitivity (Babraj et al. 2009), a finding that has since been confirmed by others (Little et al. 2011; Richards et al. 2010; Whyte et al. 2010). However, whilst these observations are interesting from a human physiological perspective, their translation into physical activity recommendations for the general population is uncertain for two reasons. Firstly, the relatively high exertion associated with ‘classic’ HIT sessions requires strong motivation and may be perceived as too strenuous for many sedentary individuals (Hawley and Gibala 2009). Secondly, although a typical HIT session requires only 2-3 minutes of actual sprint exercise, when considered as a feasible exercise session including a warm-up, recovery intervals and cool-down, the total time commitment is more than 20 minutes, reducing the time efficiency(Garber et al. 2011). Thus, there is scope for further research to determine whether the current HIT protocol can be modified to reduce levels of exertion and time-commitment whilemaintaining the associated health benefits.”

In short, they suggest that the benefits of sprinting could be obtained with a reduced workload.

Here is their formulation:

It has consistently been shown that a single 30-second Wingate sprint can reduce muscle glycogen stores in the vastus lateralis by 20-30% (Esbjornsson-Liljedahl et al. 1999; Parolin et al. 1999; Esbjornsson-Liljedahl et al. 2002; Gibala et al. 2009). What is intriguing, however, is that glycogenolysis is only activated during the first 15 seconds of the sprint and is then strongly attenuated during the final 15 seconds (Parolin et al. 1999). Moreover, activation of glycogenolysis is inhibited in subsequent repeated sprints (Parolin et al. 1999). This suggests that the traditional HIT protocol (4-6×30 seconds) may be unnecessarily strenuous as similar glycogen depletion may be achieved using 1-2 sprints of shorter duration (15-20 seconds). In turn, this would make the training sessions more time-efficient, less strenuous and more applicable to the largely sedentary general population.”

Thus, they are saying that traditional sprinting programs may be overkill in a way, and that you could deplete glycogen just as well by doing 1-2 sprints of 15 to 20 seconds.

This I think leads to a real insight: if you cut the number and duration of sprints (but keep the intensity), then I could see how you could be able to do this workout more frequently.  So while 3 days per week of 6 to 8 30-second sprints may be too much for many people, 3 days per week of 1 to 2 15-second sprints may produce similar benefits and be more appealing to people.

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