High-Intensity Interval Training (HIIT): Are You Doing It Right?

The 4 pillars to successful long VO2 max intervals

Sally is a running newbie who has entered her first marathon. She’s incredibly excited about the challenge but she’s scared that she won’t be able to complete the race. Sally has recently read that by training more, she can raise her VO2 max (amount of oxygen that your body can utilise [1] ), giving her a better chance of finishing her first marathon. Sally, however, is a full-time accountant, with a busy social life, and thus finding the time to train is a real challenge.  Sally needs to maximise her bang for buck in time spent training. But how?

 

Maximise your bang for buck in time spent training with VO2 max High-Intensity Interval Training (HIIT)

I get it, you’ve got a busy life, with many work and social commitments. Running requires a significant amount of your energy and time, so how are you going to fit it all in? Well I’ve got some GREAT news for you. HIIT provides you with an incredible bang for your buck in time spent training and should be incorporated into your running plan. But why? By performing high intensity running intermittently, not continuously, you can maintain a faster running pace for longer with less accumulated strain and fatigue whilst reaping the benefits of specific adaptations [2]. When performed correctly with adequate recovery, HIIT can provide you with rapid improvements to your race times [2]. It’s important to remember, however, that this is not about ‘NO PAIN, NO GAIN’, you should always leave your HIIT session with the knowledge that you had one more interval in you. This is a training session, not a race. Leave some energy in the tank for your next run. HIIT is a powerful but often misused tool. It’s time to take it to the next level.

 

Rest periods between each interval are an essential part of the workout —  put on your sprinters cap.

What might not spring to mind when you think about HIIT? Rest. Without sufficient rest, it’s physiologically impossible for you to repeat a running pace that will place you in your limits of physiological tolerance. i.e. your ‘severe’ intensity domain. Instead, with insufficient rest between intervals, your running pace will get sucked into the ‘heavy’ intensity (threshold) domain as this exercise domain is more sustainable. In short, this will result in your session outcome being entirely different to its desired intention. The net effect? Ineffective training that wastes your time, and time is precious.

 

The question then 'how long should your recovery periods be between intervals?'. A challenging question to answer in view of the polarising aims of a recovery period. A successful recovery period between intervals should 1) Maximise your ability to run hard during subsequent intervals, but also 2) allow you to easily accumulate minutes at >90% VO2 max in your subsequent intervals. How then can you strike the perfect balance?

The good news is that traditional long VO2 max HIIT sessions don't require a specific work to rest ratio like a tabata session for example. It appears that 2 minutes is the magic number here, having been previously shown to allow runners to reach a higher peak VO2 (mL/kg/min) compared to 1 minute of passive (walking) recovery (increase by 1.7%) and 4 minutes of passive (walking) recovery  (increase by 1.9%). The percentages increases might not significant, but when placed into context, this is an easy win that will allow you to collect more minutes in the severe intensity domain (red zone) that you can apply to your VO2 HIIT session tomorrow [3]. 

Micro intervals feel easier because they're easier.

I don't believe in the 'micro interval' interval phenomenon. Short intervals feel easier because they're easier. 

When your goal is to improve your VO2 max, you're going to want to work in and around your VO2 max during your intervals and that means working for long enough that your peak VO2 hits >90% of your VO2 max during your intervals. As per the research carried out by Professor Stephen Seiler, a world-leading researcher in endurance training, intervals less than 2 minutes in duration will not place you in the severe intensity domain (<90% of VO2 max) [4]

 

Your body takes time to respond to a sudden increase in exercise intensity, owing to its  oxygen uptake kinetics [4]. As a result, it will take time before your body begins to work in around VO2 max. This means that each interval should last at least 2 minutes [5], with a focus placed on time, as time calculated in the serve intensity domain (red zone) is key not distance ran.

 

How do you know if you’ve worked in around your VO2max during an interval session?

 

The easiest way to measure this is through your heart rate, best measured through a chest heart rate monitor strap, not the heart rate provided on your watch, as this is highly unreliable. During a successful HIIT, your heart rate should rise to 85% of your maximum heart rate (determined by a specific scientific test, not 220-your age), during your first interval. A heart rate that will gradually rise upon every interval owing to cardiovascular drift. Your target is to achieve an average heart rate that is 90% of your real max heart rate across all intervals.

References

 

(1) Whyte G. The Physiology of Training: Advances in Sport and Exercise Science series. Elsevier Health Sciences 2006.

(2) Midgley AW, McNaughton LR, Jones AM. Training to Enhance the Physiological Determinants of Long-Distance Running Performance. Sport Med 2007;37:857–80. 

(3) Seiler S, Hetleid KJ. The Impact of Rest Duration on Work Intensity and RPE during Interval Training. Med Sci Sport Exerc 2005;37:1601–7. 

(4) Seiler S, Tonnessen E. Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Sport Sci 2009; 13:32–53.

 

(5) Burnley M, Jones AM. Oxygen uptake kinetics as a determinant of sports performance. Eur J Sport Sci 2007;7:63–79.  

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