This blog post details some of my opinions around the use of high-intensity interval training (HIT) for those participating at recreational and competitive level endurance events in sports such as running, rowing, cycling, swimming, triathlon and kayaking. The information provided has been informed from my own trial and error as a PhD researcher investigating HIT in swimmers and from my own training as a competitive rower who has adopted a HIT program with some success. Whilst I don’t delve into the specific physiological mechanisms, I hope that some of the practical ideas provided can help to stimulate further thought and discussion among those participating in endurance events.
What is HIT?
High-intensity interval training is defined as repeated bouts (or intervals) of high-intensity exercise ranging from above anaerobic threshold intensity to supramaximal exercise intensity, interspersed with recovery periods of low intensity exercise or complete rest (Laursen & Jenkins, 2002). So basically you perform a fast interval (i.e. above anaerobic threshold intensity), then recover, then repeat. Simple!
Why should I use HIT?
In recent years, HIT has been receiving an increasing amount of investigation as it may allow a reduction in training volume (i.e. total distance completed per week) by increasing training intensity. This is in contrast to the traditional training methodologies of endurance sports where increasing training volume is often seen as the key to enhancing performance and the old saying “mileage makes champions” generally proves to be true. However, what if you only have 10 hours per week to train? How can you increase training volume if you simply don’t have the time? Basic training theory outlines that a training stressor (i.e. increased training volume) results in a training adaptation (i.e. enhanced performance) or so Hans Selye’s theory of the “General Adaptation Syndrome” suggests. Perhaps we can manipulate the training stressor to be more time efficient in nature by decreasing volume but increasing intensity?
How should I use HIT?
Yes, performing HIT sessions every day sounds great, but it’s not realistic. Trust me, I’ve tried it! Fast intervals every day is asking for trouble – overtraining, injury, poor skill development, etc. I’ve found that 1 – 3 sessions per week for your average recreational or competitive endurance athlete training 5 – 6 sessions per week works quite well. However the most crucial factor is that an easy day (i.e. endurance training)/hard day (i.e. HIT training) format should nearly always be followed in order to promote recovery, see Table 1 for an example of a HIT program and traditional program for a cyclist.
|Table 1. HIT Program for a Recreational Cyclist|
|HIT||60 min||60 min||Rest||60 min|
|Endur||60 min||Rest||180 min||120 min|
Quantifying the actual intensity that HIT intervals should be performed at is the difficult part. Collecting some baseline physiology data from incremental step testing can make it easier, but is not entirely necessary. I’ve provided a selection of methods below to assess interval intensity during a training session and some individual experimentation can go a long way in ensuring your intervals are actually HIT:
- Velocity – this should be greater than your velocity at anaerobic threshold which can be established using incremental step testing. However performing each interval at a “maximum sustainable intensity across the HIT session” has been regularly used to prescribe HIT velocity in high quality studies. Therefore the HIT velocity should be maximal, but sustainable across the session.
- Tempo – the interval tempo (i.e. strokes per minute for a rower, swimmer, or kayaker, cadence for a cyclist, etc) is often a good indicator of HIT interval intensity. For example rower’s race at 30 – 35 strokes per minute, therefore intervals performed close to this tempo is generally HIT. What is your racing tempo?
- Heart rate – this should be > 90% of the individual’s maximum heart rate, but it can take a number of intervals to reach this due the delayed heart rate response to short duration intervals. Peak heart rate can be easily established using the old “220 minus your age” formula.
- Rating of perceived exertion (RPE) – the interval RPE can be assessed both during the session and post session. During the session, the Borg Scale (Borg, 1982) can be used to assess the intensity of intervals, ideally the RPE of each interval should be > 16. After the session, the session-RPE method (Foster et al, 2001) can be used, ideally the session-RPE should > 6.
- Blood lactate – the interval lactate values should be > 4 mmol/L which is a widely used value to quantify HIT intensity (Seiler & Kjerland, 2006).
Table 2 provides some HIT sessions that can be easily implemented into the training program of a recreational or competitive level athlete. The HIT sessions are divided into short, medium and long duration intervals with a 1:1 work to rest ratio. A low intensity warm up and cool down of 10 – 20 minutes duration should be performed with each session.
|Table 2. Example HIT sessions for endurance sports|
|Short intervals||Medium intervals||Long intervals|
|Interval duration||30 sec||2 min||5 min|
|Rest period*||30 sec||2 min||5 min|
|Repetitions||10 – 20||5 – 10||3 – 5|
|Total HIT duration*||10 – 20 min||20 – 40 min||30 – 50 min|
|Key: Rest period: low intensity recovery between intervals or passive rest; Total HIT duration: includes rest periods.|
- Laursen, P. B., & Jenkins, D. G. (2002). The scientific basis for high-intensity interval training. Sports Med, 32(1), 53-73.
- Borg, G. A. (1982). Psychophysical bases of perceived exertion. Med Sci Sports Exerc, 14(5), 377-381.
- Foster, C., Florhaug, J. A., Franklin, J. et al. (2001). A new approach to monitoring exercise training. J Strength Cond Res, 15(1), 109-115.
- Seiler, K. S., & Kjerland, G. Ø. (2006). Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution? Scand J Med Sci Sports, 16(1), 49-56.