Sprint training for endurance: a fast-track way to performance?

In recent years, a growing body of evidence has accumulated showing that performing regular bouts of high-intensity interval training is an extremely effective training tool for endurance athletes seeking to maximise performance. Put simply, short sessions of highintensity intervals are a great way of producing gains in aerobic power, which then enables you to sustain a faster pace for longer. That’s because although intense interval training is quite different in nature to sustained, moderateintensity endurance training, it nevertheless helps activate key genes in muscle cells that are involved in aerobic metabolism. A bonus is that an effective session of high-intensity intervals can be performed in a relatively short time, making this type of training an extremely time-efficient method of improving aerobic fitness.

Although there’s been a huge amount of research into intense intervals, the precise recipe of any high-intensity interval programme for maximising gains - eg optimum interval length and intensity, the number of intervals needed, and the number of sessions per week - is still unclear. That’s because so many different studies have been conducted on different athletes of varying fitness levels using a wide array of interval protocols. But if time is really tight, some recent research by sports scientists suggests that even shorted ‘sprint intervals’ could deliver excellent results for endurance athletes.

Sprint intervals

Although sprint intervals have been researched previously, most of these studies were performed in a laboratory using expensive treadmills or ergometers. In one  study however, the researchers set out to assess the performance effects of a short -term and highly accessible training protocol based on maximal shuttle runs in the field [J Strength Cond Res. 2018 Mar;32(3):617-623]. To do this, sixteen trained trail runners completed a two-week trial during which they trained three times per week. Each training session consisted of 4-7 bouts of 30 seconds at maximal (ie sprint) intensity, interspersed by four minutes of recovery. Before and after the intervention, all the runners underwent testing to measure their maximal aerobic speed (MAS), time to exhaustion at 90% of MAS and their 3000m time trial performance.

What they found

There were several key findings, all of them positive. Firstly, MAS was significantly improved by 2.3%, while peak power and mean power increased by 2.4% and 2.8% respectively. The time the runners could maintain at 90% of their MAS also increased dramatically – by a huge 42%. Finally, their 3000m time trial times dropped by an average of 6% - a very significant improvement. Summing up the results, the researchers commented that ‘sprintinterval training is a time efficient and cost-free means of improving both endurance and power performance in trained athletes’. J Strength Cond Res. 2017 Oct 20. doi: 10.1519/ JSC.0000000000002286. [Epub ahead of print]

Implications for runners

The key take home message here is just how effective this mode of training was. Just 6.0-10.5 minutes per week of sprint-interval training was sufficient to induce significant gains in endurance performance. Importantly, these gains were observed in real athletes outside the lab in real conditions. One caveat however is that the study didn’t have a control group (ie a group who continued normal training) to compare to. Nevertheless, the findings are in good agreement with a 2015 study on recreationally active participants who increased their 5km run times by around 4.5% when following a sprint-interval training programme for four weeks and with findings showing that positive aerobic changes are observed in muscles following a period of sprint-interval training^{J Strength Cond Res. 2015 Aug;29(8):2137-41}

PRACTICAL SUGGESTIONS

• If time is tight, why not add some high-intensity sprint-interval training to your programme for maximising performance gains. Start with a just a few (4-5) sprint intervals performed no more than once a week, and build up gradually.
• When adding or increasing high-intensity interval sessions such as sprints to your programme, remember to back off a little on your steady-state training in order to avoid becoming tired and possibly overtrained.
• You should not perform sprint intervals if you are recovering from or are prone to injury. This is particularly true for runners, where the loadings and impact on joints and muscles are far greater when sprinting.