Interval training for team sport: straight up or round the houses?

In recent years, a growing body of evidence has accumulated showing that performing regular bouts of intensity interval training is an extremely effective training tool for athletes seeking to maximize performance for a relatively low training workload⁽¹⁾. Put simply, short sessions of intensity intervals are a great way of producing gains in aerobic power, enabling an athlete to sustain a higher intensity/pace/workload for longer before fatigue sets in.

What intensity?

What are the characteristics of interval sessions that are likely to produce good gains in fitness? In particular, how intense should they be? When we look at the findings from existing research, we see that best training effects in terms of improving fitness (ie increased stroke volume and oxygen delivery around the body), is achieved at training intensities between 85%–95% of maximum heart rate^(2,3), or possibly even higher⁽⁴⁾. In other words, what seems to work best are high-intensity interval sessions that manage to raise heart rate to around 90% or even 95% of maximum for a reasonable period to time.

To understand why high-intensity interval training (HIIT) is so effective, consider that the intense nature of the intervals in a session means that an athlete performing them will experience a more rapid rise and greater increase in heart rate during each interval, which will mean a greater time proportion of each interval will be spent above 90% maximum heart rate. Of course, in very intense intervals, each interval duration will be likely be shorter than a lower-intensity interval session, so the total time accumulated above 90% maximum heart rate might not be that much greater. However, as a proportion of the total work performed, HIIT provides an excellent way of ensuring an effective training stimulus.

HIIT and team sports

Team sports such as soccer, rugby, hockey, basketball are typically characterised by high intensity bursts of activity, interspersed by lower intensity activity and stoppages in play of various lengths⁽⁵⁾. Moreover, robust research shows that the ability to perform at these high intensities, recover adequately between intense bursts and to repeat these maximal intensity actions for the duration of a match is a crucial quality that team players need to develop in preparation for competition⁽⁶⁾.

A good example of the importance of high-intensity performance comes from data gathered from soccer players competing in the UK’s Premier League⁽⁷⁾. This data reveals the following:

·        A player makes on average over 1,000 changes in playing activity during a game, which equates to a change in movement every four to six seconds.

·        Although 85 to 90% of the 10-12km distance covered in a match is at low- or sub-maximal intensities the distance run at a high-intensity is significant – typically around 1.2-25kms^(8,9).

·        The distance covered performing high-intensity running is the most valid and reliable indicator of a player’s performance capability, even though it constitutes a much smaller proportion of a player’s activity profile.

·        What really marks out elite soccer players is that they run much further at a high-intensity during a game than moderate-standard players.

·        It is during high-intensity periods of play that the outcome of a game is often decided.

The application of HIIT for female players

In theory, using HIIT to improve the performance of team sport players seems ideal, but much of the research to date on HIIT and sport performance has been carried out in endurance athletes such as cyclists and runners. Also, most of the studies on HIIT and team sport performance to date have tended to use male players. However, there are some studies that have focused on HIIT and the benefits for female team sport athletes. These include studies that found^(10-12):

·        Meaningful improvements in aerobic and anaerobic capacity in amateur female soccer players.

·        Positive effects on VO2max (gains of 3.4–4.7%) in female college soccer players.

·        Moderate improvements in regional-level soccer players in the 20-metre and repeated sprint test after six weeks of training.

Overall however, the effects of HIIT on physical performance in elite female team sport players remain relatively unproven due to the scarcity of research attention.

Straight line vs. change of direction

Here’s a question: if team sport players need to perform repeated sprints while also performed numerous changes of direction, shouldn’t all HIIT training also be performed using changes of direction (COD) during the intervals? After all, the ‘specificity of training’ principle states that for maximum training adaptations, athletes should train in a way that most closely replicates the physical demands of their sport. It turns out that many team sport coaches (for example in soccer) do prefer HIIT training with changes of direction (HIIT-COD), which is more specific, in terms of movement patterns, to the female soccer match.

This question has been partially investigated in male soccer players, where researchers found that a combination of HIIT and COD training lead to improved aerobic and anaerobic capacity in male soccer players⁽¹³⁾. Perhaps more relevant to answering the question was a 2018 study on professional futsal players, which concluded that HIIT with three directional changes per running bout achieved superior improvements in aerobic capacity, running economy, and repeated sprint ability compared to one directional change in female futsal players⁽¹⁴⁾. Despite these findings, there’s not been a back-to-back test comparing the training benefits of straight-line vs. change of direction intervals, and certainly not in soccer players.