Physiological Responses to Linear/Non-Linear Soccer Simulations.

Phys Responses JSCR

Our recent study investigated the Loughborough Intermittent Shuttle Test (LIST) (Nicholas et al., 2000) and it’s effects on neuromuscular fatigue when adjusted.

The problem with this ‘gold standard’ simulation is that, though it mimics the demands of a typical soccer game, it’s ecological validity was to be questioned.. how could it mimic the demands of a soccer game if the testing was completely linear (running in one straight direction)? Nonlinear running is frequently performed during soccer matches, with professional players completing 727 (+/-) 203 swerves and turns within a single match (Bloomfield et al., 2007). Such swerves require a great deal of rapid changes of direction and decelerations.

But to successfully complete these actions in soccer, repetitive demanding muscle contractions are necessary, particularly those of an eccentric nature and the cumulative effect of performing these type of contractions ultimately leads to fatigue, less efficient movement patterns (Small et al., 2009) and an increased risk of injury (Greig & Seigler, 2009). Research has also suggested that nonlinear running induces greater heart rate (HR), perceptual, and metabolic responses than straight-line (linear) running (Dellal et al., 2010), but this has also been questioned in recent studies, where they found similar drops in jump performance regardless of the type of running (Hader et al., 2016).

JSCR Infographic

Summary of study. Credit to Adam Johnson @PreventionPhys

The aim of our study was see if a modified version of the LIST could be incorporated mimic the demands of soccer while also achieving a similar amount of swerves and turns as reported in Bloomfield’s paper. The modified LIST allowed for the inclusion of 6 x 90degree and 1 x 180degree changes of direction (COD) per run. This meant that there was a total of 720-1008 COD’s within the whole protocol without altering total simulation time or activity time during the simulation.

COD

8 university football/rugby athletes too part measures including blood lactate, heart rate (maximum and average), jump height, peak landing and isometric force, and perceived fatigue were measured across the testing period. The running was monitored through Global Positioning System (GPS) trackers attached to each participant.

Results? 

Though participants found the modified LIST harder through perceived fatigue and heart rate measures, it portrayed no changes to jump height and isometric/landing forces. The modifed LIST did not change the total distance covered in the LIST but did change the amount of decelerations and the high speed running (HSR) distance. However,  greater HSR distances were directly related to reductions in isometric hamstring force.

What does this mean?

COD’s do seem to induce higher ratings of perceived fatigue but HSR distance plays a role in hamstring fatigue, indicating how important this GPS variable is for sport scientists and coaches alike when it comes to monitoring training load and managing fatigue. It also allows for changes to training (particularly related to small sided games or metabolic conditioning) by incorporating COD’s which could reduce HSR distance but still lead to higher or similar metabolic demands.

Limitations?

The modification to the LIST was based on multi-directional running at 1.5x the timing of the maximal effort run timing of each participant. The COD’s were positioned in a manner that did not alter total distance covered by the original LIST. However, such timings and COD positionings may have given participants enough time to run and change directions at a pace which did not require a great deal of side cutting mechanics but full body turns following lesser speeds of running.

The study would ideally have aimed to recruit a larger sample size of professional athletes to see if these results reflected the larger population of professional soccer players.

Full study available here: https://www.ncbi.nlm.nih.gov/pubmed/30138235

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