Gait-related variability: a practical recovery marker in team sport athletes

Abstract

Recovery is important to both athletes and coaches as a key component of training programmes and a determinant of optimal performance. At times the subsequent performance is the ultimate measure of the success of the recovery. However, the measurement of a quality should not affect its outcome measure and assessment without incurring additional load, perhaps even without the knowledge of the athlete, would be the ideal approach. This thesis was designed to examine recovery monitoring methods in situ to meet the need of practitioners and athletes. Following an initial survey of athletes from the UK (n=53), Asia (n=112) & USA (n=152), athletes from collegiate American Football (males, n=63), collegiate soccer (females, n=17) and professional rugby (males, n=47) were monitored across a full competitive season to measure the associations of various recovery markers with gait-related variability measured at the trunk.

The research process involved initially establishing how athletes consider recovery relative to its importance and their subsequent practice. Survey studies of distinct groups of athletes on three continents established athlete and coach perceptions around recovery and showed that their perceptions did not necessarily match their behaviours or their beliefs (for example, just over half of athletes rated sleep as the most impactful recovery intervention but did not mirror that belief in their actions; whereas in contrast ~40% of athletes believed in and utilised cold water immersion). Subsequently the benefit of measuring recovery within the sport activity and without additional external load was chosen as the preferred approach. A discussion of movement variability assessment using existing accelerometry information collected for the management of external load was undertaken with decisions made on an appropriate measure of gait-related variability to track across longitudinal monitoring of athletes. This was in conjunction with a variety of subjective and objective markers already collected in their own sport.

Primarily a quality assurance assessment of the chosen tool to identify high speed running sections, occurring naturally within training and competition, matched to ensure they occurred in a linear direction, and the subsequent marker of variability (coefficient of mean determination), was undertaken. It was shown to be a stable and reliable marker for both treadmill and over-ground running in the vertical and anterior-posterior axis. In addition, it showed that analysis can occur interchangeably on data identified from GPS (outdoor sports) and accelerometer-based assessments (indoor sports).

Having established the standard statistical approach for the investigations, three different sporting models were examined using existing measures within their sport and season to investigate if recovery can be effectively monitored without additional requirements on the athlete. Firstly, American Football collegiate athletes were monitored longitudinally to examine any associations between gait-related variability, external load and subjective markers of wellness within their regular sessions. Associations between gait-related variability and fatigue (p<0.026) and 7-day acute training load (p<0.001) were established, supporting potential use in this context.

Secondly, in an additional population in the same collegiate environment, but in a different sport, objective markers of flexibility within a female collegiate soccer population were examined, but showed no relationship between gait-related variability and flexibility measured electronically. This suggests that these objective markers cannot be associated with variability changes in this context.

Finally, a group of professional male rugby union athletes were monitored across their playing season for a relationship between gait-related variability and additional objective measures of recovery (sprint speed, manually measured flexibility and additional screening measures). This population showed that changes in hours of sleep, sprint performance, general flexibility, volume and intensity of sessions were associated with a change in variability. This suggests a combination of subjective and objective measures can be associated with variability in this context.

In conclusion, there is a disconnect between athlete perceptions and beliefs of recovery behaviours; it is possible, through monitoring of accelerometry load alongside subjective markers, to get an indication of recovery status of an individual athlete to optimize any intervention to their training plan. This may drive further education of athletes around recovery practices and suggestions for practitioners to establish a parsimonious monitoring system with a combination of subjective and objective markers that could be supplemented by movement variability measures.