As we begin our return to sport following the recent lockdown, reducing our risk of injury is going to be essential. It is important to acknowledge that keeping active during lockdown by running, cycling or whatever it may be does not ensure readiness to return to sport. Upon returning to competitive sport, training load management will need to be carefully considered. What is training load? Training load is a combination of both internal (physiological responses such as heart rate, RPE etc) and external load (distance, time, weight etc), which together result in a response to training. If that combination is appropriate the desired response to training, physiological adaptation will be achieved. However, if that combination is inappropriate or excessive an undesired response such as injury is likely.
What happens when we aren’t training?
Studies have shown that the effects of detraining start to occur within 2-3 weeks of inactivity. These studies have found that endurance (exercise time to exhaustion) declines by up to 24% in 5 weeks of training cessation and VO2 max declines by up to 20% in trained athletes at 4 weeks of detraining. Strength remains relatively unchanged for the first 3 weeks of inactivity, but will decline by 7%-12% over 8-12 weeks.
How do I avoid excessive training load and therefore reduce my injury risk when returning to sport?
The per the graph below, constructed by Tim Gabbett (2016) charts what is called the ‘acute to chronic workload ratio’. The acute to chronic workload ratio compares an individual’s current average training load to their average training load of the 4-6 weeks prior. As shown in the graph, Gabbett’s work found that there is a ‘sweet spot’. This is the acute to chronic workload ratio (0.75-1.4) where injury risk is lowest. The graph above also clearly displays the ‘danger zone’, this is the acute to chronic workload (>1.5) where there is a significantly increased risk of injury.
To put all of this in perspective, Myer and colleagues conducted a study looking at Achilles tendon injuries in professional NFL players after the 2011 NFL lockout. During a regular year, NFL players would have a 14-week block of structured training before commencement of the pre-season competition. In 2011, due to the lockdown NFL players only had a 17-day block of training before commencement of the pre-season competition. Following the NFL lockout in 2011, 10 Achilles tendon injuries occured over the first 12 days of training camp and 2 additional in the subsequent 17 days. Other studies, which monitored the 1997 to 2002 NFL seasons, reported that Achilles tendon ruptures occurred at an average rate of 5 per year, including pre-season and in-season (Parekh et al). This is a prime example of acute training overload.
In summary;
Avoid resuming at the same level of exercise pre-break in order to avoid high spikes in training load.
Total load for a week (acute load) spikes above the average load over the past 4-6 weeks (chronic load) results in an increased risk of injury.
High training loads, which are achieved SAFELY, are protective from injury.
Written by: Reece Coleman – Physiotherapist
References
Myer, G. D., Faigenbaum, A. D., Cherny, C. E., Heidt Jr, R. S., & Hewett, T. E. (2011). Did the NFL lockout expose the Achilles heel of competitive sports?.
Parekh SG, Wray WH, 3rd, Brimmo O, Sennett BJ, Wapner KL. Epidemiology and outcomes of Achilles tendon ruptures in the National Football League. Foot Ankle Spec. 2009;2:283-286. http://dx.doi.org/10.1177/1938640009351138
Gabbett, T. J. (2016). The training—injury prevention paradox: should athletes be training smarter and harder?. British journal of sports medicine, 50(5), 273-280.
