Injuries commonly occur in team sports and negatively influence team success. High training loads and high frequency of game play increases injury likelihood in team sports. However, each athlete has individual and specific physical attributes. These attributes can be higher aerobic capacity, high intensity running ability and greater lean body mass improvements with increase in workload and decrease injury likelihood. Consequently, there is an optimal workload for each athlete that improves strength and conditioning without increasing the likelihood of injury. Knowing this optimal workload can help coaches keep their players in top condition.
What is Acute to Chronic Training Load Ratio (ACR)?
The Acute to Chronic load is a simple metric that uses the absolute workload performed in the current week (or acute load) relative to a four week absolute workload (or chronic load). These are presented as a ratio:
Research shows that very high ACR (>2) maintained over three weeks resulted in a 28.6% injury risk in elite athletes (Hulin et. al, 2015). For endurance athletes, any ACR above 1.5 is considered high risk for injury. Ratios between 1 and 1.5 are considered optimal and anything under 1 is considered suboptimal.
How to track ACR
The load incurred by athletes can be measured in a number of ways. Coaches typically use GPS, sEMG or heart rate (HR) technology determine a daily load, however, measures of load are not all created equal. GPS based technologies can give you insight into the external load incurred by your athletes, but only sEMG technologies can provide an accurate measure of how that external load is being manifested in the body. To learn more about how you can track ACR based on internal measures, click here.