RPE and its relationship with the risk of injury in footballers
Overtime, the competitive distance among elite football teams has shortened, so the focus is currently on those aspects that can tip the scale to one side or the other.
A rugby player’s ability to perform high-intensity intermittent exercises is associated with a higher training load (TL) which takes place during matches. Also with a higher probability of getting through more matches without getting injured, and with faster recovery time for post-match muscle damage markers.
It has also been suggested that when acute TL exceeds chronic TL, the fatigue being experienced is greater than the physical condition, thus increasing the risk of injury. A TL control method which has recently gained popularity is the one based on analysing the acute: chronic load ratio (Gabbett, 2016), which is related to an athlete’s injury risk.
A recent study (Hulin et al., 2019) analysed the relationship between physical performance, TL and injury risk in 45 professional rugby players for two consecutive seasons. They took into account all lower extremity injuries (apart from contact injuries) that resulted in missing a training session or a match. The ability to perform high-intensity exercises was assessed using the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1), and analysing other variables such as total distance completed, estimated maximum oxygen consumption (VO2max) and submaximal heart rate (HRsubmax). The acute TL (after 7 days) and chronic TL (after 28 days) were calculated in two ways:
The TL was categorised from “very low” to “very high” according to the percentile, and the recording of the TL was expressed through a binary code: 1 (when an injury occurred that day or within the next 6 days) or 0 (when no injury occurred during those 7 days). This method was used because several studies have observed that the greatest risk of injury occurs between 2 and 7 days after recording a “peak” in TL (Hulin et al. 2014; 2016).
A total of 60 injuries occurred over the course of the two seasons, and no differences were found in any variable between the two models used to calculate the TL (EWMA and rolling average). An acute: chronic TL ratio that was “very high” had the greatest risk of injury. Acute: chronic TL ratios higher than 1.9 also increased the injury rate compared to lower ratios. On the other hand, an increase in HRsubmax was associated with a 4% absolute risk of injury, which was twice as high as when the HRsubmax remained steady or was reduced. Likewise, an increase in HRsubmax was associated with a lower chronic TL, compared to an HRsubmax that was stable or reduced. Chronic TL showed an “almost perfect” association with VO2max and Yo-Yo IR1 performance, and a “very significant” negative relationship with HRsubmax. Additionally, a higher chronic TL was associated with better performance in endurance tests and a lower HRsubmax. Finally, an acute: chronic TL ratio showed an “almost perfect” negative association with VO2max, and higher acute: chronic TL ratios were associated with lower performance in terms of maximum effort as well as a higher HRsubmax.
This is the first study to demonstrate an association between performance in submaximal tests and injury risk in team sports, and showed that a decrease in the ability to perform high-intensity exercise is related to: 1) lower chronic TL; 2) higher acute: chronic TL ratio; and 3) increased risk of injury. Thus, these findings provide training professionals with information on how to apply TL derived from GPS technology, which can help improve physical performance by attempting to minimise the risk of injury.
The Barça Innovation Hub team
Gabbett TJ (2016). The training-injury prevention paradox: should athletes be training smarter and harder? Br J Sports Med. 50:273-80.
Hulin BT, Gabbett TJ, Blanch P, et al (2014). Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers. Br J Sports Med. 48:708-712.
Hulin BT, Gabbett TJ, Caputi P, et al (2016). Low chronic workload and the acute:chronic workload ratio are more predictive of injury than between-match recovery time: a two-season prospective cohort study in elite rugby league players. Br J Sports Med. 50:1008-1012
Hulin BT, Gabbett TJ, Pickworth NJ, et al (2019). Relationships Among PlayerLoad, High-Intensity Intermittent Running Ability, and Injury Risk in Professional Rugby League Players. Int J Sports Physiol Perform. 1:1-7.
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