Individual and combined effects of acute and chronic running loads on injury risk in elite Australian footballers.

A model that takes into account the current workload, and the workload the athlete has been prepared for, as an acute:chronic workload ratio has been previously used as a novel way to monitor training load and injury risk. Fifty-nine elite Australian football players from one club participated in this 2-year study. Global Positioning System technology was used to provide information on running workloads of players. An injury was defined as any non-contact "time-loss" injury. One-week (acute), along with 4-week (chronic) workloads were calculated for a range of variables. The size of the acute workload in relation to the chronic workload was calculated as an acute:chronic workload ratio. An acute:chronic workload ratio of >2.0 for total distance during the in-season was associated with a 5 to 8-fold greater injury risk in the current [relative risk (RR) = 8.65, P = 0.001] and subsequent week (RR = 5.49, P = 0.016). Players with a high-speed distance acute:chronic workload ratio of >2.0 were 5-11 times more likely to sustain an injury in the current (RR = 11.62, P = 0.006) and subsequent week (RR = 5.10, P = 0.014). These findings demonstrate that sharp increases in running workload increase the likelihood of injury in both the week the workload is performed, and the subsequent week.

Activity Profiles of Successful and Less-successful Semi-elite Rugby League Teams.

This study investigated whether match intensities during predefined periods differed among successful and less-successful rugby league teams. 4 semi-elite rugby league teams were split into 'high-success' and 'low-success' groups based on their success rates. Movement was recorded using a global positioning system (10 Hz) during 20 rugby league matches. Following the peak ball-in-play time period, the high-success group was able to maintain ball-in-play time that was: (1) 22% greater than the low-success group (P=0.01) and (2) greater than their mean period of match-play (P=0.01). In the peak and mean periods of match play, hit-up forwards from the high-success group covered less total distance (P=0.02; P=0.01), less high-intensity running distance (P=0.01; P=0.01) and were involved in a greater number of collisions (P=0.03; P=0.01) than hit-up forwards from the low-success group. These results demonstrate that greater amounts of high-intensity running and total distance are not related to competitive success in semi-elite rugby league. Rather, competitive success is associated with involvement of hit-up forwards in a greater number of collisions and the ability of high-success teams to maintain a higher ball-in-play time following the peak period. Strength and conditioning programs that: (1) emphasize high-intensity running and neglect to combine these running demands with collisions, and (2) do not offer exposure to match specific ball-in-play time demands, may not provide sufficient physiological preparation for teams to be successful in rugby league.