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Plenty of discussion about reducing the interchange with reference to injury rates, fatigue and “bringing back the little man”. Wanted to discuss what evidence suggests a reduction in interchange would do to injury prevalence (spoiler: it’s not set in stone). Thread 
There’s 2 main schools of thought:
- Increased interchange =
speed & power of players, collision forces so traumatic injury rates
- Decreased interchange = fatigue, players exposed to risk events when fatigued, decision making impaired, soft tissue strain rates
- Increased interchange =
speed & power of players, collision forces so traumatic injury rates - Decreased interchange =
fatigue, players exposed to risk events when fatigued, decision making impaired, soft tissue strain rates
In 2001 the NRL went from unlimited to 12 interchanges. Evidence at 1 club showed:
- A significant in players leaving the field due to injury
- But this didnt lead to signifificant change in number of players who were injured & unable to return to the field
- A significant
in players leaving the field due to injury- But this
didnt lead to signifificant change in number of players who were injured & unable to return to the field
- Overall there didn’t appear to be a significant change in the rate of serious injuries due to the rule change
- Reluctance of players to leave field with minor injuries: theoretically increased risk players could refuse to leave field with potentially serious injury
- Reluctance of players to leave field with minor injuries: theoretically increased risk players could refuse to leave field with potentially serious injury
A study of semi-professional rugby league players demonstrated risk of injury was significantly following introduction of limited interchange rule. injury risk was suggested to reflect fatigue-induced in match speed & impact forces associated with collisions & tackles
following introduction of limited interchange rule. injury risk was suggested to reflect fatigue-induced in match speed & impact forces associated with collisions & tackles
From 2015-2018 in the NRL, time in the game when injuries were sustained:
1st half: 46.75%
2nd half: 53.25%
Gametime blocks with:
Highest risk of injury: 31-40mins & 51-60mins (players fatigued/“freshness” imbalance?)
Lowest risk of injury: 0-10mins & 41-50mins (players fresh?)
1st half: 46.75%
2nd half: 53.25%
Gametime blocks with:
Highest risk of injury: 31-40mins & 51-60mins (players fatigued/“freshness” imbalance?)
Lowest risk of injury: 0-10mins & 41-50mins (players fresh?)
From 2016-2018 in the NRL there was no trend regarding injury rates and stage of the season (early/mid/late). Major injuries (>5 games missed) occurred more early-mid season during these years.
Overall injury rates in the NRL from 2011-2018. Missed games due to injury & risk of sustaining an injury in an NRL game both significantly decreased. Were slightly noticeable drops in these numbers from 2016; also the same year the interchange was reduced from 10 to 8
in the NRL from 2011-2018. Missed games due to injury & risk of sustaining an injury in an NRL game both significantly decreased. Were slightly noticeable drops in these numbers from 2016; also the same year the interchange was reduced from 10 to 8
There is also evidence that in semi-professional rugby league that risk of injury when playing intensity, which could suggest fatigue potentially has a protective effect against injury. If this applies to NRL level players fatigue may intensity & therefore injury rate
risk of injury when playing intensity, which could suggest fatigue potentially has a protective effect against injury. If this applies to NRL level players fatigue may intensity & therefore injury rate
Fatigue has still been shown to be a risk factor. Studies in pro soccer, NBA & rugby 7s indicated injuries were associated with fatigue & game load. In the NRL training load (? fatigue) has been shown to be significantly related to overall injury (contact + non-contact) rates
fatigue & game load. In the NRL training load (? fatigue) has been shown to be significantly related to overall injury (contact + non-contact) rates
But fatigue is hard to quantify; it’s not just physical ( focus, reaction time, performance etc).
Minutes played in a game is positively correlated with injury risk ( exposure), but effects of reducing interchange not as simple as just minutes for players
focus, reaction time, performance etc). Minutes played in a game is positively correlated with injury risk (
exposure), but effects of reducing interchange not as simple as just minutes for players
Some AFL findings: both fatigue & running speed are risk factors for hamstring injury. Was shown in the AFL regular interchanges seem to protect individual players against hamstring injuries, but increase the risk of hamstring injury for opposition players.
A player who returns after a rest on interchange may have short-term protection against injuries vulnerable to fatigue (eg hamstring strain), but rested state may contribute to average running speed for direct opponent, & the risk of injury for opposing players
average running speed for direct opponent, & the risk of injury for opposing players
If we assume injuries are caused more so by fatigue: reducing the interchange to 6 could injury rates, with players exposed to risk while fatigued, & more likely to stay on/play through injury & possibly make it worse
injury rates, with players exposed to risk while fatigued, & more likely to stay on/play through injury & possibly make it worse
If we assume injuries are caused more so by speed/power: reducing the interchange to 6 could injury rates, speed/power/“freshness” of players, collision speeds, less imbalance between fresh & fatigued players
injury rates, speed/power/“freshness” of players, collision speeds, less imbalance between fresh & fatigued players
Overall it’s likely both (fatigue + power/“freshness”) play a role in injury risk, so the challenge is finding the perfect balance between them. It doesn’t appear clear if reducing interchange to 6 will definitely increase or decrease injury risk (overcorrection?) just yet
