​The extended half-time break at Sunday’s World Cup final could heighten players’ risk of injury and weaken their performance, a physiology expert has said.The gap between the first half ending and the second half starting between Argentina and Spain is expected to be around 25 to 30 minutes, with FIFA staging a star-studded, 11-minute half-time show during the interval at the MetLife Stadium in New Jersey.AdvertisementAdvertisementAdvertisementAn extended break would be in breach of the sport’s laws, which state that half-time should not exceed 15 minutes.There are also concerns about the impact it could have on players.Dr Liam Harper, a senior lecturer in physiology at Manchester Metropolitan University’s Institute of Sport, told the Press Association: “We know a 15-minute half-time period is enough to reduce muscle temperatures back towards resting levels.“An elevated muscle temperature is associated with increased power output and rate of force development, hence why warming up is effective not only from an injury risk reduction perspective, but also an enhanced physical performance perspective.AdvertisementAdvertisementAdvertisement“With the break being extended, this reduction in muscle temperature will be potentially more pronounced.”Dr Harper believes players at the World Cup may have already become somewhat accustomed to this, however, noting that players line up in the tunnel around 15 minutes before kick-off to allow anthems to be played and so on.“The gap between the end of their initial warm-up on the field, returning to the changing room, and then the game kicking off, is likely to be around 30 minutes,” he added.Dr Harper said a 15-minute half-time break at the final would provide sufficient time for refuelling, rehydrating, and in the case of this match specifically, cooling down core temperature with temperatures expected to be around 30 degrees Celsius.AdvertisementAdvertisementAdvertisementHe did state though that the 30-minute break may be beneficial to some players in giving them a greater opportunity to refuel (particularly carbohydrates) and rehydrate, and from a coaching perspective may also be helpful.Dr Harper also suggested FIFA providing players the opportunity to conduct a two to four-minute ‘re warm up’ could mitigate the impact of the extended break.“Doing a re warm-up has been shown to be beneficial for sprint and jump performance versus not doing any sort of physical re warm-up prior to the second half,” he said.“Using foam rollers and massage guns (percussive therapy) may be a beneficial way to maintain range of motion, neuromuscular efficiency and just a general feeling of ‘staying loose’ and there is some data to support this,” he said.