Half Time Strategy - Temperature

Coping With The Effects of Temperature on The Pitch

Cool down or warm up? Maximising the impact of your half-time break

Maintaining an optimum body temperature is vital for maximising sport performance. But what are the most effective half-time strategies when the mercury rises and how can you combat second-half fatigue and injury? New PP contributor Matt Lancaster investigates

Having grown up playing Australian Rules football, my early recollections of the half-time interval are dominated by one thing – oranges. Each week either the forwards or the backs would supply the oranges, which were sliced into quarters by a dutiful parent and left waiting in a bucket for the team to grab as they entered the changing sheds. Of course, modern science would dictate that the tiny amounts of antioxidant, fructose and carbohydrate contained in our quarter orange could not significantly enhance our second-half performance. Still, on oranges alone we felt we could fly.

While sucking on an orange may have once provided a sufficient half-time recuperation strategy, succeeding in team sport often requires much greater attention to detail. Any half-time strategy should address two key aims:

  • Enhance second-half performance;
  • Effectively manage the incidence and impact of injury.

Reviewing the available science can help when devising a half-time strategy. However, the practicalities of the sport you are involved with are just as crucial. How long is the half-time break? Is there a substitution-only rule or can players be rested and then return to play at a later stage of the game? What is the injury profile of the sport? Could a half-time strategy impact on the incidence of second-half injury? And don’t forget the coach. What does the coach think?

It’s probable that more games have been won by a half-time tactical change or moment of inspiration delivered by the coach than have been by cooling the ice buckets to precisely 8Þ – or should that be 11? Ultimately, the half-time interval provides a paradoxical challenge: to recover from the first half while at the same time preparing for the second. Should we be cooling down or warming up?

Cooling down

There is clearly a trend amongst sports people, particularly within elite sport, to make use of cooling strategies. Various methods of cooling, such as ice bath immersion and contrast water therapy form the staple of many post-exercise recovery strategies. Pre-cooling has also been employed for some time, particularly by endurance athletes, and millions of viewers worldwide witnessed UK runner Paula Radcliffe donning an ice vest prior to the Athens marathon.

But what about half-time cooling strategies? The unusually high temperatures during the recent football World Cup in Germany demonstrated the difficulty of sustaining a performance level throughout a game in high ambient temperatures. Could a half-time cooling strategy help? Is cooling between bouts of exercise different to cooling after or before a single exercise session? And does the intermittent and varied intensity of activity during most team sports make cooling less relevant than for continuous endurance sports? If half-time cooling is to help performance, it is worth looking to science to gain a brief insight into temperature change and regulation during team sports.

An American study utilised a probe contained within a pill swallowed by the subjects to compare the thermal responses between American footballers and cross-country runners during training in temperatures ranging from 28 to 34ÞC(1). The footballers wore full padding, making direct comparison between the groups difficult. However, as expected, both groups had a significantly higher core temperature following practice. But while prior to training it was the footballers who had significantly higher temperatures than the cross-country runners, after training the cross-country runners had the higher temperature. Among the cross-country runners, core temperature increased steadily throughout the continuous training, while for the footballers, it rose and fell depending on the intensity of their practice.

Interestingly, despite a higher core temperature after training, the cross-country runners exhibited better hydration levels than the footballers. Exercise type, intensity and metabolic rate may be a more significant determinant of core temperature than hydration status alone, making an appreciation of the physical demands of individual player positions, as well as the overall game, important when considering a half-time cooling strategy. The pattern and effect of temperature change and regulation may be quite different between midfielders and goalkeepers, for instance, particularly in sports where protective clothing is worn.

A similar study compared the core temperature of recreational university footballers with that of professionals from an English Championship team(2). Both games were played in more comfortable ambient temperatures, ranging from 16 to 19ÞC. Core temperature was taken before the game and immediately after each half. For the recreational players, measurements were also taken at 10-minute intervals throughout each half. For the recreational players there was a significant rise in core temperature during both the first and second half of the game, despite temperature returning almost to resting levels after the half-time interval. In contrast, while there was also a significant increase in core temperature during the first half for the professional players, their temperature stabilised during the second half and did not rise significantly further by the end of the game. Put simplistically, the professional players were probably acclimatised to the demands of the game and demonstrated a greater capacity to self-regulate their temperature through more pronounced sweating.

In general terms, your pattern of temperature change and regulation during the second half of a match is likely to be determined by a complex interaction involving your level of acclimatisation to both the demands of the game and any extremely hot weather conditions you are forced to play in. Of course, nothing is quite as straightforward as it seems, and rather than slowing down directly because of a rise in core temperature, generated by the production of heat within your muscles, your brain may actually regulate the rate at which your temperature increases by limiting muscle recruitment and consequently limiting how hard you can keep going(3). The pace at which you play may actually be set quite early during the match, based on an anticipatory response to ensure that you do not reach a dangerously high temperature later on in the game. Of course, the intermittent pattern of intense activity in most team sports makes this regulation and pacing a constantly changing, dynamic process.

Your brain regulates exercise output to protect against excessive body heating. How effectively your body is acclimatised to coping with heat production, particularly on extremely hot days, will largely determine how able you are to keep going in the second half.

If you choose to instigate a half-time cooling strategy, particularly on hotter match days, you are essentially hoping to delay any rise in second half temperature and trick your brain into allowing you to keep running harder for longer. As mentioned though, pacing and work rate are ultimately set by your brain and no half-time cooling strategy can expect to entirely override your level of acclimatisation. It may be that the greatest benefit of cooling during half-time, particularly on extremely hot days to which you are not well acclimatised, is to help you feel more comfortable during the break and better able to focus on performance and the coach’s instructions.

Practical considerations

Any pre-cooling methods that aim to lower core temperature cannot be done quickly or easily. The good news is that cooling your skin, without a corresponding lowering of core temperature, can help to improve self-paced performance, even in warm, humid conditions. A study conducted at the Charles Sturt University in Bathurst, Australia showed that cooling the skin helped subjects to cycle almost a kilometre further in a 30-minute self-paced laboratory test(4).

The bad news is that, like the majority of studies which look at pre-cooling, this study was concerned with performance of continuous exercise; cooling was carried out before and not between bouts of exercise, and the cooling involved a procedure that was time-consuming – in this instance immersion in cold water (8-11ÞC) for 60 minutes! That’s a heck of a half-time break. Better news is that a recent study looked at only 12 minutes of cold-water immersion between bouts of continuous exercise(5). Subsequent self-paced running performance was enhanced by this cooling strategy, but even 12 minutes of cold-water immersion is unrealistic for most half-time breaks and the relevance to team sports remains questionable.

If you are going to use a half-time cooling strategy, utilise simple methods such as ice-packed towels draped around your shoulders. Try submerging your hands in cool water or simply removing your playing vest or any excessive protective clothing. For professional teams, a half-time change of kit may be beneficial.

Finally, have ice bags available for players to commence icing any suspected injuries as soon as they enter the changing rooms. Half-time is a convenient opportunity to assess any first-half niggles and it makes sense to start icing while you wait for the club doctor or physiotherapist to assess you properly. If you have to make a decision about an injury yourself, ask three simple questions and be honest in your replies:

  • Can I cope with the discomfort during the second half?
  • Will I be able to contribute properly to the team?
  • Will there be any consequences later on if I do continue to play?

Risking further injury during an Olympic or World Cup final is one thing, but it’s not worth compromising your long-term health and livelihood for the sake of a Sunday pub league game – really!

Warming up

It is beyond the scope of this article to look critically or in detail at the components of an effective warm-up. Frequently, however, many people attempt to draw an association between the incidence of injury and lack of an appropriate warm-up. If this were the case, then it could be expected that the majority of injuries occur early in a playing period, as players will become more, and not less, warm as the game progresses. Could this justify a warm-up strategy during the half-time break? Science doesn’t answer this question explicitly, but it does help to construct some considered views, which may help when devising a suitable half-time strategy.

Let’s start with the epidemiology of injuries. The Football Association (FA) performed a large study between July 1997 and May 1999, spanning two entire seasons of English football. Club doctors and physiotherapists from 91 of the 92 football league clubs returned audit forms to the FA researchers, providing information about the injuries suffered by their players.

Two of the most common injuries reported were hamstring strains(6) and ankle sprains(7). The graph below illustrates the timing of all hamstring injuries reported during matches. A graph detailing the timing of ankle sprains during matches is remarkably similar. Far from the majority of these injuries occurring at the beginning of a playing period, when the subjects were less likely to be warmed, the FA found that nearly 50% of the reported injuries occurred during the last third of each half. For hamstring strains, the period immediately after half-time was actually identified as having the lowest incidence of injury. While no data was recorded from these studies concerning the nature of warm-up before the game or during half-time, it is evident that fatigue plays a considerable role in the incidence of these injuries.

Another large prospective study, this time looking at 12 of the 13 professional rugby union clubs playing in the English premiership during the 2002/3 and 2003/4 seasons, reported the timing of all injuries sustained during match play(8). Once again, the majority of injuries were sustained during the latter stages of each half, particularly the second half.

In Queensland, Australia, an amateur rugby league sevens tournament was audited(9). Players were involved in three or four games over the course of a single day and, while data was not recorded for the timing of injury during a match, there was a steady increase in the incidence of injury from the first to last match. It is hard to escape the conclusion that fatigue presents a greater risk to you than not warming up adequately before the second half.

Unfortunately, this leaves you sounding a bit like you are built like a car – burn all the fuel reserves in your muscles and you can’t accelerate any more. As you may guess, fatigue, like temperature regulation, is a little more involved than this. Fatigue is often defined as an inability to sustain force production within a muscle or group of muscles. The distance covered and amount of high-intensity running towards the end of a top class football game has been shown to be lower than at the beginning(10). Other changes may also occur, such as modifications in the way you recruit muscles or your ability to balance. Certainly, it is unlikely that you are quite as fast or agile at the end of a game as you were at the beginning. But what is the fatigue mechanism leading to this reduction in your performance? Could an understanding of this process help in determining your half-time strategy?

Peripheral fatigue is the term given to changes that occur within the muscles over time, compromising performance output. Physiologists and nutritionists have looked closely at the reduction in muscle energy stores during the course of a game and certainly it is reasonable that a reduction in glycogen levels limits your capacity to sprint at the end of a game. However, it is generally accepted that fatigue also has a central component. Central fatigue refers to a reduction in the ability of your brain and nervous system to command or drive your muscles to work and help you perform at your best. It is widely considered that due to the widespread and complex connections within your brain, motivation, mood and arousal also impact on central fatigue. This may explain the observation that football players can experience fatigue temporarily during a game(11).

An interesting view on fatigue is offered by a group of South African scientists who have undertaken work considering the sensation of fatigue(12). Rather than occurring within the muscles, they suggest that fatigue is a sensation derived from feedback to the brain, such as the speed at which you are burning energy reserves. Just as changes in core temperature serve as a stimulus for your brain to regulate muscle activity, the sensation of fatigue may also form part of a constantly shifting regulatory system that determines how hard you can continue to perform in the second half of a game.

After periods of rest or less intense play, while you won’t have replenished all the glycogen reserves you have used, the rate at which you are depleting them may have lowered and you will be able to raise your performance level for a short period of time again. Your best chance of addressing fatigue during half-time may be to strive to remain motivated and set your arousal level appropriately for the second half. Sometimes this may actually mean calming down. It is probably not a coincidence or simply a matter of better conditioning that the victorious team always look fitter and fresher at the end of a match. Giving your central nervous system a last-minute wake-up may also be worthwhile, perhaps with a short series of maximal sprints as you return to the field.

Summary

Ultimately, half-time should be about performance. If you are going to implement any strategy, make sure it is planned, structured and efficient to allow the coach maximum time to focus on tactics and team matters; this really will make the biggest difference. Who knows, not only might you surprise yourself with your second-half performance, you might even get picked for the following week’s game!

Australian-born Matt Lancaster relocated to the United Kingdom in 2000 and is currently employed by the English Institute of Sport as lead physiotherapist for the London region

References:
1. J Athletic Training 2004; 39 (3):235-240
2. Br J Sports Med 2006; 40:133-138
3. Physician and Sports Medicine 2005; 33 (10): 39-58
4. J Sports Sciences 1999; 17:937-944
5. J Strength & Conditioning Research 2006; 20 (2):383
6. Br J Sports Med 2004; 38:39-41
7. Br J Sports Med 2003; 37:233-238
8. Br J Sports Med 2005; 39:757-766
9. Br J Sports Med 2002; 36:23-26
10. J Sports Sciences 2003; 21:439-449
11. J Sports Sciences 2006; 21: 24(7):665-674
12. Br J Sports Med 2005; 39:120-124

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