Exercise affects cognitive performance Optimisation strategies for the Orienteer
by Ben Rattray, www.endurancetraining.com.au
As we are all too well aware, orienteering is distinct from other running events due to the many complex cognitive tasks required. In the competition setting, map and land interpretations as well as the sequential decision making process are often performed in a fatigued state, always under time pressure and often in a distracting environment. The quality of these complex decisions is of paramount importance but must come alongside less obvious cognitive tasks. Less obvious cognitive tasks include the coordination required for terrain running in which foot placement and the hand-eye coordination required for map readings are high level skills.
These cognitive tasks must be performed during high levels of physical activity which can affect cognitive performance in a number of ways. Research investigating relationships between exercise and cognitive performance conflict considerably, even within the orienteering specific literature leaving coaches and athletes confused as to the potential implications that can be drawn. This summary should assist in practical applications of our current understanding although it must be remembered that the brain is immensely complex and not well understood.
Effect of Exercise intensity
A common theory within the psychology literature is of an inverted-U relationship between arousal and performance. More recently it has been suggested that a zone of optimal functioning is more appropriate (see figure 1). This model suggests a curvilinear relationship between arousal level and performance so that optimal performance corresponds to an intermediate arousal level. Further increases in arousal lead to subsequent attention narrowing where pertinent cues for the task involved may be missed. Exercise induces responses in the body which increase physiological arousal (largely through catecholamines [adrenaline]) and during aerobic exercise brain activity increases. There is little information however regarding the intensity of exercise providing optimal cognitive functioning although the workload is higher in trained individuals. Recently researchers have proposed the use of an adrenaline threshold (similar to lactate threshold, although it generally occurs at a higher intensity). Results suggest that the adrenaline threshold is linked to improved cognitive performance, displaying an inverted-U relationship.
|Figure 1: Inverted-U and Zone of Optimal Functioning principle|
There is a blunted adrenaline response to exercise at an absolute workload with training. An increase in the adrenaline threshold may increase the speed at which cognitive performance is optimised through adrenaline. It is unclear as to how training influences the adrenaline threshold although it seems reasonable to suspect that it is similar to shifts in the lactate threshold. Chronic training (presumably aerobic training) also improves cerebral blood flow and therefore cognitive functioning.
- Develop Adrenaline Threshold
- In order to be ready for competition, warm-up is important for a number of reasons including cognitive performance. An appropriate warm-up including some faster efforts will increase adrenaline and assist cognitive performance right from the start of the race.
- Ensure adequate and appropriate warm-up
- Caffeine is a known stimulant that is currently permissible under IOC doping laws. One of its known actions is to increase adrenaline response, this will occur prior to and during exercise. Supplements including caffeine could have an ergogenic effect from a cognitive performance perspective
- Potential caffeine supplement
Sports psychologists will warn that the individual interpretation of the adrenaline response (often perceived as “nerves”) can be viewed as a positive or negative response. From a physiological point of view it is a positive response since the “flight or fight” mechanism prepares the body for immediate action. It is up to the individual then to adopt psychological techniques to frame this response in a positive light so as not to distract from performance. Warming up with a map and focusing on process related goals may assist appease any perceived threat.
Ammonia is a compound found in the body that in excess, has inhibitory effects on both muscle cells and the brain through the central nervous system. Similar to lactate and adrenaline, ammonia levels increase with exercise intensity and reach a threshold level above which there is a disproportionate rise with increasing intensity. Similar to lactate threshold, the ammonia threshold is trainable and generally occurs at a similar but parallel intensity to lactate threshold. Ammonia however is perhaps a better indicator of exercise duration (as it continues to increase over exercise time) and therefore if it does play a role in cognitive performance, it is likely to exert its influence over time, particularly when the intensity is high.
Endurance training is known to delay the appearance of the ammonia threshold. Although not directly investigated, it makes sense to suggest that similar strategies aimed to increase lactate threshold will develop the ammonia threshold.
Effect of Exercise Duration
Increased fatigue is common after sustained exercise and anecdotally, a reduction in cognitive performance is common. Psychological factors such as motivation, commitment and discipline are likely to play important roles in continuing cognitive performance over time and should be developed. There are physiological mechanisms that will increase cognitive fatigue over time too and strategies to minimise these effects should be adopted.
The detrimental effects of dehydration on cognitive performance are well documented, affecting various abilities including decisional and perceptual tasks. The reduction in performance appears proportionate to the degree of dehydration and become significant after a loss of only 2% bodyweight (1.4kg in 70kg athlete). Rehydrating 100% of fluid loss can also improve cognitive performance although it seems logical to avoid any significant state of dehydration in the first instance.
A general guideline to hydration during exercise will ensure around 250ml of fluid are ingested every 10-15 minutes. To gain a better idea of your individual needs, you should replace 100-150mls of fluid for every 100g you lose in body weight through an exercise bout. Bear in mind that fluid losses are dependent upon exercise intensity and duration, the environmental conditions, clothing and current state of fitness.
- Endure adequate and appropriate hydration strategies
GlucoseReductions in cognitive performance can be induced through low blood glucose levels. Since the brain can only utilise glucose for energy, this reduction in performance could be through a reduction in fuel availability. Interestingly though, the recovery of cognitive performance does not improve immediately following an elevation in blood glucose suggesting additional mechanisms are at work.
It has been hypothesized that central fatigue occurs due to increased brain levels of serotonin, which result from increases in free tryptophan which cross the blood-brain barrier (trpytophan is a pre-cursor to serotonin). Tryptophan competes with branch-chain amino acids (BCAA’s) for transport across the blood-brain barrier leading researchers to hypothesize that BCAA supplementation could assist in delaying central fatigue (including reductions in cognitive performance). However, BCAA supplementation has also been shown to increase production of ammonia, previously implicated in fatigue.
The ingestion of carbohydrate during exercise also minimises the change in free tryptophan:BCAA and suppresses the rise in free fatty acids attenuating the increase in free tryptophan. Studies comparing the supplementation of carbohydrate plus BCAA’s against supplementation of carbohydrate alone are required to settle the debate. Regardless of this comparison, it must be remembered that cognitive performance is a particularly complex matter and is likely to be a result of any one mechanism either currently known or not.
A benefit of endurance training is an increase in glycogen (carbohydrate stores) provided sufficient carbohydrate has been ingested. Endurance and nutrition then is likely to assist cognitive performance through controlling tryptophan levels longer into exercise. Ingesting carbohydrate during exercise will supplement this process supporting the use of sports drinks, gels and other sources of sugar. Although at present it is unclear whether BCAA added to a carbohydrate supplement can offer additional benefits, Powergel (from the makers of Powerbar) includes BCAAs in its carbohydrate preparation.
- Develop endurance through increased glycogen stores
- Supplement carbohydrate
- Possibly supplement carbohydrate and BCAAs
Allocation of resources
The dual task paradigm determines that we have a finite attention, and that we can only perform multiple tasks if the task does not have too great attention requirements. Cognitive performance during physical activity then is constrained by the coordination demands of the physical task. The coordination demands in orienteering include foot placement, reactive adjustments, changes in stride length, small jumps, changes of direction and importantly the hand-eye coordination of map reading during movement. For particularly challenging terrain, or terrain in which a performer is unaccustomed, these demands may be high enough to constrain other cognitive performance (e.g. decision making, terrain visualisation), especially at high speeds. The likelihood of other cognitive fatigue mechanisms as suggested above will only further hinder cognitive performance.
The skill of running in terrain, and simultaneous terrain running and map reading must be practised to a very high level. The specific demands of the competitive terrain should also be practised as a skill and not just to invoke physiological adaptations.
- Develop terrain running skill/economy
- Develop simultaneous map reading and terrain running skill.
IMPLICATIONS IN A NUTSHELL
- Develop adrenaline threshold
- Ensure adequate and appropriate warm-up
- Potential caffeine supplement (?)
- Develop ammonia threshold; similar to lactate threshold (?)
- Ensure adequate and appropriate hydration strategies
- Develop endurance through increased glycogen stores
- Supplement CHO
- Possibly supplement CHO and BCAAs
- Develop terrain running skill/economy
- Develop simultaneous map reading and terrain running skill
Strategies to avoid reductions in cognitive performance are generally similar to if not the same as strategies that are adopted to optimise physical performance. The close link between the two should further emphasis the importance these strategies play as in orienteering, cognitive lapses generally lead to even greater physical effort. Some of the strategies suggested though must be treated with care. Supplements for instance generally only work if guidelines are closely followed and the risk of contaminated products – potentially leading to positive drug tests – is a risk the athlete must take on board.
Orienteering specific research
Orienteering research often suffers from methodological concerns and the research should be considered critically.
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Fach H.H. (1985). Visual attention and concentration during stepwise increased treadmill velocity in orienteers and long-distance runners. Scientific Journal of Orienteering; 1 14-23.
Hancock S. and McNaughton L. (1986). Effects of fatigue on ability to process visual information by experienced orienteers. Perceptual Motor Skills; 62(2) 491-8.
Mero A. and Rusko H. (1987). Psychophysiological performance of orienteers in graded and steady-state exercise tests. Scientific Journal of Orienteering; 3(1) 31-42.
Sellens, M.H., Hopkins W.G. and Williams L.T.R. (1999). The effect of one hour of treadmill running at race intensity on cognitive function in orienteers. Unpublished thesis, University of Otago, Dunedin, New Zealand.
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