What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
The first paper to catch my eye this month is one from Germany that, in a sense, looked at chickens and eggs. Does an athlete's onset of hyperventilation come before or after the start of the dreaded lactate pain? Indeed, is there any direct link at all? It is well understood in the world of sports physiology that lactate production increases with exercise intensity until, at a certain point, it takes off exponentially, i.e. at a much higher rate - this point is the so-called Lactate Threshold'. Similarly, ventilation increases and takes off at a very similar point, called the 'Ventilatory Threshold.'
If we can estimate our lactate threshold, by observing when we start to hyperventilate then the potential practical benefits to the coach and athlete are vast. By comparing results from athletes before and after taking doses of sodium bicarbonate the authors suggest quite strongly that there is a very clear link since, after taking specifically measured doses of bicarbonate, which serves to buffer the blood and delay the onset of acidosis, all athletes experienced a delay in the onset of hyperventilation relative to the case before bicarbonate was taken. This seems to prove by cause and effect that hyperventilation occurs (can occur) as a direct result of exercise-induced lactic acidosis. This implies that we can now estimate during training on the track, in a scientifically acceptable manner, where our lactate threshold is!! A further paper that looked at which 'laboratory variable' best related to time trial performance in the Tour de France seems to back this up further. Based on a study of several cyclists in both the 1998 and 1999 event over 58km and 57km distances respectively, they found the only measure that gave a reliable relationship to actual power output (and hence individual time trial performance) was 'ventilatory threshold' (VT). Measurement also included, for example, both VO2 max and peak power output but neither of these two measures gave as good a 'result' as the 'VT'. So, it seems that Bob Dylan was right all along "The answer is blowing in the wind'!
On the subject of reliable tests for athletes, one of the classic challenges is to identify a meaningful strength test that is a measure of functional strength that relates specifically to performance development for the legs. Many tests are bilateral and do not match the primary unilateral nature of the use of the legs in most sports. Hopping type tests are beneficial but can place undesirable stresses on the knee, for example. A paper published very recent reports on the use of a modified unilateral free-weight bearing squat test that may be used reliably to perform 1- and 3RM lifts. The test is based on the subject supporting a bar in the back-squat position but having one leg 'passive' and supported (Figure 1 below). The subjects completed squats to a 90degree knee angle, and all gained familiarization with an unloaded bar before performing the actual test measurements. The test was deemed to be more reliable than the lunge test where the variability of loading between the back leg and front leg is more difficult to control. Since the exercise is performed on an isolated leg, then it may also be used for rehabilitation purposes allowing specific comparison to the healthy leg.
One of the main areas of injury in most athletes continues to be the hamstring muscle group. Many studies have tried to identify the cause(s). The hamstring is active in a supportive capacity (i.e. eccentric - resisting leg flexion) in most sports and yet it is also largely the case that most leg strengthening exercises are based on concentric strengthening. Not surprisingly, the hamstring becomes most prone to injury when stressed eccentrically. The authors of a recent paper propose a specific eccentric hamstring strengthening routine and associated equipment to overcome this shortfall. They go on to offer a link between delayed-onset muscle soreness (DOMS - based on micro-tears) and gross muscle tears. The hypothesis is that improved eccentric training can reduce the risk of common hamstring strains. A further paper found that in comparing the effects of concentric training versus eccentric training that the latter showed higher strength values, lower fatigue, lower increase in lactate and ammonia when either the knee or ankle joints were worked. This means that for the same work levels, the body is producing fewer metabolites able to limit performance. We need more eccentrics in sport!!
Recovering from prolonged bouts of exercise requires refuelling the body and restoration of muscle glycogen levels. A review paper looked at regimes for glycogen replenishment. It concluded that best practice involves consuming carbohydrate regularly and as soon as possible after exercise such as every 30 minutes, at the rate of 1.2g to 1.5g per kg of body weight per hour. The review also found that evidence exists supporting higher glycogen storage rates by further supplementation with protein (0.2g per kg of body weight per hour). This also reduces the amount and frequency of carbohydrate required to around 0.8g per kg of body weight per hour to maximize glycogen storage. It is also concluded that the consumption of protein will assist in limiting post-exercise muscle damage. The outcome is that following this regime will impact significantly on subsequent exercise performance. A study based on endurance cyclists supports the review findings whereby 15 male cyclists underwent cycle ergometer rides firstly at 75% and then at 85% VO2 peak to exhaustion. During this time, they consumed either a carbohydrate only (7.3% concentration) beverage or a similar beverage also containing protein (1.8%). In the first trial, subjects on protein supplementation rode 29% longer (45.2mins vs 32.6mins) and in the higher-level test rode a staggering 40% longer (43.6mins vs 31.2 mins). Muscle damage was 83% lower with the beverage with added protein! It was not clear whether the performance outcome was due to higher caloric content or some, as yet, unknown protein-mediated mechanism. So, any athlete involved in multiple rounds or several days of high-level activity of this nature should take note.
Having identified the important role protein plays in an athlete's diet, another paper looks at how to choose the best! From an exhaustive survey, sources of proteins are considered, and animal sources have much in their favour. However, the study does not discount vegetable sources, except in the area of maintaining lean body mass. Positive health data does exist surrounding, for example, the consumption of soy protein. For athlete supplementation casein best supports prolonged protein synthesis, but whey protein is better initially when it may be most needed for rapid recovery and repair. The author concludes that there is insufficient research data in this field to make too many strong arguments.
Fat, the scourge of the endurance athlete is vital for ultra-endurance performance. Two recent papers[9,10] report on the benefits for such performers of moving away from the classical 'carbo-loading diet' to a high-fat diet for anything up to 5-10 days before the event itself. Getting it right is the key. A 1 to 3-day high fat diet only serves to deplete muscle glycogen leaving the body less-well prepared to deal with the distance whereas 5-6 days of a high-fat diet is sufficient to change the rate of fat oxidation within the body serving to eke out glycogen consumption. This does not benefit the 2 to 3-hour runner who can store sufficient glycogen and consume further quantities during the event to maintain effort levels for the whole event. However, for those events lasting longer than 4 hours, the fat oxidation pathway becomes critical to performance, and a high-fat diet over the designed period may reap substantial rewards.
Essential nutrients can be derived from various components of a healthy and balanced diet. So it is interesting to review a paper that looked at the effect of vegetarian diets on performance in strength sports. Among the conclusions, the author derived from his review were:
A paper that looked specifically at an intensive sprint-cycling training regime and the effects of creatine has reported improvements by as much as 6% in total work done in a series of 6s maximal bike sprints within an 80-minute window. Creatine was administered after the initial control measures for five days in 20g / day doses. Increases in muscle concentrations were reported to be by as much as 48.9%.
Another substance has appeared as a possible ergogenic aid in the shape of b-hydroxy-b-methylbutyrate (HMB) a metabolite of one of the essential amino acids leucine. The author is less than convinced of its value, especially in previously trained individuals.
The whole field of ergogenic aids has been subjected to another substantial review where the author summarises the findings of over 100 related scientific papers, some, in themselves, reviews. As well as reviewing the various classes of ergogenics, the paper reports on the findings of a survey whereby 198 Olympic hopefuls were polled concerning the taking of banned substances. If the importance of winning was ever underestimated by anyone, it most certainly cannot ever be so again. The response - of all those athletes 195 said they would take a banned substance that would ensure they would win and could not be detected. Far more frightening than this was the response that more than half of those polled said they would take such a substance if it guaranteed them winning every competition for the next five years even if it killed them after that time. The review concludes that it is important for all involved to stay up-to-date with supplements as they emerge. The FDA does not regulate these substances and there is no means of ensuring the contents match their labels. On a personal note, I requested a copy of a certificate of analysis of a supplement from a supplier who said they were happy to supply one and that this would confirm that no 'banned substances were contained in the product'. What I received was a certificate alright, which may fool the layman, but in reality, was nothing more than a standard 'white powder' assay conformity certificate and related in no way to the actual ingredients. Caveat emptor!
A recent report suggests that a simple talent identification test may save the coach, the athlete and a lot of other people a lot of time, effort and money in the search for the ultimate male power performer. Testosterone levels are related to the ratio between the lengths of a man's third finger to his index finger. The bigger the ratio, the higher the testosterone level (which as we know enhances athletic performance). So, check out your third finger - is it longer than your index finger?
In a paper by the same title, a bold author reviews four major journals. The conclusions he drew were: 'The most common topic was sports science, and very few studies related to the treatment of injuries and medical conditions. The majority of published articles used healthy subjects sampled from the sedentary population, and few studies have been carried out on injured participants. There is a dearth of studies addressing diagnostic and treatment interventions in the sports medicine literature. The evidence base for sports medicine must continue to increase in terms of volume and quality.'
It sounds like someone wants to keep me busy with reviewing!!
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About the Author
Nigel Hetherington was the Head Track & Field Coach at the internationally acclaimed Singapore Sports School. He is a former National Performance Development Manager for Scottish Athletics and National Sprints Coach for Wales. Qualified and highly active as a British Athletics level 4 performance coach in all events he has coached athletes to National and International honours in sprints, hurdles as well as a World Record holder in the Paralympic shot. He has ten years of experience as a senior coach educator and assessor trainer on behalf of British Athletics. Nigel is also an experienced athlete in the sprint (World Masters Championship level) and endurance (3-hour marathon runner plus completed the 24 hour 'Bob Graham Round' ultra-endurance event up and down 42 mountain peaks in the English Lake District). He is a chartered chemist with 26 years of experience in scientific research and publishing.