What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
The consumption of bicarbonate and its impact on muscle buffer capacity against acidosis and short-term endurance were investigated. 16 recreationally active women underwent an 8-week program of 3-times per week training of six to 12 two-minute cycle intervals at 140-170% of their lactate threshold. Half of the group consumed bicarbonate before each session and half a placebo. Both groups showed improvements in buffer capacity (19 vs. 9%) and VO2 peak (22 vs. 17%) after the training period, with no differences between groups. Pre-training buffer capacity and percent change in buffer capacity correlated well. There were greater improvements in both the lactate threshold (26 vs. 15%) and time to fatigue (164 vs. 123%) after taking bicarbonate, compared with the placebo. Pre- or post-exercise ATP and creatine, intracellular lactate concentrations and pH remained unchanged after training. The authors suggest that it is the training intensity rather than acidosis during training that may be more important to improvements in buffer capacity. The group ingesting bicarbonate before each training session had larger improvements in the lactate threshold and endurance performance, possibly because of a reduced metabolic acidosis during training and a greater improvement in muscle oxidative capacity.
The influence of low dose bovine colostrum supplementation on exercise performance in cyclists over a 10-week period including 5 days of high intensity training (HIT) was investigated. 29 highly trained male road cyclists completed a VO2max test (to estimate ventilatory threshold), a time to fatigue test (at 110% of ventilatory threshold), and a 40 km time trial. Cyclists were then assigned to either a supplement (10 g/day bovine colostrum protein concentrates (CPC)) or a placebo (10 g/day whey protein) group and resumed normal training. 5 weeks later the cyclists were retested (week 7). They then underwent five consecutive days of HIT (week 8) followed by a further series of performance tests (week 9). The influence of bovine CPC on time trial performance during normal training was unclear from the retesting results in week 7. However, after the subsequent 1-week HIT period, bovine CPC supplementation elicited a 1.9% improvement from baseline in time trial performance and a 2.3% increase in time trial intensity (% VO2max), and maintained time trial heart rate (2.5%) compared to the placebo. In addition, bovine CPC supplementation prevented a decrease in ventilatory threshold following the HIT period (4.6%). The authors concluded that low dose bovine CPC supplementation elicited improvements in time trial performance during a HIT period and maintained ventilatory threshold following five consecutive days of HIT. Colostrum is the immediate post-birth milk in mammals and is very high in protein, carbohydrate and anti-body concentrations and low in fat.
And if the previous findings made you think you now know all you need to know the next study illustrates the complexity of dietary supplementation on performance. Addition of 2% protein to a 6% carbohydrate drink made no difference whatsoever to 80km time trial performance with trained male cyclists compared to the improvement given from 6% carbohydrate alone. Previous studies appear to have provided different results to these on the basis that they failed to provide carbohydrate at a rate that was typically required by athletes in such competitive situations. One study looked at a specific sports drink (EM-PACT) as an energy and endurance pre-exercise drink in specific relation to its effect on maximal respiratory fitness i.e. VO2max and time to exhaustion. Enhancements (5.82 ml/kg/min VO2max and 4.47 minutes longer to exhaustion) were upheld in this research versus a water placebo - though I question whether participants might have been able to distinguish between the two products leading to a possible loss of control within the experiment.
Research has concluded that gender differences for carbohydrate metabolism and implications on carbohydrate loading, and hence performance for endurance events, can be overcome with a different regime. Earlier studies typically recommended 6.4g/kg body weight of carbohydrate for women and 8.2g/kg for men. Under these conditions men often found an improvement in excess of 40% while women often as low as 5%. However, subsequent studies established a nominal 'threshold' level of 8-10g/kg for either gender. More recent studies have determined that at levels of around 12g/kg women can gain as much enhancement as men. This means that in order to gain the full advantage from carbo-loading, for the 3-4 days preceding an endurance event, females need to consume extra calories rather than simply change the proportion of carbohydrate consumed. Probable interferences in carbohydrate storage and metabolism exist in women from oestradiol and so future studies will look at the impact of the phase of the menstrual cycle on carbo-loading.
From a much applied perspective the dietary needs of women involved in strength training has been studied. It concludes that female strength athletes may require more protein than their sedentary and endurance training counterparts to attain positive nitrogen balance and promote protein synthesis. Therefore, women strength athletes should put less emphasis on a very high carbohydrate intake and more emphasis on quality protein and fat consumption in the context of energy balance to enhance adaptations to training as well as improving general health. A review looked at protein ingestion with regard to 'free-living' athletes i.e. those less well monitored. Basically, the conclusion was that such athletes most frequently experience a negative energy balance and sub-optimal dietary variety, particularly with respect to protein where overtraining effects and soft-tissue recovery can be major factors. Effects are most common in those training twice daily. Supplementation with amino acids including glutamine and leucine also gain serious support in this review.
A veritable bombshell of a review paper has been dropped on my desk reporting on the use of herbal substances with regard to performance. Essentially it concludes that pretty much all evidence in support of any ergogenic activity is anecdotal. Furthermore, from a health standpoint, recent official reports question any benefit whatsoever. Moreover, many may not be safe and may have some serious side effects, particularly when used in conjunction with prescribed drugs. Some commercially available herbal products are known to contain active substances such as anabolic steroids, which may lead to a failed doping test.
Two papers drew attention in the field of sports psychology. The first looked at goal-setting and reported that athletes who avoided performance goals delivered worse performances and higher levels of both behavioural and self-reported self-handicapping when compared to either mastery or performance based goals. In some sports the use of the SMART goal acronym discourages the setting of performance-based goals and focuses solely on the process (sometimes mastery) style approach. This study appears to support the use of both forms of goal setting.
The second looked at the impact of a number of parameters encountered within group training environments on outcomes and found that athletes involved in adaptive peer relationship circumstances had a more motivation related response. So a positive social setting positively affects motivation and efficacy of an athlete-centred approach. The final batch of research reviewed this month came from the training and physiology domain.
The first compared active and passive recovery in repeated cycle sprints in which nine males performed four repeated-sprint cycle tests (six 4-s sprints, every 25 s): two tests with active recovery (~32% VO2max) and two with passive recovery. Muscle biopsies were taken during the four tests from the vastus lateralis (major part of the quadriceps group of muscles) pre-test, immediately post-test, and following 21s of recovery to determine phosphocreatine, creatine, and muscle lactate concentration.
What they found was that active recovery resulted in a greater power loss than passive recovery and lower final peak power. However, there was no significant difference in work decrease or total work. The percent of resting phosphocreatine was lower and approached significance post-test and following 21s of recovery during active recovery. Muscle lactate was significantly higher post-test during active recovery; however, no significant differences were evident following 21s of recovery. Despite no differences in the majority of performance measures, active recovery resulted in a significantly lower final peak power, a greater peak power decrement, a higher muscle lactate, and a strong trend towards lower phosphocreatine, suggesting a potential suboptimal effect of active recovery during repeated-sprint exercise. In conclusion - rest means rest!
As we get older we are usually advised to slow down! For sprint trained athletes this usually means hanging up the track spikes and just enjoying a 'plod' out along the roads. As any master athlete will tell you this is altogether a bad idea since the belief is that 'once a sprinter, always a sprinter'. Thankfully, this belief is now supported with scientific evidence from a recent study where a range of sprinters (ages 18-84) was examined by muscle biopsy from the vastus lateralis. Despite the fact that maximal isometric force decreased with age and the typical ageing related reduction in the size of the fast fibers was apparent the muscle characteristics were preserved at a high level in the oldest sprinters underlining the favourable impact of sprint exercise on aging muscle.
A study of muscle fiber adaptations in marathon runners has shown that marathon training decreases slow-twitch and fast-twitch muscle fiber size but that it maintains or improves the functional profile of these fibers i.e. the level of recruitment. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers. Through this regime we gain more functional muscle and greater access to fast twitch fibers supporting faster running!
A study was designed to examine the role of central (i.e. reduction in the neural drive or nerve-based motor command to working muscles that results in a decline in the force output) and peripheral (i.e. during physical work is considered an ability of the body to supply sufficient energy to the contracting muscles to meet the increased energy demand) fatigue on 4000-m cycling time trial performance by comparing changes in integrated electromyography (iEMG) and power output in differently paced maximal efforts. Eight well-trained men performed three time trials with different pacing strategies, in which the first 2000m were manipulated to evoke an increasing, even, and decreasing power output profile (SUB, EVEN, and SUPRA, respectively). Subjects were instructed to finish the last 2000m of all trials in the shortest time possible. iEMG of the rectus femoris, vastus lateralis, and biceps femoris muscle, mechanical power output, and gas exchange variables were measured (to calculate anaerobic and aerobic contributions to mechanical power output).
The increase in mechanical power output during the SUB time trials was always associated with an increase in iEMG in all muscles. A decrease in mechanical power output near the end of the time trials was also marked by an increase in iEMG for all muscles, except for the rectus femoris. Comparing the last 2000-m interval with the first, aerobic power output increased for all strategies. Anaerobic power output increased in SUB and decreased in EVEN and SUPRA. The relationship between iEMG and mechanical power output pattern was consistent with peripheral fatigue rather than central down-regulation of mechanical power output. Specifically, anaerobic energy resources seem to be important in regulating pacing strategy so you had better ensure you specifically work on this area in training if you will need to respond to different paces in your race.
A study looked at the prevalence and possible causes of perceived leg pain in female athletes from a number of sports including cross-country, hockey, soccer and volleyball. The findings revealed sport specific relationships to leg pain with cross-country and hockey but not for football, which seemed to relate to certain factors including foot pronation, a history of the condition and the actual sport. All other factors were ruled out.
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About the Author
Nigel Hetherington is 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 UK Athletics (UKA) 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 10 years experience as senior coach educator and assessor trainer on behalf of UKA. Nigel is also an experienced athlete in 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' experience in scientific research and publishing.
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