What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
Physical factors involved in injury prevention are becoming increasingly well characterized as the process of fitness improvement and skills development becomes better understood. A recent paper, however, looked at the prediction and prevention of injury from a psychological approach and found from a study of 470 rugby players that social support; type of coping and previous injury all interacted to maximize the effect of life stress and injury. The second part of the study looked at stress management strategies as an intervention to reducing injury among players identified in the first part as having an 'at-risk' psychological profile for injury - numbering 48 in total. The experiment ran for a whole season with half of this number randomly assigned to a control group. The outcome from those in the intervention group was a significant reduction in lost time due to injury and a reduction in worry.
Researchers looked at the effect of time of training on time of competition by preparing a group of 8 cyclists in two different ways for a 16.1km time trial started at 07:00hrs. In time trial 1 the cyclists underwent a 30min sub-maximal session at 60% VO2 peak at 07:00hrs and in time trial 2 at 12:00hrs the day before separate time trials. The outcome was that time trial 1 was completed in 1672+/- 135s while time trial 2 in 1706 +/- 159s (a difference of around 300s). The physical / physiological data from the quicker time trials following the 07:00 previous day preparation outing showed elevated work-rates, lactate accumulation and heart rate relative to the time trial completed after the 12:00hrs previous day outing. These data suggest that performing exercise at the same time in the day(s) before competition benefit the cyclist. Only one point appears unclear from the paper in relation to the recovery period following the 12:00hrs outing - this was 18.5hrs rather than 23.5 hrs before the 07:00 time trial. Could the shorter recovery have been a contributing factor to the slower time trial?
Comparing and contrasting the effectiveness of laboratory measurements provides potentially useful information. A study that compared treadmill running to cycle ergometry for estimations of anaerobic capacity (AC) was based on the examination of 10 untrained, 10 aerobic-trained and 10 anaerobic-trained (400m sprinters). The tests comprised measurement of VO2 max, individual aerobic threshold (IAT) to determine aerobic power and finally from a series of sprints at increasing speeds the work output was calculated. The results indicated absolute values of AC below those measured by cycle ergometry and it was proposed that a factor not taken account of was the horizontal work done while running on a treadmill. Also, a factor could be the duration of each sprint test. Finally, the critical velocity (max speed attainable for a long time) was higher than the IAT that must therefore lead to an underestimation of the AC value. The treadmill test allowed for differentiation between the groups but does not assign correct AC values.
An interesting paper continued the theme that was raised last month on different responses to exercise between male and female athletes. The study used two different running tests - firstly - graded exercise to exhaustion to determine maximal aerobic flow, velocity at lactate threshold and velocity at the half way point (delta 50) between these two measures and, secondly - a constant all out run at the delta 50 to determine time to exhaustion at this intensity. 8 male and 8 female middle-distance endurance-trained athletes participated in the tests. The outcome was that the female athletes all perceived exercise as being harder, felt they could endure less and had higher heart rate values than males for a given absolute velocity whereas there were no differences for a given relative velocity. (This only seems to demonstrate that the men in the study were faster runners, on average, than the women and were therefore more comfortable at the same absolute velocity but that there was no difference at velocities matched relative to their maximum). Interestingly female athletes perceived exercise as lighter and felt that they could endure more than the males for a given absolute time period whereas at a percentage time relative to the final time of exhaustion there was no difference.
A number of papers have been reviewed in general physiology in relation to oxygen consumption and recovery. The first looked at a group of competitive collegiate level footballers and the impact of pre-season training and in-season adaptations based on the Wingate test and other appropriate measurements before and during the season. The authors conclude that no change in power performance measures were observed at any time whereas the extent of muscle de-oxygenation between the start of the season and 11 weeks into the season was measurably reduced during intense exercise and that oxygen recovery kinetics improve dramatically during the competitive season - meaning shorter rest spells were necessary. A further paper based on a study of cyclists indicates that this type of improvement may be largely attributable to adaptations in the peripheral circuit rather than to central adaptations following intensive exercise bouts in well-trained endurance athletes. To help identify appropriate test measurements to support such aerobic development a paper found that in general sub-maximal indices of aerobic fitness including oxygen uptake and power output are more useful measures of actual cycling performance than VO2 max and peak power output.
Moving away from exercise predominantly involving the aerobic energy system researchers have looked at factors affecting fatigue and the recovery of power. The study used a group of 13 men performing isotonic knee extensions at the fastest rate they could until velocity reduced by 35%. In this time (ca. 38s) power was reduced by 42% and maximum voluntary contraction (MVC) by 26%. Power recovered by 5 minutes whereas MVC only recovered to 85% of baseline even after 10 minutes rest. Peripheral factors were again concluded to be the limiting factor. The implication of this information on planning a power training session are interesting since although potentially useful power work can be performed maximally after 5 minutes recovery the ability to express MVC will be depressed for longer.
One or two middle distance and endurance runners spring to mind when barefoot running is mentioned. A recent study looked at the mechanical comparison of barefoot versus shoe running. The primary findings based on a study of 35 subjects running for 4 minutes at 3.33m/s (or around 8 minutes / mile) were that barefoot running reduces contact and flight time as well as attenuating impact peak force. Barefoot running at this pace also lead to higher breaking forces and pushing impulses - perhaps not as energy efficient at this pace as when running in appropriate running shoes.
Fuelling the system is critical to support all long-term training and so a study of eating disorders and risk factors in 283 elite Spanish female athletes provides extremely useful and meaningful information. Taken from 20 different sports the athletes were questioned with various well-accepted methods to establish that the proportion suffering from some form of eating disorder was 5-times that of the general population. Key factors identified included exposure of body form in public as a general factor and specifically pressure from coaches seems to be a risk factor for bulimia.
Looking at an array of recent papers on specific dietary components or supplements revealed a whole series of interesting evidence: The first paper sought to establish a relationship between controlled caffeine consumption at different levels and hydration levels on the basis that caffeine is touted as a diuretic that may impair performance. The study could find no evidence that caffeine acts chronically as a diuretic.
The next looked at glucose feeding during endurance cycling and confirmed that over a 75 minute ride at 80% VO2 max that glucose ingestion during exercise can spare endogenous protein and carbohydrate, in fed cyclists, without glycogen depletion. Clearly this would allow the cyclist to continue for longer at this intensity.
Vitamin C supplementation was shown to attenuate exercise induced protein oxidation in a manner proportional to dose. Sparing protein oxidation may be beneficial to endurance athletes - the truth behind the legend as to why some east African endurance athletes are believed to consume large quantities of oranges prior to training bouts and why oranges are also a favourite half-time food for soccer players?
Specific supplementation with L-carnitine receives massive promotion in the gym environment promising to do everything for you except your training sessions. Much of its claimed physiological benefit seems to centre on enhancement of fat burning. A recent paper that looked at combining L-carnitine with L-tartrate actually found no impact on fat burning whatsoever but did appear to increase carbohydrate oxidation in males but not significantly in females. I guess you just have to make your own mind up as to whom and what you believe!
Finally, two massively informative review papers have appeared from different groups looking at dietary supplementation with minerals and their effect on sports performance and a second on nutrient administration and resistance training. In this issue we will focus on the latter and cover the former next month. Resistance training clearly acts to improve hypertrophy (build muscle) and to increase muscle strength and with correct practice, enhance power and explosivity. The study has reviewed the literature with a clear emphasis on amino acid supplementation and has produced a proposal for a series of guidelines as follows:
From these primary findings, it is hoped that athletes, coaches, nutritionists and researchers will be able to provide clearer advice and recommendations when consulting themselves, their players, clients, or research participants in regard to optimal administration of nutrients while participating in a resistance training program.
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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 10 years' experience as senior coach educator and assessor trainer on behalf of British Athletics. 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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