What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
Most athletes would appreciate that the potential for injury may increase with high volume endurance training, probably assuming that some form of overuse would be the route cause. A recent paper however, based on a study of female endurance runners, suggests that what actually happens is that the ground reaction force decreases with increasing fatigue - typically as a result of shorter stride length, changes in cadence and alteration in hip, knee and ankle movement patterns. It is unclear whether these changes were attempts by the runners to minimize impact forces and protect against injury or whether they were fatigue induced and, particularly in the case of change in running action, in itself became the source of potential injury. Training to maintain good technique in an environment of fatigue may be the answer to reducing injuries in endurance events. Alternatively, changing the technique to one that has been practiced and reduces ground reaction forces maybe the answer. Which comes first the chicken or the egg?
Improving bone strength through increased mineral density, size and shape may reduce the occurrence of injury in terms of bone fracture. A recent report highlighted the positive effect that regular exercise has on these parameters. One of the best forms of activity for promoting bone growth seems to be dynamic activities with progressive loadings rather than static loadings. The best time to facilitate a response is during the normal skeletal growth phase - i.e. as an individual is growing up! The best means of producing a maximal response is to exercise more frequently in shorter bouts - for example performing 120 jumps / contacts in a training session which may be appropriate for a given athlete - the bone growth index increases almost 50% if the regime is 2 sets of 60 jumps performed 8 hours apart on the same day rather than all performed in one session. The paper makes a very clear conclusion that vigorous exercise during growth and young adulthood may well reduce fracture risk in later decades and suggests that the ability of the bone to control mechanical forces may be similarly increased. A second study looked retrospectively at retired professional football players in comparison to non-athletic controls. The study concluded that the football players had consistently specific areas of bone growth (i.e. based on weight loading sites) that were well beyond the control group and related to their sport specifically e.g. bone growth on the radius was not statistically different but that at the femur neck was. Clearly the potential to protect these sportsmen from, for example, femur/hip fracture is plain.
Combining the idea of injury prevention and psychosocial risk factors including The Sport Anxiety Scale, the Life Event Scale for Collegiate Athletes and other indicators were used to screen 32 high injury-risk soccer players. The group was then split into two randomly assigned groups with one being the treatment group and the other the control. The treatment group underwent training in 6 mental skills in 6 to 8 sessions over a 19-week competitive season. The outcome was a significantly lowered injury rate amongst this group compared to the control group. Neuromuscular training in a group of 14-16 year old female basketball, soccer and volleyball players improved both their performance measures and movement biomechanics over a 6-week training program. The probability of decreased injury risk, particularly anterior cruciate ligament injury was stressed. Activities included plyometrics and movement, core strengthening and balance, resistance and speed training. Performance indicators that all showed measurable improvements included predicted 1RM squat, bench press, single leg hop, vertical jump and a 9.1m sprint. Clearly a broad approach to training for team sports players has its benefits. In a previous issue I reported that there appears to be little crossover benefits between speed and agility training and both need to be trained separately if required for a given sport. A further paper looked at the relationship between acceleration, maximum speed and agility in professional soccer players. Although degrees of correlation were found what the researchers concluded was that they are all specific qualities and are relatively unrelated. This supports the notion of specific training and testing of these qualities when working with elite athletes.
For those of you seeking the maximal proportion type 2b muscle fibres for your speed and power event it is worth noting the findings of a study that highlighted the specificity differences between proprioceptive neuromuscular facilitation (PNF) training and isokinetic (ISO) training. In the study over 8 weeks based on 24 male university students, a three times per week regime based on PNF or ISO training produced a reduction in percentage area of type 2b fibre and an increase in type 2a with PNF whereas with the ISO the opposite effect was observed with a proportionately greater percentage area of type 2b fibres resulting. The conclusion here is that we need to be absolutely clear as to what the expected outcome is for a given block of training when aiming to optimise the balance of muscle fibre type. Humans can survive endurance! One of the concerns coaches and athletes can have with respect to prolonged activity is the potential effect on the immune system. A recent paper that looked at a 4-hour cycling bout concluded that such an activity at moderate intensity do not seriously alter the function of cells as the first line of defence.
This was based on a single exercise bout only and extension of this concept to an ongoing training program would need to be investigated. Staying with prolonged cycling activities a three-year study based on elite cyclists in major tours concluded that humans adopt a pacing strategy designed to optimally distribute energy reserves over the duration of a tour irrespective of the specific demands of the course, high power outputs in sprint situations etc. This was based on a novel calculation that normalized a summation of intensity and duration in each race and yielded a remarkably constant overall figure between events for both the group, as a whole, and individual athletes.
The boundary between normal nutritional intake and supplements / ergogenic substances remains somewhat tenuous especially when substances that occur naturally in our diet become the ergogenic substance under consideration. Manufacturers and suppliers make claims of the 'scientifically proven' benefit of consuming their products that can easily encourage us to invest in them. Some recent papers, also looking at measurement methods, serve to throw additional light in this important area: Ultra-endurance athletes seeking the energy edge may consider medium chain triacylglycerol (MCT) in combination with their vital carbohydrates (CHO). However, a recent paper based on cyclists could only conclude that sprint efforts during 270 minute continuous rides were compromised by the intake of MCT before or during efforts and that 50% of those who took MCT experienced some form of GI symptom. Siberian Ginseng use is common among endurance athletes since it is suggested that it improves cardiovascular fitness and fat metabolism and hence endurance performance. A review paper found that the majority of the published literature found no benefit and that of those that claimed a benefit there were serious questions over the methodologies employed. The conclusion is that supplementation with this product up to 1.0 to 1.2g / day for 1 to 6 weeks offers no advantage during exercise ranging from 6 to 120 minutes in duration.
Looking at measurement systems for maximum oxygen uptake, of great importance to endurance athletes, the classic 20 metre multi-stage fitness test (MFT, referred to in the final paragraph in Issue 21's review) has come under scrutiny once again. One author compared the test to laboratory-based measurements and found that, at best the MFT underestimated VO2max and, at worst, provided no valid prediction at all. Meanwhile a different study approaching from the basis that the MFT is useful in quickly establishing if young male adults achieve the minimum VO2max guideline of 44 ml / kg / min to be viewed as healthy and fit proposed a modification to the calculation resulting from the MFT test. This revision improved the quality of the result. It is hoped that these modifications will be incorporated widely into the MFT calculations.
Moving up the energy spectrum into the anaerobic lactic zone a fascinating study looked at the recovery of pH and lactate from different starting states that had been created by dosing individuals with ammonium chloride (ACD), sodium bicarbonate / sodium citrate (ALK) or a placebo (PLAC). The result of blood tests after exercise showed increased acidosis from both ACD and PLAC relative to ALK. Measurements of pH recovery and clearance of lactate revealed different rates. Blood pH recovery can take longer than 45 minutes with 50% recovery taking 12 minutes whereas, complete recovery of blood lactate levels can take longer than 60 minutes with 50% recovery occurring after approximately 30 minutes. No detail was given on recovery activities but it would be reasonable to assume from the paper that recovery was at rest. An active recovery or cool down might have been expected to improve both recovery rates - either by enhanced clearance of carbon dioxide from the blood via the lungs or enhanced blood flow to remove lactate. In the same area a paper looked at using a respiratory method for assessing the anaerobic threshold that is non-invasive (blood sample analysis being the currently most reliable method). The experiment involved measurement of the respiratory exchange ratio (RER) i.e. the volume of CO2 produced divided by the volume of O2 consumed (continuous measurement was made but results were averaged for each minute of exercise) and compared these data with classical blood lactate determination as well as other methods. The conclusion was that the RER method correlates strongly with blood lactate measurement and offers some distinct advantages since it is non-invasive.
At the top end of the energy spectrum in the anaerobic alactic zone a study looked at the uptake of creatine to augment the ATP-CP energy pathway, following supplementation, into skeletal muscle and into erythrocytes (blood) with view to testing if a simple blood test could be used in favour of the current muscle biopsy to establish cellular creatine levels. Though both levels increased, the test itself showed no obvious correlation between them. However, it did serve to demonstrate the extent of muscle loading - +39.8% creatine, +7.5% phosphocreatine and +20.1% total creatine elevation based on 5 days dosage of 4 x 5g / day. This demonstrates the potential boost to the ATP-CP energy system with such a loading regime.
Finally, picking up on the psychology of athletes, two very interesting papers drew my attention. The first refers to the fearfully named concept of 'Terror Management Theory' - the concept itself is quite sufficient to scare off most readers! But, that's the point. The study looked at hand dynamometer measurements before and after the individuals wrote about their own mortality or dental pain.
Only those involved in strength training showed an increase in force generation after the written exercise. Adding this to earlier observations reported in the review series would suggest that to obtain the maximum force output an athlete should pre-activate the relevant muscle group isometrically within a few seconds of the effort while thinking about or writing about the sensation of pain or mortality. Are these two effects additive?
Last paper out of the bag this month may serve to turn on its head the criticism often aimed at the athlete who is the 'Big Fish in the Little Pond' either by their own coach or their peers. Analysis of 'self-concept' revealed that athletes have a higher value of self-concept when in this situation than when transplanted into a more gifted group. What is the risk? - Moving up might drag someone down!
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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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