What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
This month's literature review follows a simple timeline approach from fundamental training considerations through assessment of progress to preparation and execution of the event itself. Finally, several new papers have appeared recently in the area of nutrition and supplementation that raised an eyebrow on reading.
Three publications reported on strength development in different areas of the body. The first focused on core endurance in a group of forty-five College-age rowers divided into a control training group (with no specialized core training) and an intervention group. Training took place 2-days per week for 8-weeks. Trunk endurance was assessed using flexion, extension, and side flexion tests. A variety of functional performance measures were also assessed (vertical jump, broad jump, shuttle run, 40m sprint, overhead medicine ball throw, 2,000m maximal rowing ergometer test). The results revealed significant improvement in the two side flexion tests for the core group. However, no significant differences were found for any of the functional performance tests. Though the program appeared to improve selected core endurance parameters, the effectiveness of the core intervention on various key functional performance aspects was not supported.
Interesting stuff but it leaves several questions unanswered in terms of the appropriateness of the core training and its relationship to the performance tests as well as the suitability of some of the performance tests.
The second paper investigated the electromyographical muscle activation (pectoralis major and triceps brachii) of 11 men and 29 women, during a push-up (press-up) from each of three different hand positions - shoulder-width, wide-based and narrow-based. Muscle activity was greatest in the narrower hand position indicating that if the object of the exercise is to induce greater muscle activation then push-ups should be performed in this manner. The third publication gave a resounding and specific outcome benefit to a program of hip flexor training in sprinting. Over an 8-week period in a controlled experimental system hip flexion strength improved by 12.2%; 40-yard dash times were reduced by 3.8% and a 4 x short-leg (5.8m) shuttle run time was reduced by a dramatic 9%. Though the subjects were previously untrained in this study the results demonstrate the importance and benefits of performing specific strength development activities.
Periodic measurement of performance gains in a training situation is critical for athlete evaluation and a paper looked at the interpretation of changes in performance testing. The paper provides useful guidance on assessing the smallest worthwhile change that can be measured and proposes that this can be defined as about half of the typical variation in an athlete's performance from competition to competition or around 0.5 to 1.0% when expressed as a change in power output. The paper highlights the fact that the 'noise' or uncertainty in most measurement systems is usually greater than the smallest worthwhile improvement and so recognizing improvement can be problematic. The factors to be considered in the design of a test measurement system are discussed in this months 'How to' article.
Such factors include selection of a relevant test and another paper casts doubt on the applicability of the popular backward overhead medicine ball (BOMB) throw in determining power output as measured in a counter-movement vertical jump. Based on a study of forty national level football players in the USA test results showed appreciable correlation between BOMB throw distance and peak and average power but no correlation with power relative to body mass or lean body mass indicating that the BOMB throw distance may have limited potential as an indicator of total body explosive power. Furthermore, the variation in actual throw distances in each of the three trial throws completed by each subject suggested that there were technique issues, not previously considered, that indicated a learning effect across the three trials. Clearly this may be a variable that can potentially be controlled through allowing sufficient practice to lower the 'background noise'.
The ability to conduct comparative testing in a laboratory that correlates with a field performance can be very beneficial to all for obvious reasons. A study which looked at flat and uphill cycling performance and their relationship to laboratory measurable parameters found that absolute power, as determined on a progressive laboratory cycle ergometer, may predict cycling performance on the flat but that relative peak power was a better predictor of uphill cycling. This provides another example of choosing the right measurement parameter to provide feedback on targeted real world performance gains.
Moving into the next phase of our timeline a group of papers looked at warm-up and preparation factors before 'the event'. A comparison of the effects of static stretching and dynamic stretching routines prior to the measurement of leg extension power may cause you to either yawn once again as the stretching debate continues and you stick with your beliefs, or it may make you sit up and add to your evidence-based approach to coaching.
An interesting paper showed that in comparing the two stretching protocols i.e. static and dynamic, along with a control of non-stretching that there was no significant difference between non-stretching and static stretching (30s duration over 5 different days) in subsequent leg extension power measurement (1784.5 +/- 108.4W and 1788.5 +/- 85.7W respectively) whereas the power output after a dynamic stretching protocol (2022.3 +/- 121.0W) was substantially greater (13% higher in fact). Are you still not convinced!!
Event specific warm-ups are increasingly being advocated by up-to-date coaches and coach education systems - here's an example of why: Four different jump specific warm-up approaches were tested prior to measurement of vertical jump height in young adult football players from 'speed' based playing positions. The warm-up protocols comprised sub-maximal jumps (5 countermovement vertical jumps to 75% of maximum), weighted jumps (5 jumps onto a box holding 10% body weight in dumbbells), stretching (14 different stretches held for 20s each) and no warm-up.
Three vertical jumps were measured after each warm-up approach and the best height attained was used in analysis of the data. The weighted jump warm-up was statistically superior to all other warm-ups. I would advise that from a best practice perspective a progressive warm-up approach building toward the weighted jump might prove to yield a consistent and safe benefit.
The contribution to performance by clear mental focus or 'psyching-up' is anecdotally reported in many sports. We often 'know' it helps but it can be difficult to evidence. A study over 5 bench press repetitions during 3 different interventions comparing the impact of a free-choice psych-up, a cognitive distraction and an attention placebo was carried out. Peak force generated following psych-up was 764 +/- 269Nm, on average more than 11.8% greater than the distraction approach and 8.1% greater than the placebo approach.
Force production can clearly be enhanced through a suitable psyching-up step. What I want to see is a combined study to see if a loaded specific warm-up as described for the vertical jump above and a pre-exercise psych-up are additive in effect? If so, who needs banned substances when the real opportunity lies in tapping into real performance improvements from within?
Every triathlete has their own belief as to what works best for them when approaching the cycle ride and transitioning into the final run. Cycling cadence and the impact on the subsequent run was subjected to study through a 65-minute cycle into a 10km run. Fast, slow and preferred cycling cadences were compared (following determination of a maximum cycling test time and an isolated 10km time trial). All cycling sections in the two-part test were performed at 70% of the maximum but at the three different cadences corresponding to 71.8% (slow), 84.5% (preferred) and 97.3% (fast) of the maximum with the 10km runs being compared after each. Despite the fact that both the fast and preferred cadence bike legs led to faster first 500m running legs there was no significant differences between overall 10km run times for any of the three cycling cadence approaches. The slower cadence cycle produced significantly lower heart rates for the duration of the ride. The major differences recorded were in comparing the 10km time after the cycle leg to the isolated time trial 10km run (on average over 49 minutes versus under 45 minutes respectively).
Exercise has been found to diminish pain sensitivity (hypoalgesia) in numerous studies involving male athletes. In this study seventeen healthy females agreed to undergo pain assessment (electro-diagnostic) during the course of a graded exhaustive VO2 peak cycling challenge. The conclusions were clear that women also exhibit exercise-induced hypoalgesia during and after exercise with the peak effect following exhaustive exercise. Beyond pain to gain?
Thirty-two UK national track and field athletes in the junior age group (under 20) competing at the World Championships were questioned on the use of nutritional supplements. 75% of females and 62% of males used supplements with a total of seventeen different varieties being consumed - multivitamins and minerals were the most popular mainly for health and immune system reasons. However, 25% believed they were taking these supplements to improve performance. 75% felt they needed further information. Coaches (65%) had the greatest influence on supplement use while doctors (25%) and dieticians (30%) were less utilized. Clearly an opportunity exists for health professionals to become more involved in providing guidance.
A good example of this could be the findings of a study that examined the effects of the glycemic index (GI) of post-exercise carbohydrate intake on endurance capacity the following day. Nine active males completed a 90-minute run at 70% VO2 max on day 1 and were thereafter supplied with either low or high GI carbohydrate providing 8g carbohydrate per kg body mass. On day 2 subjects ran to exhaustion at 70% VO2 max The time to exhaustion was significantly longer after the low GI (108.9 minutes) replenishment than the high (96.9 minutes) indicating that the endurance capacity increase was largely due to increased fat oxidation following the low GI recovery diet.
Claims for the ergogenic properties of substances seem to only occasionally hold water when examined in a controlled study. An exception to this that has withstood scrutiny recently is the amino acid combination of L-arganine-L-aspartate. Under trials with sixteen healthy male volunteers performing an incremental cycling tests with either a placebo or the trial substance over a three-week period the trialists blood lactate and oxygen consumption levels fell when working at 150 Watts when taking L-arganine-L-aspartate compared to the placebo. Fat utilisation was also enhanced at lower work rates - 50 Watts indicating synergistic benefits from both L-arganine and L-aspartate. This is very interesting and basically says that sub-maximal workouts can benefit from both increased capacity and exercise tolerance if these substances are taken in a careful and controlled manner. Of course both are present in natural diets!
Finally a large-scale survey in France (6402 individuals) into methods and means employed to supply adolescents with doping agents and other substances to improve performance has been carried out. The findings indicate that 4% have been enticed into taking prohibited substances and 10.3% have actually received such products from an average of two different people - friends, parent and family doctor. Clearly a useful baseline study which could ultimately identify the dealers of such substances and help to eradicate the problem.
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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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