What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
With so much opinion on all matters in sport so readily available it is easy to understand how misconceptions can lead to well-intentioned coaches and their athletes avoiding forms of training or making ill-informed decisions on what benefits may be derived from them. Strength conditioning with younger athletes has been a case in point recently. A recent paper examined the impact of oral contraception use on maximum force production in women and, based on a study of 21 subjects, disproved the opinion that it may be affected at various times during the menstrual cycle depending on hormonal changes as measured in terms of maximum dynamic and isometric leg strength and other indicators. On a similar note regarding female athletes and menstrual dysfunction another highly extensive study based on over twelve hundred elite and national level female athletes highlighted that participation in sports that emphasize thinness and/or a specific weight reported a significantly higher level (24.8%) of dysfunction, e.g. amenorrhoea, compared to other sports focusing less on such factors and controls (13.1%). Enforcing 'thinness' or specific weight control for a female athlete can have consequences.
A challenge that has faced many long jump coaches is finding the balance between approach speed and the explosive strength at take off as characterized by the vertical ground reaction force (VGRF). A computer simulation experiment has demonstrated that for approach speed a 10% increase yields a 10% improvement in jump distance jump whereas, for a given approach speed, a 10% increase in VGRF only yields a 7.2% increase. On the first inspection, therefore, speed may appear to be the most important. Of course, the reality is that it is a combination of the two that increases the distance so that it is not surprising to find that a 10% increase in both approach speed and VGRF together yields a 20.4% increase in jump distance - more than the sum of the two factors independently. Most athletes who perform long jump to a reasonable standard are aware of the impact of approach speed but often fail to achieve their potential due to either a lack of appropriate training to optimize VGRF or else poor timing of the upward drive to overcome gravity (ask a throws coach about the importance of release speed, height and trajectory). When Bob Beamon shattered the World long jump Record in 1968 in Mexico (advancing it from 8.35m to 8.90m) his speed on the runway was evident, but his timing for maximum yield of his VGRF was what made all the difference - see the height he achieved! - Beamon improved the World Record that day by 6.6%. On the subject of jumping a publication looking at the effect of different jumping/landing patterns with pre-and post-pubescent females found that the post-pubescent group exhibited a reduced knee flexion on landing at initial contact - this suggesting a better energy return and supporting the paper reviewed last month indicating landing attenuation by younger athletes. The outcome here is that older athletes have adapted their biomechanics to provide more resilient landings either through development and adaptation.
Relating to the review last month on injury prevention but very much relevant to conditioning a study has highlighted that ankle sprains can still show signs of weakness two years after the injury if not properly rehabilitated. The message by now must be clear!
Sometimes even the obvious will not be accepted until someone writes a paper on the subject. A simple paper looked at the impact of golf-specific warm-up activities on the subsequent performance of a group of golfers in comparison to a matched group who continued with existing warm-up practice (or lack of it!). Clubhead speed was used as the primary indicator. After seven weeks, the exercise group increased clubhead speeds by as much as 24% while their more-traditional counterparts showed no change whatsoever. The warm-up group reached the 19th sooner also!!
Staying with the idea of 'sending' an object whether it be with a club or the arm a paper looked at the force-velocity relationship and coordination patterns for over-arm throwing of a range of ball weighs between 0.2kg and 0.8kg (with clear implications to a host of ball games as well as the less obvious javelin throw). The study concluded that coordination patterns were unaffected by weight and that although the heavier balls were acted on for longer by the applied force - i.e. they were not accelerated as quickly, the force-velocity relationship remained linear. Internal rotation of the shoulder and extension of the elbow were the two important contributors to ball velocity at release. This supports the concept of creating learning patterns with lightweight implements in novice athletes that will still be appropriate with heavier implements in later development. Caution should be practiced about velocity as in the early stages, it may be easier for the novice to throw 'fast' but with little coordination! Hence the coaching mantra to learn the skill at reduced speed and reduced loading and then progress - 'quad erat demonstrandum' What will happen with throwers is that they are likely to undergo musculoskeletal adaptation to meet demands of the throw. A paper looking at the scapular (shoulder-blade) concluded with recommendations that clinicians involved in the treatment of any related injury will need to be aware that 'normal' for a thrower may not be 'normal' for the next patient.
A couple of 'sociological' papers caught my eye this month that are worthy of reporting. In the first the authors looked at chronic or recurrent non-specific low back pain - a common scourge and reason for work (and training) absenteeism - and reported a series of specific risk indicators including a hip range of motion, abdominal muscle endurance, lumbar flexibility and lateral spine flexion. A program that seeks to improve these will reduce the risk of the chronic symptoms familiar to many individuals inactive in these areas. The second is again not good news if you are an active athlete but not so happy with your work. The paper demonstrates that the pursuit of sporting activity reduces sick leave by as much as 20 days in 4 years and even supports short periods of leave when they do occur. The benefits of sport are most evident in this study for those who lead sedentary jobs.
Complex sugar combinations can facilitate higher carbohydrate oxidation rates, and a recent report assures us that a combination of maltodextrin and fructose consumed during exercise helped cyclists achieve an elevated oxidation rate of 1.5g / min exceeding the rate for maltodextrin alone. Similarly, a paper looked at carbohydrate feeding during team sport exercise which ably demonstrated that not only did feeding preserve performance but that it also supported central nervous system function such as preservation of motor skills and mood status. Soon, we will not need to train at all - eat the right explosive energy food and stand clear! Post-resistance exercise recovery has been strongly reported as being dependent on the presence of some protein. A paper reports that although casein and whey protein act in different ways, the overall effect on muscle anabolism is comparable - you pay your money and take your choice.
A paper has highlighted the fact that one brand of sports drink (not named) produces more than three times the level of dental enamel erosion when compared to water or a prototype carbohydrate-electrolyte drink (which will have a name very soon!) Now, if you are still with me, you must be an endurance fanatic so here goes with the latest from the scientists in this area. Train the energy systems for endurance enhancement Carbohydrate loading is studied in comparison to non-loading but with an eye on the final bodily status rather than overall performance. As expected in a group of endurance cyclists carbo-loading improved mean power output for the duration of the trial but, most interestingly, the carbo-loaded cyclists and the controls ended the trial with similar muscle glycogen concentrations suggesting the possibility that glycogen levels may act as a regulator of pace during prolonged exercise. Think about it. Another glycogen based study looked at compensation effects on cyclists working exhaustively every other day for five days. The paper concluded that even well-trained male cyclists are not able to super compensate glycogen in this time even with a high carbohydrate diet in the two days recovery phase. This has implications for training regimes. It is understood that different athletes respond in different ways to altitude training. A study set out to establish if the erythropoietin response (an endogenous glycoprotein that stimulates red blood cell production) from a 4-hour hypoxic tent exposure corresponding to a training altitude of 2500m could indicate the potential benefits of altitude training for swimmers.
Measurements of erythropoietin as well as total haemoglobin mass and stepwise swimming tests were performed before and after the hypoxic experiment and then throughout a 3-week altitude-training spell. Unfortunately, the results showed that responses from individuals were varied and that there was no correlation between the hypoxic response in the tent and actual haemoglobin level increases resulting from 3 weeks of altitude training. It looks like the experiments will have to take place up in the hills for a bit longer!! Not only does training work to improve cycling capacity but resistive inspiratory loading works too. A study using inspiratory resistive loading (a kind of gym for training the breathing muscles) demonstrated a greater than 30% improvement in respiratory muscle strength and other factors in just 10 weeks. During cycling trials, heart rate and breathing rate were lowered relative to the control group with the ultimate measure being a 36% increase in cycling time to exhaustion at 75% VO2 peak. Inspirometers are available commercially!
I am often asked about training loads and intensities for performance. A paper highlights some useful interpretations but also, without intending to do so, flags some areas for further consideration. The purpose of the study was to evaluate the correlation between total training loads at different intensities and performance with well-trained, but sub-elite, cross-country runners over both short (4.175km) and long (10.130km) race distances. The conclusions were that the best correlation (0.97) was between low-intensity training time (time spent training below the ventilatory threshold (VT)) and the longer race distance and so spending more time performing low-intensity work would further improve these performances. On further consideration, the data might be suggesting that aerobic training, i.e. predominantly below VT best supports longer endurance running (>35 minutes) but that the poorer correlation of the lower form of training with the shorter race distance (0.79) might suggest that here the athlete is working above VT for at least some of the time and that therefore training volume in this potentially anaerobic lactic zone might correlate better. At this end of the energy spectrum to which we are now headed, we might not, for example, expect a very good correlation between training volume below VT and performance over 0.100km!
An interesting paper reminded me of some excellent 800m races at the international level recently (i.e. the 2004 Olympics) where victors were characterized by their even-paced running from gun to tape. A study looked at almost every elite 2000m rowing event held in the years 2000-2002 timeframe and concluded that all boats were rowed in a similar pattern that reflected a pace equivalent to 103.3% of the overall mean race pace for the first 500m sector and then 99.0%, 98.3% and 99.7% of the mean pace for each subsequent sector. An interesting case study for energy systems, perhaps?
Nice to see an alternative to laboratory testing of aerobic capacity being trialled by young elite soccer players in the form of the Hoff test. The test is based on a specific dribbling track, and results show a strong correlation to laboratory testing for maximum oxygen uptake. A recommendation is provided that under-15 soccer players should be able to cover more than 2100m in the Hoff test representing a VO2 max of above 200ml/kg/min.
Finally, a 15m multistage shuttle run test is evaluated for assessment of anaerobic capacity in female games players. It works and provides useful field information. However, I do not know many athletes who enjoy this form of assessment - questions, therefore, arise over the validity of results from the perspective of motivation to perform the task at the outset as well as tedium within the task. 20m shuttle runs are the norm, so 15m shuttle runs must increase the number of turns and so the potential for injury, particularly in the knee area, as the individual performs faster and faster 180 degree turns as they become increasingly fatigued, is all too obvious.
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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 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.