What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
This is a question we hear from many athletes who become injured at various stages in their career. It seems that only rarely do we understand how an injury came about (unless these are obvious trauma-based acute injuries or else have been fully diagnosed by a medical specialist, e.g. physiotherapist) or how to avoid the injury in the first instance. Many injuries are classified as 'overuse' at best or 'it happens!' However, neither of these is a particularly helpful situation and does little to deal with the outcome, i.e. the fact that the athlete is potentially now suffering from a chronic injury and, worse still, one that may reoccur.
Recent research publications are now trying to identify risk factors and categorize injuries to causes. It seems to me that the availability of such information, in a reference format, e.g. database, would prove extremely beneficial in reducing the incidence of injury, especially if such a database identified specific areas of bad practice or which anatomical factors correlate strongly with an injury with certain sports or types of training.
For example, a recent paper looked at knee injury incidence in footballers with a previous anterior cruciate ligament (ACL) injury. From a study group of 310 players, 24 had an ACL injury history. Throughout a season the ACL group had 4 to 5 times increased occurrence of any knee injury compared to the rest of the group based on an injury per 1000 hours of play measure. No other factors correlated, e.g. age.
A second paper looked at overuse injuries of the Achilles tendon based on a study of 69 males undergoing a 6-week basic military training program. The results showed that ten individuals sustained an Achilles tendon overuse injury and these individuals were largely characterized as initially having lower than average plantar flexor strength (i.e. reduced ability to walk high on the balls of the feet) and increased dorsiflexion excursion (i.e. the ease with which the foot flexes or 'gives' toward the lower leg as can be measured by placing the foot flat on a raised platform with the lower leg positioned vertically and then measuring the degree to which the lower leg can be angled away from the vertical by pushing the knee forward while keeping the foot flat - try it it's easier than it sounds!).
A benchmark for plantar flexion strength was below 50 N/m (not trivial to assess) and dorsiflexion excursion of greater than 9 degrees - a useful predictor. From personal experience, I would propose that both these factors in combination may lead to Achilles problems since increased ranges of movement can be tolerated provided sufficient strength is present to resist any inherent movement beyond biomechanical needs.
A third paper looked at injuries in West Indian cricketers and found, over 18 months that most injuries occurred in West Indian Test and one-day international teams. The likelihood increased 2 to 3 times in these situations with the highest chance of all being with batsmen and fast bowlers, especially when on tour away from home. Many injuries appeared to occur during fielding incidents involving catching. The recommendations were to improve early detection of injuries, focus on improved catching techniques and monitor, in particular the technique of young bowlers. Has it been implemented, and how successful was it?
The effectiveness of rehabilitation regimes was studied to determine whether quantified, auditable records of functional rehabilitation can be generated using subjective assessments of players' performance in fitness tests routinely used in professional football. The methods used encompassed a series of 10 sequential tests elements based on fitness, ball/match skills and match pace play, where physiotherapists subjectively scored the players level through each stage to gauge their recovery score. 118 injuries recorded by 55 players were included and average times for functional rehabilitation were identified for a host of different injuries. This paper is incredibly useful and could prove invaluable to all athletes undergoing rehabilitation - professional or amateur. Everyone wants to be back in training or competition 'tomorrow' but worse than this is not knowing or being able to tell someone how long rehabilitation will take - the secret is now partly out of the bag!
A series of physiological papers have been reviewed this month with the first from the world of swimming examining the basis of 'controlled frequency breathing' (CFB) used by swimmers to simulate a high-intensity workload by limiting oxygen availability and stimulating anaerobic metabolism. The study examined blood lactate levels and metabolic responses of swimmers practicing CFB. The results showed that though blood lactate was not affected, there was a measurable reduction in ventilatory and heart rate (HR) responses to exercise. Swim coaches can use CFB at moderate intensities to simulate high-intensity training but should consider adjusting HR training zones to reflect the reduction in HR associated with reduced ventilation.
Fluid intake at rates that exceed sweating rate is predicted to be the primary cause of hyponatraemia. However, a model proposed in a recent paper indicates that runners secreting relatively salty sweat can finish ultra-endurance exercise both dehydrated and hyponatraemic. Electrolyte-containing beverages are predicted to delay the development of hyponatraemia. The predictions suggest that current fluid intake recommendations sustain hydration over the 42 km distance if qualifiers - for example, running pace, body size - are followed.
It was concluded that actions to prevent hyponatraemia should focus on minimising over-drinking relative to sweating rate and attenuating salt depletion in those who excrete salty sweat. This simulation demonstrates the complexity of defining fluid and electrolyte consumption rates during athletic competition.
The impact of the competitive season on fitness factors on junior rugby league was examined during a study to answer the conundrum over balancing intense training and the needs of the competition. Following classical methods training loads progressively increased in the general preparatory phase of the season (preseason period) and declined slightly during the competitive phase of the season. Match intensity and match loads decreased throughout the season. Increases in estimated maximal aerobic power and muscular power and reductions in skinfold thickness occurred during the general preparatory phase of the season and were maintained throughout the competitive phase of the season. These findings suggest that high training loads in the general preparatory phase of the season and low match loads in the competitive phase of the season allow junior rugby league players to maintain a high level of fitness throughout an entire competitive season. QED?
Two further papers revisited the 'live high train low' (LHTL) question concerning altitude training benefits. The first study looked at world-class endurance athletes against the backdrop of the fact that it is unclear whether world-class endurance athletes, in contrast with less well-trained subjects, increase their haemoglobin mass on a regimen of LHTL. In this study, lasting 26 days, living was at 2456m and training at 1800m. Haemoglobin mass increased between 3.9% and 7.6% and race times also improved (5000m and the marathon). Based on this specific regime, it seems to work - but was it optimal?
The second study looked at swimmers and a comparison of the measured benefits of living and training at 1200m versus 1850m via a swim test performed at 1200m (5 x 200m and a 2000m maximal test). Interestingly, the short-term effects of training at 1200m appeared greater than those at the higher altitude. One is left wondering what would have been the outcome for the endurance runners if they had come down to 1200m for training - they did not fancy the long climb back!
Some interesting 'training' papers crossed my desk the first of which looked at the outcome on competitive cyclists of including explosive and high-resistance training in their training programs during the competitive season. Some of the routine endurance training was exchanged with a total of 12 sessions of 3 sets of 20 single-leg explosive jumps (repeated for each leg) alternating with 3 sets of 5 x 30s high resistance cycle sprints (60 to 70 pedal revolutions/minute) with 30s recoveries over a 4 to 5-week period. The outcome, relative to a group who had continued with the usual training, was a highly significant increase in test measurements, i.e. mean power during a 1km time trial (+8.7%); mean power 4km (+8.1%); peak power (+6.8%); lactate profile power (+3.7%) and oxygen cost (-3.0%). Quite startling results and a clear message to already well-trained cyclists - the addition of explosive and high-resistance interval training to your program will produce major gains in sprint and endurance performance partly through improvement in exercise efficiency and anaerobic threshold.
The second looked at the effects of an off-season, 5-week jump squat intervention program, on strength and power in experienced resistance-trained college football players. Both concentric and eccentric phases of the activity were emphasized in different groups versus a control group. There were no significant differences between the groups before the study commenced in terms of power, vertical jump height, 40-yard sprint speed and agility. After the study, the group who had performed both concentric and eccentric training showed significant gains over the control group in their 1RM squat (65.8kg vs 27.5kg) and the power clean (25.9kg vs 3.8kg). The group that had only performed concentric jump squat training showed no more measurable improvement than the control group. It was concluded that coaches could expect to see significant improvement in a relatively short time scale in off-season performances when combined concentric/eccentric jump squat training is incorporated into the training plan.
A further paper went on to compare recovery periods (10 or 30 seconds) with physically active men performing 2 maximal multiple cycle sprints (20 x 5 seconds). The longer recovery periods lead to significantly higher measures of maximum (ca. 4%) and mean (ca. 26%) power output. Also, significantly lower levels of fatigue were recorded with the longer recoveries. Blood lactate, as expected, increased through both protocols but was significantly lower at the end of the longer recovery period session. All of these factors need to be taken into account by coaches and sports scientists when assessing athletes.
Finally, the challenge many coaches face is balancing the advantages and perceived disadvantages of different forms of fitness component training. For example, it is a common concern with many coaches that resistance training affects flexibility - either positively or negatively. An elegant piece of research that studied the effects of resistance training found that resistance training either alone or in combination with appropriate flexibility training improved muscle strength but did not change flexibility on its own. Flexibility increased with specific training alone or in combination with resistance training. Resistance training, in this twice a week for 12-week long intervention did not interfere with the increase in joint range of motion during flexibility training. An obvious conclusion here is that particular training must be performed to increase specific fitness components. Moreover, a balanced approach will lead to a balanced athlete.
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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.
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