What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
Elastic band resistance was used in conjunction with free weights in this paper to investigate the potential impact on peak force (PF), peak power (PP) and peak rate of force development (RFD) while performing the back squat exercise. Testing was performed at 60% and 85% of 1RM (determined using a Smith machine) both with and without elastic bands and at two different elastic band settings - 20% and 35% of the total load. The results showed that PF increased by 16% at 85% 1RM when the bands contributed 15% of the load. When the band component was increased from 20% to 35%, also at 85% 1RM, there was a further increase of 5% in PF. The overall gain in PP from 0% to 35% band contribution, while also working at 85% 1RM, was 24%. No changes were measured in RFD under these conditions. These results suggest that increases in both PF and PP can be seen, when working at 85% 1RM, if a component of the resistance is provided by elastic bands as compared to working with free weights only. The use of so-called variable resistance training may be useful in developing both PF and PP without recourse to larger training volumes. This may be particularly useful during competition phases when power output needs to be maximized while resistance-training volumes are kept under tight control.
Skill-based conditioning games are more effective than traditional conditioning activities in improving prolonged acceleration (to 40m) and muscular power in rugby league players according to a recent paper. The study covered two groups of players in 9-week in-season training blocks in each of two different seasons comprising two organized training sessions per week. Improvement was demonstrated in 10m, 20m and 40m-sprints with the skill-based sessions but only in the 10m-sprint in the traditional conditioning approach. Both groups won 6 of 8 matches within the training period but the group undergoing the skill-based conditioning scored more points in attack and had a greater points difference. The study suggests that not only can specific fitness be improved through skill-based conditioning, but also that the associated skill practice is transferable to the match situation. This paper raised a whole series of issues in my mind, and more usefully it could be stated that practicing skills properly, as an integral part of a conditioning session, will continue to improve or reinforce existing skills while the conditioning element is also taking effect, thus yielding a double benefit. Furthermore, conditioning can be made much more 'interesting' by including relevant skill elements.
A view on maximizing the benefits of skill practice We might consider, for example, that when sprinters perform a traditional, and sometimes reluctant warm-up jog (using running skills inappropriate to sprinting), they may be better advised to warm-up with a running action more resembling a slowed down sprint action.
Interestingly, a 'poor quality' warm-up jog of as little as 5 minutes (300 seconds) will usually exceed, in terms of time, the entire time spent running 'correctly' in a sprint training session (e.g. 3 x 2 x 150m in 20s or 120 seconds). Then there is, of course, the cool down jog! The question is: Which form of practice will dominate in the learning process resulting from such a session - better jogger or better sprinter?
Coaches and athletes need to take account of the fact that all activities can potentially impact on skill acquisition and development - as far as this author is aware the body cannot differentiate between frequently performed activities that are or are not part of a specifically desired skill - both will be learned, or reemphasized, and, if there is a conflict, then the development of the desired specific skill may be compromised. So, the question in this case is: How much practice time would it take to perfect a skill if potentially conflicting skill practice was not going on in parallel? (Authors of any relevant papers can contact me with references immediately)
A batch of further papers relating to an array of factors affecting resistance training has been reviewed this month. In the first revisited the effect of rest between sets of bench presses at two different intensities of 80% (heavy) and 50% (light) of 1RM. Rest intervals of 1, 2 and 3-minutes were employed. The findings supported earlier work that 3-minutes rest lead to the retention of higher repetition of lifts. The sustainability of repetitions was not significantly different between the two resistance levels. In a further similar paper both the squat and bench press lifts were compared using 30s, 1 and 2-minute recoveries operating at the 15 repetition maximum load. Interestingly, the squat exercise lead to better recovery even between 1 and 2-minutes. However, in the bench press recovery of 2-minutes gave enhanced repetition performance. No specific explanation was suggested for this difference by the authors.
Two papers in this section examined stretching effects. In the first the acute effects of static stretching on eccentric muscle torque production in leg extensors of women was studied. The findings supported earlier studies that static stretching appears to influence concentric muscle torque specifically and appears to have no effect on eccentric muscle action. In the second the effects of stretching on passive muscle tension and the response to eccentric exercise were studied. Static and ballistic stretching protocols were employed for four weeks after specific measurements of flexibility. An eccentric activity was included in the program during the reassessment period lasting four days with repeat measurements each day.
The findings were that stretching groups had an increase in range of motion and stretch tolerance after 4 weeks of stretching, with no change in muscle stiffness or delayed onset muscle soreness. After eccentric exercise, the subjects also had greater range of motion and stretch tolerance than controls. Both static stretching and ballistic stretching increase range of motion, most likely as a result of enhanced stretch tolerance rather than changes in muscle elasticity.
Finally, leucine and whey protein supplementation effects on muscle hypertrophy were studied during an eight-week unilateral leg extensor-training program. Strength factors for both legs were measured and then established. The strength of each limb, muscle cross-sectional of the quadriceps femoris, and body composition were assessed pre-training and post-training in control, placebo and supplementation groups. The results indicated significant increases in strength for both limbs in the supplementation group but only the trained limb in the placebo group. The increase in strength for the trained limb of the supplementation group was greater than that for the trained limb of the placebo. There was no significant increase in strength for either limb in the control group. The findings suggest that leucine and whey protein supplementation may provide an ergogenic effect that enhances the acquisition of strength beyond that achieved with resistance training and a carbohydrate placebo.
Supplementation with creatine has been the subject of two further papers. In the first multiple sprint runs consisting of 15 x 30m repetitions with 35s recoveries were completed on 3 separate occasions by a group of 42 physically active men. After the first two trials groups were established and creatine supplementation at the rate of 4 daily doses of 5g for 5-days was compared to placebo group. In this experiment there were no significant differences between the two groups for fastest times, mean time, fatigue or post test lactate concentration. The authors concluded that despite widespread use as an ergogenic aid in sport, the results of this study suggest that creatine monohydrate supplementation conveys no benefit to multiple sprint running performance. In the second effects on selected factors of tennis specific training were studied including serving velocity, backhand/forehand velocity, arm and leg strength and others. Despite a six-day loading and four week maintenance regime no improvement in the factors above could be determined. Unfortunately, it was not apparent if the players underwent any specific training in this period that would have lead to strength and power development. The final outcome was that creatine supplementation is not recommended for tennis players.
Staying 'on court' a paper examined the changes in exercise characteristics, maximum voluntary contraction and explosive strength during prolonged tennis playing of up to 3-hours. It was found that progressive reductions in maximal voluntary strength and leg stiffness highly correlated with increases in perceived exertion and muscle soreness throughout the match, whereas explosive strength was maintained and decreased only after the match. These alterations may result in less efficient on-court movement and stroke production. They are, however, lower than those reported during continuous exercise of the same duration. The intermittent pattern of tennis and the numerous stretch-shortening cycle movements partly explain these results.
A question for consideration might be: Would it be possible to adapt the tactics of play to accommodate these findings in any way, or, do top players already do exactly that?
Plyometric training was compared to dynamic stabilization and balance training for there potential to impact on power, balance and landing force in female athletes. Neuromuscular training protocols that include both plyometrics and dynamic balance exercises are believed to significantly improve biomechanics and neuromuscular performance and reduce anterior cruciate ligament (ACL) injury risk in female athletes. In this study either plyometric or balance training was included as a component of a dynamic neuromuscular training program. Nineteen high school female athletes participated in training 3 times a week for 7 weeks. The plyometric group did not receive any dynamic balance exercises and the balance group did not receive any maximum effort jumps during training. Pre-training vs. post-training measures of impact force were recorded during a single leg hop and hold. Both groups increased hamstrings strength and vertical jump capability. The results of this study suggest that both forms of training are effective at increasing measures of neuromuscular power and control. Such a training combination may improve the effectiveness of preseason training for female athletes.
The effect of plyometric training on running velocity and squat jump performance was examined in pre-pubescent boys aged around 11 years. Based on an initial loading of 60 jump contacts in the initial session increasing over a period of 10 weeks to 100 contacts the outcome was that squat jump performance increased relative to the control group and sprint performance over 20 and 30m but not 10m also improved. The paper concluded that plyometric exercise could improve squat jump and running velocity in this age group but that it appeared to be limited to gains in maximal running velocity rather than acceleration.
Considering these findings I might suggest that this is because around 75% of top speed is gained in the first 10m largely due to 'explosiveness' and a dominance of 'pushing' forces. Younger children will tend to rise quite quickly during such sprint trials with an early transition to the striding phase where elastic components such as ground contact time, with a direct relation to plyometric training, will start to become more significant - thus supporting and possibly explaining these findings.
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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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