Bruce-Low S, Smith D. Explosive Exercises In Sports Training: A critical Review.
This paper reviews evidence relating to the effectiveness and safety of explosive exercises, such as Olympic style weight lifting, other weight training exercises performed at a fast cadence, and plyometric exercises, that are commonly used in the strength and conditioning training of athletes. Contrary to popular belief and the practices of many athletes, the peerreviewed evidence does not support the view that such exercises are more effective than traditional, slow and heavy weight training in enhancing muscle power and athletic performance. In fact, such exercises do not appear to be any more effective in this regard than weight training at a relatively slow cadence, and some evidence suggests they are less so. Also, such explosive exercises do not transfer well (if at all) to athletic performance on the sports field, and present a significant injury risk. Therefore, such exercises should not be recommended in the strength and conditioning training of athletes, except those who need to learn the specific skill of lifting heavy weights fast, such as Olympic lifters and strongmen.
Strength and conditioning training is now an integral part of athletic preparation for all serious athletes and sports teams. However, the issue of how best to train to prepare for athletic competition is very controversial. Issues such as volume and frequency of training, choice of exercise and movement cadence are debated by athletes, coaches and exercise scientists.
One of the most controversial issues in this field is the use of ‘explosive’ exercises to increase strength and power. These can be defined as “resistance exercises characterized by maximal or near-maximal rates of force development or by high acceleration” (1). Typical examples of such exercises, commonly prescribed by strength coaches, are Olympic-style lifts such as the clean and jerk and snatch, and derivatives of these such as the power clean and hang clean.
Also, so-called ‘plyometric’ exercises defined as “maximal, all out quality efforts in each repetition of exercise” (2, p.69), as well as performing any weight training exercises at a relatively fast cadence, are popularly believed to be effective in enhancing strength, power and the rate of force development. This is based on the fact that muscle fiber composition provides the potential for the neuromuscular system to produce fast speeds, in particular fast twitch fibers. However, the selective recruitment of muscle fiber types is impossible (3). As such, muscle fibers are recruited by the nervous system in a logical progression according to the force requirements and not the speed of movement (3). For example, slow twitch fibers meet the demands of low muscular intensity, whereas the fast twitch fibers are eventually recruited when the other fatigue resistant fibers are exhausted. Therefore slow twitch fibers are recruited first and fast twitch last and there is no definitive proof that undertaking explosive tasks will by-pass this process (3). Interestingly, Fleck & Kraemer (5) suggest that there are exceptions to the recruitment order by size when very high velocity movements are undertaken, although they provide no research data to support this claim.
The National Strength and Conditioning Association (NSCA), a prominent certification organization, recommends all of the above exercises for adult athletes (1). In addition, a recent position statement of the American College of Sports Medicine (6) suggested that explosive lifting was an effective way to enhance athletic performance. Many popular strength and conditioning textbooks also support this statement (e.g. 5). However, this view is not universal, and some authors advise athletes to avoid power cleans and other Olympic lifts due to question marks over both their effectiveness and safety (e.g. 3, 7). Indeed, two recent reviews (8, 9) have claimed that the research support for explosive training protocols is equivocal at best.
Somewhat surprisingly (given the importance of this topic for exercise scientists, strength and conditioning professionals and coaches) the peer-reviewed empirical research on this topic has never been systematically and comprehensively examined in a paper devoted purely to this purpose. Therefore, the aim of the current review is to examine the effects of explosive training protocols, including Olympic lifts and their derivatives, plyometrics and other weight training exercises performed with a relatively fast cadence on muscle strength, power and sports performance.
The evidence relating to the effects of these methods on muscle strength and power compared to slow and controlled weight training, the transfer of such training to enhanced performance on the sports field, and the injury risks from such training, will be examined. Evidence-based recommendations will then be given regarding the use of such training protocols to enhance sporting performance. The studies discussed in this review were discovered via a comprehensive literature search that included searches of relevant databases as well as searches of recent exercise physiology journals, searches of the reference lists of all the articles read, and internet searches.
2. EFFECT OF EXPLOSIVE EXERCISES ON MUSCLE STRENGTH AND POWER.
Given the rather strident manner in which many weight training authorities promote the use of explosive exercises (e.g. 1), it seems reasonable to assume that a strong body of scientific evidence must have been built up to support their use. However, one of the most striking results of our literature search was the relatively small number of studies that have actually tested the effects of explosive exercises, and the even smaller number of studies that have compared their effects to that of the slow, controlled weight training advocated by some authors (3, 10, 11). However, the studies that have been completed have produced some very interesting findings. For example, LaChance and Hortobagyi (12) compared the effects of repetition cadence on the number of push-ups and pull-ups subjects could complete. They found that subjects could complete fewer repetitions when performing two-second concentric and two-second eccentric muscle actions than when performing fast, self-paced repetitions, and that they could complete even fewer repetitions when performing twosecond concentric and four-second eccentric contractions. Therefore, the difficulty of the exercise decreased as repetition cadence decreased. For example, subjects performed 96% more pull-ups in 16% less time, and 145% more push-ups in 51% less time, when performing the fast repetitions than when performing repetitions with a 2/4 cadence. This suggests that faster repetitions involve less muscle tension, making it difficult to see how a faster speed of movement could be more productive.
The findings of Hay et al. (13), who measured joint torque in three males while performing biceps curls, also seem to support this view. Hay et al. (13) found that with short duration lifts (<>
Given the importance of the issue of transfer of training, Baker and Nance’s study investigating the relationship between Olympic lifting and sprint performance (22) was particularly interesting. Using trained Australian rugby league players (n = 20) they observed only weak correlations between hang clean and sprint performance (r = -0.34 for 10m sprints and r = -0.24 for 40m sprints). Therefore, the coefficients of determination (r 2) of .12 and .06 show that only 12% and 6% of the variance in the 10m and 40m sprint respectively are associated with hang clean performance. In practical terms, therefore, this shows that the assumption that there is considerable transfer from Olympic style lifting to sprint performance is incorrect; in fact, there is very little.
Several interesting studies have compared the effects of various types of explosive training, slow weight training and plyometric training (a type of training aimed at enhancing the ability of body structures to perform the stretch-shortening style, often involving depth jumps and other explosive exercises). Wilson et al. (23) compared the effects of traditional resistance training (3-6 sets of 6-10 RM squats), plyometric training and explosive training (loaded jump squats), performed twice/week for 10 weeks with experienced trainees. The traditional and explosive groups improved peak power equally on a 6 s cycle test. Both groups also increased significantly on vertical and counter-movement jump, with the explosive group increasing to a greater degree. However, the explosive group had been practicing jumping and the traditional group had not, so this was to be expected. Only the traditional group increased significantly on maximal knee-extension force. In a follow-up study, Wilson et al. (24) compared the effects of traditional weight training (squats and bench presses) with plyometric training (depth jumps and medicine ball throws). Fourteen variables related to strength and power were tested, and the traditional group increased significantly on seven variables whereas the plyometric group increased only on three. Also, both groups increased significantly on countermovement jump, with no significant between-group difference. Similarly, Holcomb et al. (25) compared the effects of resistance training and plyometric-style training involving various types of depth jump, finding no significant between-group differences in increases in jump height or power performance. These authors concluded that plyometric training was no more effective for increasing power than traditional resistance training.
Tricoli, Lamas, Carnevale and Ugrinowitsch (26) claimed that combining heavy resistance training with Olympic weightlifting improved a broader range of performance measures when compared to combining heavy resistance training with vertical jump training. The study observed increases in performance as measured by changes in a battery of tests that included sprinting (10m and 30m), agility, squat jump, countermovement jumping and half squat 1RM. However, this paper only produced two significant between-group differences, i.e. that the weightlifting group improved their 10m sprint times by 3.66% and the squat jump by 9.56% (p<0.05)>
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