Acute Effects of Different Warm-Up Protocols on ...

Pediatric Exqicise Science. 2006. 17, 64·75 © 2006 HU~ Klnelics. Inc.

with SS. There were no significant differences in AG after the 3 warm-up treat­ ments. The results of this study indicate that pre-event dynamic exercise or static stretching followed by dynamic exercise might be more beneficial than pre-event static stretching alone in teenage athletes who perform power activities.

Acute Effects of Different Warm-Up Protocols on Anaerobic Performance in Teenage Athletes Avery D. Faigenbaum The College of New Jersey

Jie Kang The College of New Jersey

James McFarland Hillsborough High School

Jason M. Bloom The College of New Jersey

James Magnatta Hillsborough High School

Nicholas A. Ratamess The College of New Jersey

Jay R. Hoffman The College of New Jersey Although pre-event static stretching (SS) is an accepted practice in most youth programs, pIe-event dynamic exercise (DY) is becoming popular. The purpose of this study was to examine the acute effects ofpre-event SS, OY, and combined SS and DY (SOY) on vertical jump (VJ), medicine-ball toss (MB), IO-yard sprint (SP), and pro-agility shuttle run (AG) in teenage athletes (15.5 ± 0.9 years). Thirty athletes participated in three testing sessions in random order on three noncon­ secutive days. Before testing, participants performed 5 min of walking/jogging followed by one ofthe following 10 min warm-up protocols: a) five static stretches (2 x 30 s), b) nine moderate-to-high-intensity dynamic movements (2 x 10 yards), or c) five static stretches (1 x 30 s) followed by the same nine dynamic movements (1 x 10 yards). Statistical analysis ofthe data revealed that performance on the VJ, MB, and SPwere significantly (p < .05) improved after OY and SOY as compared Faigenbaum, Kang, Bloom, Ratamess, and Hoffman are with the Department of Health and Exercise Science, P.O. 7718, The College of New Jersey, Ewing, NJ 08628; McFarland and Magnatta aIe with the Physical Education Department, Hillsborough High School, 466 Raider Blvd., Hillsborough. NJ 08844.

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Static stretching before participation in sports conditioning and competition is stan­ dard practice for most children and teenagers. Since static stretching can improve the range of motion in joints, it is widely believed that athletes who engage in this type of flexibility training can enhance their sports performance and reduce their risk of injury (13,17,29). The American Sport Education Program recognizes the importance of static stretching in athletic performance and recommends that young athletes perform static stretching during the warm-up phase of every training session (20). Although there is little scientific evidence documenting the injury-reducing and performance-enhancing potential ofstatic stretching (32), warm-up procedures that include static stretching have become an accepted practice in physical educa­ tion lessons and sports training programs (2,20,39). Over the past few years, long-held beliefs regarding the routine practice of pre-event static stretching have been questioned (3,32,34). Whereas long-term static stretching will increase the range of motion at a particular joint (31), some evidence indicates that an acute bout of static stretching is associated with a temporary deficit in strength or power performance (16,24,36). For example, Kokkonen et al (16) reported a significant decrease in maximal strength performance following a bout of static stretching. Young and Behm (35) also observed that static stretching had a negative influence on explosive force and jumping performance. Recently, similar findings were reported by others who noted that anaerobic performance was reduced in children and teenagers after an acute bout of static stretching (6,22,28). These findings suggest that pre-participation protocols that include static stretching might have an unintended adverse consequence on anaerobic performance in adults, as well as youth. Indeed, the President's Council for Physical Fitness and Sports reported that static stretching might compromise performance (14). Because the current practice of pre-event static stretching has been based more on intuition than scientific evidence, there has been a rising interest in warm­ up procedures that involve the performance of dynamic movements designed to elevate core body temperature, enhance motor unit excitability, improve kinesthetic awareness, and maximize active ranges of motion (19,25). This type of pre-event protocol is referred to as dynamic exercise and typically includes low-. moderate-. and high-intensity hops, skips, jumps, and various movement-based exercises for the upper and lower body. Pre-event warm-up treatments that included plyomet­ rics, heavy load resistance exercise, or maximum voluntary contractions (MVC) have been shown to positively influence muscle strength and power production in . adults (10,21,35,37). and it was recently reported that anaerobic performance in children was grea,ter after moderate-to-high-intensity dynamic exercise than after static stretching (6). Although some sport coaches suggest replacing pre-event static stretching with dynamic exercise (8.25), additional research is needed to support such recommendations. Although previous studies have compared the acute effects of static stretch­ ing or dynamic exercise on anaerobic performance in youth (6,22,28), the effects c of a warm-up protocol that includes both static stretching and dynamic exercise

representati~e of a general warm-up routine used by physical education teachers and youth coaches (20,39). The design of this protocol, however, did not allow us to isolate the independent effects of stretching on fitness perfonnance because it is· considered inappropriate to perform static stretching in a rested state without some type of aerobic warm-up. Protocol DY consisted of 10 min of 9 dynamic exercises that progressed from moderate to high intensity (Table 2). Participants performed each dynamic exercise for 10 yards, rested about 10 s, and then repeated the same exercise for 10 yards as they returned to the starting point. Participants were continually instrocted to maintain proper form and technique during the performance ofeach dynamic move­ ment. This protocol was designed to be similar to warm-up protocols typically used to prepare athletes for sports participation (19). . Protocol SDY consisted of5 min ofstatic stretching (same exercises as Protocol SS) followed by 5 min of dynamic exercise (same exercises as Protocol DY). Par­ ticipants performed only one set of each static stretch and dynamic drill, however, instead of the two Sets that were performed in protocols SS and DY.

Fitness Tests Power, speed, and agility were evaluated using the vertical jump, seated medicine­ ball toss, lO-yard sprint. and pro-agility shuttle run. Standardized protocols for fitness testing were followed according to methods previously described (12,26).

Table 2

Dynamic Warm-Up Exercises

exercises

Description

Speed skips Heel-ups In and out

Rapidly skip forward.

Rapidly kick heels toward buttocks while moving forward.

Rapidly tum toes inlheels out and toes outJheels in while hop­

piug forward.

Trunk twists

With arms behind head and body erect, rapidly hop forward l;\S hips are turned to one side then the other focusing on trunk rota­ tion. With arms extended in front of the body, lift one foot toward the extended arms and then skip as the extended leg returns to the floor as the other leg is lifted. From a standiug side stance, hop and land with feet at shoulder width and body lowered to semisquat position; move laterally while rapidly crossing feet over each other. After performiug 3 pushups, perform 3 power push-Ups by quickly pushiug your upper body off the ground and clapiug your hands.

Skipping toe touches

Drop squat/carioca

Power pUSh-Ups

Sprint series

While standiug erect., fall forward and begiu to sprint to the 5-yard mark; then accelerate as fast as possible through the 10­ yard mark.

High knee skip

While skipping, emphasize high knee lift and arm action.

The best score for two trials for each test was recorded to the nearest 0.5 em or .01 s. Briefly, the vertical jump was measured using the Vertec Jump Training System (Sports Imports, Hilliard, OR). The seated medicine-ball toss was performed with an 8-kg medicine ball (about the size of a shot-put). The participants sat on the floor with their backs against a wall and were instructed to toss the ball as far as they could with both hands (i.e., similar to a chest pass). Before each toss the ball was coated with magnesium carbonate (e.g., weightlifting chalk) so that when the ball landed on the floor it left a distinctive mark that allowed for a precise mea­ surement. The electronic Speed Trap II Timing System (Brower Timing Systems, Draper, Utah) was used to time the lO-yard sprint and pro-agility shuttle ron. For the pro-agility run, the participants started on a centerline facing the researcher. The participants sprinted 5 yards to the left, then 10 yards to the right, and 5 yards back to finish the test as they crossed the centerline. After the completion of each warm-up protocol, participants were allowed a recovery period of 1 to 2 min during which time they walked to the first testing station. The same researchers tested the same participants after each warm-up treat­ ment. All testing sessions were performed with identical equipment, positioning, technique, and test order (vertical jump, seated medicine-ball toss, lO-yard sprint, then pro-agility shuttle run). All participants rested at least 3 min between tests and completed the fitness test battery in about 15-20 min. Testing procedures used in this study were designed to be similar to fitness testing procedures used in most sports conditioning programs. All study procedures were completed within 21 days. A summary of testing procedures is shown in Figure 1. '

~ 5 Sialic SlR/dlea (2)< 30,)

~~...)I "

Figure 1-Summary of testing procedures.

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s SWic Scrclcbcs (1)erformance. It is also possible that performance on the previous fitness tests might lave canceled out the negative effects from static stretching. Our findings suggest that static stretching alone before performance of activi­ ies that require a high power output can be less effective than static stretching l.CCompanied by dynamic exercise. As such, teenage athletes should incorporate noderate-to-high-intensity dynamic exercises into their warm-up routine. In our ltudy, jumping, throwing, and sprinting performance improved about 3% after lynamic warm-up treatments as compared with static stretching. Although the mlCtiCal significance of the magnitude of the impact might be questioned, a 1% :hange in performance can have a significant impact on the outcome of a sport­ ng event, particularly in sports such as weightlifting, swimming, and track and ield. Because chronic improvements in flexibility can also be beneficial to some 'oung athletes (e.g., gymnasts), the training requirements of each athlete needs to )C evaluated individually.

A limitation of our study is that we did not have a control condition with which to compare the other warm-up treatments because it is considered inappropriate for teenage athletes to participate in anaerobic performance tests in a completely rested state. Another concern is that performance on one fitness test might have influenced, either positively or negatively, perfoffilaDce on subsequent tests. In addition, this investigation addressed the acute responses to different warm-up protocols in trained young athletes. Thus, the results of this study should not be generalized to sedentary populations because training level might affect responses to postactivation potentiation (4,10,37). In summary, this study examined the acute effects of three different warm-up protocols on anaerobic perfonnance in teenage athletes, Unique to this investiga­ tion, warm-up protocols that included dynamic exercise or static stretching fol­ lowed by dynamic exercise enhanced anaerobic performance to a greater degree than static stretching alone. Because convincing scientific evidence supporting the perfomlaDce-enhancing potential of static stretching is presently lacking, youth coaches, physical education teachers, and health care providers should consider the potential value ofpre-event dynamic exercise procedures. Future studies should look at the chronic effects ofdifferent warm-up protocols in young athletes and should examine the precise underlying neuromuscular mechanisms that might explain the performance-enhancing effects of pre-event dynamic exercise. The results from these studies will help to optimize warm-up procedures for young athletes.

Acknowledgments The authors would like to thank the administration and faculty at Hillsborough High School, Hillsborough, NJ, for their support of this research study.

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