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Effects of Stretching on Upper-Body Muscular Performance

Torres, Earlando M1; Kraemer, William J1; Vingren, Jakob L1; Volek, Jeff S1; Hatfield, Disa L1; Spiering, Barry A1; Ho, Jen Yu1; Fragala, Maren S1; Thomas, Gwendolyn A1; Anderson, Jeffrey M1; Häkkinen, Keijo2; Maresh, Carl M1

Journal of Strength and Conditioning Research: July 2008 - Volume 22 - Issue 4 - p 1279-1285
doi: 10.1519/JSC.0b013e31816eb501
Original Research
Free

Torres, EM, Kraemer, WJ, Vingren, JL, Volek, JS, Hatfield, DL, Spiering, BA, Ho, JY, Fragala, MS, Thomas, GA, Anderson, JM, Häkkinen, K, and Maresh, CM. Effects of stretching on upper-body muscular performance. J Strength Cond Res 22: 1279-1285, 2008-The purpose of this investigation was to examine the influence of upper-body static stretching and dynamic stretching on upper-body muscular performance. Eleven healthy men, who were National Collegiate Athletic Association Division I track and field athletes (age, 19.6 ± 1.7 years; body mass, 93.7 ± 13.8 kg; height, 183.6 ± 4.6 cm; bench press 1 repetition maximum [1RM], 106.2 ± 23.0 kg), participated in this study. Over 4 sessions, subjects participated in 4 different stretching protocols (i.e., no stretching, static stretching, dynamic stretching, and combined static and dynamic stretching) in a balanced randomized order followed by 4 tests: 30% of 1 RM bench throw, isometric bench press, overhead medicine ball throw, and lateral medicine ball throw. Depending on the exercise, test peak power (Pmax), peak force (Fmax), peak acceleration (Amax), peak velocity (Vmax), and peak displacement (Dmax) were measured. There were no differences among stretch trials for Pmax, Fmax, Amax, Vmax, or Dmax for the bench throw or for Fmax for the isometric bench press. For the overhead medicine ball throw, there were no differences among stretch trials for Vmax or Dmax. For the lateral medicine ball throw, there was no difference in Vmax among stretch trials; however, Dmax was significantly larger (p ≤ 0.05) for the static and dynamic condition compared to the static-only condition. In general, there was no short-term effect of stretching on upper-body muscular performance in young adult male athletes, regardless of stretch mode, potentially due to the amount of rest used after stretching before the performances. Since throwing performance was largely unaffected by static or dynamic upper-body stretching, athletes competing in the field events could perform upper-body stretching, if enough time were allowed before the performance. However, prior studies on lower-body musculature have demonstrated dramatic negative effects on speed and power. Therefore, it is recommended that a dynamic warm-up be used for the entire warm-up.

1Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut; 2Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland

Address correspondence to Dr. William J. Kraemer, william.kraemer@uconn.edu.

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Introduction

Stretching prior to physical activity is a common practice among athletes and fitness enthusiasts to increase flexibility (2). Numerous stretching techniques are used to increase flexibility, and the most common are static and dynamic stretching (7,19,21,22). Despite little scientific evidence, it is generally accepted that a warm-up that includes stretching improves performance and decreases the risk of injury by increasing the range of motion (ROM) about a joint (6,12,13,17,32-34).

Static stretching is the technique most frequently used to increase flexibility due to its safety and ease of use (1,2,19,20,33). The stretched position is normally held at a point of slight discomfort for 15 to 30 seconds; thus, proper static stretching does not activate the stretch reflex of the stretched muscle. Dynamic stretching consists of fast specific movement patterns that usually mimic sports activity (4). Dynamic stretching is often used in conjunction with, or in some cases in place of, static stretching. Some research data indicate that dynamic stretching can augment muscular performance (15,37), and it appears that dynamic stretching is superior to static stretching due to the close similarity to movements that occur during subsequent exercise. However, despite research that demonstrates that static stretching does little to prevent injuries or improve muscle function before exercise, it continues to be the primary choice of stretch (4).

Static stretching can increase flexibility, but it also appears to acutely impair muscular performance by reducing subsequent strength and power production (9,10,14,23,25,27,29). The mechanism for this deficit has not been fully elucidated but could be due to mechanical factors, such as changes in the viscoelastic properties of the musculotendinous unit (8-10,14,16,28,30), and neuromuscular factors, including decreased motor unit activation, firing frequency, and altered reflex sensitivity (3,5,10,16,31). Although the majority of studies show that static stretch has a negative impact on performance, it has been observed that static stretching may not interfere with performance (24,35).

In addition to the divergent findings on the effects of stretching, the vast majority of studies have examined only the effects of stretching on lower-body performance. To the authors' knowledge, only 2 previous studies have investigated the effects of stretching on upper-body muscular performance. Evetovich et al. (14) observed that static stretching hindered the force production capabilities of the isolated biceps brachii at both slow (i.e., 30°·s−1) and fast (i.e., 270°·s−1) elbow angular velocities. In contrast, Knudson et al. (24) demonstrated that static stretching had no influence on muscular performance during a tennis serve. It should be noted, however, that the study by Knudsen et al. (24) used a total-body stretching routine and measured performance in a whole-body movement; consequently, its application to direct upper-body performance alone is limited.

Findings on direct comparisons of different lower-body stretching modalities have found either no effect (35) or a reduction in performance (15) with static stretching compared to either no effect (35) or improved performance (24,37) following dynamic stretching or warm-up. These findings indicate that sports relying on high lower-body power output, such as track and field, could benefit from a dynamic stretch or warm-up. The mechanism by which dynamic stretching improves muscular performance has been speculated by many to be due to elevated muscle temperature or postactivation potentiation in the stretched muscle caused by voluntary contractions of the antagonist. Although several studies have examined the effects of different stretching protocols on subsequent lower-body performance, no studies have examined a stretch modality on whole upper-body performance. Thus, the purpose of this investigation was to examine the influence of upper-body static and dynamic stretching protocols on upper-body muscular performance.

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Methods

Experimental Approach to the Problem

A within-subject, balanced, randomized repeated-measures design was used to test the experimental hypotheses. Eleven athletes were familiarized with all experimental tests before baseline performance was determined. The study consisted of 4 experimental sessions. At each session, subjects performed 1 of 4 different stretching protocols (i.e., no stretching [control], static stretching, dynamic stretching, and combined static and dynamic stretching) after a standardized jogging warm-up and then completed the upper-body performance tests. The performance tests consisted of bench throw at 30% of 1 repetition maximum (1RM), isometric bench press, kneeling overhead medicine ball throw, and seated lateral medicine ball throw. Three trials were performed for each test. Depending on the test, peak power (Pmax), peak force (Fmax), peak acceleration (Amax), peak velocity (Vmax), and peak displacement (Dmax) were measured to examine the effects of the different stretch protocols. For each variable, the highest value out of the 3 attempts was used for analysis.

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Subjects

Eleven healthy men (age, 19.6 ± 1.7 years; body mass, 93.7 ± 13.8 kg; height, 183.6 ± 4.6 cm; bench press 1RM, 106.2 ± 23.0 kg) volunteered for this study. Volunteers were throwers (javelin, shot put, hammer, and discus) on a National Collegiate Athletic Association (NCAA) Division I track and field team at the University of Connecticut and were concurrently participating in a preseason training program. All subjects had previous experience with the bench press and the medicine ball throws, as they were part of their prior and current training and thus limited the potential for learning effects on the outcome measures. Before participating in the study, subjects were informed of the potential risks and benefits and provided written informed consent to participate in accordance with the policies and procedures of the University of Connecticut's Institutional Review Board for use of human subjects in research. Following written consent and prior to experimental participation, volunteers were cleared for participation by a physician. Individuals were not allowed to participate if they had any pre-existing medical condition or orthopedic limitations that put them at risk while performing the testing and stretching exercises or would influence the outcome variables or if they had taken in the past 60 days or planned to take any products containing creatine, ephedra, or high doses of caffeine. None of the athletes had taken any hormonal substances, such as anabolic steroids or dehydroepiandrosterone, as these are in violation of NCAA drug policy regulations.

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Procedures

Each subject completed 6 laboratory visits: visit 1, 1RM testing and stretching familiarization; visit 2, performance testing familiarization; and visits 3 through 6, experimental protocol visits. Treatments were balanced and randomized across the experimental conditions to limit any order of treatment effects. All exercise techniques and exercise form were carefully monitored by Certified Strength and Conditioning Specialists to ensure that the tests were performed correctly and with consistent technique at all experimental visits.

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Visit 1 (Bench Press One Repetition Maximum and Stretching Protocol Familiarization)

One repetition maximum testing was performed on a Smith Machine (Norsearch Limited, Lismore, Australia), previously described in detail (36). Briefly, linear bearings attached to either side of the bar allowed it to slide vertically along steel shafts with minimal friction. One repetition maximum for the bench press was determined by using standard procedures (25). Following 1RM testing, subjects were instructed on how to properly perform each static stretch and dynamic stretch. Following instruction, both static and dynamic stretches were repeated by using the same procedures and parameters as would appear on experimental test days.

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Visit 2 (Performance Test Familiarization).

Subjects warmed up by jogging at a moderate pace for 3 minutes (i.e., approximately 400 m), which is a general whole-body warm-up typical of track and field warm-ups before any stretching protocol. They did not do any task-specific warm-up during the jogging. Participants then practiced all tests, which consisted of a 30% of 1RM bench throw, an isometric bench press, a kneeling overhead medicine ball throw, and a seated lateral medicine ball throw.

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Thirty Percent of One Repetition Maximum Bench Throw

Subjects lay flat on their back on a bench. After proper alignment was ensured, subjects lowered the bar to their upper chest and then forcefully extended their arms to release the bar at the end of the motion. The grip was standardized for all attempts and visits, and attempts were recorded only if the exercise technique was performed correctly (i.e., going to consistent depth on the down phase and not arching the back). Power and force were measured by using a force platform and associated software (AccuPower; Advanced Mechanical Technologies, Inc., Watertown, MA). Acceleration, velocity, and displacement were measured by using the computerized Plyometric Power System (Norsearch Limited), which included a position transducer and dedicated software.

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Isometric Bench Press

The bar was placed at a set height on the rack and secured so that it was immovable. All subjects were positioned on a bench press bench with their elbows slightly bent with the starting position and elbow angles kept constant for each person over the testing protocols. Subjects were instructed to press the bar rapidly to increase the force output to maximum over 2 or 3 seconds, upon a verbal cue, and to continue to press as forcefully as possible against the bar until 10 seconds past the verbal cue, when the test was completed. Bar height, grip width, and elbow angle were standardized across all testing sessions for a particular subject. Force was measured by using a force platform and associated software (AccuPower) placed under the bench.

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Overhead and Lateral Medicine Ball Throws

For the overhead throw, subjects were seated on their knees, with their arms fully extended overhead. For the lateral throw, subjects were seated in a chair with back support, with their feet flat on the ground and their arms fully extended horizontally. Subjects then performed a countermovement throw with a 3-kg medicine ball. Velocity was measured by using a Digital Doppler Radar (Stalker Professional Sports Radar; Radar Sales, Plymouth, MN), and displacement was measured as the horizontal distance from the point of release to the point at which the medicine ball touched the floor.

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Visits 3 through 6

Each visit again consisted of a standardized 3-minute jogging warm-up (approximately 400 m). Five minutes following the warm-up, subjects began the stretching protocol. Depending on the assigned intervention, subjects would perform no stretching, a static stretch for 2 sets of 15 seconds each side, a dynamic stretch for 30 repetitions per side (i.e., 60 repetitions total), or the static and the dynamic stretching protocol. The volume of stretching was inherently different based upon what may actually be done in the field situation prior to an event. The static stretches used were as follows: head side to side, overhead reach, deltoid side press, triceps square, finger interlock, side bends, and twist and hold. The dynamic stretches used were as follows: head side to side, overhead reach, crossover arm swings, triceps pyramids, overhead arm swings, side bends, and hip twists. These exercises were used to stretch the following muscles of the upper body: sternocleidomastoid, pectoralis major and minor, trapezius, latissimus dorsi, deltoids, rhomboids, teres major and minor, subscapularis, biceps brachii, brachialis, brachioradilis, triceps, serratus, obliques, intercostals, quadratus lumborum, and erector spinae. After stretching, the subjects went immediately to the testing laboratory and performed the performance tests in the following order: bench press throw, isometric bench press, overhead medicine ball throw, and lateral medicine ball throw. Each test was performed 3 times, with 5 minutes of rest between each exercise set and each individual exercise. The 5-minute rest interval was chosen since it is the typical time between warm-up and competition performance in field events (i.e., throwing). Protocol visits (i.e., visits 3-6) were separated by a minimum of 48 hours. All testing was performed at the same time each day for each subject.

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Statistical Analyses

The data were evaluated by using 1-way repeated-measures analysis of variance. When a significant F value was found, a Fisher least significant difference post hoc test was used to determine pairwise differences. Test-retest reliability values for the testing order of tests ICCRs (intraclass correlation reliability) were ≥0.92. No statistical order effect was observed in the study data. After using the nQuery Advisor software (Statistical Solutions, Saugus, MA), the statistical power for the n size used ranged from 0.80 to 0.95. The level of significance was set at p ≤ 0.05. All statistical procedures were performed by using the Statistica software package (StatSoft, Inc., Tulsa, OK). Data are presented as mean ± SD.

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Results

Results for the 30% of 1RM bench throw are presented in Table 1. There were no significant differences between stretch protocols for Pmax, Fmax, Amax, Vmax, and Dmax following each treatment. No significant differences were found for Fmax in the isometric bench press among treatments (control, 2444.9 ± 390.6 W; static, 2524.0 ± 346.7 W; dynamic, 2492.6 ± 379.0 W; combined static and dynamic, 2504.5 ± 374.4 W).

Table 1

Table 1

Table 2 shows the results for the overhead medicine ball throw and the lateral medicine ball throw. For the overhead medicine ball throw, no significant differences among trials were found for Vmax or Dmax. For the lateral medicine ball throw, no significant differences were found for Vmax; however, Dmax for the combined static and dynamic condition was significantly larger than Dmax for the static-only condition.

Table 2

Table 2

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Discussion

The purpose of this study was to examine the acute effects of static and dynamic stretching on upper-body muscle performance. These data did not support the hypothesis of a decrease in upper-body performance following static stretching, as has been previously observed with an isolated upper-body muscle testing (14). Furthermore, the findings did not support the hypothesis of an increase in upper-body performance following dynamic stretching. With the exception of the lateral throw, which showed a significant increase in Dmax in the combined static and dynamic condition compared to the static-only condition, the stretching routines had no effect on measures of upper-body performance.

The findings of this study contribute to the growing number of conflicting findings regarding preactivity stretching. However, one must always use proper context when making such decisions on how to prepare muscle for activity or performance. Power, in particular, is one of the primary performance variables that have been shown to be significantly altered due to a stretching regimen. Previous research has observed that passive stretching is detrimental to sprint times, as they were significantly increased (29), and that static stretching decreases knee concentric isokinetic peak torque in women at angular velocities of 60°·s−1 and 240°·s−1 (9). Faigenbaum et al. (15) demonstrated that performance depends upon the type of stretching being performed; vertical jump, long jump, and shuttle run performance significantly decreased following static stretching but significantly improved following a dynamic stretching routine. In contrast, no effects of stretching on vertical jump performance have been found following either static or dynamic stretching (35). From these studies, it can be observed that the evidence is variable as it relates to the acute effects of stretching of the lower-body musculature on lower-body power.

It should be noted that nearly all studies have focused on the effects of stretching on lower-body neuromuscular performance. To the authors' understanding, only Evetovich et al. (14) and Knudson et al. (24) have investigated the effects of stretching on upper-body muscular performance. It is not clear why upper- and lower-body performances would respond differently, unless it is related to the ROM and differential involvement of the stretch-shortening cycle and the series elastic component. With so few studies focused primarily upon the upper body, much more research was needed to clarify the conditions in which stretching may or may not influence performance. Thus, this study was conducted to continue and expand this line of research on stretching.

Evetovich et al. (14) observed that static stretching hindered the full capabilities of the biceps brachii at both slow (i.e., 30°·s−1) and fast (i.e., 270°·s−1) velocities during concentric isokinetic muscle actions. Conversely, Knudson et al. (24) found that while static stretching had no influence, dynamic stretching enhanced muscular performance during a tennis serve. However, a total-body stretching routine was used, and its application to direct upper-body performance is limited because the tennis serve is a whole-body-exercise closed-kinetic chain skill.

In the current study, with the exception of Dmax in the lateral throw, no significant change in bench throw, isometric bench press, or medicine ball throw performance was found among any of the stretching conditions. These results are in contrast with findings from several previous studies, which demonstrated an effect of stretching on subsequent muscle performance (14,15,24,29,35). The current study did not examine the physiological mechanisms potentially affected by stretching; however, the absence of stretch-induced effects on muscle performance may be explained by the study design.

The 5-minute rest period given between each set of exercises and each individual exercise might have been long enough to allow acute static stretch-induced physiological responses to dissipate. Depino et al. (11) found that acute increases in flexibility resulting from static stretching were transient and gradually decreased over time and were absent only 6 minutes after the stretch. Their study employed 4 consecutive 30-second static stretches of the hamstrings separated by 15 seconds of rests. Thus, although static stretching is an effective technique when temporary gains in ROM are desired, it appears not to be effective in acutely increasing connective tissue extensibility for an extended period. Any effects, positive or negative, that the stretches in the current study might have induced could have disappeared by the time of the performance testing; interestingly, this timeframe is typical of the interval between warm-up and competitive performance in field events. However, it must not be ignored that static stretching has been shown to be negative with regards to lower-body performance, and since all throws in field events utilize speed and lower-body power generation, this finding resides in context of a larger sport performance demand of the entire body, again suggesting to coaches and athletes to be weary of stretching, especially of the lower-body musculature prior to such an event of speed, strength, and power. This study indicated that time may be a potentially important factor in the dissipation of the acute potential negative effects of static stretching, and this time-to-response relationship merits further study.

An alternative view may also be taken on the current study's findings. The amount and duration of stretching in this study was chosen to mimic an athlete's typical stretching routine; however, it is possible that the duration of stretches was too short for the elastic properties of the musculotendinous unit to be altered. A 10-minute bout of stretching has been shown to increase ROM, although muscle stiffness was unchanged (18). Magnusson et al. (26) showed that 3 sets of 45-second stretches had no acute effect on the viscoelastic properties of the hamstring muscle. Furthermore, 2 15-second passive ankle dorsiflexion stretches produced no change in muscle length (38). Therefore, the quantity of stretching used in the current study (i.e., 2 sets of 15 seconds) might not have been sufficient to alter the viscoelastic properties of the muscles or to lead to acute changes in voluntary muscle activation or reflex sensitivity and thus affect performance. Nevertheless, a combined protocol that has higher volume was used and still did not show any dramatic effects. Obviously, more work as to the volume and time interactions is needed in future study designs. In addition to stretching, a proper warm-up routine usually involves various dynamic exercises that may be especially important for maximal peak power production. The current study included only a 3-minute warm-up jog prior to the stretching protocols. Many dynamic warm-up exercises are similar in nature to the dynamic stretching exercises used in the current investigation and were therefore excluded to prevent potential confounding effects.

The divergence in findings among studies examining the impact of stretching on performance may also be attributed to the training status of the study participants. All 11 participants in the current study were highly resistance-trained NCAA Division I throwers, who used medicine balls throws and static or dynamic stretches as part of their year-round sport-specific training routine. It is possible that a pre-existing training effect may exist in which these athletes were more capable of quickly recovering from any elastic component deformation during the 5-minute recovery period. Again, this line of research is filled with many different protocol variables from training status, time of stretch, amount of stretching, type of stretching, experience with stretching techniques, and integration with lower-body kinetics in whole-body performance. Furthermore, gender and age are also considerations for such work and were not addressed in the current investigation. Continued research is needed to fill the gaps in our understanding to provide for a more optimal exercise prescription to be used prior to training or competitive events. Proper warm-ups are needed to optimize training sessions and competitive results.

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Practical Applications

Collegiate field-event athletes had similar bench and medicine ball-throwing performances following a 3-minute jog warm-up and a 3-minute jog warm-up plus static stretching, dynamic stretching, or combined static and dynamic stretching, resulting in no short-term negative effects of stretching on upper-body muscular performance. However, it must not be ignored that static stretching has been shown to produce negative effects with regard to lower-body speed, power, and strength performances. Since all throws in field events utilize speed and lower-body power generation, the current findings sit in context of this larger set of sport performance demands. Therefore, coaches and athletes still need to be wary of static stretching of the lower-body musculature prior to an event or training session in which optimal strength, power, and speed are required. This study indicates that a time of 5 minutes or longer after the upper-body stretching may allow the body to dissipate any negative effects. Thus, an athlete competing in field events may elect to perform either static or dynamic stretching of their upper-body musculature during their warm-up routine, as long as adequate rest of 5 minutes or longer is allowed.

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Keywords:

power; force; static stretch; dynamic stretch; throwing

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