The Effect of Warm-Ups Incorporating Different Volumes of Dynamic Stretching on 10- and 20-m Sprint Performance in Highly Trained Male Athletes

Abstract

Turki, O, Chaouachi, A, Behm, DG, Chtara, H, Chtara, M, Bishop, D, Chamari, K, and Amri, M. The effect of warm-ups incorporating different volumes of dynamic stretching on 10- and 20-m sprint performance in highly trained male athletes. J Strength Cond Res 26(1): 63–72, 2012—Recently, athletes have transitioned from traditional static stretching during warm-ups to incorporating dynamic stretching routines. However, the optimal volume of dynamic drills is yet to be identified. The aim of this repeated-measures study was to examine varying volumes (1, 2, and 3 sets) of active dynamic stretching (ADS) in a warm-up on 10- and 20-m sprint performance. With a within-subject design, 16 highly trained male participants (age: 20.9 ± 1.3 years; height: 179.7 ± 5.7 cm; body mass: 72.7 ± 7.9 kg; % body fat: 10.9 ± 2.4) completed a 5-minute general running warm-up before performing 3 preintervention measures of 10- to 20-m sprint. The interventions included 1, 2, and 3 sets of active dynamic stretches of the lower-body musculature (gastrocnemius, gluteals, hamstrings, quadriceps, and hip flexors) performed approximately 14 times for each exercise while walking (ADS1, ADS2, and ADS3). The active dynamic warm-ups were randomly allocated before performing a sprint-specific warm-up. Five minutes separated the end of the warm-up and the 3 postintervention measures of 10- to 20-m sprints. There were no significant time, condition, and interaction effects over the 10-m sprint time. For the 0- to 20-m sprint time, a significant main effect for the pre-post measurement (F = 10.81; p < 0.002), the dynamic stretching condition (F = 6.23; p = 0.004) and an interaction effect (F = 41.19; p = 0.0001) were observed. A significant decrease in sprint time (improvement in sprint performance) post-ADS1 (2.56%, p = 0.001) and post-ADS2 (2.61%, p = 0.001) was observed. Conversely, the results indicated a significant increase in sprint time (sprint performance impairment) post-ADS3 condition (2.58%, p = 0.001). Data indicate that performing 1–2 sets of 20 m of active dynamic stretches in a warm-up can enhance 20-m sprint performance. The results delineated that 3 sets of ADS repetitions could induce acute fatigue and impair sprint performance within 5 minutes of the warm-up.

Introduction

The effects of warm-up on performance have been investigated since the 1930s (⁶⁶). The completion of an active warm-up before training or physical competition has typically been shown to have a positive impact on athletic performance (^10,11,26,45). Performance improvements observed post–warm-up interventions have been reported to vary from <1% to approximately 20% (³¹). A classical warm-up archetype generally includes low-intensity aerobic exercise, followed by a series of stretching routines, and finishes with a sport-specific component (⁵⁷). Traditionally, the most common type of stretching performed during warm-up is static stretching. Nevertheless, cumulative results indicate a negative impact of acute static stretching on subsequent explosive (^29,45,74) and sprint performance (^{3,13,28,33,48,60,63,73}), even when combined with an aerobic warm-up (^{6,8,12,28,37,52,70}). Recently, dynamic stretching has been recommended as a substitute to other forms of stretching and particularly to the traditional static stretching during the warm-up (^{28,29,42,46,50}). Dynamic stretching has been defined as a “controlled movement through the active range of motion for each joint” with the static dynamic stretching routines performed in a stationary position (^14,37,74), whereas active dynamic routines are completed while moving (e.g., walking or running at a jogging rate) (^26,33,50).

There is some evidence to suggest that dynamic stretching enhances power (⁷⁴), agility (⁴⁵), sprinting performance (^28,29,33,42), vertical jump height (^36,50), and electromyographic activity measured during an isometric maximal voluntary contraction (³⁵) and during vertical jump performance (²⁷). Dynamic stretching during the warm-up was found to positively affect 20-m sprint performance (²⁹), in comparison with that of the prestretch condition. Similar to these findings, Little and Williams (⁴²) found shorter 0- to 10-m, and 0- to 20-m sprint times after a warm-up that included 2 sets of 30 dynamic stretches, in comparison with static stretching and no stretching. In a further study conducted by Fletcher and Anness (²⁸), a significant decrease in 50-m sprint time, that is, better performance, was observed after warm-ups involving static dynamic stretches combined with active dynamic stretches or after active dynamic stretches (2 × 20-m distance). Additionally Gelen (³³) compared different warm-up methods, including static, dynamic stretching (2 × 15-m distance), and static stretching combined with dynamic stretching, on sprint, slalom dribbling, and penalty kick performance in soccer players. A significant improvement in all performances was obtained postdynamic stretching in comparison with the control condition, which consisted of 5 minutes of jogging.

In contrast, other investigations have found no short-term benefits linked with the use of dynamic stretching on maximal strength (⁴), vertical jump height (^13,42), and short-sprint performance (^13,25). Faigenbaum et al. (²⁵) concluded that 9 dynamic stretches performed twice over 10 yd had no effect on 10-yd sprint performance in comparison with the static stretching warm-up and a weighted vest warm-up. Furthermore, a recent investigation conducted in our laboratory (¹³) observed no effect of the completion of 4 sets of 15 seconds of static dynamic stretches during the warm-up on 5- to 10- and 30-m sprint performance in highly trained individuals. An explanation for the inconsistencies in the outcomes might be partly because of differences in the numerous potential methodological differences in the various studies such as the type of dynamic stretching performed (^26,74), the number of stretched muscle groups, the volume of stretching (number of drills performed per each muscle group), whether or not stretching was combined with sport-specific tasks (strides, agility run, hops, heavy resistance exercises), and finally, the type of power test performed poststretching.

The dynamic stretching volumes used in previous protocols have ranged from a single set of 15 repetitions (⁷⁴), to 2 (^37,59), 3 (^4,43), 6 (⁴⁹), and 7 (⁶⁹) sets of 30 seconds per muscle group, and even to 6 minutes per muscle group (⁶¹). Other studies have incorporated active dynamic drills performed at a jogging pace over 10–20 m or 10–20 yd. These drills were repeated once or twice (^25,50). Fletcher and Jones (²⁹) and Fletcher and Anness (²⁸) used 2 × 8 repetitions, and 20 repetitions, of active dynamic stretches, respectively. Because fatigue and potentiation effects occur concurrently (⁵), it would be important to compare various volumes of dynamic stretching activities to ascertain the volumes of activity necessary to ensure optimal performance enhancement and to minimize concurrent fatigue. Behm and Chaouachi (⁷) in an extensive review indicated that longer durations of dynamic stretching tend to produce more consistent performance enhancements. A series of articles that surveyed North American strength and conditioning coaches from professional sports reported average stretch repetition durations of approximately 12 seconds (²⁴), 14.5 seconds (⁶⁵), 17 seconds (²³), and 18 seconds (²²) for baseball, basketball, hockey, and football players, respectively. Thus, based on previous similar research (^{4,37,43,49,59,74}) and the typical relatively short athletic stretch duration, it is necessary to investigate short durations (i.e., 1–3 sets) of dynamic stretching within a full warm-up protocol.

It appears that the conflicting findings regarding the effects of dynamic stretching on performance may be attributed to the large range of warm-up strategies used (i.e., type of dynamic stretching, number of exercises of stretching, combination or not with a specific task warm-up). Because dynamic stretching has been recommended as an important component of the warm-up in a number of recent studies (^{2,19,33,43,47}), there is a need to ascertain a proper volume of active dynamic stretching (ADS) that highly trained sportsmen could use in warm-ups to enhance power-based performance. It is not yet clear if similar to static stretching (^39,56,76), a volume effect of dynamic stretching exists on subsequent explosive performance. Thus, the purpose of this study was to investigate the effects of 1–3 sets of ADS on 10- to 20-m sprint performance. Using a null hypothesis, it was hypothesized that the ADS protocols would have no significant effect upon 10- and 20-m sprint performance.

Methods

Experimental Approach to the Problem

This study was performed partly because of conflicting findings in the existing literature regarding the effects of dynamic stretching on skeletal muscle power. To address the hypothesis that the ADS protocols would have no significant effect upon 10- and 20-m sprint performance, the current within-subject study examined the effects of different volumes (1, 2, and 3 sets) of ADS performed during the warm-up on 10- to 20-m sprint performance. The aim of this study is to provide suggestions for an optimal, realistic warm-up procedure for highly trained, team-sport players. The experimental procedure is summarized in Figure 1. Aside from the volume of dynamic stretching, each warm-up followed exactly the same procedure. In this repeated-measures design, the participants completed a general jog/run warm-up for 5 minutes before performing 3 baseline (preintervention) test measures of 10- to 20-m sprints. Within each of the 3 testing sessions, the 1, 2, or 3 sets of 20 m of active dynamic stretch conditions (ADS1, ADS2, ADS3) were randomly assigned. Immediately after the completion of the dynamic stretching protocols, the participants performed a sprint-specific warm-up. Five minutes separated the end of treatments and the 3 postintervention measures of 10- to 20-m sprints. The order in which the subjects performed the 3 2warm-up protocols (ADS1, ADS2, and ADS3) was counterbalanced to avoid potential biasing effects associated with the test sequence.

Figure 1: Summary of research design.

Subjects

This study was conducted on 16, highly trained, male athletes (Handball n = 7, and Football n = 9) who were also sports science students pursuing degrees in Exercise Science and Physical Education at the University of Sports of Tunisia (age: 20.9 ± 1.3 years; height: 179.7 ± 5.7 cm; body mass: 72.7 ± 7.9 kg; % body fat: 10.9 ± 2.4). All the subjects were members of National Athletics clubs and had a training experience of 9.2 ± 2.3 years. The players were all starters in the football and handball competitive season when the testing was conducted. They trained 5–6 times a week (∼90 minutes per session) with a competitive match taking place during the weekend in their national-level championships. The training and conditioning routines of these athletes extensively involved sprint and sprint starts. The training sessions consisted mainly of technical and tactical skill development (80% of the training time). Physical conditioning was performed twice a week and was aimed toward anaerobic and aerobic performance development as general and specific conditioning for the respective sport activity. Anaerobic training consisted of plyometrics and sprint training drills. Aerobic fitness was developed using small-sided games and short- or long-interval running. The subjects had no history of recent musculoskeletal injury before participating in the study, and none of them were taking any dietary or performance supplements or pharmaceutical drugs that might be expected to affect performance during the study. All the subjects were free of illness during the testing period. Each participant signed an informed consent before taking part in the study, which was approved by the Clinical Research Ethics Committee and the Ethic Committee of the National Centre of Medicine and Science of Sports of Tunisia before the commencement of the assessments. During all the experimental sessions, the athletes were asked to wear the same shoes on each testing day and were given standardized instructions and verbal encouragements to perform to the best of their ability.

Procedures

The participants attended a total of 5 data collection sessions, including a 2-part orientation session. Testing procedures were performed during the second stage of the competitive season (February–March 2009). Testing sessions were conducted at the same time of the day for each subject (between 09:00 and 11:00 AM) to am ensure no diurnal variations and under standard environmental conditions (17 ± 1°C and 63 ± 2% relative humidity). The subjects were encouraged to drink ad libitum to ensure adequate hydration status. During the first orientation day, each subject was familiarized with the stretching exercises and the 20-m sprint performance measures. Each subject's data pertaining to age, height, body mass, and body fat were collected during the second orientation day. The remaining 3 sessions were completed during the course of the subsequent 9 days so that approximately 72 hours separated each test day. All warm-ups with subsequent data collection and testing occurred on an outdoor synthetic court of the University of Sports Science of Tunisia. After completing one of the warm-up conditions, the subjects proceeded to the performance testing station. The time between finishing the warm-up and beginning the sprint performance testing was approximately 5 minutes.

Warm-Up Protocol

The subjects completed the general and specific warm-up sessions collectively, with the primary investigator and 2 other associate investigators leading the 3 different stretching protocols separately in 3 groups. Aside from the volume of stretching, each warm-up followed exactly the same procedure, The subjects performed a 5-minute self-paced jog/run general warm-up followed by 4 minutes of active rest, which consisted of walking on the track and then performed the 3 baseline (preintervention) measures of 10- and 20-m sprint trials. After the general warm-up activity (jog/run warm-up for 5 minutes) and the baseline sprint tests, the 3 warm-up sessions (ADS 1–3) lasted about 15–17 minutes; 20–22 minutes; and 25–27 minutes, respectively, and included 1, 2, and 3 sets of 20 m of ADS, of the lower limbs, respectively. The participants were asked to complete 1 of the 3 designated dynamic stretching protocols (ADS1, ADS2, and ADS3) in that session. Using a random selection technique, the subjects would complete the other 2 dynamic stretching protocols in the other 2 experimental sessions. Immediately after the dynamic stretching, the subjects completed a specific explosive warm-up consisting of incremental intermittent sprints (see below) that lasted 5 minutes. Postintervention sprint measures began 5 minutes after the specific explosive warm-up.

Stretching

The dynamic stretching protocol was chosen after an analysis of the warm-up practices performed by the subjects before typical training sessions and should be considered as representing their self-selected, preferred warm-up modality. The dynamic stretch protocol incorporated 5 active dynamic exercises designed to mimic parts of the sprint cycle and to dynamically stretch the lower-body musculature mainly used in sprinting (gastrocnemius, gluteals, hamstrings, quadriceps, and hip extensors). The list, order, and description of the dynamic stretches can be found in Table 1. All the exercises were performed while walking over a distance of 20 m. The movements were carried out about 14 times for each exercise. Using a randomized selection procedure, the participants underwent the 1, 2, and 3 sets of dynamic stretch conditions (ADS 1–3), respectively, on each leg independently. A rest period of 10 seconds was allowed between sets before returning to the start position. The participants were continually instructed to maintain a vertical torso, with knees toward chest, while performing the ADS exercises. The active dynamic stretches were based on the stretching protocol used by Pearce et al. (⁵⁰).

Table 1: Dynamic stretching exercises.

Specific Warm-Up

The last component of the warm-up consisted of approximately 5 minutes of incremental intermittent sprints, which included 20 m of forward running repeated thrice at 3 quarter pace, a full pace 3 × 10 m, and a full pace 2 × 20 m with a walking back recovery. According to the recommendations of Fradkin et al. (³¹), the participants should be encouraged to end the warm-up with a period of activity similar to the activity they are to perform before beginning any athletic performance.

Sprint Measurement

Although several distances have been proposed to assess sprints in team sports, no gold standard protocol is currently available to test players in field conditions (¹⁶). The 20-m sprint performance is considered to be a relevant performance parameter important to success in all sports involving sprints (^20,27). The 20-m distance was chosen for 3 reasons: Previous sprint effort studies have employed this or a similar protocol (^27,53,67), it represents the mean sprint distance in field-based team sports (⁶⁴), and because these distances were part of the subjects' regular fitness testing battery.

Five minutes after the dynamic stretching interventions, the participants performed 3 maximal 20-m sprints on an outdoor synthetic court. Sprint performance is reported to be affected by individual running strategies and abilities (¹⁵). To monitor variation in acceleration performance during the sprint test, split sprint time was assessed at 10 m of each 20-m bout. This was achieved using photocell beams set at 0, 10, and 20 m from the start point. During the recovery period (3 minutes), the subjects walked back to the starting line and waited for the next sprint. Time was recorded using photocell gates (Brower Timing Systems, Salt Lake City, UT; accuracy of 0.01 seconds) placed 0.4 m above the ground. The athletes began each trial in their own time, from a standing start 0.5 m behind the first timing gate to avoid any reaction time effect, which could be because of a starter's instruction and also to avoid triggering the electronic gate prematurely. The subjects were asked to continue sprinting at maximum effort until the finishing timing gate. No feedback was provided to the subjects who were given standard track and field instructions during the 3 experimental conditions. Each subject wore the same spikes to each testing session. The run with the fastest 20-m time was selected, and the analysis used the affiliated split time for the 10 m. A wind gauge (Springco Athletics, USA) was positioned 1.22 m above and within 2 m of the track. Wind speed and direction were recorded at 3-minute intervals, immediately before the commencement of each ‘round’ of sprints. Wind speed was measured in meters per second in either a positive (tailwind) or negative (headwind) direction.

Statistical Analyses

Mean ± SDs were used to describe variables. A 2-way, repeated measures analysis of variance (ANOVA; 3 conditions × 2 time points) was used to determine if significant differences existed between the 3 conditions (ADS1, ADS2, and ADS3) and testing (prestretch and poststretch). If significant main effects or interactions were present, a Bonferroni post hoc analysis was performed. Effect sizes (ESs) was also calculated and reported (¹⁷) (small < 0.4, moderate = 0.4–0.70, large > 0.70). Reliability of the measures (10- and 20-m sprint times) was assessed with a Cronbach model interclass correlation coefficient (ICC) via 1-way ANOVA, with a value of 0.7–0.8 being questionable and 0.9 indicating high reliability (⁷¹), and the standard error of measurement (SEM). The SEM was estimated through the usual formula (i.e., by multiplying the SD of the scores by the square root of 1 minus the ICC; SEM = SD × (1 − ICC)^0.5 (⁷²). Statistical analyses were performed using SPSS software statistical package (SPSS Inc., Chicago, IL, USA, version. 16.0), and the statistical significance was set at p ≤ 0.05.

Results

Reliability

Day-to-day ICC as a test of reliability for the baseline measures of 10- to 20-m sprint performance were high (0.9–1.0) (Table 2).

Table 2: Test-retest reliability of tests.*

Dependent Measures

Pretest and posttest means for the dependent variables are presented in Table 3. A 2-way ANOVA (condition × time) with repeated measures indicated no significant time, condition, or interaction effect for 0- to 10-m sprint times. For the 0- to 20-m sprint time, a significant main effect for time (F = 10.81; p < 0.002) and a significant interaction effect (F = 41.19; p = 0.0001) were observed. Post hoc analysis revealed that post-ADS1 and ADS2 sprint times were similar in both conditions and superior to the ADS3 condition (Table 3). A significant decrease in sprint time (sprint performance improvement) post-ADS1 (2.6%, p = 0.001, ES = 1.17), and post-ADS2 (2.6%, p = 0.001, ES = 0.91), was determined. Conversely, a significant increase in sprint time (sprint performance decrease) post-ADS3 (2.6%, p = 0.001, ES = 1.27) was observed.

Table 3: Data in this table illustrate the mean and SDs of sprint times after the 3 warm-up protocols.*

A spaghetti graph (Figure 2) using individual subject data illustrates the lack of outliers in the data.

Figure 2: Spaghetti graph of sprint times.

Discussion

The most important findings of this study were that 1 and 2 sets of dynamic stretching (ADS1 and ADS2) led to a significant decrease in 20-m sprint time (sprint performance improvement), whereas 3 sets of dynamic stretching (ADS3) led to a significant increase in 0- to 20-m sprint time. However, we also observed that none of the 3 dynamic stretching protocols (ADS1, ADS2, and ADS3) affected 0- to 10-m sprint time.

Similar to our findings, Little and Williams (⁴²) found a significant improvement in 20-m (p < 0.0005) sprint time after an active dynamic stretching protocol, in comparison with a no-stretch condition, in 18 professional soccer players. This study used a similar dynamic stretching volume to the ADS2 protocol of the present study. Fletcher and Jones (²⁹) also showed an enhanced 20-m sprint performance (p < 0.05) when active-dynamic stretching of the lower limbs was included in a warm-up, compared with active or passive static stretching conditions. Their dynamic stretching protocol consisted of 20 repetitions on each leg, independently of the lower limbs' muscle groups, performed at a jogging pace. This duration is similar to that of the 1 and 2 sets of 20 m of ADS that the participants completed in the ADS1 and ADS2 conditions in the present study. Similar results were recently reported by Fletcher and Monte Colombo (³⁰) who showed an enhanced 20-m sprint performance using an ADS volume of 2 sets of 12 movements in comparison to an active warm-up with and without static stretching. These outcomes suggest that both 1 and 2 sets of 20 m of ADS are appropriate to perform during the warm-up to acutely enhance 20-m sprint performance in highly trained team-sport players.

Dynamic stretching has been defined as “controlled movement through the active range of motion for each joint” (²⁹). Postdynamic stretching performance enhancements have been hypothesized to be because of a number of factors such as increases in skeletal muscle perfusion caused by prior contractions and relaxation of the musculature (^42,43). Fletcher and Jones (²⁹) attributed an enhanced 20-m sprint performance postdynamic stretching practice to an enhanced musculotendinous unit (MTU) stiffness. Previous investigations have demonstrated that the amount of elastic energy that can be stored in the MTU is a function of the MTU stiffness (⁶²). A stiffer MTU has been shown to enhance the stretch shortening cycle (⁹) and to allow force to be transmitted more effectively than a compliant MTU (⁴⁰). Because sprinting requires a rapid switch from eccentric to concentric contractions (decreased amortization, transition or contact time), it is possible that a stiffer muscle observed after a moderate volume of dynamic stretching (ADS 1–2) is better able to store elastic energy in its eccentric phase. The factors allowing ADS1 and ADS2 to improve sprint performance have possibly been masked by fatigue induced by the greater volume of stretching in the ADS3 protocol.

Another possibility for the positive effect of ADS1 and ADS2 on 20-m sprint performance could be related to an enhanced intramuscular coordination. As suggested by Fletcher and Jones (²⁹), dynamic stretching exercises consist of movements that partially copy the sprint cycle, which may help proprioception and improve the lower extremity muscle coordination. Furthermore, maximal intensity strides necessitate high levels of neural activation (²¹). The muscle groups involved in sprinting must be activated at the right times and intensities to maximize speed. Therefore, the ADS1 and ADS2 conditions may have aided in optimizing the synchronization of agonist and antagonist muscle activation, hence improving movement speed during the 20-m sprint performance. Although ADS3 may have also improved the synchronization of agonist and antagonist muscle activation, it is possible that fatigue induced by the greater volume of stretching may have masked this phenomenon.

Other potential mechanisms for the improved sprint performance have been hypothesized to be because of the activation of “postactivation potentiation” (PAP) (^10,58), possibly caused by previous contraction and relaxation of the antagonists of the muscles to be stretched (^{26,33,35,43,45,74,75}). Post-PAP performance enhancement has been associated with enhanced motor unit excitability (³⁴), increased motor unit recruitment and synchronization, decreased presynaptic inhibition, or greater central activation of the motor neuron (¹). The PAP-induced phosphorylation of the myosin light chain can result in an increased actin-myosin crossbridge cycling rate (⁵⁵). It is possible that after ADS1 and ADS2 conditions, PAP-related responses could have contributed to the observed enhancements of the subsequent 20-m sprint performance.

Our findings contradict those of a recent study from our laboratory (¹³) that compared the effect of 8 different stretching protocols during the warm-up on sprint, agility, and jump performance. We found no significant effect of the completion of 4 sets of 15 seconds of dynamic stretching on 5-, 10-, and 30-m sprint performance. Contrary to the findings of this study, the stretching drills used by Chaouachi et al. (¹³) were completed in a stationary position, whereas in this study, the dynamic stretches were completed while moving (i.e., walking or jogging). This result combined with our current findings supports the recommendation of Fletcher and Anness (²⁸) that prior ADS exercises should be used for enhancing sprinting performance because they better mimic the specific mechanics of the sprint cycle.

We also observed a significant decrease in 20-m sprint performance (p = 0.02) after the ADS3 condition. This finding suggest that completing 3 sets of 20 m of dynamic active stretches per muscle group can acutely compromise subsequent 20-m sprint performance. In contrast to our findings, Manoel et al. (⁴³) found increases (8.9% at 60°·s⁻¹ and 6.3% at 180°·s⁻¹) in peak knee extension power by using a similar volume (3 series of 30 seconds) of dynamic stretching in recreationally active women. Nevertheless, it should be noted that their protocol used an isokinetic modality. As suggested by Cometti et al. (¹⁸), isokinetic tests do not replicate the same limb movements involved in sprinting. An additional study (⁴⁶) investigated the effect of dynamic stretching on golf swing performance and used a volume of dynamic stretching comparable with that of the ADS3 condition. The authors concluded that (3 × 30 seconds) dynamic stretching of the lower- and upper-limb muscle groups produced better club head and ball speeds, straighter swing paths, and more central impact points than both static stretching and no stretching. The disparity in the conclusions between our study and that of Moran et al. (⁴⁶) may be partly because of the number of stretched muscle groups and also because of the type of power performances the subjects conducted after the dynamic stretching intervention.

The warm-up protocols of this study involved 5 active dynamic stretches with a specific explosive component that incorporated incremental intermittent sprints and finished with 2 series of 20-m maximal strides, with a walking recovery. This was devised to be realistic for athletes (⁷⁶), to reproduce similar styles of warm-up protocols used in previous investigations (^14,42,50) and to cause minimal decrements to subsequent power-based performance (⁴²). Previous investigations suggested that dynamic stretches (³³), and moderate to high-intensity heavy preloaded preactivity conditioning contractions (^16,41,44,51) can increase performance via PAP. Evidence indicates that fatigue and PAP can coexist in a skeletal muscle (^5,68). The level of performance attained post-PAP treatment is thought to be the product of the balance between PAP and fatigue during the recovery phase (⁵). The level of PAP elicited is reported to depend on a number of factors such as the intensity (⁵⁴), the volume (³²) of previous conditioning contractions, and also the recovery time allowed between the preload stimulus and the performance testing (³⁸). Indeed, after the use of low-to-moderate volumes of a potentiating exercise, PAP might be induced and then used rapidly, whereas, when higher volumes are used, PAP might be temporarily obscured by fatigue in the early phase of recovery so that a longer period of rest is necessary before obtaining gains in performance (⁶⁸). Therefore, the decreased 20-m sprint performance observed after the ADS3 condition (that included the highest volume among the 3 experimental conditions) might be because of the presence of concurrent fatigue. This rest interval, that is, 5 minutes, may have not been sufficient to dissipate fatigue and to benefit from PAP. The optimal recovery period to maximize PAP manifestation in peak power output (7–8% increases) is reported to be between 8 and 12 minutes (³⁸). Therefore, if the protocol of this study had included a longer duration of recovery, we may have observed increases in 20-m sprint performance post-ADS3 condition. The specific recovery time required for different dynamic stretching volumes should be assessed and be the focus of further research to determine the optimal amount of potentiating dynamic stretching exercises to be performed by athletes and the specific rest period required before a sporting performance.

The results revealed that none of the 3 experimental conditions (ADS1, ADS2, and ADS3) had an effect on 0- to 10-m sprint performance. These findings are in contrast to those obtained in a previous investigation (⁴²) that reported an enhanced 10-m sprint performance in professional soccer players, using a similar ADS volume to the ADS2 protocol performed in the present study. Nevertheless, the subjects participating in Little and William's study underwent the 10- and a 20-m sprints separately, in contrast to the continuous 0- to 20-m sprint (with the affiliated 0- to 10-m sprint lap times) that we used in this study. This could therefore, in part, explain the contrasting results obtained in this study. Moreover, although the university physical education students participating in this study were described as highly trained athletes, they were not specifically trained as sprinters. Therefore, it is likely that any performance benefits that may have been observed after the ADS1 and ADS2 conditions were masked by incorrect technique of our subjects, which affected their ability to efficiently accelerate, in comparison to a sample of more experienced sprinters.

Practical Applications

The novel finding of this study is that, during the warm-up, highly trained sportsmen can safely use up to 2 sets of 20 m of active dynamic stretches per muscle group in sports that require short-sprint performances within 5 minutes of the warm-up. This warm-up protocol can actually improve sprint performance. This study demonstrated the existence of a volume effect linked with the completion of active dynamic stretches of the lower limbs during the warm-up on 20-m sprint performance. Performing appropriate volumes of dynamic stretching should be of paramount importance if coaches want to increase their players' power-based performance. In addition, it is advised that athletes avoid the use of higher volumes, especially when a 20-m sprint is to be undertaken within 5 minutes of the completion of the warm-up.

Acknowledgments

This study was supported by the Tunisian Ministry of Scientific Research, Technology and Development of Competences. The authors thank the staff of The Tunisian Research Laboratory “Sport Performance Optimization,” and the athletes for their participation in this study.