Typically, contemporary warm-up for team sport athletes consists of 3 phases: cardiovascular, stretching, and task-specific activity (5,19,20). However, considering that the warm-up process is often completed under time constraints, unnecessary components of this process should not be included (14). The effectiveness of using a 3-phase warm-up protocol has recently been challenged within the scientific literature. Zois et al. (20) reported that both leg press exercise and small-sided games after 5 minutes of jogging improved acute team sport performance when compared with a traditional 3-phase warm-up protocol, suggesting that a 2-phase protocol may be adequate provided specific movement patterns are included. Using leg press as a mode of warm-up activity in team sports is logistically difficult, whereas the use of small-sided games does not guarantee a homogenous response and can increase injury risk because of player-to-player contact. Therefore, alternative protocols may be more practical.
Shorter more specific warm-up protocols that include a cardiovascular phase followed only by a task-specific high-intensity phase have been reported to improve power output in rowing and cycling, respectively (12,16). Yet to our knowledge, the ergogenic effects of a short, practical, 2-phase warm-up containing only cardiovascular and high-intensity task-specific activity remain unexplored in team sports. Consequently, the question of whether a shorter 2-phase warm-up protocol more effective than a traditional 3-phase warm-up when preparing for repeated sprint activity needs to be addressed. Therefore, the aim of our study was to investigate the effect of a 2-phase warm-up on repeated sprint performance in soccer players.
Experimental Approach to the Problem
Subelite soccer players were recruited to complete 3 warm-up protocols on 3 separate days of testing. After each warm-up protocol, subjects performed a repeated sprint test, with mean and fastest sprint times being recorded to investigate the effect of the warm-up protocols on repeated sprint performance.
Eleven subelite male soccer players (mean ± SD: age 24 ± 3 years; height 181 ± 5 cm; mass 73.2 ± 4.7 kg; Yo-Yo intermittent recovery test level 1: 1,412 ± 301 m) were recruited for this study. The subjects took part in soccer training a minimum of 2 times per week. Ethical approval from the Teesside University Institutional Review Board and informed consent were obtained prior to the study.
The subjects completed the 3 warm-up protocols in a counterbalanced order with a minimum of 48 hours between each testing session. All testing sessions were completed within a 2-week period in the preparatory phase of the subjects' season. All tests were conducted at the same time of day to minimize the effects of circadian rhythm on performance. The subjects were asked to prepare for each test in the same manner in terms of nutrition and prior activity on the day of testing, while avoiding strenuous activity in the 48 hours preceding the test. The warm-up protocols were structured as follows: (a) cardiovascular phase followed by a task-specific activity, (b) cardiovascular phase followed by static stretching and a task-specific activity, and (c) cardiovascular phase followed by dynamic stretching and a task-specific activity.
The cardiovascular phase and stretching protocols were adapted from Pearce et al. (13). The cardiovascular phase of warm-up was set at a standardized relative intensity of 65% maximal heart rate (Polar RS400; Polar, Kempele, Finland), and a Yo-Yo intermittent recovery level 1 test was carried out before the testing sessions to obtain maximal heart rate. Task-specific activity consisted of two 20-m slalom runs, two 40-m shuttle sprints at 50 and 75% of the subjects' perceived maximal effort, respectively, and 1 maximal 40-m sprint. The perceived intensities were chosen to replicate the typical practice used in many soccer-specific warm-up protocols. The subjects were given a minimum of 60 seconds between the warm-up sprints and as long as they felt necessary to be fully recovered before the last sprint that acted as a criterion for the repeated sprint test. The repeated sprint test consisted of 6 × 40-m maximal sprints interspersed with 20-second recovery. This test has been demonstrated to be a reliable and valid measure of repeated sprint performance in elite, subelite, and amateur soccer players (10). On completion of the final sprint, the subjects were given 5 minutes rest before commencing the repeated sprint test. All subjects were familiarized with the test before the testing sessions. Fastest and mean sprint times were measured using single beam light-sensitive timing gates (Brower Timing Systems, Draper, UT, USA). Blood lactate samples were collected immediately after the conclusion of all tests via a fingertip capillary sample (Safety Lancets, 1.8 mm super; Sarstedt, Leicestershire, United Kingdom; Microvette CB 300; Sarstedt) and analyzed using an automated blood lactate analyzer (YSI 2300; YSI UK Ltd., Fleet, Hampshire, United Kingdom).
Data are presented as mean ± SD. Data were log transformed and then back transformed to obtain the percent difference between sprint and repeated sprint performance after the warm-up protocols. This is the appropriate method for quantifying changes in athletic performance (9). In athletic performance research, it is not known whether there is an effect but how big the effect is and use of the P value alone provides no information about the direction or size of the effect or the range of feasible values (1). Consequently, effect sizes, with uncertainty of the estimates shown as 90% confidence intervals, for the between-protocol differences in fastest, mean, and rate of change in sprint time—as calculated by the time-sprint regression slope—and posttest blood lactates were determined using a custom-made spread sheet (8). The threshold value for the smallest worthwhile change in fastest and mean 40-m sprint time was set at 0.5% (10), whereas the rate of change in sprint times and changes in blood lactates were set at 0.2 between-subject standard deviation. Inference was then based on the disposition of the confidence interval for the mean difference to this smallest worthwhile effect; the probability (percent chances) that the true population difference between trials is substantial (beneficial/detrimental) or trivial was calculated as per the magnitude-based inference approach (1). These percent chances were qualified via probabilistic terms assigned using the following scale: <0.5%, most unlikely or almost certainly not; 0.5–5%, very unlikely; 5–25%, unlikely or probably not; 25–75%, possibly; 75–95%, likely or probably; 95–99.5%, very likely; and >99.5%, most likely or almost certainly (9).
Table 1 displays the mean duration and heart rate during each phase of the 3 warm-up protocols, along with repeated sprint time and posttest blood lactates. Table 2 shows the effects of the warm-up protocols on performance, demonstrating trivial differences in mean sprint time (0.2 ± 1.4%) and posttest blood lactate (3.1%) between the 2-phase warm-up and the 3-phase warm-up that included dynamic stretching, whereas the shorter warm-up had a possibly detrimental effect on fastest sprint time (0.7%).
The short 2-phase warm-up had a small but likely beneficial effect on fastest (−1.1 ± 1.4%) and mean (−1.2 ± 1.6%) sprint time and also posttest blood lactate (13.2 ± 21.6%), when compared with the 3-phase warm-up that included static stretching. The changes in sprint time across the duration of the repeated sprint test are displayed in Figure 1.
The time-sprint regression slopes were 0.52 ± 0.22 seconds for the 2-phase warm-up, 0.54 ± 0.22 seconds for the 3-phase warm-up that included static stretching, and 0.52 ± 0.41 seconds for the 3-phase warm-up protocol that included dynamic stretching. The differences between warm-up protocols for the rate of change in sprint time were trivial.
The main finding of our study was that a short practical warm-up protocol containing only cardiovascular and high-intensity task-specific running activity demonstrated likely improvements in fastest and mean sprint time, respectively, when compared with a traditional 3-phase warm-up that included static stretching. Furthermore, repeated sprint performance after the short warm-up was unaffected when compared with the longer warm-up containing a bout of dynamic stretching, although there were possibly detrimental effects on fastest sprint time. The rates of change in repeated sprint performance were unaffected by warm-up protocol.
Our findings are consistent with recent reports demonstrating that a short duration warm-up can be more effective than longer more traditional warm-up protocols in preparation for high-intensity activity (12,16,20). The performance benefits observed in our study were supported by substantially higher posttest blood lactates, suggesting a greater glycolytic contribution during the repeated sprints (17). Many of the proposed benefits of active warm-ups have been attributed to the increased muscle temperatures achieved via active movements of the major muscle groups (3). Therefore, despite less preparatory activity (approximately 10 minutes), our short 2-phase warm-up would appear to be of sufficient duration and intensity to elicit muscle temperature-related benefits and is therefore an effective preparation for subsequent repeated sprint activity. Furthermore, the use of the shorter warm-up could help to minimize the thermoregulatory strain that is associated with longer warm-ups (12,20). Although the short warm-up had a possibly detrimental effect on fastest sprint time when compared with the warm-up that included dynamic stretching, the ecological validity of this finding is questionable as it is the ability to perform repeated sprints, which is of more relevance to physical performance in intermittent sports such as soccer (10).
Our results provide further evidence for the detrimental effect of static stretching before repeated sprint performance (2,14,15). The mechanisms responsible for impaired performance after static stretching are not yet fully understood. However, it has been suggested that these mechanisms could involve increased muscle and tendon compliance (18), reduced muscle spindle sensitivity, and inhibited neural function (6,11). Also, an impaired physiological response after static stretching cannot be ruled out, given that the slower sprint performances were associated with lower posttest blood lactates, and the ergogenic effects of increased muscle temperature include increased glycogenolysis, glycolysis, and high-energy phosphate degradation (4,7). The findings provide support for existing research advising against the use of static stretching immediately before exercise within the warm-up routine (19).
In summary, the findings of the present study demonstrate that our short, practical, 2-phase warm-up before repeated sprint activity is equally as effective as a longer 3-phase protocol containing dynamic stretching and more effective than a protocol containing static stretching.
Although it is not harmful to performance to use a 3-phase warm-up that includes a dynamic stretching phase, no further performance benefits are seen when an appropriate 2-phase warm-up is used. It appears practical for athletes to complete a 2-phase warm-up protocol that consists of a cardiovascular phase followed by task-specific activities when preparing for sports dependent on repeated sprint performance. Our findings relate also to time efficiency, as the shorter warm-up would provide more time for the training exercises and tactical preparation before competition. The reduced duration may also help athletes to avoid unnecessary increases in thermoregulatory strain during the warm-up, particularly in hot ambient temperatures. Our results also indicate that static stretching should not be used as part of a warm-up protocol but may be best used as part of a postsession or postmatch flexibility program.
The authors acknowledge the support and participation of all the volunteers involved in this study. They are also grateful to Professor Will Hopkins for his valuable assistance with the data analysis.
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