The enhancement of muscle force and power through warm-up activities is a method used by athletes, coaches, and strength and conditioning specialists to improve athletic performance. Past research has indicated warm-up methods that include high-intensity muscle contractions can elicit postactivation potentiation (PAP) that can improve performance in various activities, events, and competitions. Postactivation potentiation has been described as “previous muscular activity” that can “enhance subsequent force generation and improve strength and power performance” (9) or simply “an increase in force production after a maximal or near-maximal muscle action…” (26) or “a previous muscle contraction” that may result in “force enhancement” (2). The reason for the improved performance has been attributed to light chain phosphorylation and increased recruitment of motor units (10,19,20). Enhanced light chain phosphorylation increases the sensitivity of actin-myosin activity to Ca++, altering the structure of the myosin head and resulting in higher force production of the cross-bridges (10). It has been suggested that this mechanism is thought to enhance performance in those subjects with a high percentage of type II muscle fibers, which contribute more to powerful movements (27). A secondary mechanism that has been proposed is that increased recruitment of motor units and the resultant increase in athletic performance is accomplished with the PAP preactivity contractions by enhancing the potential at the spinal cord level that lasts for several minutes and ultimately results in greater postsynaptic potentials (19). This type of warm-up has been shown to improve performance in jumping (26,30), sprinting (22) judo fitness testing (18), swim starts (13), bench press (BP) throw (9), shot put performance (SPP) (11,12), and golf head speed (21).
There are many variables that could ultimately determine the effectiveness of PAP warm-up activities (6). One of these variables is the type of warm-up that is used to induce PAP (parallel back squats [PBSs], bench and leg press, intermittent activity, plyometric exercises, isometric vs. isokinetic muscle actions, jaw clenching, and countermovement jumps). For example, Batista et al. (2) reported that intermittent activity (1 unilateral isokinetic knee extension every 30 seconds) is an effective manner for inducing PAP and Miarka et al. (18) suggested that plyometric bench jumps can improve performance if performed before a Judo fitness test. Furthermore, Esformes et al. (9) examined the effect of isometric, concentric, and eccentric muscle actions on ballistic BP throw and found that only isometric muscle actions increased upper-body power output in competitive rugby players. In addition, many studies have used dynamic weightlifting exercises to induce PAP. In particular, the PBS has been a popular exercise used to induce PAP for a variety of performance measures such as sprint time (4,16), jump height (4,17,24), and swim starts (13). Specifically, Esformes et al. (8) compared the use of quarter squats vs. PBS on countermovement jumping and reported that PBS was more beneficial to performance than quarter squats.
Another variable that may influence the effectiveness of the PAP warm-up activity is the type of athlete performing the activity. For example, Bellar et al. (3) reported that level of strength was positively correlated with SPP after warming up with an overweight shot put implement. In addition, Seitz et al. (25) concluded that “stronger” subjects exhibited a greater PAP response when compared with “weaker” subjects. In contrast, Batista et al. (1), concluded that countermovement jump performance after a PAP inducing activity was not related to training status. It was proposed that this may be due to interindividual differences in the response to the activity used to induce PAP. In fact, some studies (1,15,17,27) have suggested that there are PAP “responders” that may benefit from exercises designed to induce PAP, whereas others may not respond, a factor that may be confounding the results of numerous investigations. Furthermore, Terzis et al. (27) has proposed that PAP may be related to the type of fiber being activated in that the percentage of type II fibers was correlated with squat underhand squat throws after performing a drop jump in moderately trained male and female subjects. Thus, subject characteristics such as training status and fiber type distribution patterns may influence the effectiveness of PAP.
Another factor that may need to be considered is gender. Rixon et al. (23) reported that isometric muscle actions evoked greater PAP than dynamic actions for countermovement jumps and that the potentiation was greater in men compared with women. However, others have reported no gender differences (17). In fact, McCann et al. (17) reported that in National Collegiate Athletic Association (NCAA) Division I volleyball players, “PAP is a highly individualized phenomenon” that is not influenced by gender. Thus, the type of athlete that may find PAP warm-up activities beneficial can vary.
Given the multitude of variables in the literature that may affect athletic performance, comparison studies are warranted. In our laboratory, we conducted multiple studies to examine the effect of PAP warm-up activities on high force/powerful performance activities in highly trained, currently competing, collegiate (NCAA Division II) athletes. More specifically, 4 separate studies were undertaken to examine vertical jump (VJP) and horizontal jump performance (HJP) in male and female track athletes (study 1), SPP in male and female field athletes (study 2), sprint performance (SP) in male football athletes (study 3), and VJP in male football athletes (study 4). Few studies have examined PAP in competitive collegiate athletes (3,11,17). In addition, no studies to the best of our knowledge have examined the effect of a lower-body vs. upper-body PAP activity on SPP. Furthermore, few studies have examined the effect of PAP in highly trained female subjects (3,11,17). Therefore, the purpose of this article is to provide a summary of 4 different studies performed in the same laboratory examining the effect of a PAP-inducing activity (PBS) of similar intensity on upper- and lower-body athletic performance in current male and female NCAA Division II athletes.
Experimental Approach to the Problem
Table 1 describes the study design, subject gender and training status, PAP-inducing activity, and the performance indicator for the 4 studies. All studies had a repeated-measures design (with and without a PAP conditioning activity) and included current male and female collegiate Division II athletes as subjects. PAP was induced with a heavy load PBS before measurement of high-force powerful performance indicators (jumping, shot put, and sprinting).
All studies were approved by the Institutional Review Board of the college. After explaining the risks and benefits of the study and allowing a period of time for questions, all subjects signed an informed consent. Subjects were all collegiate athletes who participated in regular resistance training that included specific PAP test exercises (PBS and BP) at least twice a week for the past 3 consecutive months. Whenever possible, subjects were tested at the same time of day at the same point in a given season with at least 48 hours of rest between use of the tested muscle group. In addition, testing was scheduled so that is did not conflict with training or competitive schedules and subjects were instructed to report to the laboratory in a rested state and before completing any workouts. Hydration levels and diet were not controlled; however, it was assumed that collegiate athletes have been exposed to general concepts associated with proper diet and hydration as part of their athletic and education experiences.
Twelve male (mean ± SD; age = 20.2 ± 2.0 years; height = 178.1 ± 6.2 cm; weight = 73.3 ± 6.4 kg) and 8 female (age = 20.1 ± 1.0 years; height = 169.6 ± 5.5 cm; weight = 59.8 ± 7.6 kg) NCAA Division II track athletes volunteered to participate in HJP and VJP testing. Inclusion of athletes in this group required current participation in collegiate track and field events that require powerful movements such as hurdles (n = 3), sprints (n = 17), and jumping (n = 5) events with 5 of the subjects considered as multievent athletes.
The first session consisted of an introduction to explain the purpose of the research, complete a health history questionnaire, sign an informed consent, gather height and weight data, familiarize the subjects with the VJP and HJP movements, and to perform a 1 repetition maximum (1RM) PBS Testing Protocol. After a 5- to 7-minute dynamic warm-up on a cycle ergometer, the subjects completed the 1RM PBS Testing Protocol. One repetition maximum was defined as the load that caused failure on the first repetition but without loss of proper exercise technique. To establish the 1RM load, after performing warm-up repetitions, subjects attempted 1 repetition of a perceived maximal load and, if successful, the load was increased. A 5-minute rest interval was allowed between trials, with 3–5 trials typically required for determining each subject's 1RM. Subjects had to rise without help for the PBS movement.
The second session involved testing for either VJP or HJP in a randomly assigned order. For VJP, subjects completed a 5- to 7-minute dynamic warm-up on a cycle ergometer before performing the test using a Vertec measuring system (Power Systems, Inc.), The subjects performed 2 vertical jumps (starting with both feet in a stationary position) with 1-minute rest between each jump. After the second jump, the subjects rested 1 minute, then performed 3 repetitions of a PBS at 85% of 1RM. After completion of the repetitions, the subjects rested 8 minutes then performed 2 more vertical jumps with 1-minute rest between each jump. The HJP protocol was a 2-legged standing long jump that allowed for countermovement actions of the arms and legs that was performed in the same manner as the VJP regarding timing and rest intervals. All sessions were separated by at least 48 hours.
Ten (6 men and 4 women) NCAA Division II collegiate shot put throwers (mean + SD; age = 20.6 ± 0.7 years; height = 182.1 ± 9.8 cm; weight = 102.8 ± 23.6 kg) volunteered to participate in SPP testing.
Shot Put Protocol
The first session consisted of determination of 3RM. The 3RM was defined as the load that caused failure after 3 repetitions but without loss of proper exercise technique. To establish the 3RM load, after performing warm-up repetitions, subjects attempted 3 repetitions of a perceived maximal load and, if successful, the load was increased. A 5-minute rest interval was allowed between trials, with 3–5 trials typically required for determining each subject's 3RM.
In the second testing session, subjects were randomly assigned to control (C), BP, and PBS protocols with 48 hours separating each protocol. The C protocol involved performing a standard precompetition warm-up followed by 3 maximal shot put throws with 2-minute rest between throws. The BP and PBS protocols included the standard precompetition warm-up followed by a warm-up set of 8 repetitions of the designated exercise (either BP or PBS) at 50% 3RM. After a 2-minute rest, athletes performed 3RM of the designated lift followed by 8-minute rest and 3 shot put throws with 2-minute rest between each throw. The best of 3 shot put throws from each protocol was used to make statistical comparisons.
Seven male NCAA Division II football players (mean ± SD; age = 20.4 ± 1.6 years; weight = 87.8 ± 8.3 kg; height = 184.3 ± 7.2 cm) volunteered to participate in SP testing. Subjects included defensive backs, running backs, and receivers.
Subjects were randomly assigned to 2 warm-up protocols to include a C protocol, which consisted of a 5-minute warm-up on a cycle ergometer at 25 W, 5-minute rest, 36.6-m sprint test (C1), a second 5-minute rest interval followed by a second 36.6-m sprint test (C2), and a PBS protocol, which consisted of a 5-minute warm-up on a cycle ergometer at 25 W, 5-minute rest, 36.6-m sprint test (PBS1), a second 5-minute rest interval, a warm-up of 8 repetitions at 50% 1RM squat, 2-minute rest, 3RM squat, 8-minute rest, and a final 36.6-m sprint test (PBS2). The 3RM load was determined in the same manner as in study 2.
Eleven male NCAA Division II football players (mean ± SD; age = 20.3 ± 1.8 years; height = 180.6 ± 7.5 cm; weight = 86.1 ± 12.8 kg) including running/defensive backs and wide receivers volunteered to participate in VJP testing.
Subjects were randomly assigned to 2 PAP-inducing warm-up protocols to include a C protocol, which consisted of cycling 5 minutes at 25 W, 5-minute rest, VJP testing, and a PBS protocol, which consisted of cycling 5 minutes at 25 W, 5-minute rest, 8 repetitions PBS at 50% 1RM, 2-minute rest, 3RM PBS, 8-minute rest, and VJP testing. The best of 3 VJP scores with 1-minute rest between attempts was evaluated using a Vertec measuring system. The 3RM load was determined in the same manner as in study 2.
Two-way separate (time × gender) mixed factorial repeated-measures analysis of variance (ANOVA) was used to determine differences in VJP and HJP (study 1). Follow-up analyses included paired t-tests. Paired t-tests were used to determine differences in VJP and SP (studies 3 and 4), whereas a repeated-measures ANOVA was used to analyze the SPP data (study 2). All data are presented as mean ± SD, and the level of significance was set at p ≤ 0.05. Eta-squared (η2) was used as a measure of effect size (ES) and was defined as small (η2 = 0.01), medium (η2 = 0.06), and large (η2 = 0.14).
The nonsignificant (p > 0.05) 2-way ANOVA indicated that the men and women responded similarly from PRE to POST for both VJP and HJP, thus the data were collapsed across gender. Paired t-tests revealed significant (p ≤ 0.05) increases from PRE to POST for VJP (PRE = 61.9 ± 12.3 cm; POST = 63.6 ± 11.6 cm; η2 = 0.488) and HJP (PRE = 93.7 ± 11.0 cm; POST = 95.9 ± 11.5 cm; η2 = 0.522). Figure 1 displays individual vertical jump height (cm) for each subject before (Pre) and after (Post) PBS performance. Figure 2 provides individual horizontal jump distance (cm) for each subject before (Pre) and after (Post) PBS performance.
Repeated-measures 1-way ANOVA analysis with Tukey's post hoc tests indicated that SPP after PBS (11.67 ± 1.92 m) was not different vs. C (11.77 ± 1.81), but BP (11.91 ± 1.81 m) was significantly greater (p ≤ 0.05) than both PBS (η2 = 0.490) and C (η2 = 0.164). Figure 3 displays individual shot put performance (m) for each subject after PBS for BP, and C protocols inducing PAP.
There was a significant 2-way interaction for time (time 1 vs. time 2) by treatment (C vs. PBS). Paired t-tests showed that SP was not different for C1 vs. C2, but time was significantly lower for PBS2 (4.6014 ± 0.17995 seconds) vs. PBS1 (4.6557 ± 0.19603 seconds) protocol (η2 = 0.664). Figure 4 graphically represents individual 36.6-m sprint time (s) for each subject before (PBS1) and after (PBS2) performing a PBS-inducing PAP.
A paired t-test revealed no difference in VJP for C (68.35 ± 2.16 cm) vs. PBS (68.12 ± 2.51 cm) protocol (η2 = 0.003). Figure 5 displays individual vertical jump height (cm) for each subject for the C and PBS protocols inducing PAP.
The results of the present studies are in agreement with previous research investigating the effects of PAP warm-up activities, in that, athletic performance measured by jumping, sprinting, and SPP improved in trained collegiate athletes. In study 1, we showed that VJP and HJP increased significantly in male and female track athletes with no gender differences in the response to the PAP-inducing activity. This study is in agreement with McCann and Flanagan (17) who found that a back squat enhanced vertical jump performance in NCAA Division I male and female volleyball players. However, these results do not support the findings of Scott and Docherty (24) who reported that a preactivity 5RM parallel squat did not improve countermovement and vertical jump performance. It should be noted that the subjects in this study (24) were physically active men with weight training experience but not competitive collegiate athletes. Thus, it is possible that training status could account for the lack of improvement in performance. This supposition is supported by the study of Chiu et al. (7) who suggested that athletes involved in sports requiring explosive strength (much like our subjects) would have “greater activation of the musculature involved” resulting in greater potentiation. It was also suggested (7) fatigue resistance may contribute to the PAP effect and that a 5-minute rest period, like that used in this study, was sufficient for fatigue to subside in athletic but not recreationally trained populations. Scott and Docherty (24) go on to state that the effects in their study were small and that “it is doubtful they would transfer to enhancing performance of more complex motor activities.” Although an average increase in this study of 1.7 and 2.2 cm for VJP and HJP, respectively, may not seem like a meaningful improvement, in highly competitive events with highly trained athletes, it is possible those distances could make a difference in athletic performance results, and could be beneficial to athletes who need to clear certain heights or distances (high jumpers or long jumpers). Nevertheless, coaches and athletes should individually determine whether implementing a PAP warm-up activity is a worthwhile and time-effective undertaking. This is particularly true if individual athletes do not respond with an improvement in performance after performing a PAP-inducing activity given that in our study, 4 and 5 subjects remained the same or slightly decreased in jump distance/height for HJP and VJP, respectively.
For study 2, our results revealed that a PAP-inducing upper-body warm-up activity may be better for enhancing SPP when compared with a lower-body warm-up. Specifically, our results indicated that BP (all subjects improved their performance except for 1 male thrower), but not PBS potentiates SPP in collegiate athletes preperformance 3RM BP improved SPP by an average of 0.24 m, whereas back squat decreased performance by 0.10 m when compared with the control protocol. These results are in agreement with other studies (3,11,12), in that, SPP was enhanced with a near-maximal pre-event activity. However, unlike this study that implemented a near-maximal weight lifting exercise to induce PAP, most studies examining SPP used an overweight shot put for the PAP activity (3,11,12). Thus, because shot put throw uses both upper- and lower-body muscle coordination to perform the throw, it was difficult to discern whether it was warm-up of the upper body, lower body, or both that enhanced performance in these studies. In our study, an upper-body PAP activity (BP) was the most beneficial for enhancing SPP, whereas a lower-body activity (PBS) decreased performance. Thus, it is possible that optimal SPP can be accomplished by executing a targeted upper-body warm-up activity. This inference is supported by the study of Tsolakis et al. (29), who looked at both and upper-body (BP) and lower-body (isometric leg press) PAP-inducing activity in international fencers. Much like shot putters, fencers use explosive upper- and lower-body movements that demand a unique level of athleticism. This study (29) found that power levels in the lower body decreased when a lower-body PAP activity was performed. Future studies should examine whether using a heavier shot put implement but just involving the upper body and therefore not fatiguing or potentially compromising the lower body, would enhance SPP even more. Furthermore, it should be noted that in both of our studies whereby female athletes were included (studies 1 and 2) that there was no gender difference in the response to the PAP activity. Although this is in accordance with McCann and Flanagan (17), it contradicts the findings of Rixon et al. (23) and future studies should continue to examine the effectiveness of PAP in both genders.
In study 3, our results revealed an improvement in SP for Division II football players, with all subjects showing improvement. These results are in accordance with many studies that have examined the effect of a PAP activity on SP in professional soccer players (22), recreationally active male (5) and female (16) subjects, professional rugby players (4), and elite handball players (18) with variable PAP preactivities such as squats (4,16,19), depth jumps (5), and a knee extensor isometric contraction (22). There are studies, however, reporting no effect of a PAP-inducing activity on sprint time in soccer (28) and competitive track athletes (15). Similar to our previous discussion, it was again suggested there is a large variation in individual responses and if coaches want to improve sprinting performance they “should exploit the effectiveness of different PAP protocols on an individual basis” (15). Study 4 may be an even better example of this phenomenon of “non-responders” after a PAP-inducing protocol, in that, this was the only study in this article that did not result in a significant improvement in performance. Vertical jump performance did not significantly improve in football athletes after performing a 3RM squat. However, it is important to note that in this study, 6 subjects either improved (n = 3) or showed no change (n = 3) in vertical jump, and 5 had lower vertical jump scores. Many previous studies (1,15,17,28) have noted the individualized response to PAP activity. In fact, Batista et al. (1) suggested that coaches “carefully identify” which athletes respond to a PAP activity but that there may be a psychological benefit to perform intense resistance training as a warm-up even if the athlete has been identified as a nonresponder.
In conclusion, our data show that a PBS warm-up activity results in significant improvements in VJP, HJP, SPP, and SP in NCAA Division II male and female athletes. However, there are individualized responses to this type of warm-up activity that need to be considered. Thus, it is important that strength and conditioning professionals evaluate each athlete individually to determine whether implementing a more complex training method such as PAP-inducing warm-up activities would be beneficial.
This study provides consistent results for a highly specialized population (college male and female athletes) with all testing conducted in the same laboratory, examining explosive upper- and lower-body athletic performance measures (shot put, sprinting, and jumping) thus allowing the strength and conditioning practitioner to view PAP from a broader perspective. The practical message that can be gleaned from this study is that PAP may work for many athletes, particularly when they may want that slight edge. However, complex training methods take time and effort that the strength and conditioning coach needs to consider when implementing training programs. In this article, 3 of the 4 studies discussed indicated that a warm-up activity of near-maximal back squats before an explosive activity resulted in an improvement in performance in competitive Division II male and female athletes. Strength and conditioning practitioners could potentially alter their programs to include PAP protocols to aid various athletes. However, there were nonresponders in each study, and coaches and athletes need to determine whether it is worthwhile to identify nonresponders before implementing PAP protocols.
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