Effects of Sitting versus Standing after an Active Warm-Up on Vertical Jump Performance

Corresponding and First Author: H. Scott Strohmeyer, Ph.D.
Morrow 137
Department of Nutrition and Kinesiology
University of Central Missouri
Warrensburg, MO 64093
660-543-8191
strohmeyer@ucmo.edu

H. Scott Strohmeyer is a Professor in the Department of Nutrition and Kinesiology at the University of Central Missouri in Warrensburg, MO.

Second Author: Jean Eckrich, Ph.D.
Exercise and Sport Sciences Department
541 Main Street
Colby-Sawyer College
New London, NH 03257
603-525-3448
jeckrich@colby-sawyer.edu

Jean Eckrich is a professor in the Exercise and Sport Sciences Department at Colby-Sawyer College in New London, NH.

ABSTRACT
There is significant interest concerning the effect of various warm-up protocols on performance. Efforts also have focused on warm-up decrements that occur with sports that have a halftime such as soccer or wait times associated with swimming events. However, player substitutes in many sports have significant periods of inactivity after the warm-up prior to their entry into competition. In some sports, the practice is for players to sit when not in the game, while other sports have substitutes stand. The evidence to determine if there are differences in performance based on sitting versus standing is lacking. Therefore, the purpose of this study was to compare the effects of standing versus sitting over time on vertical jump performance after an active warm-up period. Thirty-five participants participated in three different testing sessions where they were to stand, sit, or continue exercising after their warm-up. Treatment order was randomly assigned. Following warm-up, baseline standing vertical jump data for that testing session was collected. Standing vertical jump performance was then tested every 10 minutes for an hour to track performance degradation for a total of seven vertical jumps each session. Repeated measures found no differences at baseline or 10 minutes across conditions. However, there were significant differences at 20, 30, 40, 50, and 60 minutes with the vertical jump performances for the exercise condition better than the sitting or standing conditions. No differences in vertical jump performances were found between sitting and standing trials. While there are other measures to consider, these findings failed to find differences between sitting and standing on vertical jump performances after an active warm-up.

Keywords: Warm-up decrement, vertical jump performance

INTRODUCTION
Coaches and researchers alike seek to enhance the performance of athletes. One area of examination has been the role of the warm-up protocol prior to activity. While dependent on the intensity, duration, and type of warm-up, some consistently found benefits of active warm-ups and have included various physiological, psychological, and biomechanical responses such as increased muscle temperature (2, 11), enhanced blood flow (2, 11), reduced muscle stiffness (13), and faster nerve conduction (2). An active warm-up also is believed to increase metabolic reactions (3, 6) and biochemical processes (6) as well as psychological arousal (1, 2).

Many efforts have focused on the effects of different types of warm-ups on various performance measures. A particular performance measure that has been examined is the vertical jump. Bishop (2003b) concluded that an active warm-up has the potential to enhance performances of less than 10 seconds if there is ample time for necessary phosphate energy stores to be restored prior to the activity. Padaduan, Pojskić, Užičanin, and Babajić (2012) examined the effects of six different warm-up protocols on a countermovement jump of football players. They found that performances were significantly better after a general warm-up, which included jogging, and a general warm-up with dynamic stretching than jump performances after no warm-up or a warm-up involving static stretching. Krčmar, Šimonek, and Polačkova (2016) also examined vertical jump performance and found that the dynamic warm-up strategies enhanced vertical jump performance in comparison to a control protocol. Sotiropoulos et al. (2010) found that warm-ups, including low and moderate intensity half-squats, enhanced vertical jump performance. In contrast, Knudson (2001) did not find that stretching alone had an impact on vertical jump kinematics.

Given the considerable evidence in support of a proper warm-up, many situations have delays, such as half-time, and rituals before the start of competition. Passive half-time scenarios have been found to be detrimental to the first few minutes of second half performances (or performance measures after an equal amount of time) in soccer players as well as referees (4, 10, 12, 14, 19).

While a warm-up decrement has been established, the impact of different lengths of time between the warm-up and performance is less definitive. International level swimmers are required to enter a call room 20 minutes prior to their event. West et al. (2013) found that 200 meter freestyle performances were better 20 minutes post warm-up in comparison to 45 minutes post warm-up. Substitutes in sports such as volleyball, basketball, soccer, and lacrosse may have longer waits than a half-time. It was found that vertical jump decreased and sprint times were increased in a linear trend when basketball players were inactive over periods of 10, 20, 30, and 40 minutes (5). For short term performance benefits, Bishop (2003b) stated that post warm-up intervals should be more than 5 minutes but less than 15-20 minutes.

In addition to the importance of understanding more about the performance decrement that occurs with progressively longer passive wait periods, it also is important to understand the impact of different practices for substitutes associated with various sports. For example, basketball substitutes generally sit during the game. However, in recent years, more and more volleyball players are standing at the end of the bench during play. In fact, the USA Volleyball blog (7, 17) had a discussion on why many teams have had their players change from sitting to standing. The analysis focused on the muscular activity required while standing versus sitting with the hypothesis that any differences in neuromuscular activity would be inconsequential. To date, there has been no systematic evaluation of performance of volleyball players after periods of rest similar to those seen during match competition. Therefore, the purpose of this study was to determine if there were differences in vertical jump performances, across time, for individuals who sat, exercised, or stood between testing bouts after an active warm-up.

METHOD
Participants
Thirty-five students who were enrolled as majors or minors in a physical education program at a Midwestern institution participated in this investigation which included three testing protocols. All subjects were free of musculoskeletal injuries for the previous year. All signed an informed consent prior to testing.

Instrumentation
Vertical jump height was assessed utilizing a KistlerTM Force Platform. Data were collected at a rate of 600Hz. Vertical jump heights were calculated from the force records for time in air using dv = vit + 1/2agt2 (where dv = vertical jump height, vi = initial vertical velocity, ag = acceleration due to gravity, and t = ½ time in air).

Protocol
There were three testing dates, for each participant, which involved the assessment of an initial maximum vertical jump following an active warm-up which was again assessed over six different time periods after a sitting, standing, or exercise period (see Figure 1). Treatment order was randomly assigned.

Figure 1 - Flow Chart

Self-selected warm-up procedures were used for the investigation. All participants warmed-up under the supervision of the same investigator until they had broken a sweat and then performed a maximum standing vertical jump. Standing vertical jump performance was then tested every 10 minutes for an hour to track vertical jump performance. Each participant was given one opportunity for a maximal effort vertical jump at each testing session. A second opportunity was only awarded if the individual indicated that they really did not feel like it was a maximum effort vertical jump or they missed the force platform upon landing. Including the baseline jump, seven vertical jumps were collected for each session.

Regardless of testing protocol (i.e., sitting, standing, or exercising) for the session, each participant watched a video of an intercollegiate volleyball match projected onto a wall during the interval between test jumps. The standing and sitting sessions consisted of watching the volleyball match, in their respective postures, between data collection bouts. The exercise group executed a protocol designed to maintain a mild sweat throughout the one-hour data collection session. The exercise protocol consisted of 20 step-ups with a right foot lead onto a .15m high step, 20 step-ups with a left foot lead onto a .15m high step, an 80m brisk walk, and 20 small jumps executed in place. The routine was repeated continually for the 60-minute session. Aside from the 80m walk, the exercise group also watched the volleyball match video during each 10-minute increment.

RESULTS
A two-way repeated measures ANOVA was run to determine the effects that sitting, standing, or exercise had on vertical jump performance over time. Analysis of the studentized residuals showed that there was normality, as assessed by the Shapiro-Wilk test of normality and that there were no outliers, as assessed by no studentized residuals greater than ±3 standard deviations. Mauchly’s test of sphericity indicated that the assumption of sphericity had been violated for the two-way interaction, χ2(77) = 127.397, p < .05. Therefore, further analysis of the interaction effect was based on the Greenhouse-Geisser adjustment which identified a significant two-way interaction of conditions by time, F(7.56, 256.88) = 4.912, p < .0005 (see Figure2). Based on the interaction effect, simple main effects were run. Figure 2 - Vertical jump performance

Effects of Conditions at Each Time Period
For the analysis of any differences at each time period, significance was set at p < .01 because of the multiple analyses. There were no differences across conditions in vertical jump performance at baseline, F(2,68) = .497, p = .611, or at 10 minutes, F(2,68) = 4.082, p = .021. At 20 minutes, there were significant differences across conditions, F(2,68)=14.591, p <.0005, at 30 minutes, F(2,68) = 23.602, p < .0005, at 40 minutes, F(2,68) = 18.715, p < .0005, at 50 minutes, F(2,68) = 21.862, p < .0005, and at 60 minutes, F(2,68) = 28.095, p <.0005. In all cases, the exercise group performed better than the standing and sitting groups while there were no differences between the sitting and standing groups. See Table 1 for means and standard deviations. Table 1 - Vertical Jump Height

The Effect of Time for Each Condition
The effects of time were analyzed, for each condition, and significance was set at
p < .015 because of the multiple analyses.

Standing
For the standing condition, sphericity was violated as assessed by Mauchly.’s test of sphericity, χ2(20) = 55.887, p < 0005 and the Greenhouse-Geisser adjustment was made. In the standing condition, there were significant differences across time, F(4.095, 139.222) = 19.358, p < .0005. Significant differences were found between the baseline vertical jump and jumps at 20 minutes (p = .001), 30 minutes (p < .0005), 40 minutes (p < .0005), 50 minutes (p < .0005), and 60 minutes (p < .0005). See Table 1 for means and standard deviations.

Exercise
In the exercise condition, there was a significant differences across time, F(6, 204) = 4.132, p = .001. The difference was found between the baseline vertical jump and the vertical jump at 40 minutes (p = .011). There were no differences between the vertical jump at the other time intervals. See Table 1 for means and standard deviations.

Sitting
For the sitting condition, sphericity was violated as assessed by Mauchly.’s test of sphericity, χ2(20) = 42.247, p = .004 and the Greenhouse-Geisser adjustment was made. There were significant differences found across times, F(4.339, 147.520) = 28.253, p < .0005. Differences were found between the baseline vertical jump and the vertical jumps at 10 minutes (p < .005), 20 minutes (p < .005), 30 minutes (p < .005), 40 minutes (p < .005), 50 minutes (p < .005), and 60 minutes (p < .005). See Table 1 for means and standard deviations.

DISCUSSION and CONCLUSIONS
The purpose of this study was to determine if there were differences in vertical jump performances, across time, for individuals who sat, exercised, or stood between testing bouts after an active warm-up. Performers were tested every 10 minutes after an active warm-up. Decrements in vertical jump performances were found across the three conditions (sitting, standing, exercise) with sitting and standing differing from light exercise while there were no differences between sitting and standing. These differences across conditions were found at all points after the assessment at 10 minutes. These decrements are consistent with findings in swimmers, soccer players, soccer referees, and basketball players (4, 5, 10, 12, 14, 18, 19). In addition, the decrements occurred at the 20-minute mark which is consistent with the recommendation of Bishop (2003b) that the time from warm-up to performance should be less than 15-20 minutes. However, there has not been evidence to date to support whether these changes differed between sitting and standing.

In addition to the comparison across conditions, each condition was analyzed separately. A difference in performance was found between baseline and for every time frame thereafter when sitting while these differences were found between baseline and every time frame beginning with 20 minutes when standing.

Currently, substitutes in many sports have significant waiting periods between their warm-up and entry into competition. The pre-competition rituals of announcing a line-up and playing of the National Anthem can take up to 10 minutes. In addition, other sports have delays which are required such as international swimming which has a holding room that athletes need to report to prior to their event. The strategies that most substitutes use involve the athletes sitting as in basketball or standing as do many volleyball players. These findings challenge the efficacy of these options with regard to performance outcomes as assessed by a vertical jump. Light physical activity maintained performance measures in this study.

These decrements of .03 meters or more, which are evident for the sitting and standing conditions as early as 30 minutes, are important performance measures. Those differences certainly have the potential to differentiate between a successful or unsuccessful block in volleyball or the height angle that a hitter has when hitting.

One performance measure was used to assess differences between sitting and standing after an active warm-up. It may be appropriate to examine the effects of sitting and standing on other physical performance measures such as agility as well as with psychological measures such as arousal and attention. Participants in this investigation commented that standing made them feel more ‘stiff’. In addition, it would be advisable to see more evidence about the length and type of physical activity that would be most beneficial for those with substantial periods of time prior to physical activity.

APPLICATIONS IN SPORT
Current practices in sport which include wait times between an active warm-up and performances are not supported. Challenges with facility set-ups and current regulations in some sports make it difficult to provide opportunities for athletes to maintain light physical activity or to get some movement prior to entry into a competition. While many volleyball programs have moved to allowing substitutes to stand, evidence suggests it is not sufficient to maintain performance. Coaches should develop strategies to maintaining post warm-up gains with the bench players as well as assuring that athletes in any sport with substantial breaks in play such as a half-time have time to get light physical activity before resuming play.

ACKNOWLEDGMENTS
None

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