Swimming is a competitive event where swimmers usually perform in the preliminary swim heats early in the morning and final heats later in the afternoon. Therefore, swimming, like many other sports, requires high muscle strength, power, and endurance. Different swimming events, ranging from 50 to 1,500 m, require different training and warm-up techniques. Typically, warm-up is used before the race to optimize athletic performance by increasing body temperature, flexibility, and stimulating greater metabolic and cardiovascular changes (2,3,18,22). However, warm-up should not cause fatigue or deplete energy stores (2,18).
Two types of warm-up are commonly used: passive (increasing body temperature by external means) and active (increasing body temperature by exercise) (2). Active warm-up is widely used across sports before short-distance and long-distance performances. Short-distance athletic performance is dependent upon the availability and breakdown of high-energy phosphate stores. If warm-up is intense enough to deplete high-energy stores, it may impair subsequent athletic performance (2,18) especially when there are multiple competitions in a single day. Therefore, the recovery period after warm-up and warm-up duration and intensity may play important roles in athletic performance (2,3).
Typical warm-up distance for the majority of swimmers consists of between 1,500 and 2,200 m for short- and long-distance events (1,25). The results are inconclusive regarding whether active warm-up improves or impairs swimming performance (3). In a review article, Bishop (3) concluded that 3-5 minutes of moderate-intensity warm-up significantly improved short-distance performance, whereas, low-intensity warm-up had no effect on short-distance performance. Bobo (4)found no significant difference among 3 different types of warm-up (no warm-up, related-swimming, and unrelated dry-land warm-up) on mean or best 100-yd freestyle performance. Therefore, the effect of active warm-up on swimming performance remains uncertain. Furthermore, warm-up procedures should be evaluated based on duration, intensity, and type.
Whole-body vibration (WBV) is an emerging training method. It is hypothesized that mechanical stimulus to the muscle can be an effective way of improving muscle strength and power (7). Research results have been equivocal with the majority of studies focusing on the effects of WBV on strength training (19), sprint performance (13), muscle activity (6), vertical jump (10), flexibility (11), and agility of the lower body (10). A proposed mechanism for the effect of WBV is increased gravitational load and acceleration forces causing the muscle to lengthen and subconsciously contract (7). Therefore, more muscle fibers are used, and a more forceful contraction may be produced (7).
Only a few studies have been completed using upper-body vibration (UBV) (as opposed to WBV). Bosco et al. (6) found a significant increase in average electromyographic (EMG) activity during UBV and a significant increase in mechanical power during max dynamic elbow flexion. However, Cochrane et al. (9) found no significant treatment effect of UBV in medicine ball throw and hand grip strength. Therefore, based on the findings, it is difficult to determine whether UBV affects performance.
To optimize swimming performance in Masters Athletes, training methods and warm-up techniques should be optimized. There is little research available on Masters Swimmers and optimal warm-up techniques. This question is important because it leads to the possible implementation of UBV in training and competition warm-up routines. For athletes with multiple competitions in a single day, the most effective warm-up that preserves total energy and performance capabilities is desirable. The information obtained from this study could benefit athletes and coaches and may provide new and improved warm-up routines that could be used as an addition or alternative to the traditional methods.
Muscle strength and power are very important factors determining swimming performance. Upper-body vibration used as a warm-up strategy might affect swimming performance because of its ability to activate multiple motor units with minimal fatigue generating a more forceful contraction (6). Thus, the purpose of this study was to evaluate the effects of 3 different types of warm-ups (regular warm-up, UBV + short warm-up, and UBV-only) on swimming performance in Masters Swimmers. We hypothesized that UBV and short warm-up or UBV-only would provide benefits greater than or equal to regular warm-up on swimming performance. In addition, we hypothesized that the stroke count would decrease after UBV and short warm-up or UBV-only because of the proposed mechanism of increased neuromuscular stimulus, increased muscle activation, and generation of more forceful contraction (6) thereby increasing the length of the stroke.
Experimental Approach to the Problem
Brief exposure to low frequency WBV has been shown to enhance strength and power in athletes (6,12,17). However, to this date, the research has not considered the acute effect of UBV as a warm-up routine to enhance performance of competitive swimmers. Therefore, the aim of this study was to evaluate the benefits and effects of different types of warm-ups (regular warm-up, UBV + short warm-up, and UBV-only) on swimming performance in Masters Swimmers. Optimum performance may be achieved with a proper warm-up routine that prepares an athlete for a race. The “regular” swimming warm-up routine is widely accepted and commonly used among competitive swimmers before a race. In addition, mechanical stimulation via vibration has been used as an alternative or addition to the traditional warm-up routines before strength training and other exercise programs (14,24). In the present study, UBV was performed for 5 1-minute sets based on previous investigations (6,12). Each participant completed performance trials in counterbalanced order, separated by at least 48 hours between each performance trial. Testing sessions were completed between 6 am and 12 pm. After the arrival to the swimming pool, participants completed the assigned warm-up for the session (regular, UBV-only, or UBV + short warm-up), then rested for 3 minutes, and then completed the 50-yd maximal performance time trial. Heart rate (HR) and rating of perceived exertion (RPE) were obtained right after the warm-up and 50-yd maximal performance time trial to evaluate perceived and actual intensity of the warm-up and time trial. Time and stroke count were recorded to evaluate the effectiveness of the warm-up routine. During the 3 minutes of rest, participants were allowed to put on caps and goggles, stand, sit, walk, and talk as they would do during a competition before the race.
The time trial distance of 50 yd was selected to more sensitively detect differences because of warm-up. That is, it would be expected that swimmers would be warmed-up after 50-100 yd of swimming even with no warm-up. Normal variations in swim performance at longer differences would tend to dilute any impact of warm-up. We felt that a short swim provided the best test of warm-up effect.
The participants of the study were 4 men and 6 women healthy Masters Swimmers between 24 and 50 years of age. The study was conducted in March and April during the active training season. To ensure that participants were trained swimmers, all participants had to have practiced at least 3 times per week for at least 6 months before the start of the study. All of the participants reported to be skilled swimmers with no <3 years of experience (Table 1).
The protocol and informed consent forms were prepared according to the guidelines of the local Institutional Review Board for the protection of Human Participants and approved before the study. Before providing written consent to participate, the purpose of the study and performance trials was explained, different types of warm-up were introduced, and health risks and benefits were explained to participants. Participants were asked to complete the Physical Activity Readiness Questionnaire, current health status questionnaire, and training status questionnaire before the study. In addition, participants were asked not to participate in physical activity and to avoid alcohol and energy drinks at least 24 hours before each test session. Only trained athletes participated and none of the requirements of this study, save the brief exposure to vibration, exceeded their normal efforts in swim training. There were no previous studies that reported any serious adverse effects of vibration (8,21).
Participants were excluded from the study if they met any of the following criteria: the participant was younger than 24 or older than 50 years; recently had a shoulder injury; screening forms indicated any previous cardiovascular, respiratory, or other major chronic diseases; participant had any type of surgery or injury that may have increased their risk of exercise participation; or participant had not practiced at least 3 times per week for at least 6 months before the start of the study.
Descriptive data including age, weight, and height were collected. The participants wore only a swimsuit during the weighing procedure. Participants' height was self reported in inches and converted to centimeters. Body composition was assessed using a skinfold caliper (LANGE, Beta Technology Incorporated, Cambridge, MD, USA). Skinfolds were measured at the thigh, chest, and abdomen for men and at the superiliac, triceps, and thigh for women (15,16). Three measures were taken at each site, and the average of the 3 was recorded. Sum of skinfolds was calculated by adding the averages of the 3 measurements. Body fat was estimated using sum of skin folds and age (15,16). Years of swimming experience, current training status, preferred stroke and distance, best 50-yd time, and prior upper-body injury were assessed using a training status questionnaire. Also, participants were verbally introduced to the 3 different warm-up types and testing procedures.
Regular warm-up: Participants completed their own swimming competition warm-up with no limits on distance, which was no <500 yd and included at least 2 25-yd sprints at 90% of their maximal effort.
Upper-body vibration + short warm-up: The participant completed a 100-yd freestyle swim. Fifty yards was completed at 40% of their maximal effort and 50 yd at 90% of their maximal effort. After the short warm-up, participant performed UBV for 5 sets of 1-minute each, with 1 minute and 15 seconds rest between sets.
Upper-body vibration-only warm-up: the participant performed UBV for 5 sets of 1-minute each, with 1 minute and 15 seconds rest in between sets.
Upper-Body Vibration Treatment
Vibration treatments were completed on a swim bench (Vasa Trainer Pro, VT, USA) with an attached UBV device (Figure 1). The swim bench was locked at an incline position. Participants kept both hands on the UBV device (American Prototype build based on Russian model, USA Swimming, Colorado Springs, CO, USA) and applied pressure. Participants were required to maintain proper technique by keeping elbows high and aligned with the shoulder. Each participant was exposed to 5 1-minute vibration sets, with 1 minute and 15 seconds of rest in between sets. This was similar to the protocol of UBV used previously during arm flexion exercise at a vibration frequency of 30 Hz (6) and during upper-body exercises at vibration frequency of 26 Hz (9). Duration of the total vibration treatment in the present study was 5 minutes with a frequency fixed at 22 Hz. Lower frequency was chosen because it is the most common application of UBV used by local USA swimming coaches in the rehabilitation and training programs.
Maximal Performance Time Trial
Participants completed 50-yd of freestyle swimming. The 50-yd freestyle required a flip turn because the short course (25-yd) pool. Master swimmers are trained and adept at flip turns with competitions held in short course pools. The 50-yd time trial was used as opposed to the longer event, which might have diminished any effect of the warm-up because of multiple laps and flip turns. Two people with identical digital stopwatches timed the performance trials, and the average of the 2 trials was recorded to give a mean performance time. Swim times were recorded to the nearest 0.1 second. To start a time trial, the following verbal command was used, “Take your mark” and “Go.”
Warm-Up Session and 50-yd Freestyle Time Trial Rating of Perceived Exertion
After each warm-up and performance time trial, participants were asked to rate their perceived exertion (RPE) on Borg's 15 point scale (6-20) (5). Each participant was visually and verbally reminded of Borg's scale after each warm-up and performance time trial. The RPE was assessed to evaluate the swimmers' subjective feelings of exertion after warm-ups and performance trials.
Fifty-yard Freestyle Time Trial Heart Rate
Before and after each performance time trial, participants were asked to obtain their HR. Heart rate was measured by the manual palpation method at the radial or carotid artery for 15 seconds. Participants were accustomed to doing this in normal swim practices. The HR was measured as an estimator of effort.
During each 50-yd freestyle performance time trial, stroke cycles were counted and recorded. One cycle was equal to 2 strokes. The cycle started when the first arm of a participant entered the water and ended when it recovered. Stroke count was measured to evaluate any impact of warm-up on force production (i.e., a change in stroke count over 50-yd would indicate the ability to cover more distance per stroke).
Differences among the warm-ups for the null hypothesis that there would be no significant difference after regular warm-up, UBV-only warm-up, and UBV + short warm-up, were analyzed using separate repeated-measures analyses of variance (ANOVAs; SPSS Version 16.0) for 50-yd (45.7 m) freestyle time, RPE post-warm-up, RPE post-time trial, HR before and after the time trial, and stroke count. When a main effect was detected, least significant difference (LSD) post hoc multiple comparisons were used to determine the difference among the 3 types of warm-ups for each analysis. An alpha value was set at 0.05. Individual data, expressed as the number of individuals who performed their best time after a given warm-up, were reported as a percentage of the total group.
Participants reported being healthy and training at least 3 days a week. Two of the male participants were triathletes. A majority of participants reported having at least 3 years of experience. Participants' age, weight, height, percent body fat, years of experience, preferred stroke and best 50-yd time are presented in Table 1. The regular warm-up swim distance before the 50-yd performance time trial was 800 ± 276 yd for women and 500 ± 0 yd for men.
No significant mean differences (p = 0.56) were found among regular, UBV-only, and UBV + short warm-ups for 50-yd freestyle times (29.1 ± 3.36, 28.9 ± 3.39, and 29.1 ± 3.55 seconds, respectively). Group mean and individual data of 50-yd freestyle times are presented in Figure 2. Individual data indicated that 40% (4 of 10) of the swimmers swam their fastest with UBV-only and 20% (2 of 10) with UBV + short warm-ups, compared to 40% (4 of 10) of the swimmers who swam their fastest with regular warm-ups.
A significant difference (p = 0.04) was found among post-warm-up mean RPEs as assessed by the overall ANOVA. However, post hoc tests found that the difference in RPE after regular warm-up (12 ± 2) and UBV-only warm-up (9 ± 2) approached, but did not reach, statistical significance (p = 0.059). The mean RPE after UBV+ short warm-up (10 ± 2) did not differ significantly from regular and UBV-only warm-ups (p = 0.160 and p = 0.089, respectively). No significant difference (p = 0.216) was found among mean post-swim time trial RPE after regular warm-up (17 ± 2), UBV-only (16 ± 1) and UBV + short warm-up (16 ± 2) (Figure 3).
A significant difference was found among mean HRs before (p = 0.023) the performance time trial. The mean HR was significantly (p = 0.02) higher after regular warm-up (88 ± 15 b·min−1) compared to UBV + short warm-up (75 ± 9 b·min−1). The HR after UBV-only (80 ± 14) did not differ significantly from regular and UBV + short warm-ups (p = 0.121 and p = 0.212, respectively) (Figure 4).
In addition, the HR after the performance time trial was significantly (p = 0.01) different among the 3 warm-ups. The HR after the time trial was found to be significantly higher after regular warm-up (148 ± 15 b·min−1) compared to the UBV-only warm-up (139 ± 12 b·min−1) and the UBV + short warm-up (138 ± 14 b·min−1) (p = 0.01 and p = 0.01, respectively) (Figure 5). Mean stroke count was not significantly different (p = 0.62) among regular (35 ± 7), UBV-only (36 ± 6), and UBV + short (35 ± 5) warm-ups (Figure 5).
The purpose of this study was to examine the effect of different types of warm-ups (regular, UBV + short, and UBV-only) on 50-yd freestyle times in Masters Swimmers. It was hypothesized that UBV + short warm-ups or UBV-only warm-ups would provide greater or the same benefits as regular warm-up on swimming performance. This hypothesis was not fully supported by the group mean data findings of no differences in performance.
Individual data of the athletes' performance are important in this study because each athlete choose to do a different style of warm-up. Six of 10 participants performed better with UBV-only, or UBV + short warm-up, compared to the regular warm-up, suggesting that UBV provided the same or greater performance benefits compared to a regular warm-up for these swimmers.
To the best of our knowledge, this is the first study examining the effects of UBV as a warm-up routine for swimming performance. The results of this study indicated that there was no significant mean difference in performance time found among the 3 types of warm-up (regular, UBV-only, or UBV + short), although, previously it has been shown that a regular swimming warm-up was superior to no warm-up and dry-land warm-up suggesting the need for neuromuscular rehearsal before the race (22). However, Bobo (4) reported no significant difference in swimming performance after no warm-up, related and unrelated to swimming warm-ups. Thus, the inconsistency in the results may be because of methodological differences of warm-up routines and limitations of the previous studies.
It is hypothesized that there is a neural component to the UBV warm-up process because of vibration increasing mechanical stimulation causing muscles to lengthen and subconsciously contract, thereby employing more muscle fibers, increasing synchronization of muscle units and causing a more forceful contraction (7). Even though mean performance time after UBV-only and UBV + short warm-ups did not differ significantly from the regular warm-up, vibration has previously been suggested to improve performance and increase EMG activity during vibration of the involved muscles (6). Bosco et al. (6) reported improved average mechanical power after 5 minutes of UBV. In addition, some previous studies have reported a similar power output even with reduced EMG, which could indicate improved neurological reorganization and reduced joint stiffness, although this is speculative (6,12).
The lack of group mean improvement after UBV in maximal performance time trial could be because of an inability to prepare race-specific muscles as regular swimming warm-ups would do. Alternatively, there may be subtle physical or physiological differences between those who respond and those who do not respond to UBV or to traditional warm-ups. In addition, lack of improvement may be related to only 1 joint position, and there was no way of determining the degree of muscle tension applied with the vibration; therefore, UBV could have had a varied effect on the experienced vibration stimulus and intensity of the warm-up. However, we would point out that some individual swimmers swam their fastest individual time trials under each of the warm-up treatments. Although participants were trained swimmers, they were not accustomed to the vibration stimulus. It is possible that UBV warm-up would have a greater ergogenic aid if swimmers were adapted to a UBV routine, which would elicit neural adaptations as would traditional resistance training. Previously, a 12-week WBV and resistance training program elicited significant improvement in static and dynamic knee-extensor strength and countermovement jump height (13). In addition, according to Rönnestad (23), higher WBV frequencies elicit higher peak power in trained and untrained participants because of an increased ability to generate more rapid firing rates of muscle spindles resulting in an increased maximum force production. Thus, if vibration stimulus was performed more often and at a higher intensity, participants may have gained greater benefits.
Stroke count was not significantly different after regular, UBV-only and UBV + short warm-ups. An observed reduction in number of strokes after UBV-only or UBV + short warm-ups was hypothesized because of the proposed mechanism of increased neuromuscular stimulus, increased muscle activation, and generation of more forceful contraction (6), which researchers hypothesized could result in an increased stroke length. Although previously it has been shown that acute exposure to WBV improves strength and power of an athlete (6,12,17), this was not seen in this study. The absence of improvement could be because of limited adaptation to the vibration load and stimulus. The vibration load used in this study may have been insufficient to generate any physiological changes associated with vibration, leaving optimal duration and frequency yet to be determined. Stroke count is a skill developed over time that maximizes an athlete's peak performance. Although this study found that stroke count remained stable and the times were almost identical, UBV-only and UBV + short warm-ups were perceived as less strenuous with reduced cardio stress. Thus, UBV warm-ups may be considered to reduce overall stress, thereby, potentially minimizing stress of the warm-up for swimmers.
The main physiological changes that occur during active and passive warm-ups are increased core and muscle temperature, which seemed to increase vasodilation within the muscles allowing for more blood and oxygen to be delivered to the active tissue (2,18). A more rapid increase in muscle temperature was documented during WBV compared to the cycling and passive warm-up by Cochrane et al. (12); thus, WBV could optimize performance. Active warm-up hypothetically prepares the cardiovascular and respiratory systems, enhancing energy availability and its production (3). After completing each warm-up and the 50-yd time trial, participants rated RPE. The RPE after regular, UBV-only, or UBV + short warm-up sessions approached, but did not reach statistical significance. The RPE after regular warm-up tended to be higher than after UBV-only warm-up or UBV + short warm-up. Participants did not feel as fatigued after UBV-only or UBV + short warm-ups, and both were perceived as less demanding warm-ups compared to the regular warm-up. RPE after the 50-yd time trial did not differ significantly among the 3 warm-ups. In addition, HRs after the warm-up routine and the 50-yd time trial were higher after regular warm-up compared to UBV-only and UBV + short warm-ups. Thus, regular warm-up apparently was more demanding on the cardiovascular system compared to UBV-only and UBV + short warm-ups. A reduced increase in the HR after WBV warm-up compared to the cycling warm-up was reported by Jacobs and Burns (17). Thus, lower RPE and HR responses could be related to reduced cardiovascular and respiratory stress compared to the regular warm-up, despite similar maximal performance time trial speeds.
Performance can be influenced by neuromuscular and environmental adaptations. Neuromuscular adaptations are influenced by specific practice skills (22) and may influence performance. However, in this study participants were actively training and adept at the flip turns required during 50-yd freestyle. Participants trained in the testing facility regularly and were familiar with the pool and its environment. Not all of the participants competed in freestyle swimming, but most of their training volume was composed of freestyle swimming.
Perception of the competitive environment varies with each individual, and a multitude of psychological and physiological responses may occur (2,18,20). Intensity, duration, recovery periods, mode, and choice of continuous or intermittent type of warm-up depend on the individual experience of the athlete and coach (2,3). Intensity and duration of the regular warm-up varied among participants because participants swam their own preferred meet warm-up with 2 25-yd sprints. Insufficient rest of only 3 minutes after the warm-up and before the performance trial could have influenced swimming performance, where in some cases, the prerace warm-up occurs an hour or more before the race (22). The similarity in mean performance after any of the warm-ups might have been influenced by motivation. Participants competed without other competitors, against only themselves and the clock, which might have decreased their effort (22).
One must note that this study used a sample size of 10 participants, which is a limitation of the study. Also, the small sample size and large age and performance variability among participants reduced the investigators ability to detect significant differences. The repeatability of swimming performance after each warm-up needs to be further investigated; therefore, this study should be considered as preliminary. In addition, inability to detect a significant difference between the mean times might be attributed to a very small effect size.
However, it should be noted that the individual results are potentially very useful to coaches and skilled swimmers. We recommend that future studies and individual coaches and swimmers test themselves for stability of response to a given warm-up, to select an individual warm-up mode that is associated with the fastest performance.
In conclusion, Master Swimmers may perform the same or better after acute UBV as a warm-up routine, compared to regular warm-up, UBV-only and UBV + short warm-ups were perceived as less strenuous with lower energy cost compared to a regular warm-up. In addition, elevated HR after the regular warm-up indicated higher demand on the cardiovascular system. If multiple races were swum in a short period, the reduced energy cost of the warm-up may improve performance, particularly of later swims.
The results of this study show that acute exposure to UBV can be used as an addition or alternative to traditional swimming warm-up routines. Upper-body vibration may serve as an effective way to optimize performance in a short period of time with minimal fatigue. This technique may be recommended to elicit immediate benefits in athletic performance and prepare athlete for a race.
We recommend that future studies and individual coaches and swimmers test themselves for stability of response to a given warm-up. Coaches should experiment during the pre and postseason to determine the optimal warm-up duration, intensity and mode to improve swimming performance. If improved results proved stable for a particular swimmer, it could be recommended to use that mode as a warm-up routine or as an addition to swimming a short warm-up before a race. UBV is a new research area that needs to be further investigated. Optimal duration of vibration loading, frequency and rest period need to be determined.
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