Introduction
Prerace strategy is an important aspect of athletic competition. One component of prerace strategy is a warm-up, which has been shown to enhance subsequent performance through several mechanisms (5,13,14). However, the planned start of a competitive race is often delayed in sports such as rowing regattas, road races, and swimming meets because of various logistical issues. Given possible delays, the duration of time between warm-up and competition can be unpredictable and may warrant athletes to alter prerace strategies. In addition, it is also possible that the physiologic benefits of a warm-up may be negated because of a prolonged delay starting the event. Furthermore, as many of the events listed take place outdoors in a cold environment, this exposure may further impact the benefit of a warm-up. However, it is unclear in the literature if time duration between warm-up and competition and/or the combination of the duration of time and exposure to cold negatively impacts athletic performance.
Benefits of warm-up on exercise performance may be the result of several mechanisms. These include increased core and muscle temperatures, aerobic metabolism, nervous system function, and enzyme activity (3,5,13,14). Increased peripheral blood flow can also stimulate O2 kinetics and perfusion, leading to a reduction in O2 deficit at the onset of a second bout of exercise, allowing an individual to reach higher levels of aerobic metabolism more quickly (5,13,14,18,19,24,26). In addition, increased physical activity of light/moderate intensity can acutely elevate blood lactate and, after a short recovery time, ultimately decreases accumulation of the metabolite during subsequent performance, potentially delaying fatigue (4,6,13,14,18,19,26). Increased muscle temperature has also been shown to reduce muscular stiffness and resistance during contraction, optimizing power generation (3,28). It is possible that any single or a combination of these mechanisms may positively enhance exercise performance.
Several authors suggest that ideal recovery time after warm-up and before a performance time trial (TT) should be between 5 and 20 minutes (3,5,14). However, the optimal amount of time between warm-up and competition has not been determined. The majority of studies conducted have examined different durations, intensities, and modes of warm-up and have used a 5-minute resting period between warm-up and subsequent exercise TT (5,6,13,14,19,26). A meta-analysis of studies on warm-up exercise published between 1966 and 2008 states that most authors did not report the amount of time that elapsed between the end of a warm-up and actual performance nor did most report the environmental temperature (11). Following exercise, subsequent exposure to the cold (4.6° C) for 30 minutes has been shown to decrease rectal and skin temperatures (Tsk) by 0.5 and 5.5° C, respectively (7). Because of accelerated heat loss after exercise, the duration of time in between the active warm-up and competition may therefore be critical when an athlete competes in a cold environment. However, no investigation has studied the impact of the duration of time following warm-up exercise in combination with cold exposure on subsequent exercise performance.
Therefore, the purpose of this investigation was to determine (a) whether a delay after warm-up affects subsequent TT performance and (b) if exposure to a cold environment has an additive effect. We hypothesized that, after an active warm-up, 30 minutes of rest in a cold (5° C) environment would negatively affect subsequent exercise performance vs. a 5-minute rest period in a temperate (24° C) environment. In collegiate (e.g., rowing) and amateur competition (e.g., road races), delays in racing are common, because of weather, logistical issues, or both. Thus, the results of this study may provide important practical guidance to assist in an athlete’s preparation before competition where delays may occur, especially in cold conditions.
Methods
Experimental Approach to the Problem
To study the impact of cold exposure and recovery time on rowing or running TT performance, each subject performed a matrix of 4 experimental trials, using his/her respective mode of exercise (Figure 1). Experimental trials consisted of a 15-minute standardized warm-up followed by a 5- or 30-minute rest, then a maximum effort TT. Each subject acted as his/her own control, and all performances were compared with the control trial, a temperate environment and 5-minute rest (5Temp). To reduce any chance of a learning effect, trials were performed in a randomized, counterbalanced order. Each subject performed his/her trials at the same time of day, and there was a minimum of 1 week separating each trial. Diet was not controlled but subjects were asked to maintain a similar diet in the days leading up to experimental trials. Subjects were also asked to not deviate from their normal training schedules throughout their participation in the study. Testing took place predominantly over the summer months.
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Figure 1: Flowchart organization of each experimental trial.
Subjects
Five rowers and 5 runners (n = 10; age range = 22-43 years) were recruited to participate in this study from the local area. Both runners and rowers were experienced in their respective sport and regularly performed the TT experimental task (2 km on a rowing ergometer for rowers and 2.4 km on a treadmill for runners) as part of their current training. Subject characteristics are presented in Table 1. The University’s institutional review board approved the use of human subjects for this study, and all subjects completed an informed consent and medical history questionnaire.
Table 1: Mean (±SD) subject characteristics (n = 10).
Procedures
Subjects came to the laboratory for a total of 5 visits. The initial visit comprised of preliminary testing and a familiarization session. In preliminary testing, anthropometric data (height, weight, and body fat %) were collected, followed by a V[Combining Dot Above]O2max test on the rowing ergometer (Concept II Model C) or treadmill (JAS Systems Trackmaster, Newton, KS, USA). Estimation of percent body fat was determined using subcutaneous skinfold measurements at 7 different sites (17). Rowing V[Combining Dot Above]O2max was modified from a study by Cosgrove et al. (10). A graded running V[Combining Dot Above]O2max test on the treadmill began with a 3-minute stage at 2.5 m·s (5.5 miles ·h) at 0% grade, followed by increases in speed and grade in 3-minute stages thereafter until volitional exhaustion. A familiarization session was then completed to accustom subjects to exercise in the environmental chamber set at 5° C. Subjects entered the chamber and rested in a seated position for 5 minutes before performing the 15-minute standardized warm-up protocol used in the experimental trials.
For visits 2 through 5, subjects performed a randomized matrix of experimental trials with their respective exercise modality (Figure 1). Rowers and runners completed all 4 trials using the same protocol but on either the rowing ergometer or treadmill. Subjects wore a short-sleeved t-shirt, shorts, socks, and gym shoes for each visit. Core temperature (Tes), Tsk, heart rate (HR), and blood lactate [La] were measured to assess physiologic and metabolic changes throughout each trial. Core temperature was measured via a flexible esophageal thermistor inserted through the nasal passage to a depth corresponding to 25% of the participant’s height (27). Tsk and Tes thermistors were connected to a digital telethermometer (Model 8502-12; Cole Parmer, IL, USA), and baseline measurements were recorded before subjects entered the environmental chamber. To calculate mean Tsk (22), 4 skin thermistors (YSI-700 Series) were all placed on the right side of the body over the triceps, upper pectoralis major, vastus lateralis, and the midline of the gastrocnemius. Subjects were fitted with a HR monitor (Polar Electro, Lake Success, NY, USA), and a flexible teflon catheter was inserted into the antecubital vein for blood collection throughout the trial.
Each experimental trial was conducted in the environmental chamber, set either at 24° C (temperate) or 5° C (cold), and began with a 5-minute seated rest. Subjects then performed a 15-minute standardized warm-up on the rowing ergometer or treadmill. The standardized warm up consisted of a 10-minute steady state exercise at ∼60–70% V[Combining Dot Above]O2max, followed by five 30-second sprints with 30 seconds of recovery in between. Steady state speed was selected based on data from each subject’s V[Combining Dot Above]O2max test, established during his/her initial visit preliminary test. Sprint speed was self-selected by the subject. After the warm-up, subjects rested for one of the rest time variables (5 or 30 minutes) and remained seated or standing in the environmental chamber. During this time, subjects were allowed to drink water ad libitum. Immediately after the rest period, subjects were instructed to complete either a 2-km rowing or a 2.4-km running TT as fast as possible. The digital monitor on the rowing ergometer was covered so that subjects could observe only meters rowed and stroke rate. On the treadmill, runners could change speed at their own will, but both time elapsed and speed were covered. Subjects were not allowed to drink during the TT.
Skin temperature, HR, and Tes were recorded every 5 minutes during warm-up and resting phases and every quarter of the TT (every 500 m rowing or 600 m running). Blood was drawn before and after warm-up, after the resting phase, and immediately after the TT and was analyzed for lactate concentration [La] via a manual enzymatic assay.
Statistical Analyses
The primary outcome variable of interest in this study was TT performance. To assess the outcome, percent change was used to compare TT performance to account for variability seen between subjects. A total sample size of 10 subjects afforded ample statistical power (β ≤ 0.20) (21) to detect a large difference in TT performance, estimated as any effect larger than the typical noise in the measurement. To determine differences among conditions (5Temp, 5Cold, 30Temp, 30Cold), at discrete time points (prewarm-up, postwarm-up, postrest, and post-TT), a 4 × 4 repeated measures analysis of variance was performed on all dependent variables. Where the assumption of sphericity was violated, F values were adjusted using Greenhouse-Geisser or Huynh-Feldt corrections as appropriate. Significant main or interaction effects for any physiologic and performance variables were investigated with Newman-Keuls post hoc procedure. Significance was set at p ≤ .05, and all data were presented as mean ± SD, unless otherwise indicated. All data were analyzed using GraphPad software (v.5.0, La Jolla, CA, USA).
In an effort to better understand any differences observed in performance, the practical importance of the effect magnitude was estimated by plotting the 95% confidence interval (CI) for the mean difference in performance between the control trial (5Temp) and all other trials. This included comparison against an a priori zone of indifference, which was based on a coefficient of variation (CV) for performance equal to ∼3.0% reported for different modes of exercise of similar duration and intensity to those performed in this study (15,25). This reported CV represents the day-to-day noise inherent within performance tests of this duration and intensity and was calculated to be 0.25 minutes in this investigation or ∼15 seconds based on the grand mean performance time of 8.5 minutes. In this study, the practical importance of a change in performance from the control trial (5Temp) was considered unequivocal only when the majority of the 95% CI was outside the zone of indifference (±15 seconds). This approach affords evaluation against an evidentiary standard other than 0 (9) and has recently been championed as a performance interpretation tool for the exercise sciences (1).
Results
Effects of Warm-Up
Table 2 lists [La], HR, Tes, and Tsk responses at prewarm-up, postwarm-up, postrest, and post-TT time points. Prewarm-up, absolute values of all dependent variables were not different (p > 0.05) among the trials. Overall, following the warm-up, changes of the physiologic variables measured changed similarly among all trials, indicating that the impact of the warm-up was comparable. Postwarm-up, blood [La] and HR measures were elevated in all trials (p ≤ 0.05). Tes increased significantly in the temperate trials (p ≤ 0.05) but not in the cold trials. Conversely, Tsk significantly decreased (p ≤ 0.05) in the cold vs. temperate trials.
Table 2: Mean (±SD) blood lactate concentration ([La]), heart rate (HR), T es, and T sk at each time point during trial (n = 10).
Effects of Five and Thirty-Minute Rest Period
After the rest period, blood [La] declined from postwarm-up values in all trials (p ≤ 0.05). Heart rate was lower (83 ± 14 b·min−1) in 30Cold compared with both 5Cold (100 ± 18 b·min−1) and 5Temp (103 ± 15 b·min−1) (p ≤ 0.05). Heart rate tended to be lower in the cold trials compared with temperate, similar to previous findings (19). Tes significantly decreased in both 30Temp and 30Cold trials (p ≤ 0.05). During rest, Tsk did not change (p > 0.05) from postwarm-up in temperate conditions. Tsk remained low in the cold trials following the 5- and 30-minute rest, and mean Tsk values were significantly lower vs. temperate trials.
Effects of Time Trial
Heart rate and [La] increased in all conditions following the TT (p ≤ 0.05). In addition, Tes increased in all trials following the TT but remained lowest in the 30Cold trial. Tsk remained lower in cold trials compared with temperate (p ≤ 0.05).
Performance Time
Table 3 displays all TT performance times in each trial. There was a large degree of variation in performance time within each condition as evident by the SD and range of times. Mean differences (±SD) in performance time relative to control (5Temp) were 9 ± 19 seconds (5Cold), 11 ± 21 seconds (30Temp), and 20 ± 27 seconds (30Cold). A conventional analysis (analysis of variance) showed no main effects for environment or duration of rest, nor was there an interaction between conditions (p > 0.05). Mean differences (±95% CI) in TT performance times are depicted in Figure 2. Six , 7, and 8 of 10 subjects performed slower in 5Cold, 30Temp, and 30Cold conditions, respectively. In 30Cold, the mean difference and more than half of the 95% CI fell outside the zone of indifference, suggesting that longer elapsed times after warm-up, in addition to cold air exposure, has a meaningful impact on performance despite the fact that the lower bound of the CI for the difference abuts 0 (i.e., p > 0.05).
Table 3: Mean ( ±SD) time trial performance times in minutes (n = 10).
Figure 2: Change of time trial performances (in seconds) compared with 5
Temp. Solid line denotes mean value with 95% confidence interval bars. Gray area depicts estimated CV (±3.0%, which equates to 15 seconds) of rowing and running trials (
25,15). Change values are calculated so that slower times appear as positive number.
Discussion
This is the first investigation that we are aware of that specifically sought to determine if: (a) duration of time after warm-up affects performance of a self-paced TT and (b) added cold exposure contributes to any impairment in TT performance. It is clear that the specificity of training for these events and the physiologic responses and muscle groups used during these activities are different. However, as sport activities such as rowing and running, particularly in collegiate or amateur settings, commonly encounter delays before the start of an event, both sports were chosen to be studied for this reason. Despite the difference listed, both of these events use similar aerobic energy systems (12) and were matched for intensity of effort and duration (∼7–9.5 minutes). Furthermore, comparisons were not made between each mode of exercise, and subjects acted as their own control by performing all experimental trials (5Temp, 5Cold, 30Temp, and 30Cold) within each exercise mode. We also reasoned that, despite differences in mode of exercise, the mechanisms proposed for any physiologic changes associated with long duration cold exposure (e.g., lower skin and muscle temperatures; increased muscle stiffness; and decreased neuromuscular activity) would impact longer duration modes of exercise in a similar manner. The current study found that subjects performed best (i.e., fastest TT) in the 5Temp condition, considered most ideal for optimal exercise performance (shortest time after warm-up and temperate environment). Duration of rest alone following the warm-up did not seem to impact TT performance. However, the longer rest period combined with cold exposure (30Cold) resulted in a change in TT performance that can be considered meaningful for athletic events where competitions are of similar distance, duration or both. It seems that the longer duration of rest in 5° C likely negated any benefit of the pervious warm-up and contributed to the slower TT performances.
Investigations studying the impact of warm-up on exercise performance have typically used a 5-minute resting period between warm-up and subsequent exercise TT (5,6,13,14,19,26). As novel in this study, both a 5- and a 30-minute delay following the warm-up were studied. We observed an 11 ± 21 seconds slower performance with 30 minutes of rest in the temperate environment. These results are similar to what has been shown by Zochowski et al. (28) who found a significantly slower 200 m swim performance after a 45-minute vs. 10-minute rest following a warm-up. Conventional analysis did not reveal a significant difference (p > 0.05) in performance change while in 24° C; however, analysis relative to the CV inherent in this type of performance test also showed that the mean and the majority of the 95% CI fell within the variation of the test (±15 seconds), suggesting that this change would not be considered important. Although our data are not definitive that a longer recovery in a temperate environment negates the benefit of a warm-up, an ∼11-second decrement in performance for events of this intensity and duration would be considered of practical importance. However, the optimal time between warm-up and competition remains unclear.
Lack of significance for TT was likely because of variation in performance times. To address the variation of the time outcome, we calculated the percent change in TT performance time in the 3 experimental trials vs. 5Temp (control trial) and made comparisons, using the mean ± 95% CI relative to a 3.0% (15 seconds) CV estimated zone of indifference (14,24) (Figure 2). Change in TT performance time for 5Cold and 30Temp (9 seconds and 11 seconds, respectively) vs. 5Temp was within the 3.0% CV. However, in 30Cold vs. 5Temp, a 4% mean decrement in performance was seen, and the majority of the 95% CI fell outside the zone of indifference, suggesting that the decline in TT performance is beyond the day-to-day variation inherent in performance tests of this duration and intensity (15). This difference can be considered meaningful despite results using conventional analysis (p > 0.05). The change in TT performance in the 30Cold trial (4% from 5Temp) resulted in a 20-second slower performance, which would be a substantial change in a running, rowing, or cycling performance of this duration, distance, or both.
We did not specifically endeavor to study the mechanisms behind the physiologic changes associated with cold exposure for long durations; however, it is likely that, whatever mechanisms are in play, they would affect any mode of exercise. In this study, the combination of longer rest time and cold exposure (30Cold) resulted in decreased Tsk (24.8° C postwarm-up vs. 22.5° C postrest) and Tes (37.9° C postwarm-up vs. 37.0° C postrest). It is possible that cooling of the exposed skin may have resulted in lower muscle temperatures, possibly reducing force production and degrading TT performance in the 30Cold TT (9). Imai et al. (16) has reported a strong correlation between declines in whole-body Tsk and power output during cycling tests. In addition, previous studies have shown that cold environments may contribute to increased muscle stiffness, decreased neuromuscular activity, and inhibition of the stretch reflex pathway (3,9,20,22,28), any/or all of which may affect exercise performance. In addition, peripheral vasoconstriction induced by cold exposure during the longer rest period (30Cold) may have partially attenuated vasodilation during the TT. This, in turn, could have resulted in a reduced blood flow and impaired O2 delivery to exercising muscle (2). Our data do not support any particular theory regarding performance degradation because of cold exposure, and mechanisms have yet to be determined.
Our findings demonstrate that, when in a cold environment, the combination of accelerated heat loss after warm-up exercise and longer rest periods (resulting in lower Tes and Tsk) results in diminishing the performance benefits of a warm-up. It seems that, when Tsk and Tes are maintained following a warm-up, aerobic TT performance is better preserved as demonstrated by the fact that subjects performed best after a 5-minute rest between warm-up and performance when exposed to a temperature environment. We observed that our perturbations of recovery time and temperature had a meaningful effect on the subsequent TT performance, evident by the large performance change in TT performance in the 30Cold trial. Although a limitation to this study was the small sample size in each sport, a combined sample size of 10 was large enough to provide for appropriate statistical power. The 2 activities were very similar in duration, intensity, and contribution of aerobic/anaerobic metabolism. From a physiologic perspective, amount of recovery time and exposure to cold should impact both modalities in a similar manner.
Practical Applications
The findings of this study are applicable to a multitude of events (rowing, running cycling, swimming, and cross-country skiing), where weather and logistics can cause a significant delay between warm-up and competition. In the attempt to maximize athletic performance in cold environments when possible, coaches and athletes need to appropriately time the warm-up before competition. In the case where this may not be viable because of unanticipated delays in the start of an event, athletic performance may be preserved by maintaining skin and body temperature following a warm-up (via clothing or other means) or, if possible, another warm-up should be performed. This study has also helped to highlight future areas of research such as determination of the mechanisms involved with impaired performance following cold exposure and the optimal amount of time between warm-up and completion, neither of which has been fully examined.
Acknowledgments
The authors thank the volunteers who donated their time and effort to participate in this study. For assistance with data collection, the authors also thank Jessica Goulder, Robert Nelson, Kelyn Rola, Bobby Tofan, and Adam Jajtner. In addition, the authors thank Dr. Samuel N. Cheuvront, Dr. John W. Castellani, and Elizabeth Caruso for analytical and editorial assistance. Funding for this project was received from the Texas Regional Chapter of the American College of Sports Medicine. Laboratory where research conducted was Texas Christian University, Department of Kinesiology, Fort Worth, TX. The views, opinions, and/or findings in this report are those of the authors and should not be construed as official Department of the Army position, policy, or decision unless so designated by other official designation. All experiments were carried out in accordance to state and federal guidelines.
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