The effect of warm-up on intermittent sprint performance and selected thermoregulatory parameters

The effect of muscle warm-up on voluntary and evoked force-time parameters: A systematic review and meta-analysis with meta-regression

BACKGROUND

While muscle contractility increases with muscle temperature, there is no consensus on the best warm-up protocol to use before resistance training or sports exercise due to the range of possible warm-up and testing combinations available. Therefore, the objective of the current study was to determine the effects of different warm-up types (active, exercise-based vs. passive) on muscle function tested using different activation methods (voluntary vs. evoked) and performance test criteria (maximum force vs. rate-dependent contractile properties), with consideration of warm-up task specificity (specific vs. non-specific), temperature measurement method (muscle vs. skin), baseline temperatures, and subject-specific variables (training status and sex).

METHODS

A systematic search was conducted in PubMed/MEDLINE, Scopus, Web of Science, Cochrane, Embase, and ProQuest. Random-effects meta-analyses and meta-regressions were used to compute the effect sizes (ES) and 95 % confidence intervals (95 %CI) to examine the effects of warm-up type, activation method, performance criterion, subject characteristics, and study design on temperature-related performance enhancement.

RESULTS

The search yielded 1272 articles, of which 33 met the inclusion criteria (n = 921). Increasing temperature positively affected both voluntary (3.7 % ± 1.8 %/°C, ES = 0.28 (95 %CI: 0.14, 0.41)) and evoked (3.2 % ± 1.5 %/°C, ES = 0.65 (95 %CI: 0.29, 1.00)) rate-dependent contractile properties (dynamic, fast-velocity force production, and rate of force development (RFD)) but not maximum force production (voluntary: -0.2 % ± 0.9 %/°C, ES = 0.08 (95 %CI: -0.05, 0.22); evoked: -0.1 % ± 0.8 %/°C, ES = -0.20 (95 %CI: -0.50, 0.10)). Active warm-up did not induce greater enhancements in rate-dependent contractile properties (p = 0.284), maximum force production (p = 0.723), or overall function (pooled, p = 0.093) than passive warm-up. Meta-regressions did not reveal a significant effect of study design, temperature measurement method, warm-up task specificity, training status, or sex on the effect of increasing temperature (p > 0.05).

CONCLUSION

Increasing muscle temperature significantly enhances rate-dependent contractile function (RFD and muscle power) but not maximum force in both evoked and voluntary contractions. In contrast to expectation, no effects of warm-up modality (active vs. passive) or temperature measurement method (muscle vs. skin) were detected, although insufficient data prevented robust sub-group analyses.

Electric Muscle Stimulation (EMS) Does Not Improve Anaerobic Performance Measures During a Repeated Wingate Test

Introduction: The aim of this study was to examine differences between a control warm-up and an Electric Muscle Stimulation (EMS)-induced warm-up in off-road cyclists when examining anaerobic performance measures from a repeated Wingate test (WAnT). Methods: Twelve trained off-road cyclists completed a randomized crossover study (age: 31 ± 10 years, height: 176.79 ± 6.09 cm, body mass: 74.57 ± 4.77 kg). Participants completed two randomized, separate testing sessions involving a control warm-up and an EMS warm-up before undergoing the repeated WAnT, which was used to collect anaerobic performance and physiolo- gical measures during both sessions. High-frequency EMS was applied to the knee extensor muscles for 4 min after a standardized warm-up during the EMS session. Results: Analysis revealed that there were no significant differences between mean power output, peak power output, and percentage decrement between the two sessions. The EMS session resulted in significantly lower average HR values and significantly lower differences in pre-to-post-test blood lactate values when compared to the control session. Discussion: According to the results of this study, an acute application of EMS is not a useful tool for off-road cyclists to improve power output or maintain anaerobic capacity. Hence, its use before competition is questionable.

Identifying the Optimal Arm Priming Exercise Intensity to Improve Maximal Leg Sprint Cycling Performance

Priming exercises improve subsequent motor performance; however, their effectiveness may depend on the workload and involved body areas. The present study aimed to estimate the effects of leg and arm priming exercises performed at different intensities on maximal sprint cycling performance. Fourteen competitive male speed-skaters visited a lab eight times, where they underwent a body composition measurement, two V̇O_2max measurements (leg and arm ergometers), and five sprint cycling sessions after different priming exercise conditions. The five priming exercise conditions included 10-minute rest (Control); 10-minute arm ergometer exercise at 20% V̇O_2max (Arm 20%); 10-minute arm ergometer exercise at 70% V̇O_2max (Arm 70%); 1-min maximal arm ergometer exercise at 140% V̇O_2max (Arm 140%); and 10-min leg ergometer exercise at 70% V̇O_2max (Leg 70%). Power outputs of 60-s maximal sprint cycling, blood lactate concentration, heart rate, muscle and skin surface temperature, and rating of perceived exertion were compared between the priming conditions at different measurement points. Our results showed that the Leg 70% was the optimal priming exercise among our experimental conditions. Priming exercise with the Arm 70% also tended to improve subsequent motor performance, while Arm 20% and Arm 140% did not. Mild elevation in blood lactate concentration by arm priming exercise may improve the performance of high-intensity exercise.

Warm-Up Intensity and Time-Course Effects on Jump Height under Cold Conditions

With this study, we aimed to investigate the effects of different warm-up intensities on counter-movement jump (CMJ) performance over time under cold conditions. Eleven male collegiate athletes volunteered. The participants performed high-intensity warm-up (HWU) at 80% VO2max and moderate-intensity warm-up (MWU) at 60% VO2max for 15 min on a bicycle ergometer in a laboratory room at 10 °C. CMJ height, vastus lateralis muscle temperature, heart rate, and perceived fatigue were measured before warm-up (Pre), immediately after (Post 0), 10 min after (Post 10), and 20 min after (Post 20). Significant main effects and interactions were found for CMJ height (time, p < 0.001 and ηp2 = 0.859; interaction, p = 0.007 and ηp2 = 0.327). HWU significantly increased CMJ height at Post 0 to Post 20 compared to that at Pre (p < 0.01), whereas MWU increased CMJ height at Post 0 only compared to that at Pre (p < 0.001). The results indicate that HWU achieved an increase in CMJ height for 20 min. MWU changed CMJ height instantly, but the change did not last compared to HWU in a cold environment.

High-fat diet affects measures of skeletal muscle contractile performance in a temperature specific manner but does not influence regional thermal sensitivity

The present study examined if 20-weeks high-fat diet (HFD) consumption had a temperature specific effect on the contractile performance and regional thermal sensitivity of isolated mouse soleus (SOL) and diaphragm (DIA) muscle. Four-week-old female CD-1 mice were randomly selected to consume either a standard laboratory diet or a standard laboratory diet in conjunction with a HFD for 20-weeks. Peripheral SOL and core DIA were isolated from each animal and maximal isometric force and work loop power were assessed at 20⁰C, 28⁰C, 35⁰C and 40⁰C. Increasing temperature to 35⁰C resulted in greater isometric stress, lower activation and relaxation time and higher work loop power in both muscles. A further increase in temperature to 40⁰C did not affect isometric force but increased work loop power output of the SOL. Conversely, isometric force of the DIA was reduced and work loop power maintained when temperature was increased to 40⁰C. HFD consumption resulted in greater isometric force and absolute work loop power of the SOL and reduced isometric stress of the DIA, effects that were less apparent at lower temperatures. When the relationship between temperature and each measure of contractile function was examined by linear regression, there was no difference in slope between the control or HFD groups for either SOL or DIA. These results indicate that whilst contractile function initially increases with temperature, the temperature to elicit maximal performance is muscle and contractile mode-specific. Furthermore, HFD effects on contractile function are temperature specific, but HFD does not influence the relationship between temperature and performance.

Tensiomyographic Responses to Warm-Up Protocols in Collegiate Male Soccer Athletes

The mechanical properties of knee flexors and extensors in 15 collegiate male soccer players following different warm-up protocols [small-sided games (SSG), dynamic (DYN), and plyometric (PLY)] were evaluated. Tensiomyography (TMG) was used to assess contraction time (Tc), delay time (Td) and maximal displacement (Dm) of the rectus femoris (RF) and biceps femoris (BF) of both legs before and after each warm-up, while countermovement jump height variables, 20 m sprint, t-test and sit-and-reach were measured following the warm-ups. TMG was analyzed using a three-way [condition × time × leg] ANOVA, while performance variables were analyzed with a repeated measures ANOVA. Main effects of time were observed for BF-Tc (p = 0.035), RF-Td (p < 0.001), and BF-Td, (p = 0.008), and a main effect of condition was seen for RF-Tc (p = 0.038). Moreover, participants' 20 m sprint improved following SSG (p = 0.021) compared to DYN and PLY. Sit-and-reach was greater following PLY (p = 0.021). No significant interactions were noted for the measured TMG variables. Warm-up-specific improvements were demonstrated in sprint speed and flexibility following SSG and PLY, respectively. The present study revealed changes in certain TMG measures following the warm-ups that suggest enhanced response of lower leg muscles regardless of specific activities used.

High-Intensity Warm-Up Increases Anaerobic Energy Contribution during 100-m Sprint

Simple Summary

Certain exercise performances or movements cause sudden changes (or increases) in metabolic response. Track and field running events that require explosive energy in the shortest time, such as a 100-m sprint, need an immediate energy supply. Referring to the relevant studies to date, metabolic responses to submaximal exercise have been well documented, while information on the metabolic responses of short-term sprint performance is relatively insufficient. In this regard, based on the evidence that the human body relies on anaerobic energy metabolism during intense, short-term exercise, we investigated anaerobic energy contributions following the acute effect of a high-intensity warm-up during a 100 m-sprint. The main finding of our study revealed that a high-intensity warm-up (HIW) increases the contribution of the anaerobic system, probably by activating key regulatory enzymes related to anaerobic energy metabolism, compared to a low-intensity warm-up, for a 100-m sprint. Therefore, an HIW is effective in increasing anaerobic energy contribution during a 100-m sprint, which can be a useful strategy for coaches and athletes in the field.

Abstract

This study aimed to evaluate the effects of warm-up intensity on energetic contribution and performance during a 100-m sprint. Ten young male sprinters performed 100-m sprints following both a high-intensity warm-up (HIW) and a low-intensity warm-up (LIW). Both the HIW and LIW were included in common baseline warm-ups and interventional warm-ups (eight 60-m runs, HIW; 60 to 95%, LIW; 40% alone). Blood lactate concentration [La⁻], time trial, and oxygen uptake (VO₂) were measured. The different energy system contribution was calculated by using physiological variables. [La⁻¹]_Max following HIW was significantly higher than in LIW (11.86 ± 2.52 vs. 9.24 ± 1.61 mmol·L⁻¹; p < 0.01, respectively). The 100-m sprint time trial was not significantly different between HIW and LIW (11.83 ± 0.57 vs. 12.10 ± 0.63 s; p > 0.05, respectively). The relative (%) phosphagen system contribution was higher in the HIW compared to the LIW (70 vs. 61%; p < 0.01, respectively). These results indicate that an HIW increases phosphagen and glycolytic system contributions as compared to an LIW for the 100-m sprint. Furthermore, an HIW prior to short-term intense exercise has no effect on a 100-m sprint time trial; however, it tends to improve times (decreased 100-m time trial; −0.27 s in HIW vs. LIW).

Warm-up durations in a hot-dry climate affect thermoregulation, mean power-output and fatigue, but not peak power in specific soccer repeated-sprint ability

Background

This study addressed the lack of data on the effect of warm-up (WU) duration in hot-dry climate (~ 30 °C; ~ 18% RH), on thermoregulation, muscular power-output, and fatigue after specific soccer repeated-sprint test (RSA).

Methods

Eleven amateur soccer players participated in a cross-over randomized study and they underwent the Bangsbo repeated-sprint test, after three WU durations (i.e. WU10, WU15 and WU20 min) at 70% of MAV, and on different days. Peak power (PP), mean power (MP) and the fatigue index (FI) were recorded and analyzed. Likewise, heart rate (HR), tympanic temperature (T_tym), mean body temperature (MBT) and rating of perceived exertion (RPE) were recorded during each session.

Results

The repeated measure ANOVA showed that MP improved after WU15 in comparison to WU10 and WU20 (p = 0.04 and p = 0.001; respectively). Nonetheless, no significant effect on PP was recorded after all WU durations. FI during RSA increased after WU20 in comparison to WU15 and WU10 (p < 0.001 and p = 0.003; respectively). Higher RPE values (p < 0.001) were recorded after WU15 and WU20 in comparison to WU10 duration. The two-way ANOVA showed higher ΔT_tym and ΔMBT values after WU15 and WU20 compared to WU10 (p = 0.039 and p < 0.001for T_tym; p = 0.005 and p < 0.001 for MBT, respectively).

Conclusions

The WU15 at 70% of MAV better assists mean power-output during soccer RSA in hot-dry (~ 30 °C; 18% RH) climate, but not peak power. Reducing WU duration up to 10 min seems to be insufficient to induce beneficial physiological changes necessary for optimizing repeated-sprint performance, while its extension up to 20 min remains detrimental for muscular power and induces higher fatigue.

Environmental Conditions, Preseason Fitness Levels, and Game Workload: Analysis of a Female NCAA DI National Championship Soccer Season

Benjamin, CL, Hosokawa, Y, Curtis, RM, Schaefer, DA, Bergin, RT, Abegg, MR, and Casa, DJ. Environmental conditions, preseason fitness levels, and game workload: Analysis of a female NCAA DI National Championship Soccer Season. J Strength Cond Res 34(4): 988-994, 2020-The purpose of this study was to determine the independent and combined moderating effect of aerobic fitness and environmental conditions on physical workloads during collegiate female soccer matches. Nineteen National Collegiate Athletic Association female soccer athletes were included in this study (mean ± SD: age, 20.6 ± 1.4 years; height, 169 ± 6.1 cm; body mass 64.7 ± 5.3 kg). Maximal oxygen consumption (V[Combining Dot Above]O2max) was estimated from the yo-yo intermittent recovery test before preseason training and wet-bulb globe temperature (WBGT) was recorded onsite for home matches and at the nearest weather station for away matches. Relative distance (TD), relative high-speed running distance (%HSD), and relative high metabolic load (%HML) performance were collected during each match using a global positioning system unit (Viper Pod; STATSports, Chicago, IL). Statistically significant differences were observed in TD between LOW WBGT and MOD WBGT (mean difference [MD] = 7.08 m·min; effect size [ES] = 0.54; p < 0.001), in %HSD between LOW WBGT and MOD WBGT (MD = 1.97%; ES = 0.64; p = 0.01) and between LOW WBGT and HIGH WBGT (MD = 2.71%; ES = 1.01; p < 0.001), and in %HML between LOW WBGT and MOD WBGT (MD = 1.24%; ES = 0.56; p < 0.001) and between LOW WBGT and HIGH WBGT (MD = 1.55%; ES = 0.78; p = 0.01). There was a significant interaction between WBGT and V[Combining Dot Above]O2max for %HSD (p = 0.03). These findings demonstrate that physical performance metrics were affected by increased WBGT. In addition, aerobic fitness seemed to moderate the effect of increasing WBGT on %HSD, meaning maximizing aerobic capacity is important for optimizing running performance in the heat. Coaches and sports medicine staff could alter training time and session length based on environmental conditions as well as potentially use aggressive cooling strategies to mitigate the imposed heat stress and decrements in physical performance.

Acute effects of two different initial heart rates on testing the repeated sprint ability in elite women soccer players

BACKGROUND

Repeated sprint ability (RSA) in women's soccer is crucial to ensure high level of performance during the game. The aim of this study is to investigate the acute effects of two different initial heart rates intensities on fatigue when testing the RSA.

METHODS

Since there are many kinds of pre-match warming-ups, the heart rate reached at the end of two different warm-up protocols (~90 vs. ≈60% HRmax) as an indicator of internal load has been selected and the respective RSA performances were compared. RSA tests were performed by 19 elite women soccer players (age: 22.5±3.3 years, height 163.9±7.3 cm, body mass 54.3±6.4 kg, BMI 20.6±1.5 kg/m2) with two sets of ten shuttle-sprints (15+15 m) with a 1:3 exercise to rest ratio, in different days (randomized order) with different initial HR% (60% and 90% HRmax). In order to compare the different sprint performances a Fatigue Index (FI%) was computed; the blood lactate concentrations (BLa-) were measured before and after testing, to compare metabolic energy.

RESULTS

Significant differences among trials within each set (P<0.01) were found, as evidence of fatigue. Differences between sets were not found, (Factorial ANOVA 2x10; P>0.05). Although the BLa- after warm-up was higher between 90% vs. 60% HRmax (P<0.05), at the completion of RSA tests (after 3 minutes) the differences were considerably low and not significant (P>0.05).

CONCLUSIONS

This study shows that, contrary to male soccer, the initial heart rates, induced by different modes of warming-up, do not affect the overall performance while testing RSA in women's soccer players.

Effects of a hot ambient operating theatre on manual dexterity, psychological and physiological parameters in staff during a simulated burn surgery

OBJECTIVES

Hot environmental conditions can result in a high core-temperature and dehydration which can impair physical and cognitive performance. This study aimed to assess the effects of a hot operating theatre on various performance, physiological and psychological parameters in staff during a simulated burn surgery.

METHODS

Due to varying activity levels, surgery staff were allocated to either an Active (n = 9) or Less-Active (n = 8) subgroup, with both subgroups performing two simulated burn surgery trials (CONTROL: ambient conditions; 23±0.2°C, 35.8±1.2% RH and HOT: 34±0°C, 28.3±1.9% RH; 150 min duration for each trial), using a crossover design with four weeks between trials. Manual dexterity, core-temperature, heart-rate, sweat-loss, thermal sensation and alertness were assessed at various time points during surgery.

RESULTS

Pre-trials, 13/17 participants were mildly-significantly dehydrated (HOT) while 12/17 participants were mildly-significantly dehydrated (CONTROL). There were no significant differences in manual dexterity scores between trials, however there was a tendency for scores to be lower/impaired during HOT (both subgroups) compared to CONTROL, at various time-points (Cohen's d = -0.74 to -0.50). Furthermore, alertness scores tended to be higher/better in HOT (Active subgroup only) for most time-points (p = 0.06) compared to CONTROL, while core-temperature and heart-rate were higher in HOT either overall (Active; p<0.05) or at numerous time points (Less-Active; p<0.05). Finally, sweat-loss and thermal sensation were greater/higher in HOT for both subgroups (p<0.05).

CONCLUSIONS

A hot operating theatre resulted in significantly higher core-temperature, heart-rate, thermal sensation and sweat-loss in staff. There was also a tendency for slight impairment in manual dexterity, while alertness improved. A longer, real-life surgery is likely to further increase physiological variables assessed here and in turn affect optimal performance/outcomes.

Effects of Warm-Up, Post-Warm-Up, and Re-Warm-Up Strategies on Explosive Efforts in Team Sports: A Systematic Review

BACKGROUND

In team sports, it is imperative that the warm-up improves acute explosive performance. However, the exact strategies, methods, and consequences of different warm-up practices remain unclear. A time delay between the warm-up and match and during half-time could negate the positive metabolic effects of the warm-up.

OBJECTIVES

We conducted a systematic review to synthesize and analyze the potential effects of strategies during a warm-up (before match), post-warm-up (time between the end of warm-up and the start of a match), and re-warm-up (half-time break within a match) on explosive performance in team sports. Furthermore, we examined optimal warm-up strategies based on the included studies.

METHODS

We performed a search of four databases (Web of Science, Scopus, PubMed, and ScienceDirect) for original research articles published between January 1981 and August 2017. A total of 30 articles met the inclusion criteria, and the Cochrane risk of bias tool was used to assess the risk of bias. The results of the included studies were recalculated to determine effect sizes using Cohen's d.

RESULTS

A warm-up comprising 8 sets of 60-m sprints (- 2.19%, d = 1.20) improved sprint performance. Additionally, 7 min of dynamic exercises after 5 min of jogging improved sprint (- 7.69%, d = 1.72), jumping (8.61%, d = 0.61), and agility performance (- 6.65%, d = 1.40). The use of small-sided games also seems to be a valid strategy, especially for jumping performance (6%, d = 0.8). These benefits resulted from the warm-up strategies combined with some passive rest (between 2 and 10 min) before the main performance. In this post-warm-up period, the use of heated garments could result in better outcomes than simple rest (- 0.89%, d = 0.39). However, if the transition was longer than 15 min, before entering the match, performing a re-warm-up with short-term explosive tasks to reactivate was the most effective approach (- 1.97%, d = - 0.86). At half-time, heated garments maintained better sprint (- 1.45%, d = 2.21) and jumping performance (3.13%, d = 1.62).

CONCLUSION

Applying properly structured strategies in the warm-up and avoiding a long rest in the post-warm-up improves explosive performance. Studies tend to recommend a short active warm-up strategy (10-15 min), gradually increasing intensity (~ 50-90% of maximum heart rate), and the use of heated garments soon after the warm-up to maintain muscle temperature. However, 2 min of active re-warm-up with short-term sprints and jumps should be needed for transitions longer than 15 min (~ 90% of maximum heart rate). Last, at the half-time re-warm-up, combining heated garments to maintain muscle temperature and performing an active strategy, with explosive tasks or small-sided games for 5 min before re-entering the game, resulted in better explosive performance than 15 min of resting.

Effects of an active warm-up on variation in bench press and back squat (upper and lower body measures)

The present study investigated the magnitude of diurnal variation in back squat and bench press using the MuscleLab linear encoder over three different loads and assessed the benefit of an active warm-up to establish whether diurnal variation could be negated. Ten resistance-trained males underwent (mean ± SD: age 21.0 ± 1.3 years, height 1.77 ± 0.06 m, and body mass 82.8 ± 14.9 kg) three sessions. These included control morning (M, 07:30 h) and evening (E, 17:30 h) sessions (5-min standardized warm-up at 150 W, on a cycle ergometer), and one further session consisting of an extended active warm-up morning trial (M_E, 07:30 h) until rectal temperature (T_rec) reached previously recorded resting evening levels (at 150 W, on a cycle ergometer). All sessions included handgrip, followed by a defined program of bench press (at 20, 40, and 60 kg) and back squat (at 30, 50, and 70 kg) exercises. A linear encoder was attached to an Olympic bar used for the exercises and average force (AF), peak velocity (PV), and time to peak velocity (tPV) were measured (MuscleLab software; MuscleLab Technology, Langesund, Norway) during the concentric phase of the movements. Values for T_rec were higher in the E session compared to values in the M session (Δ0.53 °C, P < 0.0005). Following the extended active warm-up in the morning (M_E), T_rec and T_m values were no different to the E values (P < 0.05). Values for T_m were lower in the M compared to the E condition throughout (P < 0.05). There were time-of-day effects for hand grip with higher values of 6.49% for left (P = 0.05) and 4.61% for right hand (P = 0.002) in the E compared to the M. Daily variations were apparent for both bench press and back squat performance for AF (3.28% and 2.63%), PV (13.64% and 11.50%), and tPV (-16.97% and -14.12%, where a negative number indicates a decrease in the variable from morning to evening). There was a main effect for load (P < 0.0005) such that AF and PV values were larger at higher masses on the bar than lower ones and tPV was smaller at lower masses on the bar than at higher masses for both bench press and back squat. We established that increasing T_rec in the M-E values did not result in an increase of any measures related to bench press and back squat performance (P > 0.05) to increase from M to E levels. Therefore, MuscleLab linear encoder could detect meaningful differences between the morning and evening for all variables. However, the diurnal variation in bench press and back squat (measures of lower and upper body force and power output) is not explained by time-of-day oscillations in T_rec.

Very-Short-Duration, Low-Intensity Half-Time Re-warm up Increases Subsequent Intermittent Sprint Performance

Yanaoka, T, Hamada, Y, Kashiwabara, K, Kurata, K, Yamamoto, R, Miyashita, M, and Hirose, N. Very-short-duration, low-intensity half-time re-warm up increases subsequent intermittent sprint performance. J Strength Cond Res 32(11): 3258-3266, 2018-This study investigated the effect of very-short-duration, low-intensity half-time re-warm up (RW) on subsequent intermittent sprint performance. Using a randomized cross-over design, 11 healthy men performed 3 trials. In the experimental trials, participants performed the first 40-minute intermittent exercise followed by a 15-minute half-time. The interventions at half-time were 15 minutes of seated rest (control), 3 minutes of moderate-intensity RW (cycling at 60% of maximal oxygen uptake [V[Combining Dot Above]O2max]; [60% RW]), and 3 minutes of low-intensity RW (cycling at 30% of V[Combining Dot Above]O2max; [30% RW]). After half-time, participants performed the Cycling Intermittent-Sprint Protocol (CISP), which consisted of 10 seconds of rest, 5 seconds of maximal sprint, and 105 seconds of active recovery at 50% of V[Combining Dot Above]O2max, with the cycles repeated over the 20-minute duration. The mean work and electromyogram amplitude during the sprint in the CISP were higher in both RW trials than in the control trial (p < 0.05). Muscle temperature, estimated from the skin temperature, at 60 minutes was higher in the 60% RW trial than in the control and 30% RW trials (p < 0.05). The mean change in oxygenated hemoglobin concentration during active recovery at 55-65 minutes tended to be higher in both RW trials than in the control trial (60% RW trial: p = 0.06, 30% RW trial: p = 0.06). In conclusion, very-short-duration, low-intensity RW increased intermittent sprint performance after the half-time, in comparison with a traditional passive half-time practice, and was as effective as a moderate-intensity RW when matched for total duration.

Diurnal variation in repeated sprint performance cannot be offset when rectal and muscle temperatures are at optimal levels (38.5°C)

The present study investigated whether increasing morning rectal temperatures (T_rec) to evening levels, or increasing morning and evening T_rec to an "optimal" level (38.5°C), resulting in increased muscle temperatures (T_m), would offset diurnal variation in repeated sprint (RS) performance in a causal manner. Twelve trained males underwent five sessions [age (mean ± SD) 21.0 ± 2.3 years, maximal oxygen consumption (V̇O₂max) 60.0 ± 4.4 mL.kg^-1 min^-1, height 1.79 ± 0.06 m, body mass 78.2 ± 11.8 kg]. These included control morning (M, 07:30 h) and evening (E, 17:30 h) sessions (5-min warm-up), and three further sessions consisting of a warm-up morning trial (M_E, in 39-40°C water) until T_rec reached evening levels; two "optimal" trials in the morning and evening (M_38.5 and E_38.5, in 39-40°C water) respectively, until T_rec reached 38.5°C. All sessions included 3 × 3-s task-specific warm-up sprints, thereafter 10 × 3-s RS with 30-s recoveries were performed a non-motorised treadmill. T_rec and T_m measurements were taken at the start of the protocol and following the warm-up periods. Values for T_rec and T_m at rest were higher in the evening compared to morning values (0.48°C and 0.69°C, p < 0.0005). RS performance was lower (7.8-8.3%) in the M for distance covered (DC; p = 0.002), average power (AP; p = 0.029) and average velocity (AV; p = 0.002). Increasing T_rec in the morning to evening values or optimal values (38.5°C) did not increase RS performance to evening levels (p = 1.000). However, increasing T_rec in the evening to "optimal" level through a passive warm-up significantly reduced DC (p = 0.008), AP (p < 0.0005) and AV (p = 0.007) to values found in the M condition (6.0-6.9%). Diurnal variation in T_rec and T_m is not wholly accountable for time-of-day oscillations in RS performance on a non-motorised treadmill; the exact mechanism(s) for a causal link between central temperature and human performance are still unclear and require more research.

Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms

Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid) endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM) and the AMP-activated protein kinase (AMPK) both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits.

Complementing Warm-up with Stretching Routines: Effects in Sprint Performance

The present study aimed to examine the effects of using static or dynamic stretching added to the common warm-up routine for short sprint distances and to repeated sprint performance. In 3 different sessions, 16 college-age men (n=10) and women (n=6) performed one of 3 warm-ups followed by a 2×60 m dash sprint time trial (5 min of rest) in a counterbalanced design. The control warm-up consisted of 10 min of light-intensity running, and the 2 experimental warm-ups included a static or dynamic stretching routine (5 exercises) in the control warm-up. Performance (time) and physiological variables (tympanic temperature, heart rate) were monitored. In the first 60 m time trial, there were no differences between the 3 warm-ups tested ( F =0.21, p=0.73; η _p² =0.01), as opposed to that observed in the second ( F =7.04, p<0.01; η _p² =0.32). The participants were 1.7% faster after the static stretching warm-up compared with the control warm-up. The sum of the time performed in the 2 sprints emphasizes these results, with better performances after the static stretching warm-up than the control (1%) or dynamic stretching warm-up (0.7%). These results suggest that including a set of static or dynamic stretching exercises may enhance sprinting performance. The better performance in the second trial after the warm-up including static stretching suggests that this type of stretching may positively influence repeated sprint performance (<10 s sprint).

Influence of warm-up duration and recovery interval prior to exercise on anaerobic performance

The purpose of the study was to determine the impact of different active warm-up (AWU) durations and the rest interval separating it from exercise on anaerobic performance. Eleven male physical education students (22.6 ± 2.52 years; 179.2 ± 4.3 cm; 82.5 ± 9.7 kg; mean ± SD) participated in a cross-over randomized study, and they all underwent the Wingate test after three AWU durations: 5 min (AWU5), 15 min (AWU15) and 20 min (AWU20), with recovery (WREC) or without a recovery interval (NREC) separating the AWU and anaerobic exercise performance. All the AWUs consisted of pedalling at a constant pace of 60 rpm at 50% of the maximal aerobic power. The rest interval between the end of warm-up and the beginning of exercise was set at 5 min. During the Wingate test, peak power (PP), mean power (MP) and the fatigue index (FI) were recorded and analysed. Oral temperature was recorded at rest and at the end of the warm-up. Likewise, rest, post-warm-up and post-Wingate heart rate (HR) and rating of perceived exertion (RPE) were recorded during each session. The ANOVA showed a significant effect of recovery interval, warm-up duration and measurement point on RPE scores (P<0.001). Although the effect of AWU duration on MP and PP was significant (P<0.05), the effect of the recovery interval on both parameters was not significant (P>0.05). Moreover, the analyses showed a significant interaction between recovery interval and AWU duration (P<0.001 and P<0.05 for MP and PP respectively). The AWU15 duration improves the MP and PP when associated with a recovery interval prior to exercise of 5 min. However, the AWU5 duration allows better improvement of power output when the exercise is applied immediately after the warm-up. Consequently, physically active males, as well as educators and researchers interested in anaerobic exercise, must take into account the duration of warm-up and the following recovery interval when practising or assessing activities requiring powerful lower limb muscle contractions.

Warm-Up Strategies for Sport and Exercise: Mechanisms and Applications

It is widely accepted that warming-up prior to exercise is vital for the attainment of optimum performance. Both passive and active warm-up can evoke temperature, metabolic, neural and psychology-related effects, including increased anaerobic metabolism, elevated oxygen uptake kinetics and post-activation potentiation. Passive warm-up can increase body temperature without depleting energy substrate stores, as occurs during the physical activity associated with active warm-up. While the use of passive warm-up alone is not commonplace, the idea of utilizing passive warming techniques to maintain elevated core and muscle temperature throughout the transition phase (the period between completion of the warm-up and the start of the event) is gaining in popularity. Active warm-up induces greater metabolic changes, leading to increased preparedness for a subsequent exercise task. Until recently, only modest scientific evidence was available supporting the effectiveness of pre-competition warm-ups, with early studies often containing relatively few participants and focusing mostly on physiological rather than performance-related changes. External issues faced by athletes pre-competition, including access to equipment and the length of the transition/marshalling phase, have also frequently been overlooked. Consequently, warm-up strategies have continued to develop largely on a trial-and-error basis, utilizing coach and athlete experiences rather than scientific evidence. However, over the past decade or so, new research has emerged, providing greater insight into how and why warm-up influences subsequent performance. This review identifies potential physiological mechanisms underpinning warm-ups and how they can affect subsequent exercise performance, and provides recommendations for warm-up strategy design for specific individual and team sports.

From Protecting the Heart to Improving Athletic Performance - the Benefits of Local and Remote Ischaemic Preconditioning

Remote Ischemic Preconditioning (RIPC) is a non-invasive cardioprotective intervention that involves brief cycles of limb ischemia and reperfusion. This is typically delivered by inflating and deflating a blood pressure cuff on one or more limb(s) for several cycles, each inflation-deflation being 3-5 min in duration. RIPC has shown potential for protecting the heart and other organs from injury due to lethal ischemia and reperfusion injury, in a variety of clinical settings. The mechanisms underlying RIPC are under intense investigation but are just beginning to be deciphered. Emerging evidence suggests that RIPC has the potential to improve exercise performance, via both local and remote mechanisms. This review discusses the clinical studies that have investigated the role of RIPC in cardioprotection as well as those studying its applicability in improving athletic performance, while examining the potential mechanisms involved.

Effects of sodium phosphate and beetroot juice supplementation on repeated-sprint ability in females

INTRODUCTION

Sodium phosphate (SP) and beetroot juice (BJ) supplementation was assessed on repeated-sprint ability (RSA).

METHODS

Thirteen female team-sport participants completed four trials: (1) SP and BJ (SP + BJ), (2) SP and placebo (for BJ), (3) BJ and placebo (for SP) and (4) placebo (for SP + BJ), with ~21 days separating each trial. After each trial, participants performed a simulated team-game circuit (STGC) consisting of four 15 min quarters, with a 6 × 20-m repeated-sprint set performed at the start, half-time and end.

RESULTS

Total sprint times were between 0.95-1.30 and 0.83-1.12 s faster for each RSA set and 3.25 and 3.12 s faster overall (~5% improvement) after SP compared with placebo and BJ, respectively (p = 0.02 for sets 1, 2 and overall; Cohen's effect size: d = -0.51 to -0.90 for all sets and overall). Additionally, total sprint times were 0.48 s faster after SP + BJ compared with placebo (set 2; p = 0.05, ~2% improvement). Furthermore, best sprints were 0.13-0.23 and 0.15-0.20 s faster (~6% improvement; p < 0.01) after SP compared with placebo and BJ, respectively, for all sets (d = -0.54 to -0.89).

CONCLUSION

SP improved RSA in team-sport, female athletes when fresh (set 1) and during the later sets of a STGC (sets 2 and 3). Specifically, total and best sprint times were faster after SP compared with placebo and BJ.

Inspiratory muscle warm-up does not improve cycling time-trial performance

PURPOSE

This study examined the effects of an active cycling warm-up, with and without the addition of an inspiratory muscle warm-up (IMW), on 10-km cycling time-trial performance.

METHODS

Ten cyclists (VO₂ = 65 ± 9 mL kg(-1) min(-1)) performed a habituation 10-km cycling time-trial and three further time-trials preceded by either no warm-up (CONT), a cycling-specific warm-up (CYC) comprising three consecutive 5-min bouts at powers corresponding to 70, 80, and 90% of the gas exchange threshold, or a cycling-specific warm-up preceded by an IMW (CYC + IMW) comprising two sets of 30 inspiratory efforts against a pressure-threshold load of 40% maximal inspiratory pressure (MIP). The cycling warm-up was followed by 2-min rest before the start of the time-trial.

RESULTS

Time-trial performance times during CYC (14.75 ± 0.79 min) and CYC + IMW (14.70 ± 0.75 min) were not different, although both were faster than CONT (14.99 ± 0.90 min) (P < 0.05). Throughout the time-trial, physiological (minute ventilation, breathing pattern, pulmonary gas exchange, heart rate, blood lactate concentration and pH) and perceptual (limb discomfort and dyspnoea) responses were not different between CYC and CYC + IMW. Baseline MIP during CONT and CYC was 151 ± 31 and 156 ± 39 cmH₂O, respectively, and was unchanged following the time-trial. MIP increased by 8% after IMW (152 ± 27 vs. 164 ± 27 cmH2O, P < 0.05) and returned to baseline after the time-trial.

CONCLUSIONS

Improvements in 10-km cycling time-trial performance following an active cycling warm-up were not magnified by the addition of an IMW. Therefore, an appropriately designed active whole-body warm-up does adequately prepare the inspiratory muscles for cycling time-trials lasting approximately 15 min.

Comparison of the Effects on Dynamic Balance Ability of Warming up in Water Versus on the Ground

[Purpose] This research was designed to find out how the so-called "dynamic balance" is affected by doing different types of warm up exercises. In particular, the research is focused on the difference in the effect on dynamic Balance of warming up in water versus on the ground. [Subjects and Methods] Twenty healthy adults were the subjects of this study, with 10 people assigned each to two groups, one warming up in water and another warming up on the ground. The dynamic balance was measured for all subjects before the warming up. The group warming up on the ground conducted active stretching on the ground, and the group warming up in water conducted stretching in water by using water as resistance. [Results] The results indicate that warming up in water has a more powerful effect on a subject's dynamic balance than warming up on the ground. [Conclusion] The group warming up in water, who made use of the viscosity and flow of the water, showed better balance than the group warming up on the ground. Warming up in water, which entails an element of resistance, should be implemented in warm-up routines in the future.

Warm-up strategies of professional soccer players: practitioners' perspectives

Recent research has challenged the typical pre-match and half-time (HT) interval warm-up (WU) routines currently used by professional soccer players. This study surveyed 2010/11 season WU strategies and their underpinning scientific reasoning and situational factors via an internet-based questionnaire, which was distributed to English Premier League and Championship practitioners, of which 43% responded. The pre-match WU duration was 30.8 (8.2) min, ranging between 15-45 min, and 89% of practitioners administered a WU of ≥ 25 min. Respondents also reported a 12.4 (3.8) min period between the end of the WU and match kick-off. Eighty-nine per cent recognised the physiological benefits of re-WUs during this "down-time" period, with 63% instructing players to engage in such activity. During HT, 58% instructed players to re-WU either on the pitch or within stadia facilities, but "unwillingness of the coach/manager" (42%) and a "lack of time" (63%) were major constraints. Practitioners reported that 2.6 (1.6) min might be available for HT re-WUs. Factors such as match regulations, league policy, and stadia facilities were not generally considered as major barriers to the delivery of WUand re-WU strategies. We suggest that researchers consider the time-demands and barriers faced by practitioners whendeveloping experimental designs to examine WU regimens.

A review of the thermal sensitivity of the mechanics of vertebrate skeletal muscle

Environmental temperature varies spatially and temporally, affecting many aspects of an organism's biology. In ectotherms, variation in environmental temperature can cause parallel changes in skeletal muscle temperature, potentially leading to significant alterations in muscle performance. Endotherms can also undergo meaningful changes in skeletal muscle temperature that can affect muscle performance. Alterations in skeletal muscle temperature can affect contractile performance in both endotherms and ectotherms, changing the rates of force generation and relaxation, shortening velocity, and consequently mechanical power. Such alterations in the mechanical performance of skeletal muscle can in turn affect locomotory performance and behaviour. For instance, as temperature increases, a consequent improvement in limb muscle performance causes some lizard species to be more likely to flee from a potential predator. However, at lower temperatures, they are much more likely to stand their ground, show threatening displays and even bite. There is no consistent pattern in reported effects of temperature on skeletal muscle fatigue resistance. This review focuses on the effects of temperature variation on skeletal muscle performance in vertebrates, and investigates the thermal sensitivity of different mechanical measures of skeletal muscle performance. The plasticity of thermal sensitivity in skeletal muscle performance has been reviewed to investigate the extent to which individuals can acclimate to chronic changes in their thermal environment. The effects of thermal sensitivity of muscle performance are placed in a wider context by relating thermal sensitivity of skeletal muscle performance to aspects of vertebrate species distribution.