Time-of-day effects in maximal anaerobic leg exercise in tropical environment: a first approach

Moderate intensity active recovery improves performance in a second wingate test in cyclists

Background

The aim of the present study was to compare the effects of active (AR) vs. passive recovery (PR) between two Wingate Anaerobic Tests (WAnT) on power output, blood lactate (BLa) and oxygen consumption (VO₂) in a second WAnT.

Methods

Twelve well-trained cyclists underwent three experimental sessions. In the first session, they completed an incremental test for maximum oxygen consumption (V O₂max) and lactate threshold determination. In the second and third sessions, cyclists completed, in random order, two WAnT tests separated by 30-min recovery intervals, during which they performed an AR at 70% of the V O₂ at lactate threshold (V O₂LT) or a PR. The cardiorespiratory, metabolic, and mechanical responses in the two recovery conditions were compared.

Results

No differences were found in the VO₂-on kinetics between WAnT tests (p > 0.05). As expected, blood lactate kinetics showed a greater clearance (from the 7th to the 31st min, p < 0.001) during AR; however, no differences were found in peak BLa between conditions (p > 0.05). Mean and peak power, and total work were significantly higher in the second WAnT after AR (p < 0.001), while the power decline was also lower in this condition (p < 0.05).

Conclusion

The submaximal active recovery strategy used in the present study can induce an improvement in mechanical power and total work during a second WAnT. This suggests that AR of submaximal intensity can induce a post-activation performance enhancement when used during the recovery phase between maximal anaerobic efforts.

Revisiting Motor Imagery Guidelines in a Tropical Climate: The Time-of-Day Effect

(1) Background: Motor imagery (MI) is relevantly used to improve motor performance and promote rehabilitation. As MI ability and vividness can be affected by circadian modulation, it has been proposed that MI should ideally be performed between 2 p.m. and 8 p.m. Whether such a recommendation remains effective in a hot and humid environment, such as a tropical climate, remains unknown. (2) Methods: A total of 35 acclimatized participants completed a MI questionnaire and a mental chronometry test at 7 a.m., 11 a.m., 2 p.m., and 6 p.m. Visual (VI) and kinesthetic imagery (KI) abilities, as well as temporal congruence between actual walking and MI, were collected. Ambient temperature, chronotypes, thermal comfort, affect, and fatigue were also measured. (3) Results: VI scores were higher at 6 p.m. than at 7 a.m., 11 a.m., and 2 p.m., and temporal congruence was higher at 6 p.m. than at 7 a.m. Comfort, thermal sensation, and positive affect scores were higher at 7 a.m. and 6 p.m. (4) Conclusion: Data support greater imagery ability and accuracy when participants perceive the environment as more pleasant and comfortable. MI guidelines typically provided in neutral climates should therefore be adapted to tropical climates, with MI training sessions ideally scheduled in the late afternoon.

Sex and limb comparisons of neuromuscular function in the morning versus the evening

The time-of-day influence on neuromuscular function is well-documented, but important details remain elusive. It is currently unknown whether males and females differ in their diurnal variation for optimal neuromuscular performance. The purpose of this study is to identify the time-of-day influence on neuromuscular function between sexes and determine whether these responses differ for the upper versus lower limbs. A group of males (n = 12) and females (n = 15) completed neuromuscular performance testing in the morning (07:00-09:00) and evening (17:00-19:00) on separate days in a randomized order. Maximal force, the normalized rate of force development, EMG, normalized EMG rise, and submaximal force steadiness were compared between morning and evening hours. The main findings show that maximal force was greater in the evening for the knee extensors (d = 0.570, p < 0.01) but not the elbow flexors (d = 0.212, p = 0.281), whereas maximal muscle excitation was greater in the evening for the biceps brachii (d = 0.348, p < 0.01) but not the vastus lateralis (d = 0.075, p = 0.526) with no influence of sex. However, force steadiness during knee extension was superior in the evening versus the morning for males (d = 0.734, p = 0.025) and compared to evening values for females (g = 1.19, p = 0.032). Overall, these findings show that time-of-day affects the knee extensors more than the elbow flexors and that diurnal variability between sexes appears to be task-dependent.

Diurnal Variation in Maximum Endurance and Maximum Strength Performance: A Systematic Review and Meta-analysis

INTRODUCTION

Diurnal variations in physical performance can affect athletes' success in competitive sports depending on whether the time of peak performance concurs with the time of competition. The purpose of this systematic review was to investigate the diurnal variation in maximum endurance and strength performance.

METHODS

The databases PubMed, EMBASE, and Web of Science were searched from inception to November 2020. The search string was externally reviewed according to PRESS guidelines, and the review was conducted in accordance to PRISMA guidelines and registered beforehand on PROSPERO. Eligibility criteria were that 1) the studies included humans and 2) any kind of maximum endurance or maximum strength test was performed at 3) a minimum of three different times of the day. There were no restrictions regarding study design, participants' sex, age, or fitness levels.

RESULTS

From 10,460 screened articles, 63 articles met all three inclusion criteria. Meta-analysis on the harmonizable 29 studies provided evidence for diurnal variations in physical performance. In detail, the overall effect sizes (95% confidence intervals) were 0.23 (0.05-0.40), 0.73 (0.37-1.09), 0.39 (0.18-0.60), and 0.79 (0.28-1.30) for endurance exercise tests, maximum power output in the Wingate test, handgrip strength, and jump height, respectively, all in favor of higher performance in the evening. The overall risk of bias in individual studies was moderately high.

CONCLUSIONS

There is strong evidence that anaerobic power and jump height are maximal between 1300 and 2000 h. There is some evidence that handgrip strength peaks between 1400 and 2100 h, but only little evidence that there is a time of peak performance in maximum endurance.

Factors Contributing to Diurnal Variation in Athletic Performance and Methods to Reduce Within-Day Performance Variation: A Systematic Review

ABSTRACT

Kusumoto, H, Ta, C, Brown, SM, and Mulcahey, MK. Factors contributing to diurnal variation in athletic performance and methods to reduce within-day performance variation: A systematic review. J Strength Cond Res 35(12S): S119-S135, 2021-For many individuals, athletic performance (e.g., cycle ergometer output) differs based on the time of day (TOD). This study identified factors contributing to diurnal variation in athletic performance and methods to reduce TOD performance variation. Comprehensive searches of PubMed, Ovid, EMBASE, Web of Science, and Cochrane Libraries were conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Peer-reviewed publications reporting quantitative, significant diurnal variation (p ≤ 0.05) of athletic performance with explanations for the differences were included. Studies providing effective methods to reduce diurnal variation were also included. Literature reviews, studies involving nonhuman or nonadult subjects, studies that intentionally manipulated sleep duration or quality, and studies deemed to be of poor methodological quality using NIH Quality Assessment Tools were excluded. Forty-nine studies met the inclusion criteria. Body temperature differences (n = 13), electromyographic parameters (n = 10), serum biomarker fluctuations (n = 5), athlete chronotypes (n = 4), and differential oxygen kinetics (n = 3) were investigated as significant determinants of diurnal variation in sports performance. Successful techniques for reducing diurnal athletic performance variability included active or passive warm-up (n = 9), caffeine ingestion (n = 2), and training-testing TOD synchrony (n = 3). Body temperature was the most important contributor to diurnal variation in athletic performance. In addition, extended morning warm-up was the most effective way to reduce performance variation. Recognizing contributors to diurnal variation in athletic performance may facilitate the development of more effective training regimens that allow athletes to achieve consistent performances regardless of TOD.

Does circadian rhythm have an impact on anaerobic performance, recovery and muscle damage?

This study aimed to examine the effect of circadian rhythms (CR) on anaerobic performance and subsequent recovery, muscle damage, and respiratory muscle strength. Twenty diurnally active male football players (age, 22.20 ± 3.14 y) were asked to perform the Wingate anaerobic power test three times for 30 s each at 09:00, 14:00 and 19:00 h, with a minimum recovery period of 1 week between each testing day. Pretest oral temperature, respiratory muscle strength, oxygen saturation, and rating of perceived exertion were recorded at three different time of the day. To examine post-exercise recovery, heart rate (HR) and lactic acid (LA) levels were recorded before and after the tests. Blood samples were collected 20 min after each test to assess muscle damage. The body temperature taken at 19:00 h was the highest of the three (p < .01). After the tests, the LA value at 19:00 h was higher than that at 09:00 h (p < .05). According to CR, the HR values measured after anaerobic exercise were higher at 14:00 h (p < .05). The peak power value was higher at 14:00 h than at 19:00 h (p < .058). CR does not affect muscle damage and respiratory muscle strength. Further, at 14:00 h, anaerobic power was higher and recovery occurred faster compared to the other test times of 09:00 and 19:00 h. Therefore, it is recommended that anaerobic training should be performed early in the afternoon.

Time-of-Day Effects on Short-Duration Maximal Exercise Performance

Time-of-day dependent fluctuations in exercise performance have been documented across different sports and seem to affect both endurance and resistance modes of exercise. Most of the studies published to date have shown that the performance in short-duration maximal exercises (i.e. less than 1 min - e.g. sprints, jumps, isometric contractions) exhibits diurnal fluctuations, peaking between 16:00 and 20:00 h. However, the time-of-day effects on short duration exercise performance may be minimized by the following factors: (1) short exposures to moderately warm and humid environments; (2) active warm-up protocols; (3) intermittent fasting conditions; (4) warming-up while listening to music; or (5) prolonged periods of training at a specific time of day. This suggests that short-duration maximal exercise performance throughout the day is controlled not only by body temperature, hormone levels, motivation and mood state but also by a versatile circadian system within skeletal muscle. The time of day at which short-duration maximal exercise is conducted represents an important variable for training prescription. However, the literature available to date lacks a specific review on this subject. Therefore, the present review aims to (1) elucidate time-of-day specific effects on short-duration maximal exercise performance and (2) discuss strategies to promote better performance in short-duration maximal exercises at different times of the day.

Diurnal effects of prior heat stress exposure on sprint and endurance exercise capacity in the heat

Active individuals often perform exercises in the heat following heat stress exposure (HSE) regardless of the time-of-day and its variation in body temperature. However, there is no information concerning the diurnal effects of a rise in body temperature after HSE on subsequent exercise performance in a hot environnment. This study therefore investigated the diurnal effects of prior HSE on both sprint and endurance exercise capacity in the heat. Eight male volunteers completed four trials which included sprint and endurance cycling tests at 30 °C and 50% relative humidity. At first, volunteers completed a 30-min pre-exercise routine (30-PR): a seated rest in a temperate environment in AM (AmR) or PM (PmR) (Rest trials); and a warm water immersion at 40 °C to induce a 1 °C increase in core temperature in AM (AmW) or PM (PmW) (HSE trials). Volunteers subsequently commenced exercise at 0800 h in AmR/AmW and at 1700 h in PmR/PmW. The sprint test determined a 10-sec maximal sprint power at 5 kp. Then, the endurance test was conducted to measure time to exhaustion at 60% peak oxygen uptake. Maximal sprint power was similar between trials (p = 0.787). Time to exhaustion in AmW (mean±SD; 15 ± 8 min) was less than AmR (38 ± 16 min; p < 0.01) and PmR (43 ± 24 min; p < 0.01) but similar with PmW (24 ± 9 min). Core temperature was higher from post 30-PR to 6 min into the endurance test in AmW and PmW than AmR and PmR (p < 0.05) and at post 30-PR and the start of the endurance test in PmR than AmR (p < 0.05). The rate of rise in core temperature during the endurance test was greater in AmR than AmW and PmW (p < 0.05). Mean skin temperature was higher from post 30-PR to 6 min into the endurance test in HSE trials than Rest trials (p < 0.05). Mean body temperature was higher from post 30-PR to 6 min into the endurance test in AmW and PmW than AmR and PmR (p < 0.05) and the start to 6 min into the endurance test in PmR than AmR (p < 0.05). Convective, radiant, dry and evaporative heat losses were greater on HSE trials than on Rest trials (p < 0.001). Heart rate and cutaneous vascular conductance were higher at post 30-PR in HSE trials than Rest trials (p < 0.05). Thermal sensation was higher from post 30-PR to the start of the endurance test in AmW and PmW than AmR and PmR (p < 0.05). Perceived exertion from the start to 6 min into the endurance test was higher in HSE trials than Rest trials (p < 0.05). This study demonstrates that an approximately 1 °C increase in core temperature by prior HSE has the diurnal effects on endurance exercise capacity but not on sprint exercise capacity in the heat. Moreover, prior HSE reduces endurance exercise capacity in AM, but not in PM. This reduction is associated with a large difference in pre-exercise core temperature between AM trials which is caused by a relatively lower body temperature in the morning due to the time-of-day variation and contributes to lengthening the attainment of high core temperature during exercise in AmR.

The Effect of Chronotype on Psychophysiological Responses during Aerobic Self-Paced Exercises

It was hypothesized that an individual's chronotype might influence the response to physical activity at a given time of day. This study aimed to analyze the psychophysiological responses during a walking task at different times of day in individuals with different chronotypes. 46 students ( M age = 24.8yr., SD = 7.2) filled in the Morningness-Eveningness Questionnaire to determine chronotypes. Heart rate, walking time, and the rating of perceived exertion (RPE) were measured during two self-paced walking sessions: one in the morning (08:30) and one in the afternoon (15:30). A multivariate analysis of variance found a significant interaction between chronotype and time of day. The post hoc analysis showed a significant difference for RPE in the morning session, with evening types reporing a higher RPE compared with the morning types. The chronotype and the time of day when a physical task is undertaken can influence the RPE response, although it might not influence physiological or performance parameters. This has to be taken into account, because it can affect test reliability as well as possibly have a negative influence on the affective responses to a given task.

Sleep, circadian rhythms, and athletic performance

Sleep deprivation and time of day are both known to influence performance. A growing body of research has focused on how sleep and circadian rhythms impact athletic performance. This review provides a systematic overview of this research. We searched three different databases for articles on these issues and inspected relevant reference lists. In all, 113 articles met our inclusion criteria. The most robust result is that athletic performance seems to be best in the evening around the time when the core body temperature typically is at its peak. Sleep deprivation was negatively associated with performance whereas sleep extension seems to improve performance. The effects of desynchronization of circadian rhythms depend on the local time at which performance occurs. The review includes a discussion of differences regarding types of skills involved as well as methodological issues.

Does raising morning rectal temperature to evening levels offset the diurnal variation in muscle force production?

Muscle force production and power output in active males, regardless of the site of measurement (hand, leg, or back), are higher in the evening than in the morning. This diurnal variation is attributed to motivational, peripheral and central factors, and higher core and, possibly, muscle temperatures in the evening. This study investigated whether increasing morning rectal temperatures to evening resting values, by active or passive warm-ups, leads to muscle force production and power output becoming equal to evening values in motivated subjects. Ten healthy active males (mean ± SD: age, 21.2 ± 1.9 yrs; body mass, 75.4 ± 8 kg; height, 1.76 ± .06 m) completed the study, which was approved by the University Ethics Committee. The subjects were familiarized with the techniques and protocol and then completed four sessions (separated by at least 48 h): control morning (07:30 h) and evening (17:30 h) sessions (with an active 5-min warm-up) and then two further sessions at 07:30 h but proceeded by an extended active or passive warm-up to raise rectal temperature to evening values. These last two sessions were counterbalanced in order of administration. During each trial, three measures of handgrip strength, isokinetic leg strength measurements (of knee flexion and extension at 1.05 and 4.19 rad.s(-1) through a 90° range of motion), and four measures of maximal voluntary contraction (MVC) on an isometric ergometer (utilizing the twitch-interpolation technique) were performed. Rectal and intra-aural temperatures, ratings of perceived exertion (RPE) and thermal comfort (TC) were measured. Measurements were made after the subjects had reclined for 30 min and after the warm-ups and prior to the measurement of handgrip and isokinetic and isometric ergometry. Muscle temperature was taken after the warm-up and immediately before the isokinetic and MVC measurements. Warm-ups were either active (cycle ergometer at 150 W) or passive (resting in a room at 35 °C, relative humidity 45%). Data were analyzed using analysis of variance models with repeated measures. Rectal and intra-aural temperatures were higher at rest in the evening (.56 °C and .74 °C; p < .05) than in the morning, but there were no differences after the active or passive warm-ups, the subjects' ratings of thermal comfort reflecting this. Muscle temperatures also displayed significant diurnal variation, with higher values in the evening (~.31 °C; p < .05). Grip strength, isokinetic knee flexion for peak torque and peak power at 1.05 rad.s(-1), and knee extension for peak torque at 4.19 rad.s(-1) all showed higher values in the evening. All other measures of strength or power showed a trend to be higher in the evening ( .10 > p > .05). There was no significant effect of active or passive warm-ups on any strength or power variable, and subjects reported maximal values for effort for each strength measure. In summary, effects of time of day were seen in some measures of muscle performance but, in this population of motivated subjects, there was no evidence that increasing morning rectal temperature to evening values by active or passive warm-up increased muscle strength to evening values.

The effect of training at a specific time of day: a review

This article focuses on physical performances after training at a specific time of day. To date, although the effect of time of day on aerobic performances appears to be equivocal, during anaerobic exercises, the effect of time of day has been well established with early morning nadirs and peak performances in the late afternoon. These diurnal rhythms can be influenced by several factors such as the regular training at a specific time of day. Indeed, regular training in the morning hours may increase the lower morning performances to the same or even higher level as their normal diurnal peak typically observed in the late afternoon by a greater increase of performance in the evening. However, regular training in the evening hours may increase the morning-evening (i.e., amplitude of the rhythm) difference by a greater increase of performance in the late afternoon. Therefore, adaptations to training are greater at the time of day at which training is regularly performed than at other times. Nevertheless, although modifications in resting hormones concentrations could explain this time-of-day specific adaptations, precise information on the underlying mechanisms is lacking.

Sports performance: is there evidence that the body clock plays a role?

Athletic performance shows a time-of-day effect, possible causes for which are environmental factors (which can be removed in laboratory studies), the sleep-wake cycle and the internal "body clock". The evidence currently available does not enable the roles of these last two factors to be separated. Even so, results indicate that the body clock probably does play some role in generating rhythms in sports performance, and that to deny this is unduly critical. Protocols to assess the separate roles of the body clock and time awake are then outlined. A serious impediment to experimental work is muscle fatigue, when maximal or sustained muscle exertion is required. Dealing with this problem can involve unacceptably prolonged protocols but alternatives which stress dexterity and eye-hand co-ordination exist, and these are directly relevant to many sports (shooting, for example). The review concludes with suggestions regarding the future value to sports physiology of chronobiological studies.

Effects of active warm-up and diurnal increase in temperature on muscular power

PURPOSE

To investigate the effects of both an active warm-up (AWU) and the diurnal increase in body temperature on muscular power.

METHODS

Eight male subjects performed maximal cycling sprints in the morning (7:00-9:00 a.m.) and afternoon (5:00-7:00 p.m.) either after an AWU or in a control condition. The AWU consisted of 12 min of pedaling at 50% of & OV0312;O2 max inter-spersed with three brief accelerations of 5 s.

RESULTS

Rectal temperature, maximal force developed during the cycling sprint, and muscular power were higher in the afternoon than in the morning (P<0.05). Rectal temperature, calculated muscular temperature, and muscular power were higher after AWU than in control condition (P<0.05).

CONCLUSIONS

The beneficial effect of an AWU can be combined with that of the diurnal increase in central temperature to improve muscular power.

Time of Day Influences the Environmental Effects on Muscle Force and Contractility

PURPOSE

To investigate the effects of environmental temperature and the diurnal increase in body temperature on muscle contractile processes, 11 male subjects performed maximal and submaximal isometric contractions of the knee extensors with recording of the electromyographic activity in four different conditions (morning/neutral, morning/moderately warm and humid, afternoon/neutral, and afternoon/moderately warm and humid).

METHODS

The morning experiments were conducted between 0700 and 1900 h, and the afternoon experiments were conducted between 0500 and 0700 h. The mean laboratory temperatures and humidity were 20.5 (+/-1) degrees C + 67 (+/-4)% and 29.5 (+/-0.8) degrees C + 74 (+/-10)% for the neutral and moderately warm and humid conditions, respectively.

RESULTS

Results showed a significant diurnal increase in both rectal and skin temperatures whatever the environmental conditions, and an increase in the skin temperature after a 60-min moderately warm exposure. The major finding of this study was an interaction effect of time of day and environmental conditions on the force/electromyographic activity ratio. That suggests that skeletal muscle contractility was differently increased by the passive warm-up effect of a moderately warm exposure, depending on the diurnal variation in body temperature. This conclusion is supported by an increase in force in the morning only after a 60-min warm exposure (+19%) and in a neutral environment only with the diurnal increase in body temperature (+12%).

CONCLUSION

In summary, our data showed that both the warm exposure and the diurnal increase in body temperature influence muscle contractility and consequently muscle strength. However, the improvement in muscle contractility after these two passive warm-ups cannot be combined in order to improve force to a greater level.

Time-of-day effects on anaerobic muscular power in a moderately warm environment

This study evaluated the influence of a neutral vs. a moderately warm environment on the diurnal variation in muscular power. Twelve male subjects [27.0 (+/-4) years] performed two different jump tests [a squat jump (SJ) and a counter-movement jump (CMJ)] and a brief maximal sprint on cycle ergometer (CS) in four different conditions (morning/neutral, morning/moderately warm and humid, afternoon/neutral, and afternoon/moderately warm and humid). The morning experiments were conducted between 07:00 and 09:00 h, and the afternoon experiments were conducted between 17:00 and 19:00 h. The mean laboratory temperatures and humidity were 20 (+/-1) degrees C, 70 (+/-5)% and 29 (+/-1) degrees C, 57 (+/-4)% for the neutral and moderately warm and humid conditions, respectively. Rectal temperature and leg skin temperature were significantly dependent on both time-of-day and ambient temperature. An interaction effect (P < 0.05) was noted between time-of-day and ambient temperature for the power developed for the CMJ, the SJ, and half of a pedal revolution during the cycling sprint. In summary, (i) the same subjects were influenced by time-of-day differently, depending on the ambient temperature during testing; (ii) time-of-day affected muscular performance only in the neutral condition, (iii) the moderately warm and humid condition blunted the diurnal variation in muscular performance, and (iv) the effect of the ambient temperature was dependent on time-of-day.