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Exercise and the Circadian Variation in Body Temperature Measures
Abstract
This study examined the existence of circadian rhythms in rectal temperature (Tr) and selected skin temperatures at rest and during light (82 W) and medium (147 W) exercise on a cycle ergometer. Each intensity was sustained for 5 min and then followed by a graded exercise test to exhaustion. The Tr and skin temperatures were also measured on cessation of exercise and 4 min post-exercise. Fifteen males participated, measurements covering six interspersed times of day. The mean exercise time to exhaustion of 19.83 min was independent of the time of day and caused a constant rise of 0.7 degree C in Tr. Significant rhythms were observed in Tr, Tc (chest), and Ta (arm) under all conditions: findings for Tl (leg) were nonsignificant at maximal exercise and post-exercise (P greater than 0.05). The crest time for Tl had a significant lead over that of Tr and the other skin sites which were in phase concordance, mean difference in crest times being 4.73 h at rest and 4.42 h during submaximal exercise. The results demonstrated constancy with time of day in the thermal load imposed by fixed exercise. This was reinforced when mean skin and mean body temperatures were computed. The general pattern did not apply to the exercised limb, the pre-exercise rhythm disappearing after 10 min exercise. Differential heat conductances according to skin sites are implicated in the phase differences between the leg and the other temperature sites.
... In this experiment, it was also observed that the cutaneous temperature did not differ between sex, but between the evaluated periods, evidencing an 0.23°C increase in mean abdominal surface temperature during the afternoon period. The same temperature elevation effect was also observed in other studies in humans, in which face 40 and of thoracic surface temperatures were measured 41 . The authors concluded that, just like body temperature, cutaneous temperature follows circadian patterns, influenced by hormonal action and catecholamines throughout the amplitude of the day 41 . ...
... The same temperature elevation effect was also observed in other studies in humans, in which face 40 and of thoracic surface temperatures were measured 41 . The authors concluded that, just like body temperature, cutaneous temperature follows circadian patterns, influenced by hormonal action and catecholamines throughout the amplitude of the day 41 . In these circumstances, vasomotor tonus disparity occurs between periods, and in the afternoon period vasodilatation and consequent greater peripheral blood flow were observed 42 . ...
... Temperatures were milder in the morning, with peaks between 00-04 hours and with acrophase phase between 16-20 hours on the afternoon period 41 . ...
... Therefore, as the temperature rises from the moment of waking up to 6 o'clock and the physical performance of the troops is heavily influenced by the temperature variation of the body, the best time to increase efficiency and mobilize your troops for missions is in the afternoon hours. Reilly et al. [38] showed that in the early morning, the reaction times (both for audio and visual stimuli) is faster because the body temperature is at its maximum. Souissi et al. [39] also showed that the time to maximize and minimize sports performances, especially anaerobic exercise, can be estimated by recording the subterranean temperature. ...
... The results showed that subjects undergoing training in the afternoon showed an increase in VO 2max and a significant decrease in blood lactic acid and heart rate. The results indicate that the aerobic capacity is often higher in the afternoon [38]. ...
... 15 VO 2max measured in athletes who practice at afternoon is higher and there is a significant decrease in blood lactate and heart rate [38]. It is recommended that competitions such as physical fitness and endurance running with different distances that emphasize the aerobic factor should be held in the afternoon. ...
Background
Disruption of the circadian rhythm also has significant influences on the exercise function. Therefore, the aim of this study was to review the effects of circadian rhythm on physical fitness and athletic performance in military personnel.MethodologyAn online search was done in web of science (WoS), Ovid, Scopus and PubMed (MeSH) databases with the following combination of keywords: “chronobiology” AND “performance of military” AND “exercise”.ResultsA total of articles were identified, physical fitness and sport performance of military forces is severely affected by the science of chronobiology and 24-h circadian rhythm. In humans, these articles showed circadian rhythm with affects on performance of various organs in the body, such that the body temperature, heart rate, hormonal secretion, electrolyte excretion, blood pressure, plasma tyrosine concentrations, free amino acids, cholesterol production and even behavior can affect physical fitness and athletic performance in the military force.Conclusions
Based on the analyzed articles, it is concluded that circadian rhythm has a significant effect on exercise performance, aerobic and anaerobic power, muscular endurance and flexibility, and hormonal secretion. For this reason, it is recommended to the organizers of the competitions and coaches should take into consideration the effects of circadian rhythm on the athletic performance of the military, the scheduling of competitions and exercises.
... Body composition in terms of sum of skinfolds (Harpenden skinfold caliper; Baty International, West Sussex, United Kingdom) was assessed through an 8-site skinfold test. 19 On interval testing session days, subjects were asked to complete a Recovery-Stress Questionnaire for Athletes prior to exercise. Nude body weight was taken prior to and following the interval session protocol. ...
... PPO was significantly different between intervals (P = .002) with the fifth interval (final; 570[19] W) significantly higher than the second (517[19] W; P = .008), third (410[15] W; P = .001), ...
... PPO was significantly different between intervals (P = .002) with the fifth interval (final; 570[19] W) significantly higher than the second (517[19] W; P = .008), third (410[15] W; P = .001), ...
Purpose:
To examine the effect of environmental temperature (TA) on performance and physiological responses (eg, body temperature, cardiopulmonary measures) during a high-intensity aerobic interval session. It was hypothesized that power output would be highest in the 13°C condition and lower in the 5°C, 22°C, and 35°C conditions.
Methods:
Eleven well-trained cyclists randomly completed 4 interval sessions at 5°C, 13°C, 22°C, and 35°C (55% [13%] relative humidity), each involving five 4-min intervals interspersed with 5 min of recovery. During the intervals, power output, core temperature (TC), skin temperature, VO2, and heart rate were recorded.
Results:
Mean session power output for 13°C (366 [32] W) was not higher than 5°C (363 [32] W; P = 1.00, effect size = 0.085), 22°C (364 [36] W; P = 1.00, effect size = 0.061), or 35°C (352 [31] W; P = .129, effect size = 0.441). The 5th interval of the 35°C condition had a lower power output compared with all other TA. TC was higher in 22°C compared with both 5°C and 13°C (P = .001). VO2 was not significantly different across TA (P = .187). Heart rate was higher in the 4th and 5th intervals of 35°C compared with 5°C and 13°C.
Conclusions:
This study demonstrates that while mean power outputs for intervals are similar across TA, hot TA (≥35°C) reduces interval power output later in a training session. Well-trained cyclists performing maximal high-intensity aerobic intervals can achieve near-optimal power output over a broader range of TA than previous literature would indicate.
... Nude body weight was taken prior to and following the interval session protocol. Interval sessions were performed at the same time of day for each participant to avoid circadian body temperature variations 166 . Participants were instructed to wear the same athletic clothing to each interval session and cycling jerseys remained zipped up in all TA. ...
... Mallinckrodt Medical, St. Luis, MO, USA) inserted ~10 cm past the anal sphincter. TSk was Test sessions measuring TC and TSk temperature were performed at the same time of day for each participant to avoid circadian body temperature variations166 . Fluctuations in temperature data of greater than 0.10°C/second were removed. ...
Endurance athletes typically spend the large majority of training (> 70%) at low intensities (i.e. below lactate threshold) coupled with short and intermittent bouts of high-intensity exercise or interval training (HIIT). Despite HIIT being a relatively small part of training in terms of duration, it has a substantial effect on the adaptations to endurance training. While it is well-established endurance exercise performance is affected in both hot and cold environmental conditions, the effect ambient temperature (TA; frequently referred to as environmental temperature) has on HIIT as performed by an endurance athlete population is not well understood. Therefore, the overall purpose of this thesis was to investigate the effects TA has on HIIT in an endurance trained population. Specifically, this thesis aimed to increase the understanding of how TA acutely affects performance and physiological responses during high-intensity intervals (Study 1); how repeated exposure to TA manipulates physiological responses during high-intensity intervals (Study 2), and how TA affects performance outcomes of a HIIT intervention (Study 3).
In Study 1, eleven well-trained cyclists completed 4 interval sessions at 5°C, 13°C, 22°C, and 35°C (55 ± 13% RH) in a randomised order. Each session involved 5 x 4-minute intervals interspersed with 5 minutes of recovery. During the intervals, power output, core temperature (TC), oxygen consumption (VO2), and heart rate (HR) were recorded. It was hypothesized that the 13°C condition would have the highest mean power output compared to the other TA conditions. However, mean session power output for 13°C (366 ± 32 W) was not significantly different than 5°C (363 ± 32 W), 22°C (364 ± 36 W), or 35°C (352 ± 31 W). Power output was lower in the 5th interval of the 35°C condition, compared with all other TA. TC was higher in 22°C compared with both 5°C and 13°C (P= .001). VO2 was not different across TA. HR was higher in the 4th and 5th intervals of 35°C compared with 5°C and 13°C. It was concluded well-trained cyclists performing maximal high-intensity aerobic intervals can achieve near optimal power output over a broader range of TA than previous literature may indicate.
Study 1 indicated TA had acute effects on performance and physiological responses during high-intensity aerobic intervals, especially in terms of cardiovascular stress. However, whether acute cardiorespiratory and thermoregulatory responses during high-intensity intervals change as a result of repeated TA exposures (i.e. during HIIT) was unknown. In Study 2, 20 trained cyclists and triathletes completed a 4-week (8 session) HIIT intervention in either cool (13°C) or hot (35°C) conditions. The HIIT intervention utilized the interval protocol from Study 1 and recorded cardiopulmonary and thermoregulatory measures during the first (INT8) and last (INT8) sessions. It was observed that time spent at or near maximal oxygen consumption (VO2max) during HIIT was greater in 13°C (877 ± 297 seconds) than 35°C (421 ± 395 seconds), but did not change for either TA condition between INT1 and INT8. HR was not significantly different between 13°C (164 ± 9 bpm) and 35°C HIIT (164 ± 12 bpm). TC significantly decreased in 35°C HIIT between INT1 and INT8. These results potentially indicate the relationship between time spent at or near VO2max and cardiovascular strain during HIIT is influenced by TA. Additionally, HIIT performed intermittently (~2x per week) at 35°C resulted in demonstrated evidence for heat acclimation in endurance athletes.
Study 1 and Study 2 provided findings for performance, cardiorespiratory, and thermoregulatory responses during acute high-intensity interval sessions and after repeated exposure to TA. In particular, differences in time spent at or near VO2max between 13°C and 35°C HIIT, and changes in thermoregulatory responses over the course of a HIIT intervention both have the potential to affect endurance performance outcomes and coinciding physiological responses. In order to investigate this, Study 3 evaluated submaximal warm-ups and 20 km time-trials in temperate conditions (22°C) before (TT1) and after (TT2) the HIIT interventions from Study 2. Gross mechanical efficiency (GME) was measured during the warm-up (at 50% peak power output), whilst power output and HR were measured during the 20 km TT. Rate of perceived exertion (RPE) and body temperature (TB) were measured through the warm-up and time-trial. It was demonstrated that time-trial power output was increased after HIIT interventions in both the 13°C (3%; HIIT13) and 35°C (7%; HIIT35), yet no differences between groups for power output, HR, or RPE were noted. Within subject increases for HR and RPE during the 20 km time-trial were noted in HIIT13, but not in HIIT35. GME approached a significant decrease (P= .051) in HIIT13. A significant interaction in TB was observed between groups and TT1 and TT2 during both the 20 km time-trial and submaximal warm-up. These findings indicate that HIIT performed in hot and cool conditions result in similar temperate time-trial performance outcomes. However, changes in cardiorespiratory, thermoregulatory, and subjective responses during aerobic exercise after a HIIT intervention appear to be dependent on the TA HIIT is performed in.
The results of this thesis demonstrate TA acutely affects performance, and cardiorespiratory and thermoregulatory responses during high-intensity intervals; repeated exposures to TA during HIIT can stimulate changes in thermoregulatory responses; and TA exposure during HIIT has limited effect on temperate endurance performance, yet affects coinciding cardiorespiratory, thermoregulatory, and subjective responses. These findings will assist coaches and athletes to make better informed decisions relating to HIIT prescription and acclimating endurance athletes to TA.
... The association of the circadian rhythm with a great number of physiological variables in a sportive performance has attracted the attention of the researchers and it has been researched extensively. Studies have found circadian changes in maximal aerobic strength (Hill et al. 1992;Hill 1996), heart rate (Akkurt et al. 1996;Gunes et al. 1998;Reilly and Brooks 1986), blood pressure (Gunes et al. 1998;Reilly et al. 1984) and the central body heat (Reilly and Brooks 1986). In addition, age, type and intensity of exercise, jet-lag effect, sleeplessness and training time have also been found to affect the aforementioned daily changes (Reilly et al. 2000). ...
... The association of the circadian rhythm with a great number of physiological variables in a sportive performance has attracted the attention of the researchers and it has been researched extensively. Studies have found circadian changes in maximal aerobic strength (Hill et al. 1992;Hill 1996), heart rate (Akkurt et al. 1996;Gunes et al. 1998;Reilly and Brooks 1986), blood pressure (Gunes et al. 1998;Reilly et al. 1984) and the central body heat (Reilly and Brooks 1986). In addition, age, type and intensity of exercise, jet-lag effect, sleeplessness and training time have also been found to affect the aforementioned daily changes (Reilly et al. 2000). ...
The aim of this study was to investigate the endurance performance according to the Circadian Cycle. For this aim, 38 male students studying at the Faculty of Sports Sciences (age between 20-27 years) participated in the study. 20 m Shuttle Run test was used to measure the aerobic endurance of the performance. The measurements were taken in the morning (09:00am), afternoon (2:00pm) or evening (7:00pm) time. The test sessions were performed in a random order. For the statistical analysis Friedman Two Way Variance analyses and Wilcoxon Signed Rank test were used. The results of the study showed that the number of shuttles were found to be higher in the afternoon than in the morning time (p<0.0167). Although there is no statistically significant difference, the number of shuttles were found more in the afternoon than the number of shuttles in the evening. As a conclusion, the best aerobic performance was performed in the afternoon. Due to the presence of such a difference, the measurement times have been noted for future scientific studies.
... Several studies have investigated circadian variations of various body systems. Circadian variation in some cardiovascular parameters such as cardiac output during exercise has yet to be identified [24]. Other variables such as systolic, diastolic blood pressure and heart rate tend to exhibit circadian rhythmicity, although there are difficulties measuring such parameters with the required accuracy under exercise conditions. ...
... Other studies using an incremental exercise task have demonstrated the heart rate irrespective just prior to exhaustion, when exercise intensity is maximal, does not vary with time of day [25]. Such discrepancies might be related to a reduction in the range of circadian variability with increasing levels of exercise or a failure to detect the circadian rhythm as the ceiling of physiological capability is reached during the exercise test [24,26]. ...
The present study investigated the circadian rhythm variations of heart rate and blood pressure due to 1 (60 minutes) and 2 split exercise sessions (2 × 30 minutes) a day. Fourteen healthy students from the University of Tabriz volunteered to participate in current study. Two groups of subjects in a crossover design were randomly allocated as group I (one session per day, twice a day) and vice versa for group II. Having completed the test (treadmill running with an intensity of 70 per cent of Maximum Heart rate), heart rate and blood pressure (both systolic and diastolic) were measured every two hours for 24 hours. Repeated measure (ANOVA) was used for analysis. Each of variables showed normal circadian rhythm. Compared to two split exercise sessions a day, one session a day demonstrated that the level of heart rate circadian rhythm has been set at a rate of five percent below. Circadian rhythm of systolic and diastolic blood pressure in the two split sessions compared with one session a day tended to be set at a lower level and higher level respectively. One aerobic exercise session compared to two split sessions a day with the same total time of exercise a day may decrease systolic blood pressure and heart rate within 24 hours following aerobic treadmill running exercise. Split exercise session could be an appropriate approach for increasing more calories and lowering blood pressure among health seekers while it may delay recovery for the next day training or competition for professional athletes.
... The association of the circadian rhythm with a great number of physiological variables in a sportive performance has attracted the attention of the researchers and it has been researched extensively. Studies have found circadian changes in maximal aerobic strength (Hill et al. 1992;Hill 1996), heart rate (Akkurt et al. 1996;Gunes et al. 1998;Reilly and Brooks 1986), blood pressure (Gunes et al. 1998;Reilly et al. 1984) and the central body heat (Reilly and Brooks 1986). In addition, age, type and intensity of exercise, jet-lag effect, sleeplessness and training time have also been found to affect the aforementioned daily changes (Reilly et al. 2000). ...
... The association of the circadian rhythm with a great number of physiological variables in a sportive performance has attracted the attention of the researchers and it has been researched extensively. Studies have found circadian changes in maximal aerobic strength (Hill et al. 1992;Hill 1996), heart rate (Akkurt et al. 1996;Gunes et al. 1998;Reilly and Brooks 1986), blood pressure (Gunes et al. 1998;Reilly et al. 1984) and the central body heat (Reilly and Brooks 1986). In addition, age, type and intensity of exercise, jet-lag effect, sleeplessness and training time have also been found to affect the aforementioned daily changes (Reilly et al. 2000). ...
The aim of this study was to investigate the endurance performance according to the Circadian Cycle.
For this aim, 38 male students studying at the Faculty of Sports Sciences (age between 20-27 years) participated in the study. 20 m Shuttle Run test was used to measure the aerobic endurance of the performance. The measurements were taken in the morning (09:00am), afternoon (2:00pm) or evening (7:00pm) time. The test sessions were performed in a random order. For the statistical analysis Friedman Two Way Variance analyses and Wilcoxon Signed Rank test were used. The results of the study showed that the number of shuttles were found to be higher in the afternoon than in the morning time (p<0.0167). Although there is no statistically significant difference, the number of shuttles were found more in the afternoon than the number of shuttles in the evening. As a conclusion, the best aerobic performance was performed in the afternoon. Due to the presence of such a difference, the measurement times have been noted for future scientific studies.
... Teams are made up of 15 players, with positional groups broken down into defenders (full-back and half-back), midfielders, and forwards (half-forwards and full-forwards) (16). Playing positions place specific workrate demands on players who require the necessary fitness to meet these demands (21,26). Significant differences in global and demarcated distances covered by the central 3 positions are indicative of the unique role they play linking defensive and attacking play (21). ...
... All tests were conducted in the same venue to remove external interferences, with anthropometric assessments preceding performance assessments. Testing took place at the same time of day to minimize the effects of circadian variations on the variables measured (26). Before testing, participants were provided with nutrition and hydration strategies to optimize performance. ...
There is limited research assessing the anthropometric and performance variations in elite Gaelic football. The aim of the current study was to assess the anthropometric and performance characteristics of an elite inter-county squad within a season. Following ethical approval and informed consent 26 participants were assessed at the start of pre-season (November), following early in-season (January) and mid-season (March). Measurements included stature, body mass, sum of 8 skinfold sites (ΣSkf8), estimated body fat (bf%), squat jump (SJ) and countermovement jump (CMJ), 5-, 10- and 20- m sprint time, upper and lower body strength (1RM) and Yo-Yo intermittent recovery test 2 (Yo-Yo IR2). A multivariate analysis of variance (MANOVA) was used to determine seasonal and positional variations. Anthropometric variations were observed with an overall increase in participants' body mass and a concomitant decrease in ΣSkf8 and bf% (-21.5%, p = 0.002, η = 0.15; -1.43 %, p = 0.004, η = 0.13). Performance variations showed improvements in sprint time over 5- (p = 0.001, η = 0.19) and 10-m (p = 0.008, η = 0.11), SJ (p = 0.013, η = 0.1), CMJ (p = 0.013, η = 0.1) height and Yo-Yo IRT2 (p < 0.001, η = 0.34) noted from pre-season to mid-season. Significant anthropometric variations are observed between the pre-season and early in-season, meanwhile significant performance variations are observed between the pre-season and mid-season. Distinct positional variations are evident for both anthropometric and performance characteristics at all time points. Applied practitioners should consider these findings when implementing a seasonal training plan.
... Before the tests, the participants completed a 15-minute warm-up session, consisting of 8-minute low-intensity jogging, four minutes of 40-60 m accelerations and decelerations, and three minutes of dynamic stretching for the hamstrings, hip extensors and flexors, and quad group muscles. All the trials were performed at the same hours (9:30-11:30 a.m.) of the day to minimize the effects of circadian variation (Reilly & Brooks, 1986). The temperature was between 18° and 25°C and humidity was between 40% and 47.1%. ...
The purpose of this research was to compare the effects of maximal aerobic speed (MAS) training, small-sided games (SSG) training, and combined training (CT) on sprint, agility, lactate accumulation, repeated sprint, aerobic, and anaerobic endurance performances. Thirty under-16 male players participated in a 6-week randomized training study. Pre- and post-training all players completed a test battery involving body composition (body height and Dual Energy X-Ray Absorptiometry-DEXA), sprint tests (10 m, 20 m, and 30 m), Yo-Yo 1 test, Arrowhead agility test, blood lactate test, and Yo-Yo 2 test. A global positioning system (GPS) was used for monitoring. After the pre-tests, the players were randomly assigned to three groups as MAS, SSG, and CT. Mixed two-way ANOVA was used to compare the pre-test and post-test performance of the three groups. While the CT group had higher changes in body composition, repeated sprint, aerobic, and anaerobic endurance parameters compared to the MAS training group (p<.05); the SSG training group had similar changes as the CT group (p>.05). In conclusion, coaches and sports scientists are advised to choose CT for more efficient training, considering the differences between the MAS training and CT methods.
... In order to measure the demands placed on an athlete during match play in relation to the actual demands of the game, Reilly (2005) proposed that physiological responses to the activity (heart rate [HR], rating of perceived exertion, blood lactate and oxygen consumption (VO 2 ) may be used for insightful evaluation. When conducting assessments and fitness interventions, this information is frequently taken into consideration (Reilly and Brooks, 1986). These physiological measurements could be used to describe how intense the soccer match-play simulation was. ...
The physical demands of football during match play have been observed, investigated and mimicked in a more controlled laboratory setting through a number of studies meant to resemble the activity of an actual soccer match. However, there have been variations in the simulation’s design across studies. This mini-review aims to assemble and align various protocols in simulating youth soccer match play in order to identify and assess the viability of combining numerous simulations into various research in the sport. This article is the first narrative review to discuss numerous protocols used in research towards reproducing youth soccer match-play demands in a laboratory-controlled environment.
... Throughout the simulation, the participants' heart rate and rate of perceived exertion were monitored. All participants completed the simulation at the same time of day to account for circadian variation [19]. The participants were tested in a 3 h' post absorptive state with no vigorous physical exertions or any alcohol and caffeine consumption 24 h prior to testing. ...
The Ball-Oriented Soccer Simulation (BOSS) is an innovation from soccer match-play simulations previously used in scientific studies that aim to replicate soccer match-play demands. Several shortcomings from the previous simulations may include the utility of unidirectional treadmill running, large spatial requirement, or lack of individual ball-handling actions. With the utility of the multidirectional overground running, compact, BOSS in soccer studies, much of these shortcomings may be easily overcome in a safe, controlled, laboratory setting. The ball-handling activities in the BOSS were designed to closely follow match-play frequencies and distances to create an ecologically valid soccer match-play simulation. Mean heart rate and rating of perceived exertion during the BOSS was found to be similar to previous overground soccer match simulations (HR: 155±6 bpm; RPE: 14±1). Practical applications of the BOSS include its utility in multiple research disciplines such as exercise physiology, nutrition, sports psychology, sports biomechanics as well as skills and motor control. The BOSS may also be used in real-world settings such as using the protocol on injury risk screening during pre-season or as a return-to-play biomechanical assessment protocol for players following post-injury or post-surgical rehabilitation. In the future, perhaps the BOSS may be used as a blueprint for the development of different sport-specific simulation protocol for the betterment of sports research as well as sports equipment production.KeywordsBOSSSoccerSimulationAssessment
... All physical performance tests were completed at approximately the same time of day to reduce any circadian rhythm effect (Reilly & Brooks, 1986). Tests were completed in a single session and in the same order (anthropometry, jumps, linear speed and Yo-Yo Intermittent Recovery Test Level 1 [Yo-Yo IR1]) on each test occasion. ...
... The HOT HRT was performed on week 1 and the COOLING HRT on week 2. Each test was undertaken with five participants in the environmental chamber at a time, with each test being performed with the same athletes to account for any competitive effects. Participants performed all testing sessions at the same time of day (Monday mornings) across 2 weeks to account for circadian rhythms (Reilly & Brooks, 1986). All participants were familiar with the testing protocol, as this has been evaluated recently from the same laboratory (Fenemor et al., 2022). ...
Purpose: The ingestion of ice slurry and application of ice towels can elicit favorable physiological, perceptual, and performance benefits when used individually; however, the combined use and effectiveness of these practical cooling strategies have not been assessed using a sport-specific performance test, based on actual match demands, in an elite team sport context. Methods: Ten non-heat acclimated elite male rugby sevens athletes undertook two cycling heat response tests (HRT) designed to be specific to the demands of rugby sevens in hot conditions (35°C, 80% rH). In a crossover design, the HRTs were conducted with (COOLING) and without (HOT) the combined use of internal (ice slushy ingestion) and external (application of ice towels to the head, neck, and face) pre- and per-cooling strategies. Physiological, perceptual, and performance variables were monitored throughout each HRT. Results: COOLING resulted in reductions in mean tympanic temperature (−0.4 ± 0.2°C; d = 1.18); mean heart rate (−5 ± 8 bpm; d = 0.53); thermal discomfort (−0.5 ± 0.9 AU; d = 0.48); and thirst sensation (−1.0 ± 1.1 AU; d = 0.61) during the HRT. COOLING also resulted in a small increase in 4-min time trial power output (by 7 ± 33 W, ~3%; d = 0.35) compared to HOT. Discussion: A combination of internal and external pre- and per-cooling strategies can result in a range of small physiological, perceptual, and performance benefits during a rugby sevens specific HRT, compared to undertaking no cooling. Practitioners should include such strategies when performing in hot conditions.
... It was proposed by Reilly (2005) that to measure the demands imposed by an athlete during match-play in relation to the actual demands of the game, physiological responses to the activity (i.e. heart rate (HR), rating of perceived exertion (RPE), blood lactate (BLa) and oxygen consumption (VO2)) may be used for insightful evaluation, and these information are often considered during assessments and designing injury prevention and fitness interventions (Reilly & Brooks, 1986). These physiological parameters could be used to describe the intensity of the soccer match-play simulation. ...
Soccer is the most popular sport that has attracted not only participants and spectators, but also numerous researchers into studying a myriad of disciplines relating to the sport. The demands of the sport have been observed, studied, and replicated to be reproduced in a more controlled, laboratory setting in forms of various exercise protocols designed to mimic actual soccer match-play. However, the development and selection of a simulation has varied across studies. This review aims to compile and align various protocols in simulating soccer match-play to identify and evaluate the feasibility of incorporating different simulations into various studies in the sport. Overground and treadmill simulations may offer cost efficient reproduction of soccer match-play demands, with arguably the best control for uniform exertion to reduce injuries during simulations. This paper is the first narrative review to discuss numerous protocols used in research towards reproducing soccer match-play demands in a lab-controlled environment.
... rH. Participants performed all testing sessions at the same time of day (Monday mornings) across two weeks to account for circadian rhythms (Reilly & Brooks, 1986). All participants were familiar with the testing protocol, as this has been evaluated recently from the same laboratory (Fenemor et al 2022). ...
To investigate effectiveness and retention of heat acclimation (HA) integrated within an elite rugby sevens team training program, 12 elite male rugby sevens athletes undertook 10-days of mixed active/passive HA across two-weeks of normal training. Physiological and performance variables were assessed using a sport specific, repeated high-intensity heat-response test Pre-HA; after five days (Mid-HA); after 10 days (Post-HA); and 16-days post-HA (Decay). Resting, submaximal, and end-exercise core temperature were lower at Mid-HA (≤ -0.26 °C; d ≥-0.47), Post-HA (≤ -0.30 °C; d ≥-0.72), and Decay (≤ -0.29 °C; d ≥-0.56), compared to Pre-HA. Sweat rate was greater Post-HA compared to Pre-HA (0.3 ± 0.3 L·hr-1; d =0.63). Submaximal HR was lower at Mid (-9 ±4 bpm; d =-0.68) and Post-HA (-11 ± 4 bpm; d =-0.90) compared to Pre-HA. Mean and peak 6-s power output improved Mid-HA (83 ± 52 W; 112 ± 67 W; d ≥0.47) and Post-HA (125 ± 62 W; 172 ± 85 W; d ≥0.72) compared to Pre-HA. Improvements in HR and performance persisted at Decay (d ≥0.66). The initial five days of mixed-methods HA elicited many typical HA adaptations, with an additional five days eliciting further thermoregulatory, sudomotor, and performance improvements. Adaptations were well-retained after 16-days of normal training, without any further heat stimulus. The trial was retrospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12622000732785).
... All HRTs were performed in an environmental chamber set at 20 • C, 50% rH for the RUN:AMB condition and 35 • C, 80% rH for the RUN:HOT and CYCLE:HOT conditions. Participants performed all testing sessions at the same time of day (Monday a.m.) across three weeks to account for circadian rhythms [15] and weekly training schedules. During all conditions, participants consumed a standardised amount of 6% carbohydrate sports drink (Gatorade, The Gatorade Company, Inc. Chicago, IL., USA) at room temperature (200 mL pre warm-up, 200 mL post warm-up, 120 mL at half-time, 120 mL pre time-trial; 640 mL total). ...
A heat response test (HRT) assesses adaptations to heat stress and athlete readiness to perform in hot conditions. However, testing is often not sport-specific, and is challenging to incorporate into elite team-sports schedules due to competing training priorities. Seven non-heat acclimated elite rugby sevens athletes (25 ± 3 years; 95.3 ± 6.5 kg; 190 ± 3 cm) undertook two rugby sevens specific running tests in ambient (20 °C, 50% rH; RUN:AMB), and hot (35 °C, 80% rH; RUN:HOT) conditions, along with a heart rate (HR) matched cycling-based HRT (CYCLE:HOT). Physiological and perceptual variables were monitored throughout each test. Mean tympanic temperature (TTymp), HR, thermal sensation, rate of perceived exertion, and sweat loss significantly increased, while thermal discomfort and performance decreased in RUN:HOT compared with RUN:AMB, (all d > 1.40; p < 0.05). Significant reductions in mean TTymp and HR were evident in CYCLE:HOT compared with RUN:HOT (both d > 1.10; p < 0.05), whereas there were no clear differences in any perceptual variables. Mean peak TTymp was 39.5 ± 0.5 °C in RUN:HOT and 38.8 ± 0.4 °C CYCLE:HOT, respectively. Acute heat stress is detrimental to performance in non-heat acclimated elite rugby sevens athletes. High-intensity cycling in the heat can replicate the perceptual (but not the physiological) stress associated with high-intensity running in the heat. Cycling-based HRT could be used to avoid additional mechanical load associated with running-based heat testing.
... Human thermoregulation processes include chemical reactions, perfusion inside the body, and heat transfer with the environment through radiation, conduction, convection, and evaporation. Temperatures at different peripheral body sites can be quite different and have more fluctuation due to factors such as ambient temperature [9,10], exercise [11], metabolic rate [12], circadian rhythm [13,14], age [15], and menstrual cycle [16]. Therefore, it is difficult to accurately define the relation between temperatures at two different body sites with a mathematical model due to the complexity of human thermoregulation mechanisms. ...
Infrared thermographs (IRTs) implemented according to standardized best practices have shown strong potential for detecting elevated body temperatures (EBT), which may be useful in clinical settings and during infectious disease epidemics. However, optimal IRT calibration methods have not been established and the clinical performance of these devices relative to the more common non-contact infrared thermometers (NCITs) remains unclear. In addition to confirming the findings of our preliminary analysis of clinical study results, the primary intent of this study was to compare methods for IRT calibration and identify best practices for assessing the performance of IRTs intended to detect EBT. A key secondary aim was to compare IRT clinical accuracy to that of NCITs. We performed a clinical thermographic imaging study of more than 1000 subjects, acquiring temperature data from several facial locations that, along with reference oral temperatures, were used to calibrate two IRT systems based on seven different regression methods. Oral temperatures imputed from facial data were used to evaluate IRT clinical accuracy based on metrics such as clinical bias (Δcb), repeatability, root-mean-square difference, and sensitivity/specificity. We proposed several calibration approaches designed to account for the non-uniform data density across the temperature range and a constant offset approach tended to show better ability to detect EBT. As in our prior study, inner canthi or full-face maximum temperatures provided the highest clinical accuracy. With an optimal calibration approach, these methods achieved a Δcb between ±0.03 °C with standard deviation (σΔcb) less than 0.3 °C, and sensitivity/specificity between 84% and 94%. Results of forehead-center measurements with NCITs or IRTs indicated reduced performance. An analysis of the complete clinical data set confirms the essential findings of our preliminary evaluation, with minor differences. Our findings provide novel insights into methods and metrics for the clinical accuracy assessment of IRTs. Furthermore, our results indicate that calibration approaches providing the highest clinical accuracy in the 37–38.5 °C range may be most effective for measuring EBT. While device performance depends on many factors, IRTs can provide superior performance to NCITs.
... Players performed a standardised, generic warm-up prior to commencement of the physical assessments. All physical performance tests were completed at approximately the same time of day to reduce any circadian rhythm e ect (Reilly and Brooks 1986). Tests were completed in a single session and in the same order (CMJ, linear speed and Yo-Yo IR1) on each test occasion. ...
Introduction:
Valid and informed interpretations of changes in physical performance test data are important within athletic development programmes. At present, there is a lack of consensus regarding a suitable method for deeming whether a change in physical performance is practically relevant or not.
Methods:
We compared true population variance in mean test scores between those derived from evidence synthesis of observational studies to those derived from practioner opinion (n = 30), and to those derived from a measurement error (minimal detectable change) quantification (n = 140). All these methods can help to obtain 'target' change score values for performance variables.
Results:
We found that the conventional 'blanket' target change of 0.2 (between-subjects SD) systematically underestimated practically relevant and more informed changes derived for 5-m sprinting, 30-m sprinting, CMJ, and Yo-Yo Intermittent Recovery Level 1 (IR1) tests in elite female soccer players.
Conclusions:
For the first time in the field of sport and exercise sciences, we have illustrated the use of a principled approach for comparing different methods for the definition of changes in physical performance test variables that are practically relevant. Our between-method comparison approach provides preliminary guidance for arriving at target change values that may be useful for research purposes and tracking of individual female soccer player's physical performance.
... Day 2-sprint performance (5, 10, 20 m), followed by a 30-min recovery period before completing the Yo-YoIRT1. Assessments took place at a similar time of day (18:00-20:00) across the two testing days to avoid any circadian variation in performance [24]. Testing was organized and conducted in the same manner for all six teams. ...
There is currently no information available on the variation in anthropometric and performance characteristics of starters and non-starters in elite Gaelic football. The aim of the current study was to determine if variations exist for elite male Gaelic football players with respect to position and playing role (starter or non-starter). One-hundred-and-sixty-two footballers from six elite teams underwent anthropometric and performance assessments. Players were categorised into six positional groups (goalkeeper, full back, half back, midfield, half forward and full forward) and two playing role groups (starter and non-starter). A significant position × role interaction was observed for Yo-YoIRT1 distance ( p = 0.031, p η ² = 0.078), with starters covering a greater distance in all positions when compared to non-starters (all p < 0.05), except for half backs. Goalkeepers covered a significantly lower Yo-YoIRT1 distance compared to all other positions ( p ≤ 0.001, p η ² = 0.35), while half backs completed a significantly greater distance compared to full backs ( p = 0.014, p η ² = 0.35) and full forwards ( p ≤ 0.001, p η ² = 0.35). Starters had a significantly greater CMJ height ( p ≤ 0.001, p η ² = 0.082) and CMJ PP ( p = 0.001, p η ² = 0.08) compared to non-starters. This research is the first of its kind within Gaelic football to provide anthropometric and performance values with respect to playing role. The data obtained may aid coaches to individualize training regimes to enhance role-specific preparation for competitive match-play.
... All participants were instructed to maintain their regular diet before each subsequent visit. The trials were conducted at the same time of day at least 1 week apart using a randomized crossover design (Reilly and Brooks, 1986). ...
Delays in the restoration of thermoregulation after exercise in a hot environment are associated with post-exercise hypotension. This study tested the hypothesis that simultaneous internal cooling and rehydration by ingesting ice slurry prevents the excessive decrease in mean arterial pressure (MAP) and promotes recovery of core and skin temperatures in male athletes. Seven male athletes participated in this randomized controlled trial with a crossover design. The participants ran on a treadmill at 75% of their maximal oxygen uptake in the heat (35 °C, 60% relative humidity), up to exhaustion. Immediately after exercise, participants ingested either 4 g⋅kg ⁻¹ body weight of ice slurry (0.5 °C, ICE) or a control beverage (28 °C, CON). The participants then recovered by sitting for 20 min. We measured participants' rectal temperature (Tre), skin temperature (Tsk), mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), and physiological strain index (PSI) before exercise (Pre), after running to exhaustion (PEx), and at 0 (P0), 10 (P10), and 20 (P20) minutes after ice slurry or control beverage ingestion. MAP, CO, HR, TPR, or PSI did not change significantly during the recovery period. At P20 and P10, Tre and Tsk significantly decreased in the ICE group compared to the CON group (p < 0.05). These results suggested that ingestion of ice slurry, post-exercise, promoted core and skin temperature recovery but did not affect the central and peripheral cardiovascular responses during the acute recovery period.
... To reduce the extent of external interference, data collection was completed within an indoor environment [7,8]. Data collection was also completed at the same time of day (17:00-21:00 h) to minimize the circadian variation across all teams and participants [21]. Participants were encouraged to refrain from vigorous activity for 24-48 h prior to testing. ...
The aim of the current study was to identify the specific differences in anthropometric and performance profiles between elite and sub-elite hurling players with respect to position and level of play. One hundred and thirty-seven (n = 137) hurlers at the elite (n = 61) and sub-elite (n = 76) level completed a series of anthropometric [height, body mass, the sum of seven skinfolds, adipose tissue percentage estimates (%AT), fat-free mass estimations (FFM)) and performance ((countermovement jump height (CMJ), CMJ peak power (CMJ PP), CMJ relative peak power (CMJ RPP), acceleration (5, 10 and 20 m), and yo-yo intermittent recovery test level 1 (Yo-Yo IRT1)) assessments during the “early in-season” phase of the competition. Data were categorized into positions at both levels (full-backs, half-backs, midfielders, half-forwards, full-forwards). Multiple two-way ANOVA’s were performed to determine the effect of two fixed factors (level and position) on several anthropometric and performance variables. Elite level players had a significantly lower sum of seven skinfolds across all positions compared to the sub-elite (η2 = 0.441, large). At half-back, half-forward, and full-forward elite players had significantly lower %AT (η2 = 0.087–0.167, small–medium) and greater FFM (η2 = 0.040–0.065, small). Jump performance assessment showed elite players performed significantly better across all positions for CMJ (η2 = 0.526, large), CMJ PP (η2 = 0.385, large) and CMJ RPP (η2 = 0.520, large). When Yo-Yo IRT1 was considered, elite players completed an increased distance than the sub-elite across all positions (η2 = 0.526, large). The current data are the first to show differences in positional anthropometric and performance profiles between standards of play within hurling. Applied practitioners should consider these normative data when implementing training programs to maximize position-specific preparation for competition. Furthermore, these data could improve the considerations regarding the transitioning of players from the sub-elite to the elite level of play.
... Participants performed three experimental trials ingesting WA, SD (100Plus, Fraser and Neave, Limited, Singapore; carbohydrate = 6.2%) and DD (Drip Drop, Inc., San Francisco, CA, USA; carbohydrate = 3.3%; Table 1). The experimental trials commenced in the morning at the same time to control for circadian variations in T c [24]. Table 1. ...
This study investigated the efficacy of ingesting an oral rehydration solution (DD) that has a high electrolyte concentration after exercise on fluid balance and cycling performance in comparison with a sports drink (SD) and water (WA). Nine healthy males aged 24 ± 2 years (mean ± SD), with peak oxygen uptake (VO2 peak) 55 ± 6 mL·kg−1·min−1 completed three experimental trials in a randomised manner ingesting WA, SD (carbohydrates: 62 g·L−1, sodium: 31 ± 3 mmol·L−1) or DD (carbohydrates: 33 g·L−1, sodium: 60 ± 3 mmol·L−1). On all trials, fluid was ingested during 75 min cycling at 65% VO2 peak (temperature: 30.4 ± 0.3 °C, relative humidity: 76 ± 1%, simulated wind speed: 8.0 ± 0.6 m·s−1) and during 2 h of recovery (temperature: 23.0 ± 1.0 °C, relative humidity: 67 ± 2%), with the total volume equivalent to 150% of sweat loss during the ride. A 45 min pre-load cycling time trial at a 65% VO2 peak followed by a 20 km time trial was conducted after a further 3 h of recovery. Fluid retention was higher with DD (30 ± 15%) than WA (−4 ± 19%; p < 0.001) and SD (10 ± 15%; p = 0.002). Mean ratings of palatability were similar among drinks (WA: 4.25 ± 2.60; SD: 5.61 ± 1.79; DD: 5.40 ± 1.58; p = 0.33). Although time trial performance was similar across all three trials (WA: 2365 ± 321 s; SD: 2252 ± 174 s; DD: 2268 ± 184 s; p = 0.65), the completion time was faster in eight participants with SD and seven participants with DD than with WA. Comparing SD with DD, completion time was reduced in five participants and increased in four participants. DD was more effective at restoring the fluid deficit during recovery from exercise than SD and WA without compromising the drink’s palatability with increased sodium concentration. Most individuals demonstrated better endurance exercise time trial performance with DD and SD than with WA.
... Our findings support that active cool-down is one of the most used recovery modalities in soccer players either after training or competition [1,43]. Some of the benefits of using this strategy are a better perception of recovery and fatigue, faster blood lactate concentration clearance, sleep facilitation and increased muscle contraction restoration [21,[44][45][46][47][48]. Data revealed that ALB usage (twenty-two teams; 96%) was higher than AWB (eleven teams; 48%), a fact that could be related to the need for specialized equipment and facilities to undertake these last ones. ...
Objectives:
different active and passive post-exercise recovery techniques such as massage, foam rolling, stretching or ice baths among others, are used by elite athletes to promote effective physiological, physical, and mental restoration. However, limited research is available investigating the use of recovery strategies in professional soccer. As such, we aimed to explore and describe the use of strategies by professional teams throughout the season, describing competitive and preparatory phases.
Methods:
the present study collected data from all professional Spanish soccer teams who played in "LaLiga" (The Spanish first division), during the season 2018-2019 (n=20) and the ones promoted for the season 2019-2020 (n=3). A six-section online survey was responded once.
Results:
teams used different recovery protocols and combinations, although natural and physical strategies such as sleep/nap, food/fluid replacement, cold/ice bath/shower/immersion, and massage were always present. However, there is no agreement in the protocols and timings employed. Three physical strategies showed a higher presence in the recovery protocols after competition: cold/ice bath/shower/immersion, massage and foam rolling; always used by seventeen teams (74%), sixteen (70%) and thirteen (57%) respectively. The design and supervision of recovery are multidisciplinary tasks in 87% of the teams. Our findings also demonstrate that although there is a body of scientific evidence on recovery, a gap between theory and practice exists with 13% of the teams acknowledging that insufficient logistics and economic resources limit the use of some strategies, and two teams (9%) not periodizing or individualizing recovery.
Conclusion:
the investigation provided insight into the current use of recovery strategies by "LaLiga" teams, highlighting that all clubs used them to one extent or another, but also that significant variability responding to individualized perceptions exists. Moreover, this study provides relevant contextual information that may be useful for professional soccer staff concerning the use of recovery strategies.
... The testing sessions were conducted during a preparatory period: 2-3 h after a standardized breakfast in an air-conditioned laboratory, with the temperature and the relative humidity specified as 20 • C and 50%, respectively. Both running protocols were performed at the same time of the day to ignore circadian effects on the physiological characteristics (Reilly and Brooks, 1986) and on an identical motorized treadmill (HP Cosmos, Germany). The HIIE running protocol opened with a 7 min warm-up at 70% VO 2max , followed by six 3 min bouts at 90% VO 2max . ...
PurposeThe purpose of this study was to determine the (i) cardiac biomarker (cTnI and NT-proBNP) responses to moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE) in the middle-aged and young groups, (ii) relationship of post-exercise cardiac biomarker release between these two age groups, and (iii) investigate whether insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene is associated with predisposition to cardiac damage after exercise in Iranian men.Methods
We examined cTnI and NT-proBNP in 29 middle-aged (54.5 ± 4.6 years) and 28 young (22.7 ± 4.2 years) soccer players before and after HIIE and MICE running tests.ResultsThe middle-aged soccer players had higher baseline cTnI (0.015 ± 0.007 ng/ml vs. 0.010 ± 0.006 ng/ml; P = 0.01) and NT-proBNP (30.7 ± 13.6 ng/L vs. 18.4 ± 8.3 ng/L; p < 0.001) values compared with the young group. The changes with exercise (ΔcTnI: 13 vs. 11 ng/ml and ΔNT-proBNP: 18 vs. 11 ng/L) were also higher in the middle-aged group. No subject exceeded the upper reference limit for cTnI and NT-proBNP. Considering three ACE genotypes, the mean cTnI and NT-proBNP values of middle-aged and young groups did not show any significant difference.Conclusion
Marked differences in baseline and post-exercise cTnI and NT-proBNP values were observed, which were related to age differences but not to ACE genotypes.
... All subjects were informed to stop smoking, drinking alcoholic or caffeine-containing products, taking medicine, cosmetics application, and violent exercise within 12 hours before the acquisition of facial IRT. e time of collection was limited between 9 and 10 a.m. to avoid changes of temperature distribution in human body caused by changes in the physiological rhythm of human body [25]. Before the acquisition of facial IRT, subjects were informed to sit quietly in the test environment for 20 minutes to adapt to the room temperature. ...
Infrared thermography (IRT), as a noncontact tool for temperature measurement, is widely applied in the study of acupuncture modernization. The aim of this study was to assess the intra- and interrater reliability of infrared image analysis of facial acupoints of subjects with facial paralysis and determine the factors influencing the variability of the measured values. A total of 26 patients with facial paralysis on one side, aged 26 to 53 years, participated voluntarily in the study. Facial infrared thermal images of all participants were analyzed by two trained raters at two different time points at a one-week interval. The intraclass correlation coefficient (ICC) was used to determine the intra- and interrater reliability of IRT measurements. The ICC values varied depending on the analyzed acupoints. The reliability of temperature measurement ranged from moderate to excellent (intrarater, ICC ranged from 0.669 to 0.990; interrater, ICC ranged from 0.661 to 0.987). The reliability of temperature difference measurement ranged from low to excellent (intrarater, ICC ranged from 0.412 to 0.882; interrater, ICC ranged from 0.334 to 0.828). The main influencing factor of reliability is the incomplete consistency in selecting acupoint positions when repeatedly positioning the same acupoint manually. Despite low reliability of temperature difference measurement at some acupoints, some auxiliary measures can be used to reduce the error of manual positioning. Thus, infrared thermal imaging still has the potential to assist in objective and quantitative research on acupuncture.
... In addition, all participants were instructed to maintain their normal diet before each subsequent visit. The trials were conducted at the same time of day at least 1 week apart using a randomized crossover design (Reilly and Brooks, 1986). Upon arrival at the laboratory, a small urine sample was collected, 1 mL of which was used to measure urine specific gravity (USG) with a digital optical refractometer (PAL-09S; Atago, Tokyo, Japan). ...
Although numerous studies have shown the benefits of cooling strategies for reducing thermal strain and subsequent exercise performance in the heat, few studies have focused on a combination of external and internal cooling. Therefore, the purpose of the present study was to examine the impact of a cooling strategy combining forearm water immersion and a low dose of ice slurry ingestion on physiological response and subsequent exercise performance in the heat. Eight non-heat-acclimated males participated in this study. After reaching a rectal temperature of 38.5 °C through a bout of cycling exercise in the heat (35 °C, 60% relative humidity), the participants were subjected to one of the following four conditions for a 15-min period: W: forearm cooling; ICE: ice slurry (–1 °C) ingestion; MIX: both W and ICE, and CON: no cooling intervention. After the intervention, the participants performed time to exhaustion (TTE) cycling exercise at 75% V˙O2max. The rate of decrease in rectal temperature in the MIX group was significantly lower than that in the CON group from 6 min to the end of the cooling intervention period (P < 0.05). In addition, mean skin temperature, heart rate, physiological strain index, and perceptual strain were significantly reduced for MIX and W compared with ICE and CON. However, TTE was longer for ICE compared with the other interventions. These results suggest the effectiveness of the newly developed cooling strategy combining external and internal cooling for reducing thermal strain in a short-term recovery period during exercise in the heat.
... All physical performance tests were completed at approximately the same time of day to reduce any circadian rhythm effect (Reilly & Brooks, 1986). Tests were completed in a single session and in the same order (anthropometry, jumps, linear speed and Yo-Yo Intermittent Recovery Test Level 1 [Yo-Yo IR1]) on each test occasion. ...
Talent identification and development programmes have received broad attention in the last decades, yet evidence regarding the predictive utility of physical performance in female soccer players is limited. Using a retrospective design, we appraised the predictive value of performance-related measures in a sample of 228 youth female soccer players previously involved in residential Elite Performance Camps (age range: 12.7–15.3 years). With 10-m sprinting, 30-m sprinting, counter-movement jump height, and Yo-Yo Intermittent Recovery Test Level 1 (IR1) distance as primary predictor variables, the Akaike Information Criterion (AIC) assessed the relative quality of four penalised logistic regression models for determining future competitive international squads U17–U20 level selection. The model including Yo-Yo IR1 was the best for predicting career outcome. Predicted probabilities of future selection to the international squad increased with higher Yo-Yo IR1 distances, from 4.5% (95% confidence interval, 0.8 to 8.2%) for a distance lower than 440 m to 64.7% (95% confidence interval, 47.3 to 82.1%) for a score of 2040 m. The present study highlights the predictive utility of high-intensity endurance capacity for informing career progression in elite youth female soccer and provides reference values for staff involved in the talent development of elite youth female soccer players.
... All experimental procedures were completed in the environmental chamber (TIS Services, Hampshire, United Kingdom) in the School of Sport, Exercise and Rehabilitation Sciences building at the University of Birmingham. Participants performed all heat acclimation and testing sessions at the same time of day (±2 h), and at similar times to their normal training sessions so as not to disrupt their normal circadian rhythms (Reilly and Brooks, 1986). This included mornings, afternoons, or evenings. ...
Although emerging as a cost and time efficient way to prepare for competition in the heat, recent evidence indicates that "short-term" heat acclimation (<7 days) may not be sufficient for females to adapt to repeated heat stress. Furthermore, self-paced performance following either short-term, or longer (>7 days) heat acclimation has not been examined in a female cohort. Therefore, the aim of this study was to investigate self-paced endurance performance in hot conditions following 4- and 9-days of a high-intensity isothermic heat acclimation protocol in a female cohort. Eight female endurance athletes (mean ± SD, age 27 ± 5 years, mass 61 ± 5 kg, VO2peak 47 ± 6 ml⋅kg⋅min-1) performed 15-min self-paced cycling time trials in hot conditions (35°C, 30%RH) before (HTT1), and after 4-days (HTT2), and 9-days (HTT3) isothermic heat acclimation (HA, with power output manipulated to increase and maintain rectal temperature (Trec) at ∼38.5°C for 90-min cycling in 40°C, 30%RH) with permissive dehydration. There were no significant changes in distance cycled (p = 0.47), mean power output (p = 0.55) or cycling speed (p = 0.44) following 4-days HA (i.e., from HTT1 to HTT2). Distance cycled (+3.2%, p = 0.01; +1.8%, p = 0.04), mean power output (+8.1%, p = 0.01; +4.8%, p = 0.05) and cycling speed (+3.0%, p = 0.01; +1.6%, p = 0.05) were significantly greater in HTT3 than in HTT1 and HTT2, respectively. There was an increase in the number of active sweat glands per cm2 in HTT3 as compared to HTT1 (+32%; p = 0.02) and HTT2 (+22%; p < 0.01), whereas thermal sensation immediately before HTT3 decreased ("Slightly Warm," p = 0.03) compared to ratings taken before HTT1 ("Warm") in 35°C, 30%RH. Four-days HA was insufficient to improve performance in the heat in females as observed following 9-days HA.
... order. Also, all tests were performed at the same time of the day with an interval of at least 48 h in between to avoid the circadian variation impact [38]. Participants were asked to swallow a ...
The hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and ventilation fans developed by the authors has shown good performance on the alleviation of heat strain of wearers in a hot environment (e.g., the maximum core temperature reduction could reach 0.4 °C as compared to no cooling at 36 °C and 59% RH). . Nevertheless, a recent numerical study has revealed that PCMs in the HPCS absorbed a large amount of heat from the hot environment during melting, which shortened the melting duration of the PCMs significantly and thereby, reduced the total effective cooling time of the HPCS. In this study, the HPCS was redesigned by placing an insulation layer onto the outer surface of PCM packs to reduce the heat absorption from the hot environment. The Tanabe’s thermoregulation model coupled with a heat and moisture transfer clothing model was modified to numerically investigate the cooling performance of the novel HPCS. The coupled model was validated by human wear trials. Further, a numerical parametric study was carried out to explore the thermal management performance of the new HPCS. Particularly, the effects of parameters such as the thermal resistance of the insulation layer, and the melting temperature & latent heat of the PCMs on heat and moisture transfer through the new HPCS were examined. Results showed that the insulation layer with greater thermal resistances and PCMs with high melting temperatures/latent heat are beneficial to the body cooling performance. This study may provide an important guideline for designing energy-efficient and high-performance HPCSs.
... Field tests should take minimal time away from the coaching program to avoid conflicts of interest [62]. To reduce the effect of circadian variations, testing sessions should be performed at the same time of day [134]. As soccer is a team sport testing would ideally be conducted on many players simultaneously. ...
It is important that players and coaches have access to objective information on soccer player's physical status for team selection and training purposes. Physiological tests can provide this information. Physiological testing in laboratories and field settings are very common, but both methods have been questioned because of their specificity and accuracy respectively. Currently, football players have their direct aerobic fitness assessed in laboratories using treadmills or cycle ergometers, whilst indirect measures (using estimation of aerobic performance) are performed in the field, typically comprising multiple shuttle runs back and forth over a set distance. The purpose of this review is to discuss the applied techniques and technologies used for evaluating soccer players' health and fitness variables with a specific focus on cardiorespiratory testing. A clear distinction of the functionality and the specificity between the field tests and laboratory tests is well established in the literature. The review findings prioritize field tests over laboratory tests, not only for commodity purpose but also for motivational and specificity reasons. Moreover, the research literature suggests a combination of various tests to provide a comprehensive assessment of the players. Finally, more research needs to be conducted to develop a specific and comprehensive test model through the combination of various exercise modes for soccer players.
... The order and content of the sessions were: (1) isotonic endurance (bench press); (2) isotonic endurance (leg press) and (3) isometric and isokinetic lower limb endurance. Time of day was standardised for each participant to control for the influence of circadian variation on performance (Reilly and Brooks 1986). For safety purposes, two investigators, who were blinded to the treatment allocation, supervised each session. ...
β-Alanine (BA) supplementation may be ergogenic during high-intensity exercise, primarily due to the buffering of hydrogen cations, although the effects of beta-alanine supplementation on strength endurance are equivocal. The aim of the study was to determine the effects of 4 weeks of beta-alanine supplementation on skeletal muscle endurance using a battery of performance tests. This study employed a parallel group, repeated measures, randomised, double-blinded and placebo-controlled design. Twenty recreationally strength-trained healthy males completed tests of isotonic strength endurance (repeated bench and leg press), along with tests of isometric and isokinetic endurance conducted using an isokinetic dynamometer. Tests were performed before and after a 4 week intervention, comprising an intake of 6.4 g day⁻¹ of BA (n = 9) or placebo (maltodextrin, n = 11). Time-to-exhaustion during the isometric endurance test improved by ~ 17% in the BA group (p < 0.01), while PL remained unchanged. No significant within-group differences (p > 0.1) were shown for any of the performance variables in the isokinetic test (peak torque, fatigue index, total work) nor for the total number of repetitions performed in the isotonic endurance tests (leg or bench press). Four weeks of BA supplementation (6.4 g day⁻¹) improved isometric, but not isokinetic or isotonic endurance performance.
... perature [3,12,25] . The importance of temperature in performance is supported by extensive data from heating and cooling experiments which have demonstrated that maximal anaerobic power declines by 5 % for every 1 ° C drop in muscle temperature [5] . ...
We have previously shown that the performance of a loaded counter-movement jump, which is frequently used in the assessment of an athlete's neuromuscular capabilities, is affected by the time of day that the assessment is conducted. This study aimed to extend those findings by examining whether such variations in performance can be accounted for by the diurnal fluctuations known to exist in body temperature. Eight recreationally trained males (29.8 ± 5.2 yrs; 178.3 ± 5.2 cm; 80.3 ± 6.5 kg) with a minimum of 6 months resistance training history completed four separate sessions (differing in time of day and type of warm-up completed). In a randomised order, jump performance was assessed following (a) control warm-up at 8am (b) control warm-up at 4pm (c) extended warm-up at 8am and (d) extended warm-up at 4pm. The control warm-up consisted of dynamic exercises and practice jumps equivalent to the standard warm-up for strength and power assessment used in our laboratory. The extended warm-up incorporated a 20min general warm-up period on a stationary bike (150 - 200 W), prior to completion of the control warm-up. Body temperature was measured using a combination of skin and core temperature to estimate overall body temperature. Peak power, mean power, peak velocity, peak force and jump height were measured using a linear position transducer attached to an Olympic lifting bar with an additional load of 20kg (i.e. total load of 40kg). Subjects performed 2 sets of 3 repetitions of maximal effort countermovement jumps with the bar across their shoulders. Prior to jump testing for the AM and PM control conditions, whole body temperature was 36.5 and 36.8°C respectively, which increased to 36.8 and 36.9°C during AM and PM extended warm-up conditions. All kinetic and kinematic variables were higher (ES range = 0.2 - 0.3) during the PM as compared to the AM control condition (Table 1). Following the extended AM warm-up, when body temperature was ∼ equivalent to the PM control condition, performance was comparable (ES < 0.1), except for peak power where the AM extended condition produced greater results (ES = 0.3). The results of this study indicate that the diurnal variation in whole body temperature, which peaks in the early evening, may explain the diurnal performance differences existent in explosive power output and associated variables. The performance of an extended warmup, designed to increase the whole body temperature, resulted in an improvement in the kinetic and kinematic variables commonly reported from jump performance in the AM condition. It is suggested that warm-up protocols designed to increase body temperature may be beneficial for reducing diurnal differences in jump performance. This is important for ensuring maximal performance results, and for monitoring performance changes over time, when it may be impractical to standardise the time of day that testing takes place.Table 1. Mean (SD) results for kinetic and kinematic variables (mean of 6 trials) measured during 40kg countermovement jumps.
... In this context, the current study showed a morning-evening difference of ROT. Indeed, evening ROT for team handball players was higher than the one measured in the morning with amplitude of 0.4 ± 0.5°C, which was close to the ROT circadian variation typically observed in studies over the 24-h cycle (Reilly & Brooks, 1986) and in the study of Bambaeichi et al. (2005) among sedentary eumenorrheic females. These results are consistent with numerous investigations which revealed that circadian rhythms of human performances are parallel to the circadian variation in core temperature, peaking in the late afternoon Chtourou et al., 2013;Hammouda et al., 2011;Melhim, 1993;Pullinger et al., 2014;Racinais et al., 2005;Reilly et al., 2007;Zarrouk et al., 2012). ...
... Measuring T b during the active season can also provide information on locomotor activity of animals. It is well known that physical exercise leads to an increase in T b in several species, ranging from small mammals to humans (Hart and Heroux 1955;Reilly and Brooks 1986). Not surprisingly then, there is a close correlation between changes in T b and locomotor activity (Heldmaier et al. 1989;Fuller et al. 1998;Weinert and Waterhouse 1998;Hart and Heroux 1955;Golombek et al. 1993). ...
Measuring Tb during the active season can provide information about the timing of reproduction and the use of short bouts of torpor and may be used as a proxy for the locomotor activity of animals (i.e., maximum Tb). This kind of information is especially important to understand life-history strategies and energetic costs and demands in hibernating mammals. We investigated Tb throughout the active season in edible dormice (Glis glis), since they (i) have an expensive arboreal life-style, (ii) are known to show short bouts of torpor, and (iii) are adapted to pulsed resources (mast of beech trees). We show here for the first time that maximum Tb’s in free-living active dormice (during the night) increase regularly and for up to 8 h above 40 °C, which corresponds to slight hyperthermia, probably due to locomotor activity. The highest weekly mean maximum Tb was recorded 1 week prior to hibernation (40.45 ± 0.07 °C). At the beginning of the active season and immediately prior to hibernation, the mean maximum Tb’s were lower. The time dormice spent at Tb above 40 °C varied between sexes, depending on mast conditions. The date of parturition could be determined by a sudden increase in mean Tb (plus 0.49 ± 0.04 °C). The occurrence of short torpor bouts (<24 h) was strongly affected by the mast situation with much higher torpor frequencies in mast-failure years. Our data suggest that locomotor activity is strongly affected by environmental conditions, and that sexes respond differently to these changes.
... Although it is possible that the effect of time of day on muscle contractile properties could be attributed in part to intracellular variations in the muscle (e.g. a circadian variation in inorganic phosphate concentration [192]), the more common hypothesis is that performance differences are causally related to the circadian rhythm in body temperature since previous researchers have observed a general parallelism between rhythms of physical performance and core temperature [17,75,237]. The importance of temperature in performance is supported by extensive data from heating and cooling experiments which have demonstrated that maximal anaerobic power declines by 5% for every 1ºC drop in muscle temperature [27]. ...
With improving professionalism of sports around the world, the volume and frequency of training required for competitive performances at the elite level has increased concurrently. With this amplification in training load comes an increased need to closely monitor the associated fatigue responses, since maximising the adaptive response to training is also reliant on avoiding the negative consequences of excessive fatigue. The rationale for the experimental chapters in this thesis was established after considering survey responses regarding current best practice for monitoring fatigue in high performance sporting environments (Chapter 3). On the basis of the results, vertical jump assessments were selected for further investigation regarding their utility in determining neuromuscular fatigue responses. Outcomes from the subsequent series of studies aimed to provide practitioners working in high performance sport with guidelines for using vertical jumps to monitor athletic fatigue.
The results from Chapter 4 indicate using the mean value of at least six jumps enhances the ability to detect small but practically important changes in performance from week to week. This study also highlighted large differences (4-6%) in morning and afternoon performance, indicating that the time of day performance is assessed needs to be accounted for when monitoring changes in jump performance. Chapter 5 explored the theory that the time of day effect observed in Chapter 4 can be explained by internal temperature differences. This theory was supported by demonstrating that an extended warm-up period can negate differences in jump performance in the morning and the afternoon. Researchers who are unable to standardise the time of day that assessment occurs are able, therefore, to control for performance differences by manipulating the warm-up protocols.
The third study examined changes in vertical jump performance over a three month training period and produced several novel outcomes. A major finding was that unloaded jumps were more sensitive to neuromuscular fatigue during intensive training than loaded jumps (Chapter 6). Furthermore, this set of results showed that all subjects changed their jump technique via a reduction in the amplitude of the countermovement when they were highly fatigued. Using the same data, an analysis was performed to quantify individual differences in within-subject variation (Chapter 7) during normal and intensive training. These results provided the first indication that within-subject variability in vertical jump performance is substantially different between individuals and between different training phases, an important consideration for interpreting the practical importance of performance changes.
In Chapter 8 the relationship between vertical jump performance and electrically elicited force of the knee extensors was examined to better understand the mechanism(s) of changes in jump performance associated with neuromuscular fatigue during intensive overload training. The results showed that the fatigue assessed by vertical jump performance was likely not only peripheral in origin as previously suggested by other authors. Further research is required to further understand the mechanisms of reduced performance during overload training, although the preliminary evidence presented implicates central mechanisms. To conclude the thesis, the findings presented in the experimental chapters are summarised, with a series of practical recommendations for using vertical jumps to monitor athletic fatigue presented.
... All assessments were conducted at the same time of the day to avoid the circadian variation in body temperature. 17 Players were not allowed to consume fluid at any time during the fatigue assessments. The study was approved by the Liverpool John Moores University ethics committee. ...
Purpose:
To determine the sensitivity of a range of potential fatigue measures to daily training load accumulated over the previous two, three and four days during a short in-season competitive period in elite senior soccer players (n=10).
Methods:
Total high-speed running distance, perceived ratings of wellness (fatigue, muscle soreness, sleep quality), counter-movement jump height (CMJ), submaximal heart rate (HRex), post-exercise heart rate recovery (HRR) and heart rate variability (HRV: Ln rMSSD) were analysed during an in-season competitive period (17 days). General linear models were used to evaluate the influence of two, three and four day total high-speed running distance accumulation on fatigue measures.
Results:
Fluctuations in perceived ratings of fatigue were correlated with fluctuations in total high-speed running distance accumulation covered on the previous 2-days (r=-0.31; small), 3 -days (r=-0.42; moderate) and 4-days (r=-0.28; small) (p<0.05). Changes in HRex (r=0.28; small; p= 0.02) were correlated with changes in 4-day total high-speed running distance accumulation only. Correlations between variability in muscle soreness, sleep quality, CMJ, HRR% and HRV and total high-speed running distance were negligible and not statistically significant for all accumulation training loads.
Conclusions:
Perceived ratings of fatigue and HRex were sensitive to fluctuations in acute total high-speed running distance accumulation, although, sensitivity was not systematically influenced by the number of previous days over which the training load was accumulated. The present findings indicate that the sensitivity of morning-measured fatigue variables to changes in training load is generally not improved when compared with training loads beyond the previous days training.
... In the short term, low-intensity aerobic activity leads to a faster decrease of blood lactic acid concentration (1,42,43,45,46,66), which suggests an increased blood flow, which in turn would result in a fast elimination of blood lactate through its oxidation by the liver, heart, and muscle, as the physiological mechanism (43,66). Other possible beneficial effects are the restoration of the muscle contraction capacity, damaged by the eccentric actions of training or competition (42,62), a less sudden drop of the core temperature that would contribute to reduce the arousal level of the central nervous system, making it easier to fall asleep the night after the game (52,64), the possible contribution to the cicatrization of microruptures produced by eccentric actions (41,62), and the feeling of a better state of well-being put into operation through scales of perceived recovery (total quality recovery scale [TQR]) and muscle fatigue (12,33,54). A possible positive effect has even been suggested on the immunosuppression experienced during 4-6 hours after the competition due to the "openwindow" theory (51). ...
AS A RESULT OF TRAINING AND COMPETITION LOAD IN SOCCER, THE MAJORITY OF THE BODY'S PHYSIOLOGICAL SYSTEMS ARE STRESSED. TO ACCELERATE THE RECOVERY PROCESS AND ENHANCE PERFORMANCE IN SOCCER, DIFFERENT POSTEXERCISE RECOVERY MODES HAVE BEEN SUGGESTED AND ARE BROADLY CLASSIFIED INTO 2 CATEGORIES: ACTIVE RECOVERY OR PASSIVE RECOVERY. DESPITE THE POPULARITY, THERE IS A LACK OF SCIENTIFIC EVIDENCE FOR THE VALIDITY OF THESE RECOVERY INTERVENTIONS. THIS REVIEW SUMMARIZES THE EVIDENCE BASE FOR USING ACTIVE RECOVERY, COLD WATER IMMERSION, WHOLE-BODY VIBRATION, NEUROMUSCULAR ELECTRICAL STIMULATION, AND COMPRESSION GARMENTS, AS EXERCISE RECOVERY AIDS IN SOCCER, AND WHERE POSSIBLE, PROVIDES PRACTICAL RECOMMENDATIONS REGARDING USAGE.
... All participants attended the laboratory on six separate occasions following a minimum 6-h fasting period. All trials were performed at the same time of day for each participant (between 08:00 hours and 20:00 hours) to ensure results were not affected by circadian variation (Reilly & Brooks, 1986). All tests were performed on a cycle ergometer (Lode Excalibur, Lode B.V., Groningen, Netherlands) and separated by a minimum of 72 h. ...
We investigated the effects of supplement identification on exercise performance with caffeine supplementation. Forty-two trained cyclists (age 37 ± 8 years, body mass [BM] 74.3 ± 8.4 kg, height 1.76 ± 0.06 m, maximum oxygen uptake 50.0 ± 6.8 mL/kg/min) performed a ~30 min cycling time-trial 1 h following either 6 mg/kgBM caffeine (CAF) or placebo (PLA) supplementation and one control (CON) session without supplementation. Participants identified which supplement they believed they had ingested (“caffeine”, “placebo”, “don't know”) pre- and post-exercise. Subsequently, participants were allocated to subgroups for analysis according to their identifications. Overall and subgroup analyses were performed using mixed-model and magnitude-based inference analyses. Caffeine improved performance vs PLA and CON (P ≤ 0.001). Correct pre- and post-exercise identification of caffeine in CAF improved exercise performance (+4.8 and +6.5%) vs CON, with slightly greater relative increases than the overall effect of caffeine (+4.1%). Performance was not different between PLA and CON within subgroups (all P > 0.05), although there was a tendency toward improved performance when participants believed they had ingested caffeine post-exercise (P = 0.06; 87% likely beneficial). Participants who correctly identified placebo in PLA showed possible harmful effects on performance compared to CON. Supplement identification appeared to influence exercise outcome and may be a source of bias in sports nutrition.
... Participants were required to attend the laboratory on eight separate occasions, with all trials being performed at the same time of day to ensure results were not affected by circadian variation [11]. There were two preliminary trials, which comprised of an incremental cycling test to exhaustion to determine W max , followed by a familiarisation trial of the high-intensity cycling capacity test to exhaustion at 110% of W max (CCT 110% ). ...
The objective of this work was to develop a temperature sensor system that accurately measures core body temperature from an ear-worn device. Two digital temperature sensors were embedded in a hearing aid shell along the thermal gradient of the ear canal to form a linear heat balance relationship. This relationship was used to determine best fit parameters for estimating body temperature. The predicted body temperatures resulted in intersubject limits of agreement (LOA) of ±0.49 °C over a range of physiologic and ambient temperatures without calibration. The newly developed hearing aid-based temperature sensor system can estimate core body temperature at an accuracy level equal to or better than many devices currently on the market. An accurate, continuously worn, temperature monitoring and tracking device may help provide early detection of illnesses, which could prove especially beneficial during pandemics and in the elderly demographic of hearing aid wearers.
The aim of this study is to examine the daytime effects on flip turn performance [i.e., 3 m round trip time (3mRTT) as measure of turning performance] as well as global performance during a 50 m freestyle at maximal speed. Twelve college swimmers performed 3 × 50 m freestyle at maximum speed with a flip turn and glide in a 25 m pool in two experimental trials, one in the morning (08:00 h) and one in the evening (18:00 h). Kinematic and dynamic parameters of flip turn performance are analyzed using one underwater camera and a force platform recording wall force peak and time contact. Results showed that oral temperature is significantly higher (p < 0.001) in the evening than in the morning. Also, this study reported that daily variations have been observed for both, changes in swim performance and changes in (3mRTT). Thus, kinematic and dynamic flip turn variables associated with an improvement of freestyle swim performance. It is concluded that maximal swimming trials are performed better in the evening than in the morning, and that this might be linked to variations in oral temperature; also, might be explained by better flip turn performance at this time.
Abstract: Problem statement:
To quantify the effect of exhausting exercise induc
ed muscular fatigue
on functional stability.
Approach:
About 30 male professional athletes with mean age
23±2.1 years
old, mean weight 82±1.3 kg and mean height1 81±9.7
cm were selected for participation in this study.
In this study Unstable Biodex platform (level 3) us
ed for stability evaluation. Balance performance
was quantified as a stability index and the mean de
flection of the platform. Running Based Anaerobic
Test (RAST test) used for fatigue execution.
Results:
Results showed no significant (p>0.05) main
effect for exercise duration in the stability index
, suggesting that balance performance was maintaine
d
throughout the competition. Hence there wasn’t a si
gnificant relationship between lactate acid
accumulation and variations of stability indices (r
= -0/661, p<0.05).
Conclusion:
Therefore, the
improvement of proprioception in the ankle and knee
joint is recommended as a prevention role to the
injuries in the abovementioned joints.
The study aims at exploring the :
Effects of the morning and late afternoon chronobiological variations
in the Hemodynamic in resting position for the Study sample .
Effects of the morning and late afternoon chronobiological variations
after anaerobic repeated effort in maximum intensity for the Study
sample .
Effects of the morning and late afternoon chronobiological variations
on the core temperature and some blood serum variables in resting
position for the Study sample .
Effects of the morning and late afternoon chronobiological variations
on the core temperature and some blood serum variables after
anaerobic repeated effort in maximum intensity for the Study sample.
Effects of the morning and late afternoon chronobiological variations
in fatigue index for in the level of reduce in anaerobic power for six
repeated fast start
The sample has been collected randomly which includes (10)
students of physical Education Department in Basic Education College
(23.62 + 1.92).
The Running-based Anaerobic Sprint Test, RAST, was applied by
sample. The physiological variables consist of: (center core temperature,
systolic and diastolic blood pressures, pulse pressure , Mean arterial
blood pressure , blood sugar and calcium ion) . Having collected the data,
they were analyzed statistically by using arithmetic means, standard
deviations, and "t" test for two paired samples.
After presenting and discussing the result, we can conclude the
following:
The change in Biological rhythm have a significant effect on some
study variables (systolic blood pressure , pulse pressure and calcium
ion ) . they were higher in the more than in the late afternoon after
performing the anaerobic effort.
The change in Biological rhythm have a significant effect on some
study variables (Center core and calcium ion) which are higher in the
morning than in the late afternoon in resting position .
Background and purpose: Plasma levels of lipid profile is one of the main factors in assessing the risk of cardiovascular diseases. The aim of this study was to evaluate the effect of 8 weeks aerobic training on lipid profile, body fat percentage, body mass index, and maximal oxygen uptake in sedentary overweight females in the morning or evening.
Materials and methods: In this semi experimental study, 36 overweight women (mean age 29.71±3.05 years and body mass index 27.25±1.26 kg) were selected using purposive sampling. They were divided in two exercise (n= 10) and control groups (n= 8). Training program included aerobic exercises at 8 am and 6 pm, three days a week. The target heart rate was 60% maximum heart rate (MHR) for 25 minutes in first week which reached 85% MHR for 45 minutes in last week. To determine the lipid profile, a 12 h fasting blood sample was taken before and after the intervention.
Results: The results showed that following training in both morning and afternoon, HDL-c levels increased significantly (P=0.001) but LDL-c levels decreased significantly (P=0.002). Triglycerides and total cholesterol levels did not change significantly after the intervention (P=0.27, P=0.38, respectively). Maximum oxygen consumption increased significantly in evening exercises (P= 0.013). Body fat percentage and body mass index decreased significantly in both the morning and evening (P= 0.001).
Conclusion: Our findings revealed that aerobic exercises in the morning and evening had similar influence on lipid profile while the increase in aerobic capacity in the evening was more than that in the morning.
It is important for human health and efficiency to maintain physiological and biochemical processes within narrow bands in spite of external influences. This homeostasis is achieved by means of negative feedback control loops, and superimposed on the “constancy” produced by it, there are rhythmic changes. The main rhythms can have a period—the length of time that elapses until the cycle is repeated—of a day, week, month, or year. Ultradian rhythms refer to cycles with a period of <20 h and that recur within a single day. With regard to those rhythms with a period of a day, which are therefore known as circadian rhythms, there is now good evidence that an internal “body clock” contributes to their control.
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