Influence of circadian time structure on acute hormonal responses to a single bout of heavy-resistance exercise in weight-trained men

Supplementation Strategies for Strength and Power Athletes: Carbohydrate, Protein, and Amino Acid Ingestion

It is a common belief amongst strength and power athletes that nutritional supplementation strategies aid recovery by shifting the anabolic/catabolic profile toward anabolism. Factors such as nutrient quantity, nutrient quality, and nutrient timing significantly impact upon the effectiveness of nutritional strategies in optimizing the acute responses to resistance exercise and the adaptive response to resistance training (i.e., muscle growth and strength expression). Specifically, the aim of this review is to address carbohydrates (CHOs), protein (PRO), and/or amino acids (AAs) supplementation strategies, as there is growing evidence suggesting a link between nutrient signaling and the initiation of protein synthesis, muscle glycogen resynthesis, and the attenuation of myofibrillar protein degradation following resistance exercise. Collectively, the current scientific literature indicates that nutritional supplementation strategies utilizing CHO, PRO, and/or AA represents an important approach aimed at enhancing muscular responses for strength and power athletes, primarily increased muscular hypertrophy and enhanced strength expression. There appears to be a critical interaction between resistance exercise and nutrient-cell signaling associated with the principle of nutrient timing (i.e., pre-exercise, during, and post-exercise). Recommendations for nutritional supplementation strategies to promote muscular responses for strength and athletes are provided.

The Influence of Weather Conditions on the Diurnal Variation in Range of Motion in Older Adults with Knee Osteoarthritis

(1) Background: This study investigated the relationship between weather conditions, diurnal patterns, and total knee range of motion (ROM), as well as the severity of symptoms (pain and stiffness) in older adults with knee osteoarthritis. (2) Methods: An exploratory longitudinal study was conducted on 28 older adults with knee osteoarthritis (mean age 71.86 ± 4.49 years; 46.4% men, 53.6% women). We used as assessment tools the Visual Analog Scales (VAS) for self-reported local knee pain and stiffness, and goniometry for ROM. Measurements were taken twice, six months apart, in winter and summer, in the morning and evening of each selected day. Recorded weather factors comprised temperature, relative humidity, barometric pressure, and maximum wind speed. (3) Results: The study revealed significant effects of season and time of day on pain and stiffness, respectively (p < 0.001). Additionally, a significant interaction between season and time influenced total knee ROM (p < 0.001). Moreover, there was a statistically significant relationship between time and total knee ROM (p < 0.001). (4) Conclusions: This research underscores the complex link between seasonal fluctuations and daily variations in some symptomatic and functional aspects of knee osteoarthritis in older adults.

Caffeine ingestion attenuates diurnal variation of lower-body ballistic performance in resistance-trained women

ABSTRACTThe present study investigates the effect of an acute intake of caffeine on the diurnal variation of neuromuscular performance in resistance-trained women. A total of 15 resistance-trained women participated in the current triple-blind, placebo-controlled, crossover experimental study. We assessed neuromuscular performance (i.e. ballistic (countermovement jump [CMJ] height and bench press throw [BPT] peak velocity), maximal strength (squat and bench press [BP] one-repetition maximum [1RM]), and strength-endurance [average velocity of the set during squat and number of repetitions-to-failure in BP]) four times at within 7 days. The participants ingested an acute dose of caffeine (3 mg/kg) or a placebo at 9-11 am and/or 17-19 pm. CMJ height (P = .016) and BP peak velocity (P = .012) were higher in the afternoon than in the morning. Compared to placebo, caffeine intake increased CMJ height by 3.1% in the morning and 1.6% in the afternoon (P = .035), but it had no effect on BPT peak velocity (P = .381). Maximal strength and strength-endurance performances were not affected by the time-of-day or caffeine intake (all P > .3). No significant interaction (time-of-day x substance) was observed in any of the above-mentioned outcomes (all P > .1). In conclusion, an acute dose of caffeine in the morning was effective to restore CMJ performance to levels found in the afternoon, while this effect was not observed neither in BPTpeak velocity nor in lower- and upper-body maximal strength and strength-endurance performance. Moreover, lower- and upper-body ballistic performance were greater in the afternoon than in the morning in resistance-trained women, while the acute intake of caffeine was only effective to increase CMJ height.HighlightsBallistic performance is probably higher in the afternoon than in the morning in resistance-trained women.An acute intake of caffeine is effective to increase countermovement jump performance.The ingestion of an acute dose of caffeine in the morning restored countermovement jump performance to levels found in the afternoon.

Effects of Morning Vs. Evening exercise on appetite, energy intake, performance and metabolism, in lean males and females

Exercise is an important component of a weight management strategy. However, little is known about whether circadian variations in physiological and behavioural processes can influence the appetite and energy balance responses to exercise performed at different times of the day. This study compared the effects of morning and evening exercise on appetite, post-exercise energy intake, and voluntary performance. In randomised, counterbalanced order, 16 healthy males and females (n = 8 each) completed two trials, performing morning exercise at 10:30 (AMEx) or evening exercise at 18:30 (PMEx). Exercise consisted of 30 min steady-state cycling (60% V˙ O_2peak), and a 15-min performance test. A standardised meal (543 ± 86 kcal) was consumed 2-h before exercise and ad-libitum energy intake was assessed 15 min after exercise, with subjective appetite measured throughout. Absolute ad-libitum energy intake was 152 ± 126 kcal greater during PMEx (P < 0.001), but there was no differences in subjective appetite between trials immediately pre-exercise, or immediately before the post-exercise meal (P ≥ 0.060). Resting energy expenditure (P < 0.01) and carbohydrate oxidation (P < 0.05) were greater during AMEx, but there were no differences in substrate oxidation or energy expenditure during exercise (P ≥ 0.155). Exercise performance was not different between trials (P = 0.628). In conclusion, acute morning and evening exercise prompt similar appetite responses, but post-exercise ad-libitum energy intake is greater following evening exercise. These findings demonstrate discordant responses between subjective appetite and ad-libitum energy intake but suggest that exercise might offset circadian variations in appetite. Longer-term studies are required to determine how exercise timing affects adherence and weight management outcomes to exercise interventions. TRIAL REGISTRATION: NCT04742530, February 8, 2021.

Testosterone and lean mass show a positive correlation with the technical performance of footballers

BACKGROUND

Monitoring technical performance during a soccer match has become an indispensable practice, since the players perform different functions within the tactical system adopted by the team, resulting in specific technical actions that are fully responsive to the individual technical level of each player. Thus, current study aimed to investigate the possible direct and mediating relationship between salivary testosterone and the technical performance of semi-professional footballers during a training game.

METHODS

To characterize the sample, the anthropometric profile, body composition, biological maturation, lower limb power, speed, estimation of maximum oxygen consumption, and physical performance were used. To determine testosterone concentrations, saliva was collected before and after the training game, for subsequent measurement using enzyme immunoassay (ELISA) and Salimetrics Kits. For quantification of technical performance and participation with the ball during the training game, scout software was used from the footage of the training game. The reliability of the technical performance analyses was determined through the repetition test of two attempts (Cohen's Kappa agreement index).

RESULTS

The direct relationship between post-game testosterone and total participation with the ball in the second half; the direct relationship between the percentage of lean mass with post-game testosterone and an apparent relationship between percentage of lean mass and total participation with the ball from the set of relations mediated by post-game testosterone concentrations.

CONCLUSIONS

The results suggest that testosterone concentrations combined with high levels of lean mass may have a important role in the technical performance and participation with the ball of semi-professional footballers.

Eat, Train, Sleep-Retreat? Hormonal Interactions of Intermittent Fasting, Exercise and Circadian Rhythm

The circadian rhythmicity of endogenous metabolic and hormonal processes is controlled by a complex system of central and peripheral pacemakers, influenced by exogenous factors like light/dark-cycles, nutrition and exercise timing. There is evidence that alterations in this system may be involved in the pathogenesis of metabolic diseases. It has been shown that disruptions to normal diurnal rhythms lead to drastic changes in circadian processes, as often seen in modern society due to excessive exposure to unnatural light sources. Out of that, research has focused on time-restricted feeding and exercise, as both seem to be able to reset disruptions in circadian pacemakers. Based on these results and personal physical goals, optimal time periods for food intake and exercise have been identified. This review shows that appropriate nutrition and exercise timing are powerful tools to support, rather than not disturb, the circadian rhythm and potentially contribute to the prevention of metabolic diseases. Nevertheless, both lifestyle interventions are unable to address the real issue: the misalignment of our biological with our social time.

Diurnal Variation: Does it Affect Short-term Maximal Performance and Biological Parameters in Police Officers?

Objectives: This study aimed to assess the diurnal variation of short term maximal performance and biological markers of hormonal [cortisol (CRT), testosterone (TST), melatonin (MLT)], biochemical [creatine phosphokinase (CPK), blood glucose (GLC), uric acid (UA)] and hematological [white blood cells (WBC), monocytes (MO), neutrophils (NE), lymphocytes (LY), red blood cells (RBC), hemoglobin (HB), hematocrit (HMT)] parameters in male police officers. Methods: Twenty male police officers performed a running-based anaerobic sprint test (RAST) at two different times of the day (TOD), in the morning (6:00 h - 7:00 h) and evening (19:00 - 20:00) where blood samples were collected from the participants on these two occasions before each exercise session. Results: Short term maximal performance [Peak power (PP), average power (AP) and minimal power (MP)] was higher in the evening as compared to the morning. It was noted that biological markers of hormonal, biochemical and hematological parameters exhibit diurnal fluctuation. Some of them peak in the morning (MLT, CRT, TST, UA, RBC, HB, and HMT) and others peak in the evening (GLC, CPK, WBC, NE, LY, and MO). Conclusions: Short term maximal performance, hormonal, biochemical and hematological parameters were strongly affected by the TOD in police officers. Thus, understanding changes in short term maximal exercice and these circulating mediators during different TOD provide a better understanding of the anaerobic metabolism and could help modulate and quantify training load.

The Use of Acute Exercise Interventions as Game Day Priming Strategies to Improve Physical Performance and Athlete Readiness in Team-Sport Athletes: A Systematic Review

BACKGROUND

The use of exercise as a priming strategy to enhance sport performance is becoming increasingly popular in professional sports and as an area of research interest. Early research suggests that the acute physiological responses to exercise can positively influence performance for up to 48 h. There is yet to be a comprehensive review of exercise strategies which could be implemented specifically on the day of competition.

OBJECTIVES

The aim of this systematic review was to provide a synthesis of research investigating acute exercise interventions as game day priming strategies for team-sport athletes to improve physical performance and athlete readiness when implemented in the 1-12 h prior to competition.

METHODS

A literature search of SPORTDiscus, PubMed and Cochrane Central Register for Controlled Trials was conducted. A total of 6428 studies were retrieved and assessed against the following inclusion criteria: (1) randomised controlled trials and non-randomised comparative studies with reported pre-post intervention outcomes; (2) exercise interventions were applied 1-12 h prior to the assessment of outcome measures. Studies were excluded if they used nutrition, supplementation, pre-heating, pre-cooling, stretching, massage or vibration training as the priming strategies, or if interventions were performed at altitude or in hypoxic environments. Studies were assessed for methodological quality at the study level using the Physiotherapy Evidence Database (PEDro) scale.

RESULTS

Twenty-nine studies satisfied the eligibility criteria and were included in this review. Studies were categorised as resistance training; cycling; running; and other strategies. Resistance training using heavy loads at low volumes increased strength and power measures following a 4-6 h recovery, with limited improvements observed following shorter (1-3 h) and longer (6-12 h) recovery periods. Running-based sprint priming led to improvements in subsequent sprint and repeat sprint performance following a 5-6 h recovery, whereas cycling improved counter-movement jump height in a single study only. No significant differences were reported in any performance measures following endurance-based running or cycling strategies. Physiological markers, such a hormone and blood lactate responses, showed mixed results between studies.

CONCLUSIONS

High-intensity low-volume resistance training leads to a greater physiological and performance response than high-volume resistance training. Maximal running sprints may be more effective than maximal cycling sprints due to an increased physiological demand; however, loading protocols must also be considered in conjunction with exercise volume and movement specificity to achieve a beneficial response for subsequent performance. There is limited evidence to suggest endurance cycling or running exercise is beneficial as a priming strategy.

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

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

Effects of natural polyphenol-rich pomegranate juice on the acute and delayed response of Homocysteine and steroidal hormones following weightlifting exercises: a double-blind, placebo-controlled trial

BACKGROUND

Maximal strength-speed exercise is a powerful stimulus to acutely increase concentrations of circulating steroid hormones and homocysteine [Hcy]. There is some evidence that antioxidant beverages rich in polyphenols can attenuate [Hcy] levels and modulate endocrine responses in favor of an anabolic environment. Polyphenols-rich pomegranate (POM) have been reported to possess one of the highest antioxidant capacities compared to other purported nutraceuticals and other food stuffs. Studies focused on proving the beneficial effect of POM consumption during maximal strength exercises have only measured physical performance, muscle damage, oxidative stress and inflammatory responses, while POM effects on [Hcy] and hormonal adaptations are lacking. The aim of the present study was to investigate the effect of consuming natural polyphenol-rich pomegranate juice (POMj) on the acute and delayed [Hcy] and steroidal hormonal responses to a weightlifting exercises session.

METHODS

Nine elite weightlifters (21.0 ± 1 years) performed two Olympic-weightlifting sessions after ingesting either the placebo (PLA) or POMj supplements. Venous blood samples were collected at rest and 3 min and 48 h after each session.

RESULTS

Compared to baseline values, circulating cortisol [C] decreased (p < 0.01) and testosterone/cortisol [T/C] ratio increased immediately following the training session in both PLA and POMj conditions (p = 0.003 for PLA and p = 0.02 for POM). During the 48 h recovery period, all tested parameters were shown to recover to baseline values in both conditions with significant increases in [C] and decreases in [T/C] (p < 0.01 for PLA and p < 0.05 for POMj) from 3 min to 48 h post-exercises. Compared to PLA, a lower level of plasma testosterone [T] was registered 3 min post exercise using POMj supplementation (p = 0.012) and a significant decrease (p = 0.04, %change = - 14%) in plasma [Hcy] was registered during the 48 h recovery period only using POMj. A moderate correlation was observed between [Hcy] and [T] responses (p = 0.002, r = - 0.50).

CONCLUSION

In conclusion, supplementation with POMj has the potential to attenuate the acute plasma [T] response, but did not effect 48 h recovery kinetics of [Hcy] following weightlifting exercise. Further studies investigating androgen levels in both plasma and muscular tissue are needed to resolve the functional consequences of the observed acute POMj effect on plasma [T].

TRIAL REGISTRATION

Clinical Trials.gov, ID: NCT02697903. Registered 03 March 2016.

Bouts of exercise elicit discordant testosterone: cortisol ratios in runners and non-runners

OBJECTIVE

The testosterone:cortisol ratio (T:C) is suggested to be used in order to examine whether physical exercise generates either a "catabolic environment" or an "anabolic environment". The present study aims to evaluate the acute time-course profile of cortisol and testosterone due to an episode of physical exercise. A biphasic profile in the T:C ratio response was hypothesized.

MATERIALS AND METHODS

Morning sessions of treadmill running at two different intensities (Heart Rate at 65% and 80% of the maximum cardiac reserve) were performed by 6 male non-runners (NR) and 12 trained male runners (subdivided into trained runners T1 and T2). Cortisol and testosterone were measured in saliva. NR and T1 ran for 30 minutes at both intensities, and T2 ran for 46 minutes (± 4.1) at 65% and 42 minutes (± 3.5) at 80%.

RESULTS

In the 80% heart rate target, both groups of runners showed the biphasic time-profile, while the non-runners group did not. However, at the 65% level, none of the groups presented the hypothesized biphasic response.

CONCLUSIONS

A biphasic time-profile in the testosterone:cortisol ratio can be seen in short-bout, high intensity exercise (treadmill running) during the morning in men trained for this specific physical activity.

Anabolic Heterogeneity Following Resistance Training: A Role for Circadian Rhythm?

It is now well established that resistance exercise stimulates muscle protein synthesis and promotes gains in muscle mass and strength. However, considerable variability exists following standardized resistance training programs in the magnitude of muscle cross-sectional area and strength responses from one individual to another. Several studies have recently posited that alterations in satellite cell population, myogenic gene expression and microRNAs may contribute to individual variability in anabolic adaptation. One emerging factor that may also explain the variability in responses to resistance exercise is circadian rhythms and underlying molecular clock signals. The molecular clock is found in most cells within the body, including skeletal muscle, and principally functions to optimize the timing of specific cellular events around a 24 h cycle. Accumulating evidence investigating the skeletal muscle molecular clock indicates that exercise-induced contraction and its timing may regulate gene expression and protein synthesis responses which, over time, can influence and modulate key physiological responses such as muscle hypertrophy and increased strength. Therefore, the circadian clock may play a key role in the heterogeneous anabolic responses with resistance exercise. The central aim of this Hypothesis and Theory is to discuss and propose the potential interplay between the circadian molecular clock and established molecular mechanisms mediating muscle anabolic responses with resistance training. This article begins with a current review of the mechanisms associated with the heterogeneity in muscle anabolism with resistance training before introducing the molecular pathways regulating circadian function in skeletal muscle. Recent work showing members of the core molecular clock system can regulate myogenic and translational signaling pathways is also discussed, forming the basis for a possible role of the circadian clock in the variable anabolic responses with resistance exercise.

Diurnal Rhythm of Muscular Strength Depends on Temporal Specificity of Self-Resistance Training

The study investigated the effect of the time-of-day at which maximal isometric voluntary co-contraction (MIVCC) training is conducted on the adaptation and diurnal variation of maximal and explosive force production. Twenty active men underwent a 6-week (3 times per week) MIVCC training of the right elbow joint. The participants were randomly assigned to a morning training group (MTG, 07:00-08:00 hours) and evening training group (ETG, 17:00-18:00 hours). The maximal voluntary force (MVF) and maximal rate of force development (MRFD) during isometric elbow flexion (MVFF and MRFD(F)) and extension (MVF(E) and MRFD(E)) were recorded before (T0) and after (T1) training in the morning and evening. At T0, MVF and MRFD were higher in the evening compared with those in the morning for the MTG and ETG (p ≤ 0.05). At T1, MVFF and MVFE increased in the morning and evening for both groups (p < 0.001). The MRFD(F) and MRFD(E) increased only if training and test session were scheduled at the same time. The relative increase of MVF was greater at the specific time of training for the MTG (12 and 17.6% in MVF(F) and MVF(E), respectively) and ETG (9.8 and 13.4% in MVF(F) and MVF(E), respectively). The diurnal variations in MVF and MRF(D) during flexion and extension disappeared in the MTG and persisted in the ETG. Maximal isometric voluntary co-contraction training enhanced muscle strength whatever the time-of-day at which the training was scheduled without alteration of explosive force. In contrast, to optimize the muscle strength, our results suggested that morning training may be accompanied by the greatest muscle strength gain and blunted muscle strength variation observed between the morning and evening.

The Differential Hormonal Milieu of Morning versus Evening May Have an Impact on Muscle Hypertrophic Potential

Substantial gains in muscle strength and hypertrophy are clearly associated with the routine performance of resistance training. What is less evident is the optimal timing of the resistance training stimulus to elicit these significant functional and structural skeletal muscle changes. Therefore, this investigation determined the impact of a single bout of resistance training performed either in the morning or evening upon acute anabolic signalling (insulin-like growth factor-binding protein-3 (IGFBP-3), myogenic index and differentiation) and catabolic processes (cortisol). Twenty-four male participants (age 21.4±1.9yrs, mass 83.7±13.7kg) with no sustained resistance training experience were allocated to a resistance exercise group (REP). Sixteen of the 24 participants were randomly selected to perform an additional non-exercising control group (CP) protocol. REP performed two bouts of resistance exercise (80% 1RM) in the morning (AM: 0800 hrs) and evening (PM: 1800 hrs), with the sessions separated by a minimum of 72 hours. Venous blood was collected immediately prior to, and 5 min after, each resistance exercise and control sessions. Serum cortisol and IGFBP-3 levels, myogenic index, myotube width, were determined at each sampling period. All data are reported as mean ± SEM, statistical significance was set at P≤0.05. As expected a significant reduction in evening cortisol concentration was observed at pre (AM: 98.4±10.5, PM: 49.8±4.4 ng/ml, P<0.001) and post (AM: 98.0±9.0, PM: 52.7±6.0 ng/ml, P<0.001) exercise. Interestingly, individual cortisol differences pre vs post exercise indicate a time-of-day effect (AM difference: -2±2.6%, PM difference: 14.0±6.7%, P = 0.03). A time-of-day related elevation in serum IGFBP-3 (AM: 3274.9 ± 345.2, PM: 3605.1 ± 367.5, p = 0.032) was also evident. Pre exercise myogenic index (AM: 8.0±0.6%, PM: 16.8±1.1%) and myotube width (AM: 48.0±3.0, PM: 71.6±1.9 μm) were significantly elevated (P<0.001) in the evening. Post exercise myogenic index was greater AM (11.5±1.6%) compared with PM (4.6±0.9%). No difference was observed in myotube width (AM: 48.5±1.5, PM: 47.8±1.8 μm) (P>0.05). Timing of resistance training regimen in the evening appears to augment some markers of hypertrophic potential, with elevated IGFBP-3, suppressed cortisol and a superior cellular environment. Further investigation, to further elucidate the time course of peak anabolic signalling in morning vs evening training conditions, are timely.

The effect of inter-set rest intervals on resistance exercise-induced muscle hypertrophy

Due to a scarcity of longitudinal trials directly measuring changes in muscle girth, previous recommendations for inter-set rest intervals in resistance training programs designed to stimulate muscular hypertrophy were primarily based on the post-exercise endocrinological response and other mechanisms theoretically related to muscle growth. New research regarding the effects of inter-set rest interval manipulation on resistance training-induced muscular hypertrophy is reviewed here to evaluate current practices and provide directions for future research. Of the studies measuring long-term muscle hypertrophy in groups employing different rest intervals, none have found superior muscle growth in the shorter compared with the longer rest interval group and one study has found the opposite. Rest intervals less than 1 minute can result in acute increases in serum growth hormone levels and these rest intervals also decrease the serum testosterone to cortisol ratio. Long-term adaptations may abate the post-exercise endocrinological response and the relationship between the transient change in hormonal production and chronic muscular hypertrophy is highly contentious and appears to be weak. The relationship between the rest interval-mediated effect on immune system response, muscle damage, metabolic stress, or energy production capacity and muscle hypertrophy is still ambiguous and largely theoretical. In conclusion, the literature does not support the hypothesis that training for muscle hypertrophy requires shorter rest intervals than training for strength development or that predetermined rest intervals are preferable to auto-regulated rest periods in this regard.

Trained and untrained males show reliable salivary testosterone responses to a physical stimulus, but not a psychological stimulus

BACKGROUND

The testosterone (T) responses to a physical stimulus are thought to be more stable and reproducible compared to a psychological stimulus.

PURPOSE

This study compared the salivary T (Sal-T) responses to both stimuli in four groups of men: professional rugby players (n = 17), recreational rugby players (n = 10), a mixed athlete group (n = 14) and untrained controls (n = 12).

METHODS

Each group completed three treatments: (1) watching a video with aggressive rugby footage, (2) performing a short bout of sprint exercise and (3) a control session. Saliva samples were taken before and 15 min after each treatment.

RESULTS

The sprint exercise changes in Sal-T levels were similar in the elite rugby (17.1 ± 11.1%), recreational rugby (11.9 ± 15.9%), mixed athlete (27.6 ± 32.0%) and control groups (25.3 ± 23.6%). In response to the video, Sal-T increased in the elite rugby (6.9 ± 6.4%) and untrained groups (11.9 ± 13.5%), but decreased in the recreational rugby players (-7.5 ± 11.0%). The individual Sal-T responses to the sprints were also correlated (r = 0.69 to 0.82) with other treatment responses.

CONCLUSIONS

Sprint exercise had a more consistent effect on Sal-T than a video with aggressive content and thus, could provide a reliable stimulus for increasing T availability in men with different training backgrounds. Individual Sal-T reactivity also appears to be somewhat stable across different treatments. These data provide further understanding around the induction, moderation and interpretation of T physiology.

Morning and evening exercise

A growing body of evidence suggests that exercise may contribute to preventing pathological changes, treating multiple chronic diseases, and reducing mortality and morbidity ratios. Scientific evidence moreover shows that exercise plays a key role in improving health-related physical fitness components and hormone function. Regular exercise training is one of the few strategies that has been strictly adapted in healthy individuals and in athletes. However, time-dependent exercise has different outcomes, based on the exercise type, duration, and hormone adaptation. In the present review, we therefore briefly describe the type, duration, and adaptation of exercise performed in the morning and evening. In addition, we discuss the clinical considerations and indications for exercise training.

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

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

Effect of conjugated linoleic acid on testosterone levels in vitro and in vivo after an acute bout of resistance exercise

The purposes of the present study were to investigate the effect of conjugated linoleic acid (CLA) supplementation on testosterone levels in vitro on a cell line derived from Leydig cells (R2C) and in vivo in the blood of physically active subjects before and after a resistance exercise bout. In vitro R2C cells were treated with different CLA concentrations (0-30 μM) for 24 and 48 hours. After treatment, supernatant media were tested to determine testosterone secretion. The CLA increased the testosterone secretion only after 48 hours. In vivo, 10 resistance-trained male subjects, in a double-blind placebo-controlled and crossover study design were randomized for 3 weeks of either 6 g·d⁻¹ CLA or placebo. Blood was drawn pre and post each resistance exercise bout to determine the total testosterone and sex hormone-binding globulin (SHBG) levels. No significant differences were observed for total testosterone or SHBG pre and post each resistance exercise bout; although after the resistance exercise bouts, total testosterone increased moderately (effect size = moderate), whereas after CLA supplementation, there was a large increase in total testosterone (effect size = large). CLA supplementation induced an increase in testosterone levels in Leydig cells in vitro after 48 hours but not in vivo before and after a resistance exercise bout. These findings suggest that CLA supplementation may promote testosterone synthesis through a molecular pathway that should be investigated in the future, although this effect did not have an anabolic relevance in our in vivo model.

The effect of training at the same time of day and tapering period on the diurnal variation of short exercise performances

The purpose of this investigation was to assess the effects of training and tapering at the same time of the day on the diurnal variations of short exercise performances. Thirty-one physically active men underwent 12 weeks of lower-extremity resistance training and 2 weeks of tapering. These subjects were matched and randomly assigned to a morning training group (MTG, training times 0700-0800 hours, n = 10), an evening training group (ETG, training times 1700-1800 hours, n = 11), and a control group (CG, completed all tests but did not train, n = 10). Muscular strength and power testing was conducted before (T0) and after 12 weeks of training (T1) and after 2 weeks of tapering (T2) in the morning (0700-0800 hours) and in the evening (1700-1800 hours). All morning and evening tests were performed in separate sessions (minimum interval = 36 hours) in a randomized design. In T0, the oral temperature and performances during the Wingate, vertical jump (squat jump and countermovement jump), and maximal voluntary contraction tests were higher in the evening than in the morning for all the groups. In T1, these diurnal variations were blunted in the MTG and persisted in the ETG and CG. In T2, the 2 weeks of tapering resulted in further time of day-specific adaptations and increases in short-term maximal performances. However, there was no significant difference in the relative increase between the MTG and the ETG after both training and tapering. From a practical point of view, if the time of competition is known, training and tapering sessions before a major competition must be conducted at the same time of the day at which one's critical performance is programmed. Moreover, if the time of the competition is not known, a tapering phase after resistance training program could be performed at any time of the day with the same benefit.

The effect of strength training at the same time of the day on the diurnal fluctuations of muscular anaerobic performances

The aim of this study was to examine the effects of training at the same time of the day on the diurnal variations of anaerobic performances to provide some recommendations to adjust training hours with the time of the day of competitive events. Thirty participants underwent 8 weeks of lower-extremity progressive resistance training performed 3 times per week designed to promote muscular strength and power. These subjects were randomly assigned to a morning training group (MTG, 07:00-08:00 hours, n = 10), an evening training group (ETG, 17:00-18:00 hours, n = 10), and a control group (CG, completed all tests but did not train, n = 10). Performance in the squat jump, the countermovement jump, the Wingate and 1 repetition maximum (1RM) during leg extension, leg curl, and squat tests was recorded just before and 2 weeks after an 8-week course of regular training. For all the subjects, the morning and evening tests were scheduled at the same time of the day as for the morning and evening training sessions. Before training, the results indicated a significant increase in performance from morning to evening tests (ca. 2.84-17.55% for all tests) for all groups. After training, the diurnal variations in anaerobic performances were blunted in the MTG. In fact, there was no significant difference in muscular power or strength between morning and evening tests. However, these intradaily variations in anaerobic performances persisted in the ETG and CG. From a practical point of view, adaptation to strength training is greater at the time of the day at which training was scheduled than at other times.

Caffeine ingestion reverses the circadian rhythm effects on neuromuscular performance in highly resistance-trained men

PURPOSE

To investigate whether caffeine ingestion counteracts the morning reduction in neuromuscular performance associated with the circadian rhythm pattern.

METHODS

Twelve highly resistance-trained men underwent a battery of neuromuscular tests under three different conditions; i) morning (10:00 a.m.) with caffeine ingestion (i.e., 3 mg kg(-1); AM(CAFF) trial); ii) morning (10:00 a.m.) with placebo ingestion (AM(PLAC) trial); and iii) afternoon (18:00 p.m.) with placebo ingestion (PM(PLAC) trial). A randomized, double-blind, crossover, placebo controlled experimental design was used, with all subjects serving as their own controls. The neuromuscular test battery consisted in the measurement of bar displacement velocity during free-weight full-squat (SQ) and bench press (BP) exercises against loads that elicit maximum strength (75% 1RM load) and muscle power adaptations (1 m s(-1) load). Isometric maximum voluntary contraction (MVC(LEG)) and isometric electrically evoked strength of the right knee (EVOK(LEG)) were measured to identify caffeine's action mechanisms. Steroid hormone levels (serum testosterone, cortisol and growth hormone) were evaluated at the beginning of each trial (PRE). In addition, plasma norepinephrine (NE) and epinephrine were measured PRE and at the end of each trial following a standardized intense (85% 1RM) 6 repetitions bout of SQ (POST).

RESULTS

In the PM(PLAC) trial, dynamic muscle strength and power output were significantly enhanced compared with AM(PLAC) treatment (3.0%-7.5%; p≤0.05). During AM(CAFF) trial, muscle strength and power output increased above AM(PLAC) levels (4.6%-5.7%; p≤0.05) except for BP velocity with 1 m s(-1) load (p = 0.06). During AM(CAFF), EVOK(LEG) and NE (a surrogate of maximal muscle sympathetic nerve activation) were increased above AM(PLAC) trial (14.6% and 96.8% respectively; p≤0.05).

CONCLUSIONS

These results indicate that caffeine ingestion reverses the morning neuromuscular declines in highly resistance-trained men, raising performance to the levels of the afternoon trial. Our electrical stimulation data, along with the NE values, suggest that caffeine increases neuromuscular performance having a direct effect in the muscle.

Periodization paradigms in the 21st century: evidence-led or tradition-driven?

The planning and organization of athletic training have historically been much discussed and debated in the coaching and sports science literature. Various influential periodization theorists have devised, promoted, and substantiated particular training-planning models based on interpretation of the scientific evidence and individual beliefs and experiences. Superficially, these proposed planning models appear to differ substantially. However, at a deeper level, it can be suggested that such models share a deep-rooted cultural heritage underpinned by a common set of historically pervasive planning beliefs and assumptions. A concern with certain of these formative assumptions is that, although no longer scientifically justifiable, their shaping influence remains deeply embedded. In recent years substantial evidence has emerged demonstrating that training responses vary extensively, depending upon multiple underlying factors. Such findings challenge the appropriateness of applying generic methodologies, founded in overly simplistic rule-based decision making, to the planning problems posed by inherently complex biological systems. The purpose of this review is not to suggest a whole-scale rejection of periodization theories but to promote a refined awareness of their various strengths and weaknesses. Eminent periodization theorists-and their variously proposed periodization models-have contributed substantially to the evolution of training-planning practice. However, there is a logical line of reasoning suggesting an urgent need for periodization theories to be realigned with contemporary elite practice and modern scientific conceptual models. In concluding, it is recommended that increased emphasis be placed on the design and implementation of sensitive and responsive training systems that facilitate the guided emergence of customized context-specific training-planning solutions.

Diaphragmatic breathing reduces exercise-induced oxidative stress

Diaphragmatic breathing is relaxing and therapeutic, reduces stress, and is a fundamental procedure of Pranayama Yoga, Zen, transcendental meditation and other meditation practices. Analysis of oxidative stress levels in people who meditate indicated that meditation correlates with lower oxidative stress levels, lower cortisol levels and higher melatonin levels. It is known that cortisol inhibits enzymes responsible for the antioxidant activity of cells and that melatonin is a strong antioxidant; therefore, in this study, we investigated the effects of diaphragmatic breathing on exercise-induced oxidative stress and the putative role of cortisol and melatonin hormones in this stress pathway. We monitored 16 athletes during an exhaustive training session. After the exercise, athletes were divided in two equivalent groups of eight subjects. Subjects of the studied group spent 1 h relaxing performing diaphragmatic breathing and concentrating on their breath in a quiet place. The other eight subjects, representing the control group, spent the same time sitting in an equivalent quite place. Results demonstrate that relaxation induced by diaphragmatic breathing increases the antioxidant defense status in athletes after exhaustive exercise. These effects correlate with the concomitant decrease in cortisol and the increase in melatonin. The consequence is a lower level of oxidative stress, which suggests that an appropriate diaphragmatic breathing could protect athletes from long-term adverse effects of free radicals.

Effect of Pedal Rate on Diurnal Variations in Cardiorespiratory Variables

Recently, it was observed that the freely chosen pedal rate of elite cyclists was significantly lower at 06:00 than at 18:00 h, and that ankle kinematics during cycling exhibits diurnal variation. The modification of the pedaling technique and pedal rate observed throughout the day could be brought about to limit the effect of diurnal variation on physiological variables. Imposing a pedal rate should limit the subject's possibility of adaptation and clarify the influence of time of day on physiological variables. The purpose of this study was to determine whether diurnal variation in cardiorespiratory variables depends on pedal rate. Ten male cyclists performed a submaximal 15 min exercise on a cycle ergometer (50% Wmax). Five test sessions were performed at 06:00, 10:00, 14:00, 18:00, and 22:00 h. The exercise bout was divided into three equivalent 5 min periods during which different pedal rates were imposed (70 rev x min(-1), 90 rev x min(-1) and 120 rev x min(-1)). No significant diurnal variation was observed in heart rate and oxygen consumption, whatever the pedal rate. A significant diurnal variation was observed in minute ventilation (p=0.01). In addition, the amplitude of the diurnal variation in minute ventilation depended on pedal rate: the higher the pedal rate, the greater the amplitude of its diurnal variation (p=0.03). The increase of minute ventilation throughout the day is mainly due to variation in breath frequency (p=0.01)--the diurnal variation of tidal volume (all pedal rate conditions taken together) being non-significant--but the effect of pedal rate x time of day interaction on minute ventilation specific to the higher pedal rate conditions (p=0.03) can only be explained by the increase of tidal volume throughout the day. Even though an influence of pedal rate on diurnal rhythms in overall physiological variables was not also evidenced, high pedal rate should have been imposed when diurnal variations of physiological variables in cycling were studied.

Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion

Previous studies of contracting muscle with low loading and partial vascular occlusion demonstrated hypertrophy and strength adaptations similar to and exceeding those observed with traditional moderate to high resistance (Shinohara M, Kouzaki M, Yoshihisa T, and Fukunaga T. Eur J Physiol 77: 189-191, 1998; Takarada Y, Takazawa H, Sato Y, Takebayashi S, Tanaka Y, and Ishii N. J Appl Physiol 88: 2097-2106, 2000; Takarada Y, Sato Y, and Ishii N. Eur J Physiol 86: 308-314, 2002). The purpose of the study was to determine the anabolic and catabolic hormone responses to light resistance exercise combined with partial vascular occlusion. Three experimental conditions of light resistance with partial occlusion (LRO), moderate resistance with no occlusion (MR), and partial occlusion without exercise (OO) were performed by eight healthy subjects [mean 21 yr (SD 1.8)]. Three sets of single-arm biceps curls and single-leg calf presses were completed to failure with 1-min interset rest periods. Workloads of 30 and 70% one repetition maximum for each exercise were lifted for the LRO and MR trials, respectively. Blood samples were taken preexercise, postexercise, and 15 min postexercise for each experimental condition. Lactate increased significantly in the LRO and MR trials and was not significantly different from each other at any time point. Growth hormone (GH) increased significantly by fourfold from pre- to postexercise in the LRO session but did not change significantly during this time period in the MR and OO trials (8.3 +/- 2.3 vs. 2.1 +/- 1.2 and 2.6 +/- 0.94 microg/l; respectively, P < 0.05). There were no changes in resting total testosterone [T; mean 15.7 +/- 1.6 (SE) nmol/l], free testosterone (FT; 54.1 +/- 4.5 pmol/l), or cortisol (267.6 +/- 22 nmol/l) across all trials and times. In conclusion, with similar lactate responses, light exercise combined with partial vascular occlusion elicits a greater GH response than moderate exercise without occlusion but does not affect T, FT, or cortisol.

Liquid carbohydrate/essential amino acid ingestion during a short-term bout of resistance exercise suppresses myofibrillar protein degradation

A number of physiological events including the level of contractile activity, nutrient status, and hormonal action influence the magnitude of exercise-induced skeletal muscle growth. However, it is not the independent action of a single mechanism, but the complex interaction between events that enhance the long-term adaptations to resistance training. The purpose of the present investigation was to examine the influence of liquid carbohydrate (CHO) and essential amino acid (EAA) ingestion during resistance exercise and modification of the immediate hormonal response on myofibrillar protein degradation as assessed by 3-methylhistidine (3-MH) excretion. After a 4-hour fast, 32 untrained young men (18-29 years) performed a single bout of resistance exercise (complete body; 3 setsx10 repetitions at 75% of 1-repetition maximum; 1-minute rest between sets), during which they consumed a 6% CHO (n=8) solution, a 6-g EAA (n=8) mixture, a combined CHO+EAA (n=8) supplement, or placebo (PLA; n=8) beverage. Resistance exercise performed in conjunction with CHO and CHO+EAA ingestion resulted in significantly elevated (P<.001) glucose and insulin concentrations above baseline, whereas EAA ingestion only increased the postexercise insulin response (P<.05). Time matched at 60 minutes, the PLA group exhibited a peak cortisol increase of 105% (P<.001) with no significant change in glucose or insulin concentrations. Conversely, the CHO and CHO+EAA groups displayed a decrease in cortisol levels of 11% and 7%, respectively. Coinciding with these hormonal response patterns were significant differences in myofibrillar protein degradation. Ingestion of the EAA and CHO treatments attenuated 3-MH excretion 48 hours after the exercise bout. Moreover, this response was synergistically potentiated when the 2 treatments were combined, with CHO+EAA ingestion resulting in a 27% reduction (P<.01) in 3-MH excretion. In contrast, the PLA group displayed a 56% increase (P<.01) in 3-MH excretion. These data demonstrate that not only does CHO and EAA ingestion during the exercise bout suppress exercise-induced cortisol release; the stimulatory effect of resistance exercise on myofibrillar protein degradation can be attenuated, most dramatically when the treatments are combined (CHO+EAA). Through an "anticatabolic effect," this altered balance may better favor the conservation of myofibrillar protein.

Effects of liquid carbohydrate/essential amino acid ingestion on acute hormonal response during a single bout of resistance exercise in untrained men

OBJECTIVE

The primary objective of this study was to investigate the influence of nutritive interventions on acute hormonal responses to a single bout of resistance exercise in untrained young men. Specifically, the aim was to determine whether the acute hormonal milieu conducive to enhancing skeletal muscle hypertrophic adaptation to resistance training could be created. The potential role of cortisol in inhibiting training-induced muscle growth is of particular interest, as is whether exercise-induced cortisol release can be attenuated by nutritive interventions.

METHODS

After a 4-h fast, 32 subjects performed a single bout of resistance exercise ( approximately 60 min), during which they consumed a 6% carbohydrate (CHO) solution, a 6-g essential amino acid (EAA) mixture, a combined CHO+EAA supplement, or a placebo beverage. Blood samples were collected every 15 min throughout the exercise bout, immediately after exercise, and 15 and 30 min after exercise for analysis of total testosterone, cortisol, growth hormone, insulin, and glucose.

RESULTS

No significant change in glucose or insulin was observed for placebo. CHO and CHO+EAA ingestion resulted in significantly (P < 0.001) increased glucose and insulin concentrations above baseline, whereas EAA resulted in significant postexercise increases (P < 0.05) in insulin only. Placebo exhibited a significant increase in cortisol within 30 min (P < 0.01), with a peak increase of 105% (P < 0.001) immediately after exercise, and cortisol remained 54% above baseline at 30 min after exercise (P < 0.05). Conversely, the treatment groups displayed no significant change in cortisol during the exercise bout, with CHO and CHO+EAA finishing 27% (P < 0.01) and 23% (P < 0.05), respectively, below baseline at 30 min after exercise. No between-group differences in exercise-induced growth hormone or testosterone concentrations after nutritive intervention were present.

CONCLUSION

These data indicate that CHO and/or EAA ingestion during a single bout of resistance exercise suppresses the exercise-induced cortisol response, in addition to stimulating insulin release. We conclude that the exercise-induced hormonal profile can be influenced by nutritive interventions toward a profile more favorable for anabolism.

Possible Stimuli for Strength and Power Adaptation

The endocrine system plays an important role in strength and power development by mediating the remodelling of muscle protein. Resistance training scheme design regulates muscle protein turnover by modifying the anabolic (testosterone, growth hormone) and catabolic (cortisol) responses to a workout. Although resistance exercise increases the concentrations of insulin-like growth factor 1 in blood following exercise, the effect of scheme design is less clear, most likely due to the different release mechanisms of this growth factor (liver vs muscle). Insulin is non-responsive to the exercise stimulus, but in the presence of appropriate nutritional intake, elevated blood insulin levels combined with resistance exercise promotes protein anabolism. Factors such as sex, age, training status and nutrition also impact upon the acute hormonal environment and, hence, the adaptive response to resistance training. However, gaps within research, as well as inconsistent findings, limit our understanding of the endocrine contribution to adaptation. Research interpretation is also difficult due to problems with experimental design (e.g. sampling errors) and various other issues (e.g. hormone rhythms, biological fluid examined). In addition to the hormonal responses to resistance exercise, the contribution of other acute training factors, particularly those relating to the mechanical stimulus (e.g. forces, work, time under tension) must also be appreciated. Enhancing our understanding in these areas would also improve the prescription of resistance training for stimulating strength and power adaptation.