Effects of Time-of-Day Training Preference on Resistance-Exercise Performance

Salivary testosterone and cortisol responses to seven weeks of practical blood flow restriction training in collegiate American football players

Purpose

The purpose of this study was to examine the effects of a 7-week supplemental BFR training intervention on both acute and chronic alterations in salivary testosterone (sTes) and cortisol (sCort) in collegiate American football players.

Methods

58 males were divided into 4 groups: 3 completed an upper- and lower-body split resistance training routine (H, H/S, H/S/R; H = Heavy, S = Supplemental, R = BFR), with H/S/R performing end-of-session practical BFR training, and H/S serving as the volume-matched non-BFR group. The final group (M/S/R) completed modified resistance training programming with the same practical BFR protocol as H/S/R. Athletes were further split into AM and PM training groups based upon their pre-determined training schedules, in cooperation with University strength and conditioning staff. Practical BFR consisted of end-of-session barbell bench press and back squat using 20% 1 repetition maximum (1RM) for 30-20-20-20 repetitions across 4 sets, with 45-seconds rest. Saliva samples were taken pre- and post- the first lower-body training sessions in week 1 and week 7 (i.e., test 1 and test 2) of the program, yielding four total. sTes and sCort were analyzed using 4-way (4 × 2 × 2 × 2) mixed model ANOVA's.

Results

Hormonal variables all exhibited main effects for time-of-day (p < 0.001). A significant group × time interaction effect (F3,50 = 3.246, p < 0.05) indicated increases in sTes post-training cycle for the H/S/R group only. Further, PM post-exercise sCort decreased from test 1 to test 2 (nmol·L-1: 95% CI: PM test 1 post-exercise = 10.7-17.1, PM test 2 post-exercise = 5.0-8.9). For the testosterone-to-cortisol ratio (T/C), AM pre-exercise was lower than PM (p < 0.05), with no change in post-exercise T/C for both AM and PM conditions when collapsed across testing times.

Discussion

Overall, these findings suggest an ecologically valid method of BFR implementation is capable of inducing heightened concentrations of sTes in well-resistance trained American football athletes, providing additional insight on possible physiological mechanisms underpinning BFR's ability to elicit beneficial muscle hypertrophy and maximal strength adaptations when performed during regimented training programs. Additionally, notable rises in T/C, and a null sCort response post-exercise were observed post-program for all groups, possibly indicative of positive physiological adaptation.

Ergogenic and Sympathomimetic Effects of Yohimbine: A Review

The purpose of this review is to compile and discuss available evidence in humans on the efficacy of YHM supplementation on performance in different exercise modalities. Yohimbine (YHM) is a naturally occurring alkaloid that induces increases in sympathetic nervous system (SNS) activation effectively initiating "fight or flight" responses. In supplement form, YHM is commonly sold as an isolated product or combined into multi-ingredient exercise supplements and is widely consumed in fitness settings despite the lack of empirical support until recently. YHM primarily acts as an α2-adrenergic receptor antagonist effectively increasing norepinephrine release from sympathetic neurons. YHM has been implicated in improving or altering cardiovascular function, blood flow, lactate metabolism, and muscle function. Emerging evidence has suggested that YHM may have the potential to improve performance in a wide range of exercise modes including endurance, sprint, and resistance exercise. Performance enhancement with YHM is mediated by mechanistic underpinnings of physiological and psychological alterations to exercise responses including increased sympathetic activation, adaptive hemodynamic changes, increased alertness, and decreased fatigue. However, YHM use is not without risk as it has high interindividual variability in bioavailability, can be deceptively potent, lacks widely accepted dosing recommendations, and, when taken in large doses, has been empirically documented to result in serious side effects. Despite this, the evidence presented in this review suggests low doses of YHM are tolerable and may serve as an ideal exercise training aid due to acute enhancement of physical performance. However, safety concerns remain outstanding and temperance should be used when using YHM and similar sympathomimetics.

A Comparison of Three Protocols for Determining Barbell Bench Press Single Repetition Maximum, Barbell Kinetics, and Subsequent Measures of Muscular Performance in Resistance-Trained Adults

BACKGROUND

One repetition maximum (1RM) is a vital metric for exercise professionals, but various testing protocols exist, and their impacts on the resulting 1RM, barbell kinetics, and subsequent muscular performance testing are not well understood. This study aimed to compare two previously established protocols and a novel self-led method for determining bench press 1RM, 1RM barbell kinetics, and subsequent muscular performance measures.

METHODS

Twenty-four resistance-trained males (n = 12, 24 ± 6.1 years) and females (n = 12, 22.5 ± 5.5 years) completed three laboratory visits in a randomized crossover fashion. During each visit, a 1RM was established using one of the three protocols followed by a single set to volitional fatigue using 80% of their 1RM. A Sex:Protocol repeated measures ANOVA was used to determine the effects of sex and differences between protocols.

RESULTS

No significant differences were observed between the protocols for any measure, except for 1RM peak power (p = 0.036). Post hoc pairwise comparisons failed to identify any differences. Males showed significantly higher 1RM, average, and peak power (ps < 0.001), while females demonstrated a greater average concentric velocity (p = 0.031) at 1RM.

CONCLUSIONS

These data suggest the protocol used to establish 1RM may have minimal impact on the final 1RM, 1RM barbell kinetics, and subsequent muscular endurance in a laboratory setting.

Nrf2 modulates the benefits of evening exercise in type 2 diabetes

Exercise has well-characterized therapeutic benefits in the management of type 2 diabetes mellitus (T2DM). Most of the beneficial effects of exercise arise from the impact of nuclear factor erythroid 2 related factor-2 (Nrf2) activation of glucose metabolism. Nrf2 is an essential controller of cellular anti-oxidative capacity and circadian rhythms. The circadian rhythm of Nrf2 is influenced by circadian genes on its expression, where the timing of exercise effects the activation of Nrf2 and the rhythmicity of Nrf2 and signaling, such that the timing of exercise has differential physiological effects. Exercise in the evening has beneficial effects on diabetes management, such as lowering of blood glucose and weight. The mechanisms responsible for these effects have not yet been associated with the influence of exercise on the circadian rhythm of Nrf2 activity. A better understanding of exercise-induced Nrf2 activation on Nrf2 rhythm and signaling can improve our appreciation of the distinct effects of morning and evening exercise. This review hypothesizes that activation of Nrf2 by exercise in the morning, when Nrf2 level is already at high levels, leads to hyperactivation and decrease in Nrf2 signaling, while activation of Nrf2 in the evening, when Nrf2 levels are at nadir levels, improves Nrf2 signaling and lowers blood glucose levels and increases fatty acid oxidation. Exploring the effects of Nrf2 activators on rhythmic signaling could also provide valuable insights into the optimal timing of their application, while also holding promise for timed treatment of type 2 diabetes.

Diurnal Variation of Specific Tests' Performance and Related Psychological Aspects in Young Judo Athletes

Purpose: This study investigated the effects of time-of-day on judo athletes' performances and the associated psychological variables and perceived exertion following judo-specific tests. Methods: Twelve male judo athletes (age: 16 ± 1 years) performed in a randomized and counterbalanced order the special judo fitness test (SJFT), the judo physical fitness test (JPFT), the dynamic and isometric judogi chin-up tests in the morning (8:00 a.m), midday (12:00 p.m), and afternoon (5:00 p.m). Oral temperature and psychological variables [profile of mood state (POMS), Hooper questionnaire, total quality of recovery (TQR)] were assessed before and after the tests, and ratings of perceived exertion (RPE) and the physical activity enjoyment scale (PACES) were assessed only after the tests. Results: RPE score was higher in the morning compared to the afternoon after the JPFT (d = 0.38, p = .045). PACES after JPFT was higher in the morning compared to midday (d = 0.85, p < .001). The isometric and dynamic performances during chin-up tests were higher in the afternoon compared to the morning (d = 0.38, p = .048 and 0.047, respectively). Also, oral temperature was higher in the afternoon compared to the morning (d = 0.41, p = .050) and the midday (p = .047) for dynamic test, while TQR, well-being indices, and POMS did not differ according to time-of-day (p > .05). Conclusions: These results suggest that dynamic and isometric judo chin-up tests are time-of-day dependent with higher performance recorded in the afternoon than in the morning. However, performances in the JPFT and SJFT were not time-of-day dependent.

Morning Exercise Reduces Abdominal Fat and Blood Pressure in Women; Evening Exercise Increases Muscular Performance in Women and Lowers Blood Pressure in Men

The ideal exercise time of day (ETOD) remains elusive regarding simultaneous effects on health and performance outcomes, especially in women.

Purpose: Given known sex differences in response to exercise training, this study quantified health and performance outcomes in separate cohorts of women and men adhering to different ETOD.

Methods: Thirty exercise-trained women (BMI = 24 ± 3 kg/m²; 42 ± 8 years) and twenty-six men (BMI = 25.5 ± 3 kg/m²; 45 ± 8 years) were randomized to multimodal ETOD in the morning (0600–0800 h, AM) or evening (1830–2030 h, PM) for 12 weeks and analyzed as separate cohorts. Baseline (week 0) and post (week 12) muscular strength (1-RM bench/leg press), endurance (sit-ups/push-ups) and power (squat jumps, SJ; bench throws, BT), body composition (iDXA; fat mass, FM; abdominal fat, Abfat), systolic/diastolic blood pressure (BP), respiratory exchange ratio (RER), profile of mood states (POMS), and dietary intake were assessed.

Results: Twenty-seven women and twenty men completed the 12-week intervention. No differences at baseline existed between groups (AM vs PM) for both women and men cohorts. In women, significant interactions (p < 0.05) existed for 1RM bench (8 ± 2 vs 12 ± 2, ∆kg), pushups (9 ± 1 vs 13 ± 2, ∆reps), BT (10 ± 6 vs 45 ± 28, ∆watts), SJ (135 ± 6 vs 39 ± 8, ∆watts), fat mass (−1.0 ± 0.2 vs −0.3 ± 0.2, ∆kg), Abfat (−2.6 ± 0.3 vs −0.9 ± 0.5, ∆kg), diastolic (−10 ± 1 vs−5 ± 5, ∆mmHg) and systolic (−12.5 ± 2.7 vs 2.3 ± 3, mmHg) BP, AM vs PM, respectively. In men, significant interactions (p < 0.05) existed for systolic BP (−3.5 ± 2.6 vs −14.9 ± 5.1, ∆mmHg), RER (−0.01 ± 0.01 vs −0.06 ± 0.01, ∆VCO₂/VO₂), and fatigue (−0.8 ± 2 vs −5.9 ± 2, ∆mm), AM vs PM, respectively. Macronutrient intake was similar among AM and PM groups.

Conclusion: Morning exercise (AM) reduced abdominal fat and blood pressure and evening exercise (PM) enhanced muscular performance in the women cohort. In the men cohort, PM increased fat oxidation and reduced systolic BP and fatigue. Thus, ETOD may be important to optimize individual exercise-induced health and performance outcomes in physically active individuals and may be independent of macronutrient intake.

Exercise Training Programs Improve Cardiorespiratory and Functional Fitness in Adults With Asthma: A SYSTEMATIC REVIEW AND META-ANALYSIS

PURPOSE

This systematic review aimed to identify the characteristics and determine the effects of exercise interventions on improving health-related physical fitness in adults with asthma.

REVIEW METHODS

A systematic search was completed in MEDLINE, CINAHL, Embase, and SPORTDiscus for peer-reviewed publications of experimental studies that investigated the effects of an exercise training intervention on performance-based health-related physical fitness outcomes in adults with asthma. Two reviewers independently screened studies for inclusion according to predetermined criteria and performed data extraction and quality assessment of included studies.

SUMMARY

Forty-five articles were included, in which results for 39 unique studies were reported. Subjects (n = 2135) were aged 22 ± 4 to 71 ± 11 yr with mild-severe asthma. Most exercise programs used aerobic exercise, either alone or in combination with resistance or breathing/stretching exercises. The most common exercise program characteristics were supervised moderate-to-vigorous intensity aerobic exercise performed for 30-45 min 3 d/wk. Meta-analyses revealed significant improvements in cardiorespiratory fitness (V˙o2peak: unstandardized mean difference [MD] 3.1 mL/kg/min, 95% CI, 1.9-4.3), functional fitness (walking distance: MD 41 m, 95% CI, 27-54), and overall health-related physical fitness (standardized mean difference [SMD] 0.67, 95% CI, 0.46-0.89) in favor of groups who underwent experimental exercise training interventions. Aerobic exercise elicited superior improvements in health-related physical fitness compared with breathing/stretching exercise (SMD 0.47, 95% CI, 0.14-0.81).Supervised exercise training programs, particularly those aerobic in nature, are effective in eliciting clinically meaningful improvements in cardiorespiratory and functional fitness in adults with asthma.PROSPERO registration ID number = CRD42018092828.

A Narrative Review of Limb Dominance: Task Specificity and the Importance of Fitness Testing

ABSTRACT

Virgile, A and Bishop, C. A narrative review of limb dominance: Task specificity and the importance of fitness testing. J Strength Cond Res 35(3): 846-858, 2021-Preferential limb function must be sustained through repetitious asymmetrical activities for continuous athletic development and, ultimately, optimal athletic performance. As such, the prevalence of limb dominance and between-limb differences is common in athletes. Severe between-limb differences have been associated with reductions in athletic performance and increased injury risk in athletes. However, in the current literature, the terms limb preference and limb dominance have been used interchangeably. Together, these terms include a limb that is subjectively preferred and one that is objectively dominant in 1 or more performance measures from a variety of athletic tasks. In this review, we (a) discuss reported correspondence between task-specific limb preference and limb dominance outcomes in athletes, (b) provide greater context and distinction between the terms limb preference and limb dominance, and (c) offer pragmatic strategies for practitioners to assess context-specific limb dominance. A limb that is subjectively preferred is not necessarily objectively dominant in 1 or more athletic qualities or sport-specific tasks. Further to this, a limb that is objectively superior in 1 task may not exhibit such superiority in a separate task. Thus, limb preference and limb dominance are both task-specific. As such, we propose that practitioners intentionally select tasks for limb dominance assessment which resemble the most relevant demands of sport. Because limb dominance profiles are inconsistent, we suggest that practitioners increase assessment frequency by integrating limb dominance testing into standard training activities. This will allow practitioners to better understand when changes reflect sport-specific adaptation vs. potential performance or injury ramifications.

Acute Beetroot Juice Supplementation Attenuates Morning-Associated Decrements in Supramaximal Exercise Performance in Trained Sprinters

Diurnal fluctuations in power output have been well established with power loss typically occurring in morning (AM) times. Beetroot juice (BRJ) is a source of dietary nitrate that possess ergogenic properties, but it is unknown if ingestion can mitigate performance decrements in the morning. The purpose of this study was to examine the effects of acute BRJ supplementation on diurnal fluctuations in anaerobic performance in trained sprinters. Male Division 1 National Collegiate Athletic Association (NCAA) sprinters (n = 10) participated. In a double-blinded crossover study design, participants completed three counterbalanced exercise trials under different conditions: Morning–placebo (8:00 HR, AM-PL), Morning–BRJ (8:00 HR, AM-BRJ), and Afternoon–no supplement (15:00 HR, PM). For each trial, participants completed 3 × 15 s Wingate anaerobic tests separated by 2 min of rest. Each trial was separated by a 72 h washout period. Mean power output (p = 0.043), anaerobic capacity (p = 0.023), and total work (p = 0.026) were significantly lower with the AM-PL condition compared to PM. However, BRJ supplementation prevented AM losses of mean power output (p = 0.994), anaerobic capacity (p = 0.941), and total work (p = 0.933) in the AM-BRJ compared to the PM condition. Rate of perceived exertion was not significantly different between any conditions (p = 0.516). Heart rate was significantly lower during the AM-BRJ condition compared to AM-PL (p = 0.030) and PM (p < 0.001). Findings suggest anaerobic capacity suffers during AM versus PM times in trained sprinters, but BRJ ingestion abolishes AM-associated decrements in performance.