Minimal influence of the menstrual cycle or hormonal contraceptives on performance in female rugby league athletes.

We examined performance across one menstrual cycle (MC) and 3 weeks of hormonal contraceptives (HC) use to identify whether known fluctuations in estrogen and progesterone/progestin are associated with functional performance changes. National Rugby League Indigenous Women's Academy athletes [n = 11 naturally menstruating (NM), n = 13 using HC] completed performance tests [countermovement jump (CMJ), squat jump (SJ), isometric mid-thigh pull, 20 m sprint, power pass and Stroop test] during three phases of a MC or three weeks of HC usage, confirmed through ovulation tests alongside serum estrogen and progesterone concentrations. MC phase or HC use did not influence jump height, peak force, sprint time, distance thrown or Stroop effect. However, there were small variations in kinetic and kinematic CMJ/SJ outputs. NM athletes produced greater mean concentric power in MC phase four than one [+0.41 W·kg-1 (+16.8%), p = 0.021] during the CMJ, alongside greater impulse at 50 ms at phase one than four [+1.7 N·s (+4.7%), p = 0.031] during the SJ, without differences between tests for HC users. Among NM athletes, estradiol negatively correlated with mean velocity and power (r = -0.44 to -0.50, p < 0.047), progesterone positively correlated with contraction time (r = 0.45, p = 0.045), and both negatively correlated with the rate of force development and impulse (r = -0.45 to -0.64, p < 0.043) during the SJ. During the CMJ, estradiol positively correlated to 200 ms impulse (r = 0.45, p = 0.049) and progesterone to mean power (r = 0.51, p = 0.021). Evidence of changes in testing performance across a MC, or during active HC use, is insufficient to justify "phase-based testing"; however, kinetic or kinematic outputs may be altered in NM athletes.

Effect of Menstrual Cycle Phase and Hormonal Contraceptives on Resting Metabolic Rate and Body Composition.

The cyclical changes in sex hormones across the menstrual cycle (MC) are associated with various biological changes that may alter resting metabolic rate (RMR) and body composition estimates. Hormonal contraceptive (HC) use must also be considered given their impact on endogenous sex hormone concentrations and synchronous exogenous profiles. The purpose of this study was to determine if RMR and dual-energy X-ray absorptiometry body composition estimates change across the MC and differ compared with HC users. This was accomplished during a 5-week training camp involving naturally cycling athletes (n = 11) and HC users (n = 7 subdermal progestin implant, n = 4 combined monophasic oral contraceptive pill, n = 1 injection) from the National Rugby League Indigenous Women's Academy. MC phase was retrospectively confirmed via serum estradiol and progesterone concentrations and a positive ovulation test. HC users had serum estradiol and progesterone concentrations assessed at the time point of testing. Results were analyzed using general linear mixed model. There was no effect of MC phase on absolute RMR (p = .877), relative RMR (p = .957), or dual-energy X-ray absorptiometry body composition estimates (p > .05). There was no effect of HC use on absolute RMR (p = .069), relative RMR (p = .679), or fat mass estimates (p = .766), but HC users had a greater fat-free mass and lean body mass than naturally cycling athletes (p = .028). Our findings suggest that RMR and dual-energy X-ray absorptiometry body composition estimates do not significantly differ due to changes in sex hormones in a group of athletes, and measurements can be compared between MC phases or with HC usage without variations in sex hormones causing additional noise.

Effect of repeated post-resistance exercise cold or hot water immersion on in-season inflammatory responses in academy rugby players: a randomised controlled cross-over design.

PURPOSE: Uncertainty exists if post-resistance exercise hydrotherapy attenuates chronic inflammatory and hormone responses. The effects of repeated post-resistance exercise water immersion on inflammatory and hormone responses in athletes were investigated. METHODS: Male, academy Super Rugby players (n = 18, 19.9 ± 1.5 y, 1.85 ± 0.06 m, 98.3 ± 10.7 kg) participated in a 12-week programme divided into 3 × 4-week blocks of post-resistance exercise water immersion (either, no immersion control [CON]; cold [CWI]; or hot [HWI] water immersion), utilising a randomised cross-over pre-post design. Fasted, morning blood measures were collected prior to commencement of first intervention block, and every fourth week thereafter. Linear mixed-effects models were used to analyse main (treatment, time) and interaction effects. RESULTS: Repeated CWI (p = 0.025, g = 0.05) and HWI (p < 0.001, g = 0.62) reduced creatine kinase (CK), compared to CON. HWI decreased (p = 0.013, g = 0.59) interleukin (IL)-1ra, compared to CON. HWI increased (p < 0.001-0.026, g = 0.06-0.17) growth factors (PDGF-BB, IGF-1), compared to CON and CWI. CWI increased (p = 0.004, g = 0.46) heat shock protein-72 (HSP-72), compared to HWI. CONCLUSION: Post-resistance exercise CWI or HWI resulted in trivial and moderate reductions in CK, respectively, which may be partly due to hydrostatic effects of water immersion. Post-resistance exercise HWI moderately decreased IL-1ra, which may be associated with post-resistance exercise skeletal muscle inflammation influencing chronic resistance exercise adaptive responses. Following post-resistance exercise water immersion, CWI increased HSP-72 suggesting a thermoregulatory response indicating improved adaptive inflammatory responses to temperature changes, while HWI increased growth factors (PDGF-BB, IGF-1) indicating different systematic signalling pathway activation. Our data supports the continued use of post-resistance exercise water immersion recovery strategies of any temperature during in-season competition phases for improved inflammatory adaptive responses in athletes.

Iron Absorption in Highly Trained Male Runners: Does it Matter When and Where You Eat Your Iron?

PURPOSE: We examined iron absorption and its regulation during two common scenarios experienced by endurance athletes. Our aims were to: (i) compare the effects of preexercise versus postexercise iron intake on iron absorption; and (ii) compare the impact of training at altitude (1800 m) on iron absorption preexercise. METHODS: Male runners (n = 18) completed three exercise trials over a 5-wk period, each preceded by 24 h of standardized low-iron diets. First, athletes completed two 60-min treadmill running trials at 65% V̇O2max at near sea-level (580 m). In a randomized order, preexercise and postexercise test meals labeled with 4 mg of 57Fe or 58Fe were consumed 30 min before or 30 min after exercise. Then, the same exercise trial was performed after living and training at altitude (~1800 m) for 7 d, with the labeled test meal consumed 30 min preexercise. We collected venous blood samples preexercise and postexercise for markers of iron status and regulation, and 14 d later to measure erythrocyte isotope incorporation. RESULTS: No differences in fractional iron absorption were evident when test meals were consumed preexercise (7.3% [4.4, 12.1]) or postexercise (6.2% [3.1, 12.5]) (n = 18; P = 0.058). Iron absorption preexercise was greater at altitude (18.4% [10.6, 32.0]) than at near sea-level (n = 17; P < 0.001) and hepcidin concentrations at altitude were lower at rest and 3 h postexercise compared with near sea level (P < 0.001). CONCLUSIONS: In an acute setting, preexercise and postexercise iron absorption is comparable if consumed within 30 min of exercise. Preexercise iron absorption increases 2.6-fold at altitude compared with near sea-level, likely due to the homeostatic response to provide iron for enhanced erythropoiesis and maintain iron stores.

The Impact of a Short-Term Ketogenic Low-Carbohydrate High-Fat Diet on Biomarkers of Intestinal Epithelial Integrity and Gastrointestinal Symptoms.

Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk. Twenty-eight male race walkers adhered to a high carbohydrate (CHO)/energy diet (65% CHO, energy availability = 40 kcal·kg FFM-1·day-1) for 6 days prior to a Baseline 25-km race walk. Athletes were then split into three subgroups: high CHO/energy diet (n = 10); low-CHO, high-fat diet (LCHF: n = 8; <50 g/day CHO, energy availability = 40 kcal·kg FFM-1·day-1); and low energy availability (n = 10; 65% CHO, energy availability = 15 kcal·kg FFM-1·day-1) for a further 6-day dietary intervention period prior to a second 25-km race walk (Adaptation). During both trials, venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for markers of intestinal epithelial disruption. Intestinal fatty acid-binding protein concentration was significantly higher (twofold increase) in response to exercise during Adaptation compared to Baseline in the LCHF group (p = .001). Similar findings were observed for soluble CD14 (p < .001) and lipopolysaccharide-binding protein (p = .003), where postexercise concentrations were higher (53% and 36%, respectively) during Adaptation than Baseline in LCHF. No differences in high CHO/energy diet or low energy availability were apparent for any blood markers assessed (p > .05). A short-term LCHF diet increased intestinal epithelial cell injury in response to a 25-km race walk. No effect of low energy availability on gastrointestinal injury or symptoms was observed.

Adherence to a Ketogenic Low-Carbohydrate, High-Fat Diet Is Associated With Diminished Training Quality in Elite Racewalkers.

PURPOSE: To examine the effects of a high-carbohydrate diet (HCHO), periodized-carbohydrate (CHO) diet (PCHO), and ketogenic low-CHO high-fat diet (LCHF) on training capacity. METHODS: Elite male racewalkers completed 3 weeks of periodic training while adhering to their dietary intervention. Twenty-nine data sets were collected from 21 athletes. Each week, 6 mandatory training sessions were completed, with additional sessions performed at the athlete's discretion. Mandatory sessions included an interval session (10 × 1-km efforts on a 6-min cycle), tempo session (14 km with a 450-m elevation gain), 2 long walks (25-40 km), and 2 easy walks (8-12 km) where "sleep-low" and "train-low" dietary strategies were employed for PCHO. Racewalking speed, heart rate, rating of perceived exhaustion, and blood metabolites were collected around key sessions. RESULTS: LCHF covered less total distance than HCHO and PCHO (P < .001); however, no differences in training load between groups were evident (P = .285). During the interval sessions, walking speed was slower in LCHF (P = .001), equating to a 2.8% and 5.6% faster speed in HCHO and PCHO, respectively. LCHF was also 3.2% slower in completing the tempo session than HCHO and PCHO (P = .001). Heart rate was higher (P = .002) and lactate concentrations were lower (P < .001) in LCHF compared to other groups, despite slower walking speeds during the interval session. No between-groups differences in rating of perceived exhaustion were evident (P = .077). CONCLUSION: Athletes adhering to an LCHF diet showed impaired training capacity relative to their high-CHO-supported counterparts, completing lower training volumes at slower speeds, with higher heart rates.

Acute Performance, Daily Well-Being, and Hormone Responses to Water Immersion After Resistance Exercise in Junior International and Subelite Male Volleyball Athletes.

ABSTRACT: Horgan, BG, Tee, N, West, NP, Drinkwater, EJ, Halson, SL, Colomer, CME, Fonda, CJ, Tatham, J, Chapman, DW, and Haff, GG. Acute performance, daily well-being and hormone responses to water immersion after resistance exercise in junior international and subelite male volleyball athletes. J Strength Cond Res 37(8): 1643-1653, 2023-Athletes use postexercise hydrotherapy strategies to improve recovery and competition performance and to enhance adaptative responses to training. Using a randomized cross-over design, the acute effects of 3 postresistance exercise water immersion strategies on perceived recovery, neuromuscular performance, and hormone concentrations in junior international and subelite male volleyball athletes ( n = 18) were investigated. After resistance exercise, subjects randomly completed either 15-minute passive control (CON), contrast water therapy (CWT), cold (CWI), or hot water immersion (HWI) interventions. A treatment effect occurred after HWI; reducing perceptions of fatigue (HWI > CWT: p = 0.05, g = 0.43); improved sleep quality, compared with CON ( p < 0.001, g = 1.15), CWI ( p = 0.017, g = 0.70), and CWT ( p = 0.018, g = 0.51); as well as increasing testosterone concentration (HWI > CWT: p = 0.038, g = 0.24). There were trivial to small ( p < 0.001-0.039, g = 0.02-0.34) improvements (treatment effect) in jump performance (i.e., squat jump and countermovement jump) after all water immersion strategies, as compared with CON, with high variability in the individual responses. There were no significant differences (interaction effect, p > 0.05) observed between the water immersion intervention strategies and CON in performance ( p = 0.153-0.99), hormone ( p = 0.207-0.938), nor perceptual ( p = 0.368-0.955) measures. To optimize recovery and performance responses, e.g., during an in-season competition phase, postresistance exercise HWI may assist with providing small-to-large improvements for up to 38 hours in perceived recovery (i.e., increased sleep quality and reduced fatigue) and increases in circulating testosterone concentration. Practitioners should consider individual athlete neuromuscular performance responses when prescribing postexercise hydrotherapy. These findings apply to athletes who aim to improve their recovery status, where postresistance exercise HWI optimizes sleep quality and next-day perceptions of fatigue.

Short Severe Energy Restriction with Refueling Reduces Body Mass without Altering Training-Associated Performance Improvement.

PURPOSE: We investigated short-term (9 d) exposure to low energy availability (LEA) in elite endurance athletes during a block of intensified training on self-reported well-being, body composition, and performance. METHODS: Twenty-three highly trained race walkers undertook an ~3-wk research-embedded training camp during which they undertook baseline testing and 6 d of high energy/carbohydrate (HCHO) availability (40 kcal·kg FFM -1 ·d -1 ) before being allocated to 9 d continuation of this diet ( n = 10 M, 2 F) or a significant decrease in energy availability to 15 kcal·kg FFM -1 ·d -1 (LEA: n = 10 M, 1 F). A real-world 10,000-m race walking event was undertaken before (baseline) and after (adaptation) these phases, with races being preceded by standardized carbohydrate fueling (8 g·kg body mass [BM] -1 for 24 h and 2 g·kg BM -1 prerace meal). RESULTS: Dual-energy x-ray absorptiometry-assessed body composition showed BM loss (2.0 kg, P < 0.001), primarily due to a 1.6-kg fat mass reduction ( P < 0.001) in LEA, with smaller losses (BM = 0.9 kg, P = 0.008; fat mass = 0.9 kg, P < 0.001) in HCHO. The 76-item Recovery-Stress Questionnaire for Athletes, undertaken at the end of each dietary phase, showed significant diet-trial effects for overall stress ( P = 0.021), overall recovery ( P = 0.024), sport-specific stress ( P = 0.003), and sport-specific recovery ( P = 0.012). However, improvements in race performance were similar: 4.5% ± 4.1% and 3.5% ± 1.8% for HCHO and LEA, respectively ( P < 0.001). The relationship between changes in performance and prerace BM was not significant ( r = -0.08 [-0.49 to 0.35], P = 0.717). CONCLUSIONS: A series of strategically timed but brief phases of substantially restricted energy availability might achieve ideal race weight as part of a long-term periodization of physique by high-performance athletes, but the relationship between BM, training quality, and performance in weight-dependent endurance sports is complicated.

No effect of repeated post-resistance exercise cold or hot water immersion on in-season body composition and performance responses in academy rugby players: a randomised controlled cross-over design.

PURPOSE: Following resistance exercise, uncertainty exists as to whether the regular application of cold water immersion attenuates lean muscle mass increases in athletes. The effects of repeated post-resistance exercise cold versus hot water immersion on body composition and neuromuscular jump performance responses in athletes were investigated. METHODS: Male, academy Super Rugby players (n = 18, 19.9 ± 1.5 y, 1.85 ± 0.06 m, 98.3 ± 10.7 kg) participated in a 12-week (4-week × 3-intervention, i.e., control [CON], cold [CWI] or hot [HWI] water immersion) resistance exercise programme, utilising a randomised cross-over pre-post-design. Body composition measures were collected using dual-energy X-ray absorptiometry prior to commencement and every fourth week thereafter. Neuromuscular squat (SJ) and counter-movement jump (CMJ) performance were measured weekly. Linear mixed-effects models were used to analyse main (treatment, time) and interaction effects. RESULTS: There were no changes in lean (p = 0.960) nor fat mass (p = 0.801) between interventions. CON (p = 0.004) and CWI (p = 0.003) increased (g = 0.08-0.19) SJ height, compared to HWI. There were no changes in CMJ height (p = 0.482) between interventions. CONCLUSION: Repeated post-resistance exercise whole-body CWI or HWI does not attenuate (nor promote) increases in lean muscle mass in athletes. Post-resistance exercise CON or CWI results in trivial increases in SJ height, compared to HWI. During an in-season competition phase, our data support the continued use of post-resistance exercise whole-body CWI by athletes as a recovery strategy which does not attenuate body composition increases in lean muscle mass, while promoting trivial increases in neuromuscular concentric-only squat jump performance.

The Impact of Acute Calcium Intake on Bone Turnover Markers during a Training Day in Elite Male Rowers.

INTRODUCTION: Although an acute exercise session typically increases bone turnover markers (BTM), the impact of subsequent sessions and the interaction with preexercise calcium intake remain unclear despite the application to the "real-life" training of many competitive athletes. METHODS: Using a randomized crossover design, elite male rowers ( n = 16) completed two trials, a week apart, consisting of two 90-min rowing ergometer sessions (EX1, EX2) separated by 150 min. Before each trial, participants consumed a high (CAL; ~1000 mg) or isocaloric low (CON; <10 mg) calcium meal. Biochemical markers including parathyroid hormone (PTH), serum ionized calcium (iCa) and BTMs (C-terminal telopeptide of type I collagen, osteocalcin) were monitored from baseline to 3 h after EX2. RESULTS: Although each session caused perturbances of serum iCa, CAL maintained calcium concentrations above those of CON for most time points, 4.5% and 2.4% higher after EX1 and EX2, respectively. The decrease in iCa in CON was associated with an elevation of blood PTH ( P < 0.05) and C-terminal telopeptide of type I collagen ( P < 0.0001) over this period of repeated training sessions and their recovery, particularly during and after EX2. Preexercise intake of calcium-rich foods lowered BTM over the course of a day with several training sessions. CONCLUSIONS: Preexercise intake of a calcium-rich meal before training sessions undertaken within the same day had a cumulative and prolonged effect on the stabilization of blood iCa during exercise. In turn, this reduced the postexercise PTH response, potentially attenuating the increase in markers of bone resorption. Such practical strategies may be integrated into the athlete's overall sports nutrition plan, with the potential to safeguard long-term bone health and reduce the risk of bone stress injuries.

Short-Term Carbohydrate Restriction Impairs Bone Formation at Rest and During Prolonged Exercise to a Greater Degree than Low Energy Availability.

Bone stress injuries are common in athletes, resulting in time lost from training and competition. Diets that are low in energy availability have been associated with increased circulating bone resorption and reduced bone formation markers, particularly in response to prolonged exercise. However, studies have not separated the effects of low energy availability per se from the associated reduction in carbohydrate availability. The current study aimed to compare the effects of these two restricted states directly. In a parallel group design, 28 elite racewalkers completed two 6-day phases. In the Baseline phase, all athletes adhered to a high carbohydrate/high energy availability diet (CON). During the Adaptation phase, athletes were allocated to one of three dietary groups: CON, low carbohydrate/high fat with high energy availability (LCHF), or low energy availability (LEA). At the end of each phase, a 25-km racewalk was completed, with venous blood taken fasted, pre-exercise, and 0, 1, 3 hours postexercise to measure carboxyterminal telopeptide (CTX), procollagen-1 N-terminal peptide (P1NP), and osteocalcin (carboxylated, gla-OC; undercarboxylated, glu-OC). Following Adaptation, LCHF showed decreased fasted P1NP (~26%; p < 0.0001, d = 3.6), gla-OC (~22%; p = 0.01, d = 1.8), and glu-OC (~41%; p = 0.004, d = 2.1), which were all significantly different from CON (p < 0.01), whereas LEA demonstrated significant, but smaller, reductions in fasted P1NP (~14%; p = 0.02, d = 1.7) and glu-OC (~24%; p = 0.049, d = 1.4). Both LCHF (p = 0.008, d = 1.9) and LEA (p = 0.01, d = 1.7) had significantly higher CTX pre-exercise to 3 hours post-exercise but only LCHF showed lower P1NP concentrations (p < 0.0001, d = 3.2). All markers remained unchanged from Baseline in CON. Short-term carbohydrate restriction appears to result in reduced bone formation markers at rest and during exercise with further exercise-related increases in a marker of bone resorption. Bone formation markers during exercise seem to be maintained with LEA although resorption increased. In contrast, nutritional support with adequate energy and carbohydrate appears to reduce unfavorable bone turnover responses to exercise in elite endurance athletes. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Short-Term Very High Carbohydrate Diet and Gut-Training Have Minor Effects on Gastrointestinal Status and Performance in Highly Trained Endurance Athletes.

We implemented a multi-pronged strategy (MAX) involving chronic (2 weeks high carbohydrate [CHO] diet + gut-training) and acute (CHO loading + 90 g·h−1 CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON) in two groups of athletes. Nineteen elite male race walkers (MAX: 9; CON:10) undertook a 26 km race-walking session before and after the respective interventions to investigate gastrointestinal function (absorption capacity), integrity (epithelial injury), and symptoms (GIS). We observed considerable individual variability in responses, resulting in a statistically significant (p < 0.001) yet likely clinically insignificant increase (Δ 736 pg·mL−1) in I-FABP after exercise across all trials, with no significant differences in breath H2 across exercise (p = 0.970). MAX was associated with increased GIS in the second half of the exercise, especially in upper GIS (p < 0.01). Eighteen highly trained male and female distance runners (MAX: 10; CON: 8) then completed a 35 km run (28 km steady-state + 7 km time-trial) supported by either a slightly modified MAX or CON strategy. Inter-individual variability was observed, without major differences in epithelial cell intestinal fatty acid binding protein (I-FABP) or GIS, due to exercise, trial, or group, despite the 3-fold increase in exercise CHO intake in MAX post-intervention. The tight-junction (claudin-3) response decreased in both groups from pre- to post-intervention. Groups achieved a similar performance improvement from pre- to post-intervention (CON = 39 s [95 CI 15−63 s]; MAX = 36 s [13−59 s]; p = 0.002). Although this suggests that further increases in CHO availability above current guidelines do not confer additional advantages, limitations in our study execution (e.g., confounding loss of BM in several individuals despite a live-in training camp environment and significant increases in aerobic capacity due to intensified training) may have masked small differences. Therefore, athletes should meet the minimum CHO guidelines for training and competition goals, noting that, with practice, increased CHO intake can be tolerated, and may contribute to performance outcomes.

Prickly pear juice consumption after fat intake affects postprandial heart rate variability but not traditional risk factors of cardiovascular disease in healthy men.

OBJECTIVE: Prickly Pear (PP) fruit is proposed to have anti-atherosclerotic and anti-hyperglycemic effects. The aim of this study was to examine the effects of a single consumption of PP juice on modifiable blood and physiological markers of cardiovascular disease risk in healthy men using a postprandial hyperlipidemia model. METHODS: This was a double-blind, randomized, placebo-controlled, crossover trial with 17 healthy men (body mass index 22.6 ± 2.04 kg/m2; 29.5 ± 7.19 y of age). Participants consumed PP juice (250 mL; 45 mg betalain content; reduced fiber) or a simple placebo drink (water-based), with a high-fat muffin (50 g fat) to determine potential effects on physiologic and biological responses, for up to 3 h post-consumption (hourly, 2 sessions, 7-d washout period). Blood pressure, heart rate variability (HRV), total cholesterol (TC), triacylglycerides (TGs), low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C, respectively), and glucose were measured. RESULTS: Key findings included a lower HRV measure after PP consumption (main effect for group, P ≤0.001-0.020) but no differences for TC, TG, LDL-C, or HDL-C. CONCLUSION: Consumption of PP (with high-fat muffin), did not alter traditional cardiovascular disease risk responses but rather markers of HRV, beyond an expected increase in glucose attributed to the carbohydrate content of the trials foods. Additionally, macronutrient content is important when understanding HRV responses to meals.

Six Days of Low Carbohydrate, Not Energy Availability, Alters the Iron and Immune Response to Exercise in Elite Athletes.

PURPOSE: To quantify the effects of a short-term (6-d) low carbohydrate (CHO) high fat (LCHF), and low energy availability (LEA) diet on immune, inflammatory, and iron-regulatory responses to exercise in endurance athletes. METHODS: Twenty-eight elite male race walkers completed two 6-d diet/training phases. During phase 1 (Baseline), all athletes consumed a high CHO/energy availability (CON) diet (65% CHO and ~40 kcal·kg-1 fat-free mass (FFM)·d-1). In phase 2 (Adaptation), athletes were allocated to either a CON (n = 10), LCHF (n = 8; <50 g·d-1 CHO and ~40 kcal·kg-1·FFM-1·d-1), or LEA diet (n = 10; 60% CHO and 15 kcal·kg-1·FFM-1·d-1). At the end of each phase, athletes completed a 25-km race walk protocol at ~75% V˙O2max. On each occasion, venous blood was collected before and after exercise for interleukin-6, hepcidin, cortisol, and glucose concentrations, as well as white blood cell counts. RESULTS: The LCHF athletes displayed a greater IL-6 (P = 0.019) and hepcidin (P = 0.011) response to exercise after Adaptation, compared with Baseline. Similarly, postexercise increases in total white blood cell counts (P = 0.026) and cortisol levels (P < 0.001) were larger compared with Baseline after LCHF Adaptation. Decreases in blood glucose concentrations were evident postexercise during Adaptation in LCHF (P = 0.049), whereas no change occurred in CON or LEA (P > 0.05). No differences between CON and LEA were evident for any of the measured biological markers (all P > 0.05). CONCLUSIONS: Short-term adherence to a LCHF diet elicited small yet unfavorable iron, immune, and stress responses to exercise. In contrast, no substantial alterations to athlete health were observed when athletes restricted energy availability compared with athletes with adequate energy availability. Therefore, short-term restriction of CHO, rather than energy, may have greater negative impacts on athlete health.

Acute Inflammatory, Anthropometric, and Perceptual (Muscle Soreness) Effects of Postresistance Exercise Water Immersion in Junior International and Subelite Male Volleyball Athletes.

ABSTRACT: Horgan, BG, West, NP, Tee, N, Drinkwater, EJ, Halson, SL, Vider, J, Fonda, CJ, Haff, GG, and Chapman, DW. Acute inflammatory, anthropometric, and perceptual (muscle soreness) effects of postresistance exercise water immersion in junior international and subelite male volleyball athletes. J Strength Cond Res 36(12): 3473-3484, 2022-Athletes use water immersion strategies to recover from training and competition. This study investigated the acute effects of postexercise water immersion after resistance exercise. Eighteen elite and subelite male volleyball athletes participated in an intervention using a randomized cross-over design. On separate occasions after resistance exercise, subjects completed 1 of 4 15-minute interventions: control (CON), cold water immersion (CWI), contrast water therapy (CWT), or hot water immersion (HWI). Significance was accepted at p ≤ 0.05. Resistance exercise induced significant temporal changes (time effect) for inflammatory, anthropometric, perceptual, and performance measures. Serum creatine kinase was reduced ( g = 0.02-0.30) after CWI ( p = 0.007), CWT ( p = 0.006), or HWI ( p < 0.001) vs. CON, whereas it increased significantly ( g = 0.50) after CWI vs. HWI. Contrast water therapy resulted in significantly higher ( g = 0.56) interleukin-6 concentrations vs. HWI. Thigh girth increased ( g = 0.06-0.16) after CWI vs. CON ( p = 0.013) and HWI ( p < 0.001) and between CWT vs. HWI ( p = 0.050). Similarly, calf girth increased ( g = 0.01-0.12) after CWI vs. CON ( p = 0.039) and CWT ( p = 0.018), and HWI vs. CON ( p = 0.041) and CWT ( p = 0.018). Subject belief in a postexercise intervention strategy was associated with HSP72 ("believer">"nonbeliever," p = 0.026), muscle soreness ("believer">"nonbeliever," p = 0.002), and interleukin-4 ("nonbeliever">"believer," p = 0.002). There were no significant treatment × time (interaction effect) pairwise comparisons. Choice of postexercise water immersion strategy (i.e., cold, contrast, or hot) combined with a belief in the efficacy of that strategy to enhance recovery or performance improves biological and perceptual markers of muscle damage and soreness. On same or subsequent days where resistance exercise bouts are performed, practitioners should consider athlete beliefs when prescribing postexercise water immersion, to reduce muscle soreness.

Sequential Submaximal Training in Elite Male Rowers Does Not Result in Amplified Increases in Interleukin-6 or Hepcidin.

Previous research investigating single bouts of exercise have identified baseline iron status and circulating concentrations of interleukin-6 (IL-6) as contributors to the magnitude of postexercise hepcidin increase. The current study examined the effects of repeated training bouts in close succession on IL-6 and hepcidin responses. In a randomized, crossover design, 16 elite male rowers completed two trials, a week apart, with either high (1,000 mg) or low (<50 mg) calcium pre-exercise meals. Each trial involved two, submaximal 90-min rowing ergometer sessions, 2.5 hr apart, with venous blood sampled at baseline; pre-exercise; and 0, 1, 2, and 3 hr after each session. Peak elevations in IL-6 (approximately 7.5-fold, p < .0001) and hepcidin (approximately threefold, p < .0001) concentrations relative to baseline were seen at 2 and 3 hr after the first session, respectively. Following the second session, concentrations of both IL-6 and hepcidin remained elevated above baseline, exhibiting a plateau rather than an additive increase (2 hr post first session vs. 2 hr post second session, p = 1.00). Pre-exercise calcium resulted in a slightly greater elevation in hepcidin across all time points compared with control (p = .0005); however, no effect on IL-6 was evident (p = .27). Performing multiple submaximal training sessions in close succession with adequate nutritional support does not result in an amplified increase in IL-6 or hepcidin concentrations following the second session in male elite rowers. Although effects of calcium intake require further investigation, athletes should continue to prioritize iron consumption around morning exercise prior to exercise-induced hepcidin elevations to maximize absorption.

Neither Beetroot Juice Supplementation nor Increased Carbohydrate Oxidation Enhance Economy of Prolonged Exercise in Elite Race Walkers.

Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes' economy as well as the performance effects in elite groups.

Exercise and Heat Stress: Inflammation and the Iron Regulatory Response.

This study determined the impact of heat stress on postexercise inflammation and hepcidin levels. Twelve moderately trained males completed three, 60-min treadmill running sessions under different conditions: (a) COOL, 18 °C with speed maintained at 80% maximum heart rate; (b) HOTHR, 35 °C with speed maintained at 80% maximum heart rate; and (c) HOTPACE, 35 °C completed at the average running speed from the COOL trial. Venous blood samples were collected pre-, post-, and 3-hr postexercise and analyzed for serum ferritin, interleukin-6 (IL-6), and hepcidin concentrations. Average HR was highest during HOTPACE compared with HOTHR and COOL (p < .001). Running speed was slowest in HOTHR compared with COOL and HOTPACE (p < .001). The postexercise increase in IL-6 was greatest during HOTPACE (295%; p = .003). No differences in the IL-6 response immediately postexercise between COOL (115%) and HOTHR (116%) were evident (p = .992). No differences in hepcidin concentrations between the three trials were evident at 3 hr postexercise (p = .407). Findings from this study suggest the IL-6 response to exercise is greatest in hot compared with cool conditions when the absolute running speed was matched. No differences in IL-6 between hot and cool conditions were evident when HR was matched, suggesting the increased physiological strain induced from training at higher intensities in hot environments, rather than the heat per se, is likely responsible for this elevated response. Environmental temperature had no impact on hepcidin levels, indicating that exercising in hot conditions is unlikely to further impact transient alterations in iron regulation, beyond that expected in temperate conditions.

Sustained Exposure to High Carbohydrate Availability Does Not Influence Iron-Regulatory Responses in Elite Endurance Athletes.

This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17-23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p = .004) and hotter trial ambient temperatures (p = .014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise.

Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability.

KEY POINTS: Brief (5-6 days) adaptation to a low carbohydrate high fat diet in elite athletes increased exercise fat oxidation to rates previously observed with medium (3-4 weeks) or chronic (>12 months) adherence to this diet, with metabolic changes being washed out in a similar time frame. Increased fat utilisation during exercise was associated with a 5-8% increase in oxygen cost at speeds related to Olympic Programme races. Acute restoration of endogenous carbohydrate (CHO) availability (24 h high CHO diet, pre-race CHO) only partially restored substrate utilisation during a race warm-up. Fat oxidation continued to be elevated above baseline values although it was lower than achieved by 5-6 days' keto adaptation; CHO oxidation only reached 61% and 78% of values previously seen at exercise intensities related to race events. Acute restoration of CHO availability failed to overturn the impairment of high-intensity endurance performance previously associated with low carbohydrate high fat adaptation, potentially due to the blunted capacity for CHO oxidation. ABSTRACT: We investigated substrate utilisation during exercise after brief (5-6 days) adaptation to a ketogenic low-carbohydrate (CHO), high-fat (LCHF) diet and similar washout period. Thirteen world-class male race walkers completed economy testing, 25 km training and a 10,000 m race (Baseline), with high CHO availability (HCHO), repeating this (Adaptation) after 5-6 days' LCHF (n = 7; CHO: <50 g day-1 , protein: 2.2 g kg-1 day-1 ; 80% fat) or HCHO (n = 6; CHO: 9.7 g kg-1 day-1 ; protein: 2.2 g kg-1 day-1 ) diet. An Adaptation race was undertaken after 24 h HCHO and pre-race CHO (2 g kg-1 ) diet, identical to the Baseline race. Substantial (>200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of ∼1.43 g min-1 . However, relative V̇O2 (ml min-1  kg-1 ) was higher (P < 0.0001), by ∼8% and 5% at speeds related to 50 km and 20 km events. During Adaptation race warm-up in the LCHF group, rates of fat and CHO oxidation at these speeds were decreased and increased, respectively (P < 0.001), compared with the previous day, but were not restored to Baseline values. Performance changes differed between groups (P = 0.009), with all HCHO athletes improving in the Adaptation race (5.7 (5.6)%), while 6/7 LCHF athletes were slower (2.2 (3.4)%). Substrate utilisation returned to Baseline values after 5-6 days of HCHO diet. In summary, robust changes in exercise substrate use occurred in 5-6 days of extreme changes in CHO intake. However, adaptation to a LCHF diet plus acute restoration of endogenous CHO availability failed to restore high-intensity endurance performance, with CHO oxidation rates remaining blunted.