Altered carbohydrate oxidation during exercise in overreached endurance athletes is applicable to training monitoring with continuous glucose monitors.

PURPOSE: The purpose of the study was to investigate whether carbohydrate utilization is altered during exercise in overreached endurance athletes and examine the utility of continuous glucose monitors (CGM) to detect overreaching status. METHODS: Eleven endurance athletes (M:8, F:3) completed a 5-week training block consisting of 1 week of reduced training (PRE), 3 weeks of high-intensity overload training (POST), and 1 week of recovery training (REC). Participants completed a Lamberts and Lambert Submaximal Cycling Test (LSCT) and 5 km time-trial at PRE, POST, and REC time points, 15 min following the ingestion of a 50 g glucose beverage with glucose recorded each minute via CGM. RESULTS: Performance in the 5 km time-trial was reduced at POST (∆-7 ± 10 W, p = 0.04, η p 2 = 0.35) and improved at REC (∆12 ± 9 W from PRE, p = 0.01, η p 2 = 0.66), with reductions in peak lactate (∆-3.0 ± 2.0 mmol/L, p = 0.001, η p 2 = 0.71), peak HR (∆-6 ± 3 bpm, p < 0.001, η p 2 = 0.86), and Hooper-Mackinnon well-being scores (∆10 ± 5 a.u., p < 0.001, η p 2 = 0.79), indicating athletes were functionally overreached. The respiratory exchange ratio was suppressed at POST relative to REC during the 60% (POST: 0.80 ± 0.05, REC: 0.87 ± 0.05, p < 0.001, η p 2 = 0.74), and 80% (POST: 0.93 ± 0.05, REC: 1.00 ± 0.05, p = 0.003, η p 2 = 0.68) of HR-matched submaximal stages of the LSCT. CGM glucose was reduced during HR-matched submaximal exercise in the LSCT at POST (p = 0.047, η p 2 = 0.36), but not the 5 km time-trial (p = 0.07, η p 2 = 0.28) in overreached athletes. CONCLUSION: This preliminary investigation demonstrates a reduction in CGM-derived glucose and carbohydrate oxidation during submaximal exercise in overreached athletes. The use of CGM during submaximal exercise following standardized nutrition could be employed as a monitoring tool to detect overreaching in endurance athletes.

Cardiac Remodeling in Elite Aquatic Sport Athletes.

OBJECTIVE: To characterize and compare the sport-specific cardiac structure of elite swimmers (SW), water polo players (WP), and artistic swimmers (AS). DESIGN: A cross-sectional assessment of elite aquatic athletes' hearts. SETTING: The athletes' village at the 2019 FINA World Championships. PARTICIPANTS: Ninety athletes from swimming (SW) (20 M/17 F), water polo (WP) (21 M/9 F), and artistic swimming (AS) (23 F). ASSESSMENT AND MAIN OUTCOME MEASURES: An echocardiographic assessment of cardiac structure was performed on noncompetition days. RESULTS: Male SW displayed primarily eccentric volume-driven remodeling, whereas male WP had a greater incidence of pressure-driven concentric geometry (SW = 5%, WP = 25%) with elevated relative wall-thickness (RWT) (SW = 0.35 ± 0.04, WP = 0.44 ± 0.08, P < 0.001). Female SW and WP hearts were similar with primarily eccentric-remodeling, but SW and WP had greater concentricity index than artistic swimmers (SW = 6.74 ± 1.45 g/(mL)2/3, WP = 6.80 ± 1.24 g/(mL)2/3, AS = 5.52 ± 1.08 g/(mL)2/3, P = 0.007). AS had normal geometry, but with increased posterior-wall specific RWT (SW = 0.32 ± 0.05, AS = 0.42 ± 0.11, P = 0.004) and greater left atrial area than SW (SW = 9.7 ± 0.9 cm2/m2, AS = 11.0 ± 1.1 cm2/m2, P = 0.003). All females had greater incidence of left ventricular (LV) posterior/septal wall-thickness ≥11 mm than typically reported (SW = 24%, WP = 11%, AS = 17%). CONCLUSIONS: Male athletes presented classic sport-specific differentiation, with SW demonstrating primarily volume-driven eccentric remodelling, and WP with greater concentric geometry indicative of pressure-driven remodeling. Female SW and WP did not display this divergence, likely because of sex-differences in adaptation. AS had unique LV-specific adaptations suggesting elevated pressure under low-volume conditions. The overall incidence of elevated wall-thickness in female athletes may point to an aquatic specific pressure-stress.

Exercise alters cardiac function independent of acute systemic inflammation in healthy men.

Acute elevations in inflammatory cytokines have been demonstrated to increase aortic and left ventricular stiffness and reduce endothelial function in healthy subjects. As vascular and cardiac functions are often transiently reduced following prolonged exercise, it is possible that cytokines released during exercise may contribute to these alterations. The a priori aims of this study were to determine whether vaccine-induced increases in inflammatory cytokines would reduce vascular and left ventricular function, whether vascular alterations would drive cardiac impairments, and whether this would be potentiated by moderate exercise. In a randomized crossover fashion, 16 male participants were tested under control (CON) and inflammatory (INF) conditions, wherein INF testing occurred 8 h following administration of an influenza vaccine. On both days, participants underwent measures of echocardiography performed during light cycling (stress-echocardiography), carotid-femoral pulse wave velocity (cf-PWV), and superficial femoral flow-mediated dilation (FMD) before and after cycling for 90 min at ∼85% of their first ventilatory threshold. IL-6 increased significantly (Δ1.9 ± 1.3 pg/mL, P < 0.001), whereas TNFα was nonsignificantly augmented (Δ0.05 ± 0.11 pg/mL, P = 0.09), 8 h following vaccination. Vascular function was unaltered following cycling or inflammation (all P > 0.05). The use of echocardiography during light cycling revealed cardiac alterations traditionally expected to occur only with greater exercise loads, with reduced systolic (e.g., longitudinal strain CON: Δ3.3 ± 4.4%, INF: Δ1.7 ± 2.7%, P = 0.002) and diastolic function (e.g., E/A ratio CON: Δ-0.32 ± 0.34 a.u., INF:Δ-0.25 ± 0.27 a.u., P = 0.002) following cycling, independent of inflammation. The vaccine reduced stroke volume (SV) (main effect of condition P = 0.009) before-and-after cycling. These findings indicate that reduced cardiac function following exercise occurs largely independent of additional inflammatory load.NEW & NOTEWORHTHY This experimental investigation sought to determine the role of inflammation on the occurrence of cardiovascular alterations following exercise. Despite successfully stimulating systemic inflammation via vaccination, vascular and cardiac functions were largely unaltered. Prolonged exercise itself reduced cardiac function assessed via echocardiography performed during light exercise stress. This demonstrates a potential advantage to using stress-echocardiography for measuring exercise-induced cardiac fatigue, as typical resting measures following similar exercise exposures commonly suggest no effect.

Cardiac autonomic recovery following traditional and augmented remote ischemic preconditioning.

PURPOSE: While the possible ergogenic benefits of remote ischemic preconditioning (RIPC) make it an attractive training modality, the mechanisms of action remain unclear. Alterations in neural tone have been demonstrated in conjunction with circulatory occlusion, yet investigation of the autonomic nervous system following RIPC treatment has received little attention. We sought to characterize alterations in autonomic balance to both RIPC and augmented RIPC (RIPCaug) performed while cycling, using acute and sustained autonomic indices. METHODS: Thirteen participants (8M:5F) recorded baseline waking heart rate variability (HRV) for 5 days prior to treatment. Participants then completed control exercise (CON), RIPC, and RIPCaug interventions in a randomized cross-over design. Cardiovascular measurements were recorded immediately before and after each intervention at rest, and during an orthostatic challenge. Waking HRV was repeated the morning after each intervention. RESULTS: RIPC resulted in acutely reduced resting heart rates (HR) (∆ - 4 ± 6 bpm, P = 0.02) and suppressed HR 30 s following the orthostatic challenge compared to CON (64 ± 10 vs 74 ± 9 bpm, P = 0.003). RIPCaug yielded elevated HRs compared to CON and RIPC prior to (P = 0.003) and during the orthostatic challenge (P = 0.002). RIPCaug reduced LnSDNN (Baseline 4.39 ± 0.27; CON 4.44 ± 0.39; RIPC 4.41 ± 0.34; RIPCaug 4.22 ± 0.29, P = 0.02) and LnHfa power (Baseline 7.82 ± 0.54; CON 7.73 ± 1.11; RIPC 7.89 ± 0.78; RIPCaug 7.23 ± 0.87, P = 0.04) the morning after treatment compared to all other conditions. CONCLUSIONS: Our data suggest that RIPC may influence HR acutely, possibly through a reduction in cardiac sympathetic activity, and that RIPCaug reduces HRV through cardiac vagal withdrawal or increased cardiac sympathetic modulation, with alterations persisting until the following morning. These findings imply a dose-response relationship with potential for optimization of performance.

Blood flow restriction in the presence or absence of muscle contractions does not preserve vasculature structure and function following 14-days of limb immobilization.

PURPOSE: Limb immobilization causes local vasculature to experience detrimental adaptations. Simple strategies to increase blood flow (heating, fidgeting) successfully prevent acute (≤ 1 day) impairments; however, none have leveraged the hyperemic response over prolonged periods (weeks) mirroring injury rehabilitation. Throughout a 14-day unilateral limb immobilization, we sought to preserve vascular structure and responsiveness by repeatedly activating a reactive hyperemic response via blood flow restriction (BFR) and amplifying this stimulus by combining BFR with electric muscle stimulation (EMS). METHODS: Young healthy adults (M:F = 14:17, age = 22.4 ± 3.7 years) were randomly assigned to control, BFR, or BFR + EMS groups. BFR and BFR + EMS groups were treated for 30 min twice daily (3 × 10 min ischemia-reperfusion cycles; 15% maximal voluntary contraction EMS), 5 days/week (20 total sessions). Before and after immobilization, artery diameter, flow-mediated dilation (FMD) and blood flow measures were collected in the superficial femoral artery (SFA). RESULTS: Following immobilization, there was less retrograde blood velocity (+ 1.8 ± 3.6 cm s-1, P = 0.01), but not retrograde shear (P = 0.097). All groups displayed reduced baseline and peak SFA diameter following immobilization (- 0.46 ± 0.41 mm and - 0.43 ± 0.39 mm, P < 0.01); however, there were no differences by group or across time for FMD (% diameter change, shear-corrected, or allometrically scaled) nor microvascular function assessed by peak flow capacity. CONCLUSION: Following immobilization, our results reveal (1) neither BFR nor BFR + EMS mitigate artery structure impairments, (2) intervention-induced shear stress did not affect vascular function assessed by FMD, and (3) retrograde blood velocity is reduced at rest offering potential insight to mechanisms of flow regulation. In conclusion, BFR appears insufficient as a treatment strategy for preventing macrovascular dysfunction during limb immobilization.

Examining the relationship between arterial stiffness and swim-training volume in elite aquatic athletes.

PURPOSE: Factors such as prone body position, hydrostatic pressure, and intermittent breath-holding subject aquatic athletes to unique physical and environmental stressors during swimming exercise. The relationship between exposure to aquatic exercise and both arterial stiffness and wave reflection properties is not well-understood. This study assessed central artery stiffness and wave reflection properties in elite pool-swimmers (SW), long-distance open-water swimmers (OW), and water polo players (WP) to examine the relationship between these variables and aquatic exercise. METHODS: Athletes competing in SW, OW and WP events at the FINA World Championships were recruited. Carotid-femoral pulse wave velocity, and pulse wave analysis were used to quantify arterial stiffness, and central wave reflection properties. RESULTS: Athletes undertook differing amounts of weekly swimming distance in training according to their discipline (SW: 40.2 ± 21.1 km, OW: 59.7 ± 28.4 km, WP: 11.4 ± 6.3 km; all p < 0.05). Pulse wave velocity (Males [SW: 6.0 ± 0.6 m/s, OW: 6.5 ± 0.8 m/s, WP: 6.7 ± 0.9 m/s], Females [SW: 5.4 ± 0.6 m/s, OW: 5.3 ± 0.5 m/s, WP: 5.2 ± 0.8 m/s; p = 0.4]) was similar across disciplines for females but was greater in male WP compared to male SW (p = 0.005). Augmentation index (Males [SW: - 3.4 ± 11%, OW: - 9.6 ± 6.4%, WP: 1.7 ± 10.9%], Females [SW: 3.5 ± 13.5%, OW: - 13.2 ± 10.7%, WP: - 2.8 ± 10.7%]) was lower in male OW compared to WP (p = 0.03), and higher in female SW compared to OW (p = 0.002). Augmentation index normalized to a heart rate of 75 bpm was inversely related to weekly swim distance in training (r = - 0.27, p = 0.004). CONCLUSIONS: This study provides evidence that the central vasculature of elite aquatic athletes differs by discipline, and this is associated with training load.

Prevalence of Indicators of Low Energy Availability in Elite Female Sprinters.

Low energy availability (LEA), and subsequent relative energy deficiency in sport, has been observed in endurance, aesthetic, and team sport athletes, with limited data on prevalence in athletes in short-burst activities such as sprinting. We examined prevalence of signs and symptoms of LEA in elite female sprinters at the start of the training season (PRE), and at the end of a 5-month indoor training period (POST). Four of 13 female sprinters (31%) presented at PRE testing with at least one primary (amenorrhea, low bone mineral density, low follicle-stimulating hormone, luteinizing hormone, or estradiol, resting metabolic rate ≤29 kcal/kg fat-free mass, Low Energy Availability in Females Questionnaire score ≥8) and one secondary indicator of LEA (fasting blood glucose <4 mmol/L, free triiodothyronine <3.5 pmol/L, ferritin <25 µg/L, low-density lipoprotein cholesterol >3.0 mmol/L, fasting insulin <20 pmol/L, low insulin-like growth factor-1, systolic blood pressure <90 mmHg, and/or diastolic blood pressure <60 mmHg). At POST, seven out of 13 athletes (54%) presented with at least one primary and one secondary indicator of LEA, three of whom had also presented with indicators of LEA at PRE. Five out of 13 (39%) athletes had previous stress fracture history, though this was not associated with current indicators of LEA (PRE: r = .52, p = .07; POST: r = -.07, p = .82). In conclusion, elite female sprinters may present with signs and symptoms of LEA, even after off-season rest. Medical and coaching staff should be aware of the signs and symptoms of LEA and relative energy deficiency in sport and should include appropriate screening and intervention strategies when working with sprinters.

Cannabis containing THC impairs 20-min cycling time trial performance irrespective of the method of inhalation.

Herein, we examine the human exercise response following cannabis inhalation, taking into consideration varied cannabinoid concentrations and different inhalation methods. A semirandomized crossover study design was used, with measures of perceived exertion and physiological responses to submaximal and maximal exercise. Participants (n = 14, 9 males 5 females) completed exercise after 1) smoking Δ-9-tetrahydrocannabinol (THC)-predominant cannabis (S-THC), 2) inhaling aerosol (vaporizing) from THC-predominant cannabis (V-THC), 3) inhaling aerosol from cannabidiol (CBD)-predominant cannabis (V-CBD), or 4) under control conditions. All exercise was performed on a cycle ergometer, with submaximal testing performed at 100 W followed by an evaluation of maximal exercise performance using an all-out 20-min time trial. Metabolism was characterized via the analysis of expired gases while subjective ratings of perceived exertion (RPE) were reported. During submaximal cycling, heart rate was higher during S-THC and V-THC compared with both control and V-CBD (all P < 0.02). During maximal exercise, V̇e was lower in V-THC compared with control, S-THC, and V-CBD (all P < 0.03), as was S-THC compared with control (P < 0.05). Both V̇o2 and RPE were similar between conditions during maximal exercise (both P > 0.1). Mean power output during the 20-min time trial was significantly lower in the S-THC and V-THC conditions compared with both control and V-CBD (all P < 0.04). Cannabis containing THC alters the physiological response to maximal and submaximal exercise, largely independent of the inhalation method. THC-containing cannabis negatively impacts vigorous exercise performance during a sustained 20-min effort, likely due to physiological and psychotropic effects. Inhalation of cannabis devoid of THC and primarily containing CBD has little physiological effect on the exercise response or performance.NEW & NOTEWORTHY Inhalation of cannabis containing THC alters physiological responses to both submaximal and maximal exercise and reduces mean power output during a 20-min time trial, regardless of whether it is inhaled as smoke or aerosol. In contrast, cannabis devoid of THC and predominantly containing CBD has no effect on physiological responses to exercise or performance.

Impact of Blood Flow Restriction Exercise on Central Hemodynamics and Fluid Regulating Hormones.

PURPOSE: The purpose of this study is to characterize both the efficacy of altered restriction pressures and consequences of optimized blood flow restriction (BFR) for altering the cardiovascular and fluid regulating response in humans. METHODS: This work comprised a series of related trials. Phase 1: during semi-recumbent cycling (5 min, 60 W) with BFR at 0%, 50%, 75%, 100%, and 125% of participants' lowest arterial occlusion pressure (LOP) echocardiographic images were collected alongside continuous heart rate (HR) and blood pressure (BP). In phase 2, 24 h fluid balance (intake-output) and fluid-regulating hormone responses were measured after a practical BFR exercise session (treadmill walking: 5·3 min, 1 min rest, 5 km·h -1 , 5% incline, 100% LOP). Phase 3 examined the magnitude and effect of blood volume distribution following BFR treadmill walking using a modified CO-rebreathe technique. RESULTS: Cardiac ejection fraction remained stable irrespective of cuff pressure and despite a reduction in end-diastolic volume (Δ of 11 ± 9 mL, P = 0.02). HR and BP were highest at 100% LOP (ΔHR = 18 ± 19 bpm, ΔSBP = 51 ± 30 mm Hg, ΔDBP = 33 ± 15 mm Hg, ΔRate Pressure Product = 76 ± 32 bpm·mm Hg·100 -1 ). BFR treadmill walking stimulated a greater release of fluid-regulating hormones than normal walking (Δrenin = BFR: 25.3 ± 24.2 vs CON: 9.1 ± 11.8 ng·L -1 ; Δcopeptin = BFR: 50.1 ± 97.9 vs. CON: 0.43 ± 0.8 pmol·L -1 ), but no difference in fluid retention was observed ( P = 0.2). Approximately 27% of total blood volume was confined to the legs during BFR, but the relative volume trapped in the legs was not related to fluid-regulating hormone release (renin r = -0.04, P = 0.9; copeptin r = 0.27, P = 0.3). CONCLUSIONS: BFR exercise elicits the largest cardiovascular effect using 100% LOP, with evidence of appreciable fluid regulating hormonal response during a typical BFR exercise session. The relative volume of blood sequestered in the limb does not appear to drive this response.

Blood Flow Restricted Training and Time Trial Performance: A Cohort Study of World Class Rowers.

INTRODUCTION: This study aimed to explore the potential impact of incorporating blood-flow restriction (BFR) training within a training block characterized by minimal high-intensity work on 2000-m rowing ergometer time-trial (TT) performance in elite/world-class rowers. Physiological markers often associated with endurance performance (maximal aerobic capacity - VO2max, blood lactate thresholds and hemoglobin mass - Hbmass) were measured to determine whether changes are related to an improvement in performance. METHODS: Using a quasi-experimental, observational study design (no control group), 2000-m TT performance, VO2max, submaximal work rates eliciting blood lactate concentrations of ~2 and ~ 4 mmol·L-1, and Hbmass were measured before and after 4 weeks of non-competitive season training, which included BFR rowing. BFR training consisted of 11 sessions of 2x10 minutes of BFR rowing at a workload equating to blood lactate concentrations of ~2 mmol·L-1. Paired t-tests were used to compare pre/post values, and Pearson correlation was used to examine whether physiological changes were associated with changes to TT performance. RESULTS: TT performance improved in both female (1.09 ± 1.2%, ~4.6 ± 5.2 s; p < 0.01) and male (1.17 ± 0.48%, ~4.5 ± 1.9 s; p < 0.001) athletes. VO2max increased in female rowers only (p < 0.01), but both sexes had an increase in work rates eliciting blood lactate concentrations of 2 (female:184 ± 16 to 195 ± 15 W, p < 0.01; male:288 ± 23 to 317 ± 26 W, p = 0.04) and 4 mmol·L-1 (female:217 ± 13 to 227 ± 14 W, p = 0.02; male:339 ± 43 to 364 ± 39 W, p < 0.01). No changes in Hbmass (both sexes, p = 0.8) were observed. Improvements in TT performance were not related to physiological changes (all correlations p ≥ 0.2). CONCLUSIONS: After 4 weeks of training with BFR, the improvement in TT performance was greater than what is typical for this population. Physiological variables improved during this training block but did not explain improved TT performance.

High-Intensity Interval vs. Moderate-Intensity Continuous Training in Parkinson's Disease: A Randomized Trial.

Exercise training is recommended to improve quality of life in those living with Parkinson's Disease (PD); however, the optimal prescription to improve cardiorespiratory fitness and disease-related motor symptoms remains unknown. Twenty-nine participants with PD were randomly allocated to either 10-weeks of high-intensity interval training (HIIT) (n=15; 6 female) or moderate-intensity continuous training (MICT) (n=14; 5 female). The primary outcome was the change in maximal oxygen consumption (VO2peak). Secondary outcomes included changes in the Unified Parkinson's Disease Rating Scale (UPDRS) Part III motor score, Parkinson's Disease Fatigue Scale (PFS-16), resting and exercise cardiovascular measures, gait, balance, and knee extensor strength and fatigability. Exercise training increased VO2peak (main effect of time, P<0.01), with a clinically-meaningful difference in the change following HIIT vs. MICT (∆3.7±3.7 vs. 1.7±3.2 ml∙kg-1∙min-1, P=0.099). The UPDRS motor score improved over time (P<0.001) but without any differences between HIIT vs. MICT (∆-9.7±1.3 vs. -8.4±1.4, P=0.51). Self-reported subjective fatigue (PFS-16) decreased over time (P<0.01) but was similar between HIIT and MICT groups (P=0.6). Gait, balance, blood pressure, and heart rate were unchanged with training (all P>0.09). Knee extensor strength increased over time (P=0.03) but did not differ between HIIT vs. MICT (∆8.2±5.9 vs. 11.7±6.2 Nm, P=0.69). HIIT alone increased muscular endurance of the knee extensors during an isotonic task to failure (P=0.04). In participants with PD, HIIT and MICT both increased VO2peak and led to improvements in motor symptoms and perceived fatigue; HIIT may offer the potential for larger changes in VO2peak and reduced knee extensor fatigability.

Investigating sensor location on the effectiveness of continuous glucose monitoring during exercise in a non-diabetic population.

The purpose of this investigation was to evaluate whether continuous glucose monitoring (CGM) sensors worn on the active muscle may provide enhanced insight into glucose control in non-diabetic participants during cycling exercise compared to traditional sensor placement on the arm. Data from 9 healthy participants (F:3) was recorded using CGM sensors on the arm (triceps brachii) and leg (vastus medialis) following 100 g glucose ingestion during 30 min experimental visits of: resting control, graded cycling, electrically stimulated quadriceps contractions, and passive whole-body heating. Finger capillary glucose was used to assess sensor accuracy. Under control conditions, the traditional arm sensor better reflected capillary glucose, with a mean absolute relative difference (MARD) of 12.4 ± 9.3% versus 18.3 ± 11.4% in the leg (P = 0.02). For the intended use during exercise, the sensor-site difference was attenuated, with similar MARDs during cycling (arm:15.5 ± 12% versus leg:16.7 ± 10.8%, P = 0.96) and quadriceps stimulation (arm:15.5 ± 14.8% versus leg:13.9 ± 9.5%, P = 0.9). At rest, glucose at the leg was consistently lower than the arm (P = 0.01); whereas, during graded cycling, the leg-glucose was lower only after maximal intensity exercise (P = 0.02). There was no difference between sensors during quadriceps stimulation (P = 0.8). Passive heating caused leg-skin temperature to increase by 3.1 ± 1.8°C versus 1.1 ± 0.72°C at the arm (P = 0.002), elevating MARD in the leg (23.5 ± 16.2%) and lowering glucose in the leg (P < 0.001). At rest, traditional placement of CGM sensors on the arm may best reflect blood glucose; however, during cycling, placement on the leg may offer greater insight to working muscle glucose concentrations, and this is likely due to greater blood-flow rather than muscle contractions.HighlightsWearing a continuous glucose monitoring (CGM) sensor on the arm may better reflect capillary glucose concentrations compared to wearing a sensor on the inner thigh at rest.With passive or active leg-muscle contractions, site-specific differences compared to capillary samples are attenuated; therefore, wearing a CGM sensor on the active-muscle during exercise may provide greater information to non-diabetic athletes regarding glucose flux at the active muscle.Discrepancies in CGM sensors worn at different sites likely primarily reflects differences in blood flow, as passive skin heating caused the largest magnitude difference between arm and leg sensor readings compared to the other experimental conditions (control, electric muscle stimulation, and cycling exercise).

Investigating the roles of exercise intensity and biological sex on postexercise alterations in cardiac function.

The term exercise-induced cardiac fatigue (EICF) has typically been used to describe a transient reduction in cardiac function following prolonged-strenuous exercise. Recent evidence demonstrates that EICF can occur following only 45 min of high-intensity exercise when assessed using exercising stress echocardiography. This investigation sought to examine whether sprint intervals (SIT; 6 × 30 s Wingate tests), or 90-min moderate-cycling with sprint intervals (MIX; 90 min with 1 × 30 s Wingate test every 15 min) would cause greater EICF than 90 min (CON) or 3 h (LONG) moderate-cycling assessed using stress echocardiography, with a secondary aim to interrogate sex differences in EICF. Seventeen participants (M: 9, F: 8) underwent three cycling sessions with stress-echocardiography performed before-and-after each condition at a target heart rate (HR) of 100 beats·min-1, with the CON testing occurring at the mid-point of the 3 h LONG condition. For all conditions, measures of left ventricular (LV) systolic [stroke volume, ejection fraction (EF), peak longitudinal strain, isovolumetric contraction time, S') and diastolic (E/A, E', isovolumetric relaxation time, longitudinal strain rate) function were reduced after exercise (all P < 0.05). In the right ventricle (RV), systolic function was reduced (tricuspid annular plane systolic excursion, S', peak longitudinal strain and strain rate) following all conditions, and fractional area change was reduced to the greatest degree following SIT (condition × time, P = 0.01). Females demonstrated lesser impairments in LV EF, and elastance (ESP/ESV) compared with males (P < 0.05). Markers of EICF occurred similarly following all cycling loads, suggesting the functional changes may be due to altered loading conditions and reduced stress-echocardiography workload. However, males experienced greater cardiac alterations in some measures, likely due to greater changes in postexercise loading conditions.NEW & NOTEWORTHY This investigation sought to determine the role of exercise intensity on the magnitude of exercise-induced cardiac fatigue using stress echocardiography to maintain loading conditions, with a secondary purpose of assessing sex differences. Unexpectedly, it was found that all cycling loads elicited the same magnitude of functional alteration, which likely represents a common response to exercise and stress echocardiography, rather than intrinsic cardiac impairment. Males demonstrated greater alterations than females, likely due to sex differences in postexercise hemodynamics.

Time Management Strategies of Rock Climbers in World Cup Bouldering Finals.

Competitive rock climbing recently made its Olympic debut, but minimal published research exists regarding training and competition strategies. Time management strategies define the structured approach climbers take in bouldering competitions to successfully obtain a "top" or a "zone" hold. During finals rounds of the International Federation of Sport Climbing bouldering competitions, climbers are allotted 240 s to complete a boulder. Variables influencing a climber's time management strategies include their work-to-rest intervals, and the frequency of their attempts or rests. Video analysis of International Federation of Sport Climbing competitions was used to collect time management strategy data of professional climbers. Fifty-six boulders (28 female and 28 male boulders) over the 2019 International Federation of Sport Climbing season were analyzed. Time management strategies variables were compared between slab/slab-like and non-slab bouldering styles using generalized estimating equations with significance set to p < 0.05. Additionally, we determined trends in success rates for various styles of boulders. There were no differences in the number of attempts taken per boulder between slab/slab-like and non-slab boulders (3.7 ± 2.3 and 3.8 ± 2.4, p = 0.97), but climbers spent more time actively climbing on slab/slab-like (92 ± 36 s) compared to non-slab boulders (65 ± 26 s, p < 0.001). Trends in the success rate suggest climbers who take more than 6 attempts on any boulder style are unsuccessful. The results of this study provide practical information that can be used by coaches and athletes to guide training and competition strategy.

A Perspective on High-Intensity Interval Training for Performance and Health.

Interval training is a simple concept that refers to repeated bouts of relatively hard work interspersed with recovery periods of easier work or rest. The method has been used by high-level athletes for over a century to improve performance in endurance-type sports and events such as middle- and long-distance running. The concept of interval training to improve health, including in a rehabilitative context or when practiced by individuals who are relatively inactive or deconditioned, has also been advanced for decades. An important issue that affects the interpretation and application of interval training is the lack of standardized terminology. This particularly relates to the classification of intensity. There is no common definition of the term "high-intensity interval training" (HIIT) despite its widespread use. We contend that in a performance context, HIIT can be characterized as intermittent exercise bouts performed above the heavy-intensity domain. This categorization of HIIT is primarily encompassed by the severe-intensity domain. It is demarcated by indicators that principally include the critical power or critical speed, or other indices, including the second lactate threshold, maximal lactate steady state, or lactate turnpoint. In a health context, we contend that HIIT can be characterized as intermittent exercise bouts performed above moderate intensity. This categorization of HIIT is primarily encompassed by the classification of vigorous intensity. It is demarcated by various indicators related to perceived exertion, oxygen uptake, or heart rate as defined in authoritative public health and exercise prescription guidelines. A particularly intense variant of HIIT commonly termed "sprint interval training" can be distinguished as repeated bouts performed with near-maximal to "all out" effort. This characterization coincides with the highest intensity classification identified in training zone models or exercise prescription guidelines, including the extreme-intensity domain, anaerobic speed reserve, or near-maximal to maximal intensity classification. HIIT is considered an essential training component for the enhancement of athletic performance, but the optimal intensity distribution and specific HIIT prescription for endurance athletes is unclear. HIIT is also a viable method to improve cardiorespiratory fitness and other health-related indices in people who are insufficiently active, including those with cardiometabolic diseases. Research is needed to clarify responses to different HIIT strategies using robust study designs that employ best practices. We offer a perspective on the topic of HIIT for performance and health, including a conceptual framework that builds on the work of others and outlines how the method can be defined and operationalized within each context.

Markers of Low Energy Availability in Overreached Athletes: A Systematic Review and Meta-analysis.

BACKGROUND: Overreaching is the transient reduction in performance that occurs following training overload and is driven by an imbalance between stress and recovery. Low energy availability (LEA) may drive underperformance by compounding training stress; however, this has yet to be investigated systematically. OBJECTIVE: The aim of this study was to quantify changes in markers of LEA in athletes who demonstrated underperformance, and exercise performance in athletes with markers of LEA. METHODS: Studies using a ≥ 2-week training block with maintained or increased training loads that measured exercise performance and markers of LEA were identified using a systematic search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Changes from pre- to post-training were analyzed for (1) markers of LEA in underperforming athletes and (2) performance in athletes with ≥ 2 markers of LEA. RESULTS: From 56 identified studies, 14 separate groups of athletes demonstrated underperformance, with 50% also displaying ≥ 2 markers of LEA post-training. Eleven groups demonstrated ≥ 2 markers of LEA independent of underperformance and 37 had no performance reduction or ≥ 2 markers of LEA. In underperforming athletes, fat mass (d = - 0.29, 95% confidence interval [CI] - 0.54 to - 0.04; p = 0.02), resting metabolic rate (d = - 0.63, 95% CI - 1.22 to - 0.05; p = 0.03), and leptin (d = - 0.72, 95% CI - 1.08 to - 0.35; p < 0.0001) were decreased, whereas body mass (d = - 0.04, 95% CI - 0.21 to 0.14; p = 0.70), cortisol (d = - 0.06, 95% CI - 0.35 to 0.23; p = 0.68), insulin (d = - 0.12, 95% CI - 0.43 to 0.19; p = 0.46), and testosterone (d = - 0.31, 95% CI - 0.69 to 0.08; p = 0.12) were unaltered. In athletes with ≥ 2 LEA markers, performance was unaffected (d = 0.09, 95% CI - 0.30 to 0.49; p = 0.6), and the high heterogeneity in performance outcomes (I2 = 84.86%) could not be explained by the performance tests used or the length of the training block. CONCLUSION: Underperforming athletes may present with markers of LEA, but overreaching is also observed in the absence of LEA. The lack of a specific effect and high variability of outcomes with LEA on performance suggests that LEA is not obligatory for underperformance.

Blood flow restriction and stimulated muscle contractions do not improve metabolic or vascular outcomes following glucose ingestion in young, active individuals.

Glucose ingestion and absorption into the bloodstream can challenge glycemic regulation and vascular endothelial function. Muscular contractions in exercise promote a return to homeostasis by increasing glucose uptake and blood flow. Similarly, muscle hypoxia supports glycemic regulation by increasing glucose oxidation. Blood flow restriction (BFR) induces muscle hypoxia during occlusion and reactive hyperemia upon release. Thus, in the absence of exercise, electric muscle stimulation (EMS) and BFR may offer circulatory and glucoregulatory improvements. In 13 healthy, active participants (27 ± 3 yr, 7 females), we tracked post-glucose (oral 100 g) glycemic, cardiometabolic, and vascular function measures over 120 min following four interventions: 1) BFR, 2) EMS, 3) BFR + EMS, or 4) control. BFR was applied at 2-min intervals for 30 min (70% occlusion), and EMS was continuous for 30 min (maximum-tolerable intensity). Glycemic and insulinemic responses did not differ between interventions (partial η2 = 0.11-0.15, P = 0.2), however, only BFR + EMS demonstrated cyclic effects on oxygen consumption, carbohydrate oxidation, muscle oxygenation, heart rate, and blood pressure (all P < 0.01). Endothelial function was reduced 60 min post-glucose ingestion across interventions and recovered by 120 min (5.9 ± 2.6% vs 8.4 ± 2.7%; P < 0.001). Estimated microvascular function was not meaningfully different. Leg blood flow increased during EMS and BFR + EMS (+656 ± 519 mL·min-1, +433 ± 510 mL·min-1; P < 0.001); however, only remained elevated following BFR intervention 90 min post-glucose (+94 ± 94 mL·min-1; P = 0.02). Superimposition of EMS onto cyclic BFR did not preferentially improve post-glucose metabolic or vascular function among young, active participants. Cyclic BFR increased blood flow delivery 60 min beyond intervention, and BFR + EMS selectively increased carbohydrate usage and reduced muscle oxygenation warranting future clinical assessments.NEW & NOTEWORTHY Glucose ingestion challenges glycemic and vascular function. Exercise effectively counteracts these impairments, but is not always feasible. Blood flow restriction (BFR) and electric muscle stimulation (EMS) passively generate muscle hypoxia and contractions mimicking aspects of exercise. We tested BFR, EMS, and BFR + EMS in young, active participants post-glucose. No significant primary glycemic or vascular outcomes are observed. Cyclic BFR increased leg blood flow while BFR + EMS activated greater carbohydrate oxidation and lowered muscle oxygenation warranting future consideration.

Differences in Left Ventricular Function at Rest and during Isometric Handgrip Exercise in Elite Aquatic Sport Athletes.

PURPOSE: Elite swimmers (Sw) have lower diastolic function compared with elite runners, possibly as an adaptation to the aquatic training environment. Water polo players (WP) and artistic swimmers (AS) are exposed to the same hydrostatic pressures as Sw, but they are subject to different training intensities, postures, and hemodynamic stressors. Our purpose was to compare resting and exercising cardiac function in elite Sw, WP, and AS, to characterize the influence of training for aquatic sport on left ventricular (LV) adaptation. METHODS: Ninety athletes (Sw, 20M/17F; WP, 21M/9F; AS, 23F) at the 2019 Fédération Internationale de Natation World Championships volunteered for resting and stress (3 min 30% maximal isometric handgrip) echocardiographic assessment of LV global function and mechanics. RESULTS: Male Sw displayed greater resting systolic and diastolic function compared with WP; however, both groups maintained stroke volume under high-pressure handgrip stress (Sw, ∆-4% ± 12%; WP, ∆-1% ± 13%, P = 0.11). There were no differences between female Sw and WP resting LV function, but Sw demonstrated greater function over AS. During isometric handgrip, all female sport athletes maintained stroke volume (Sw, ∆3% ± 16%; WP, ∆-10% ± 11%; AS, ∆-2% ± 14%, P = 0.46), but WP had improved apical rotation (∆1.7° ± 4.5°), which was reduced in AS (∆-3.1° ± 4.5°) and maintained in Sw (∆-0.5° ± 3.8°, P = 0.04). Unlike Sw and WP, AS displayed a unique maintenance of early filling velocity during handgrip exercise (Sw, ∆-3.5 ± 14.7 cm·s-1; WP, ∆-15.1 ± 10.8 cm·s-1; AS, ∆1.5 ± 15.3 cm·s-1, P = 0.02). CONCLUSIONS: Among male athletes, Sw display primarily volume-based functional adaptations distinct from the mixed volume-pressure adaptations of WP; however, both groups can maintain stroke volume with increased afterload. Female Sw and WP do not demonstrate sport-specific differences like males, perhaps owing to sex differences in adaptation, but have greater volume-based adaptations than AS. Lastly, AS display unique functional adaptations that may be driven by elevated pressures under low-volume conditions.