The efficacy of weekly and bi-weekly heat training to maintain the physiological benefits of heat acclimation

ObjectivesTo examine the efficacy of weekly and bi-weekly heat training to maintain heat acclimatization (HAz) and heat acclimation (HA) for 8 weeks in aerobically trained athletes.DesignRandomized, between-group.MethodsTwenty-four males (mean [m ± standard deviation [sd]; (age, 34 ± 12 y; body mass, 72.6 ± 8.8 kg, VO_2peak, 57.7 ± 6.8 mL·kg^?1·min^?1) completed five trials (baseline, following HAz, following HA (HAz + HA), four weeks into heat training [HT_WK4], and eight weeks into HT [HT_WK8] that involved 60 min of steady-state exercise (59.1 ± 1.8% vVO_2peak) in an environmental laboratory (wet bulb globe temperature [WBGT], 29.6 ± 1.4 °C) on a motorized treadmill. Throughout exercise, heart rate (HR) and rectal temperature (T_rec) were recorded. Following HAz + HA, participants were assigned to three groups: control group (HT₀), once per week heat training (HT₁), and twice per week heat training (HT₂). HT involved heated exercise (WBGT, 33.3 ± 1.3 °C) to achieve hyperthermia (38.5–39.75 °C) for 60 min. Repeated measures ANOVAs were used to determine differences.ResultsHAz + HA resulted in significant improvements in HR (p < 0.001) and T_rec (p < 0.001). At HT_WK8, HR was significantly higher in HT₀ (174 ± 22 beats?min^?1) compared to HT₂ (151 ± 17 beats?min^?1, p < 0.023), but was not different than HT₁ (159 ± 17 beats?min^?1, p = 0.112). There was no difference in % change of T_rec from post-HAz + HA to HT_WK4 (0.6 ± 1.3%; p = 0.218), however, HT_WK8 (1.8 ± 1.4%) was significantly greater than post-HAz + HA in HT₀ (p = 0.009).ConclusionsBi-weekly HT provided clear evidence for the ability to maintain physiological adaptions for 8 weeks following HA.     

Exercise heat acclimation and post-exercise hot water immersion improve resting and exercise responses to heat stress in the elderly

ObjectivesTo investigate the efficacy of heat acclimation (HA) in the young (Y_EX) and elderly (E_EX) following exercise-HA, and the elderly utilising post-exercise hot water immersion HA (E_HWI).DesignCross-sectional study.MethodTwenty-six participants (Y_EX: n = 11 aged 22 ± 2 years, E_EX: n = 8 aged 68 ± 3 years, E_HWI: n = 7 aged 73 ± 3 years) completed two pre-/post-tests, separated by five intervention days. Y_EX and E_EX exercised in hot conditions to raise rectal temperature (T_rec) ≥38.5 °C within 60 min, with this increase maintained for a further 60 min. E_HWI completed 30 min of cycling in temperate conditions, then 30 min of HWI (40 °C), followed by 30 min seated blanket wrap. Pre- and post-testing comprised 30 min rest, followed by 30 min of cycling exercise (3.5 W·kg⁻¹ Ḣ_prod), and a six-minute walk test (6MWT), all in 35 °C, 50% RH.ResultsThe HA protocols did not elicit different mean heart rate (HR), T_rec, and duration T_rec ≥ 38.5 °C (p > 0.05) between Y_EX, E_EX, and E_HWI groups. Resting T_rec, peak skin temperature, systolic and mean arterial pressure, perceived exertion and thermal sensation decreased, and 6MWT distance increased pre- to post-HA (p < 0.05), with no difference between groups. Y_EX also demonstrated a reduction in resting HR (p < 0.05). No change was observed in peak T_rec or HR, vascular conductance, sweat rate, or thermal comfort in any group (p > 0.05).ConclusionsIrrespective of age or intervention, HA induced thermoregulatory, perceptual and exercise performance improvements. Both exercise-HA (E_EX), and post-exercise HWI (E_HWI) are considered viable interventions to prepare the elderly for heat stress.     

Concentric not eccentric cycling sprint intervals acutely impair balance and jump performance in healthy active young adults: A randomized controlled cross-over study

IntroductionModerate aerobic, high-intensity and sprint running or cycling training can transiently impair postural control. However, the acute effects of modified sprint interval training (mSIT) at different muscle working modes have not yet been examined. Thus, this study aimed at investigating acute effects of time-matched eccentric (ECC) versus concentric mSIT cycling session (CON) on jumping and functional balance performance.MethodsTwenty-five healthy and active males (30.0 ± 6.0 years; 80.1 ± 9.1 kg; V̇O_2max: 64.2 ± 7.9 mL kg⁻¹ min⁻¹) were enrolled in this acute randomized controlled crossover trial. Counter-Movement-Jump (CMJ) and functional balance testing (Y-Balance-Test composite score [YBT_CS]; Posturomed total distance: Posturomed_TD) were assessed as primary outcomes before, and immediately after cessation of ECC and CON (10 × 10 s maximum sprints and 50 s of active recovery).ResultsA significant mode × time interaction effect for CMJ (F = 9.620, p = 0.005, η_p² = 0.29) was observed. Subsequent post-hoc testing revealed significant moderate reductions in jumping height after CON (0.31 ± 0.06 vs. 0.27 ± 0.06m; p = 0.004, SMD = 0.59), whilst ECC remained unchanged. YBT_CS (mode × time interaction: F = 6.880, p = 0.015, η_p² = 0.22) showed small but significant balance impairments after CON (0.964 ± 0.068 vs. 0.960 ± 0.063 AU; p = 0.009, SMD = 0.28) and did not significantly change after ECC. Although large significant interaction effects (p = 0.029, η_p² = 0.18) were observed for Posturomed_TD, follow up post-hoc testing did not reveal relevant pre-post differences, neither for ECC nor CON.ConclusionBoth functional balance and jumping performance are deteriorated after acute concentric but not eccentric mSIT cycling. Although higher pedal forces at lower perceived efforts and heart rates during eccentric mSIT were observed, it seems that the cardiocirculatory demanding CON session elicited more pronounced balance and jump performance impairments than eccentric cycling.     

Men's lacrosse protective equipment increases strain during exercise in the heat

ObjectivesThe purpose of this study was to determine thermoregulatory and cardiovascular effects of wearing men's lacrosse protective equipment during simulated lacrosse activities in the heat.DesignWe conducted a randomized, controlled, crossover study.MethodsThirteen healthy men (22 ± 3 y, 76.2 ± 8.9 kg, 181 ± 6 cm, 16.06 ± 6.16% body fat) completed two matched exercise trials in the heat (WBGT: 25.5 ± 0.8 °C). In randomized order, participants donned full men's lacrosse equipment (helmet, shoulder/elbow pads, and gloves) in one trial while the other included no equipment. Participants completed a topography body scan to determine specific body surface area covered with equipment. Rectal temperature (T_re), heart rate (HR), and mean weighted skin temperature (T_sk) were measured throughout trials. Whole body sweat rate was assessed for trial comparisons.ResultsThe equipment covered 32.62 ± 2.53% body surface area in our participants. Post-exercise T_re was significantly greater with equipment (39.36 ± 0.04 °C) compared to control (38.98 ± 0.49 °C; p = .007). The overall rate of rise of T_re was significantly greater with equipment (0.043 ± 0.015 °C·min⁻¹) compared to control (0.031 ± 0.008 °Cmin⁻¹; p = .041). Regardless of time point, HR and T_sk were significantly elevated with equipment compared to control trial (p ≤ .026). Sweat rates were elevated with equipment (1.76 ± 0.74 L·h⁻¹) compared to shorts and t-shirt (1.13 ± 0.26 L·h⁻¹), but this difference was not significant (p = .058).ConclusionsOur data indicate impairments in heat dissipation and increased cardiovascular strain imposed by men's lacrosse equipment.     

Effects of mild heat exposure on fatigue responses during two sets of repeated sprints matched for initial mechanical output

ObjectivesWe examined whether mild heat exposure alters performance, perceptual responses and neural drive to the quadriceps during two sets of repeated sprints matched for initial mechanical output.DesignRepeated measures.MethodsTwelve males performed 10 × 6-s sprints (recovery = 30 s), followed 6 min later by 5 × 6-s sprints (recovery = 30 s) in either COOL (24 °C/30% rH) or HOT (35 °C/40% rH) conditions. Subsequently, two sets of five consecutive sprints matched for initial mechanical output were compared.ResultsOn the basis of peak power, performance in sprint 2 was not significantly different to sprint 11 in both conditions (p ≥ 0.32). Average peak power across the five sprints compared (i.e., sprints 2–6 and 11–15, respectively) was 2.6 ± 3.4% higher in HOT compared to COOL (p = 0.025). Electromyographic activity (root mean square value) of the vastus lateralis muscle remained unchanged. Core (sprints 2–6: 37.85 ± 0.21 vs. 37.53 ± 0.19 °C, sprints 11–15: 38.26 ± 0.33 vs. 37.89 ± 0.24 °C; p < 0.001) and skin (sprints 2–6: 36.21 ± 0.29 vs. 30.72 ± 0.52 °C, sprints 11–15: 36.37 ± 0.28 vs. 30.99 ± 0.55 °C; p < 0.001) temperatures were overall higher in HOT compared to COOL. Heart rate, thermal sensation and comfort were significantly elevated in HOT compared to COOL (p ≤ 0.02), irrespective of sprint number.ConclusionsWhen two sets of repeated sprints were matched for initial mechanical output, performance was enhanced with mild heat exposure. This occurred despite higher thermal, cardiovascular, and perceptual strain, and without alterations in quadriceps neural drive.     

Assessing the impact of brachytherapy boost and androgen deprivation therapy on survival outcomes for patients with unfavorable intermediate-risk prostate cancer patients treated with external beam radiotherapy

BACKGROUNDCurrent recommendations regarding radiotherapy treatment for unfavorable intermediate-risk prostate cancer (UIR-PCa) include external beam radiotherapy (EBRT) ± brachytherapy boost (BT) ± androgen deprivation therapy (ADT). The ideal radiotherapy treatment approach for UIR-PCa has not been well-defined. We hypothesized that EBRT+BT±ADT is associated with improved overall survival (OS) relative to EBRT±ADT in men with UIR-PCa.MATERIALS AND METHODSThe National Cancer Database (NCDB) was used to retrospectively identify 32,246 men diagnosed between 2004 and 2015 with UIR-PCa who received EBRT (n = 13,265), EBRT+ADT (n = 13,123), EBRT+BT (n = 3440), or EBRT+BT+ADT (n = 2418). OS was the primary outcome. Inverse probability of treatment weighting was used to adjust for covariable imbalances and weight-adjusted multivariable analysis using Cox regression modeling was used to compare OS hazard ratios.RESULTSMedian follow-up was 60 months (range: 3–168 months). EBRT+ADT correlated with improved OS relative to EBRT alone on multivariable analysis (Hazard Ratio (HR): 0.92, [95% Confidence Interval: 0.87–0.98], p = 0.005). Compared to EBRT+ADT, EBRT+BT (HR: 0.77 [0.69–0.85], p = 3 × 10^?7) and EBRT+BT+ADT (HR: 0.75 [0.67–0.83], p = 6 × 10^?8) were associated with improved OS. Eight-years OS for the EBRT+ADT versus EBRT+BT+ADT was 70% and 78% (p < 0.0001), which is similar to historical clinical trials (ASCENDE-RT 9-year OS: 74% vs. 78%, p = 0.29). Relative to EBRT+BT, EBRT+BT+ADT was not associated with improved OS (HR: 0.99 [0.87–1.11], p = 0.82).CONCLUSIONSIn a large retrospective cohort, the addition of brachytherapy to EBRT correlated with improved survival in men with UIR-PCa. Men receiving EBRT+ADT+BT had improved OS relative to EBRT+ADT. The addition of ADT to EBRT, but not to EBRT+BT, correlated with improved OS.     

Potential relationship between passive plantar flexor stiffness and sprint performance in sprinters

ObjectiveTo investigate the relationship between passive planter flexor stiffness and sprint performance in sprinters.DesignCross-sectional study.ParticipantsFifty well-trained male sprinters (age: 20.7 ± 1.9 years, height: 175.6 ± 4.9 cm, weight: 66.7 ± 5.1 kg) were participated in this study. Their best personal times in a 100-m sprint ranged from 10.22 to 11.86 s (mean, 11.12 ± 0.43 s).MethodsPassive stiffness of the plantar flexors measured using a dynamometer system. Passive stiffness during passive dorsiflexion was calculated from the slope of the linear portion of the torque-angle curve.ResultsPlantar flexor passive stiffness was significantly correlated with personal best 100-m sprint time (r = −0.334, P = 0.018).ConclusionThe present findings suggest that although the relationship between plantar flexor passive stiffness and personal best 100-m sprint time was relatively minimal, a higher plantar flexor passive stiffness may be a potential factor for achieving superior sprint performance in sprinters. Therefore, in the clinical setting, measurement of passive planter flexor stiffness may be useful for assessing sprint performance.     

Sex differences in the Buffalo Concussion Treadmill Test in adolescents with acute sport-related concussion

ObjectivesThe Buffalo Concussion Treadmill Test (BCTT) is a safe and validated tool to assess exercise tolerance after sport-related concussion (SRC). Sex differences may affect the interpretation of this systematic exertion test in the concussed population, which is important for clinicians. The purpose of this study was to examine sex differences in BCTT performance in adolescents with acute SRC.DesignProspective cohort.MethodsMale (n = 103, 15.3 ± 2 years) and female (n = 87, 15.1 ± 2 years) adolescents with SRC performed the BCTT within 10 days of injury. Heart rate (HR), HR threshold (HRt), Delta HR (difference between resting HR and HRt), symptom severity on Visual Analog Scale (VAS) and symptoms exacerbated on the BCTT were collected and compared.ResultsMales had lower resting HR (M: 70.9 ± 12 vs F: 75.7 ± 13 bpm, p < 0.01) and reached a lower HRt than females (M: 134.7 ± 23 vs F: 141.5 ± 25 bpm, p = 0.05). Sexes did not differ on Delta HR (M: 63.8 ± 26 vs F: 65.9 ± 24 bpm, p = 0.57), total treadmill time (M: 9.3 ± 5 vs F: 8.4 ± 4 min, p = 0.20), maximum VAS (M: 5.0 ± 2 vs F: 5.4 ± 2, p = 0.18) or incidence of a change in VAS (M: 91% vs F: 94%, p = 0.43) on the BCTT.ConclusionsAlthough males may reach symptom exacerbation at a slightly lower mean HRt than females on the BCTT within 10 days of SRC, the BCTT provides comparable information and both sexes reach symptom exacerbation at similar Delta HR.     

Évolution du pouls d'oxygène durant 4 jours d'exercices prolongés

Summary – The aim of the study was to evaluate the adaptative cardiodynamic adjustment to 4 days of prolonged exercises by the alterations of oxygen pulse and to examine the role of plasma volume (PV) in this adaptative response.Methods and results – Thirty healthy males (aged 24 ± 2 yrs) exercised 5 h per day on cycle ergometer alternately with treadmill, at moderate intensity (58–63 % VO_2max). From the 1st to the 4th day, oxygen pulse was increased by 3 ± 2 ml O₂.beat^–1 (cycle p < 0.0001) and 1 ± 1 (treadmill, p = 0.02). Heart rate (HR) decreased (14 ± 4 ± beats min^–1, cycle p < 0.0001 and 10 ± 4, treadmill p = 0.001) since VO₂, external mechanical output and running speed were unchanged. The decrease in HR is significantly correlated with PV expansion (+ 8.5 ± 4.7 %) (p = 0.02, r² = 0.403).Conclusion – PV expansion is an important factor in cardiac adaptation to prolonged and repeated exercises. Oxygen pulse drift must be taken into account for exercise intensity and energy expenditure calculation to avoid under estimation.     

Physical and physiological demands of U-19 basketball refereeing: Aerobic and anaerobic demands

Objectives: This study aimed to examine the physical and physiological demands of basketball refereeing.

Methods: 16 elite-level basketball referees were studied during U-19 basketball games (n=8) for time-motion analyses, exercise heart rates (HR) and blood lactate concentration [La]. Game activities were considered as time spent and distance covered in five locomotors activities (standing, walking, jogging, running and sprinting).

Results: Referees spent more time (p<0.01) walking (63.72±2.02 min) than jogging (3.10±0.29 min), running (4.24±0.46 min) and sprinting (1.69±0.24 min). Referees covered more distance (p<0.01) walking than jogging, running and sprinting across the quarters (Q). Mean HR (74.89±6.86 %HR_max) was not significantly different across the game Q (Q1 to Q4) and halves. [La] did not show significant changes (p=0.221) when comparing the half-time (4.30±3.92 mmol.L^?1) and the end of the game (6.70±4.90 mmol.L^?1).

Conclusion: In light of this study, we conclude that U-19 basketball refereeing is a moderate intensity activity where referees spent 81% of total game time at low-intensity with bouts of high-intensity activities throughout the game.     

Vascular and oxygenation responses of local ischemia and systemic hypoxia during arm cycling repeated sprints

ObjectivesThe purpose of this study was to investigate the acute vascular and oxygenation responses to repeated sprint exercise during arm cycling with either blood flow restriction (BFR) or systemic hypoxia alone or in combination.DesignThe study design was a single-blinded repeated-measures assessment of four conditions with two levels of normobaric hypoxia (400 m and 3800 m) and two levels of BFR (0% and 45% of total occlusion).MethodsSixteen active participants (eleven men and five women; mean ± SD; 26.4 ± 4.0 years old; 73.8 ± 9.8 kg; 1.79 ± 0.07 m) completed 5 sessions (1 familiarization, 4 conditions). During each test visit, participants performed a repeated sprint arm cycling test to exhaustion (10 s maximal sprints with 20 s recovery until exhaustion) to measure power output, metabolic equivalents, blood flow, as well as oxygenation (near-infrared spectroscopy) of the biceps brachii muscle tissue.ResultsRepeated sprint performance was decreased with both BFR and systemic hypoxia conditions. Greater changes between minimum-maximum of sprints in total hemoglobin concentration (Δ[tHb]) were demonstrated with BFR (400 m, 45% and 3800 m, 45%) than without (400 m, 0% and 3800 m, 0%) (p < 0.001 for both). Additionally, delta tissue saturation index (ΔTSI) decreased more with both BFR conditions than without (p < 0.001 for both). The absolute maximum TSI was progressively reduced with both BFR and systemic hypoxia (p < 0.001).ConclusionsBy combining high-intensity, repeated sprint exercise with BFR and/or systemic hypoxia, there is a robust stimulus detected by increased changes in blood perfusion placed on specific vascular mechanisms, which were more prominent in BFR conditions.     

Mild hypohydration impairs cycle ergometry performance in the heat: A blinded study

The aim of the present study was to observe the effect of mild hypohydration on exercise performance with subjects blinded to their hydration status. Eleven male cyclists (weight 75.8 ± 6.4 kg, VO_2peak: 64.9 ± 5.6 mL/kg/min, body fat: 12.0 ± 5.8%, Power_max: 409 ± 40 W) performed three sets of criterium‐like cycling, consisting of 20‐minute steady‐state cycling (50% peak power output), each followed by a 5‐km time trial at 3% grade. Following a familiarization trial, subjects completed the experimental trials, in counter‐balanced fashion, on two separate occasions in dry heat (30°C, 30% rh) either hypohydrated (HYP) or euhydrated (EUH). In both trials, subjects ingested 25 mL of water every 5 minutes during the steady‐state and every 1 km of the 5‐km time trials. In the EUH trial, sweat losses were fully replaced via intravenous infusion of isotonic saline, while in the HYP trial, a sham IV was instrumented. Following the exercise protocol, the subjects’ bodyweight was changed by ?0.1 ± 0.1% and ?1.8 ± 0.2% for the EUH and HYP trial, respectively (P < 0.05). During the second and third time trials, subjects averaged higher power output (309 ± 5 and 306 ± 5 W) and faster cycling speed (27.5 ± 3.0 and 27.2 ± 3.1 km/h) in the EUH trial compared to the HYP trial (Power: 287 ± 4 and 276 ± 5 W, Speed: 26.2 ± 2.9 and 25.5 ± 3.3 km/h, all P < 0.05). Core temperature (T_re) was higher in the HYP trial throughout the third steady‐state and 5‐km time trial (P < 0.05). These data suggest that mild hypohydration, even when subjects were unaware of their hydration state, impaired cycle ergometry performance in the heat probably due to greater thermoregulatory strain.     

Effect of hydration state on testosterone and cortisol responses to training-intensity exercise in collegiate runners

Exercise intensity powerfully influences testosterone, cortisol, and testosterone : cortisol ratio (T:C) responses to endurance exercise. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to endurance exercise and training. This study examined the effect of running intensity on testosterone, cortisol, and T : C when exercise was initiated in a hypohydrated state. Nine male collegiate runners (age = 20 +/- 0 y, height = 178 +/- 2 cm, mass = 67.0 +/- 1.8 kg, body fat % = 9.8 +/- 0.7 %, V.O2max = 65.7 +/- 1.1 ml.kg (-1).min (-1)) completed four 10-min treadmill runs differing in pre-exercise hydration status (euhydrated, or hypohydrated by 5 % of body mass) and exercise intensity (70 % or 85 % V.O2max). Body mass, urine osmolality, and urine-specific gravity documented fluid balance; blood samples drawn pre-, immediately post-, and 20 min post-exercise were analyzed for testosterone, cortisol, and T : C. Except for heart rate measured during the 70 % V.O2max trials, heart rate, V.O2, and plasma lactate were similar between euhydrated and hypohydrated conditions for a given intensity, suggesting hypohydration did not measurably increase the physiological stress of the exercise bouts. Furthermore, hydration state had no measurable effect on testosterone concentrations before, during, or after exercise at either intensity. Regardless of exercise intensity, cortisol concentrations were greater during hypohydration than euhydration pre-exercise and 20 min post-exercise. Additionally, T : C was significantly lower 20 min post-exercise at 70 % V.O2max when subjects were initially hypohydrated (T : C = 0.055) versus euhydrated (T : C = 0.072). These findings suggest that depending on exercise intensity, T : C may be altered by hydration state, therefore influencing the balance between anabolism and catabolism in response to running exercise performed at typical training intensities.     

The use of inertial measurement units to assess gait and postural control following concussion

BackgroundImpairments in gait and balance function are typical after concussion. There is evidence that these neuromuscular deficits persist past the typical time of symptom resolution. The ability to quantify these changes in gait and balance may provide useful information when making return to play decisions in clinical settings.Research QuestionAre changes in gait function and postural control evident across the course of a concussion management program?MethodsA retrospective analysis of a convenience sample of 38 patients who were seen for concussion between October 2017 and May 2019 was performed. Gait and balance measures were assessed at their initial clinic visit post-injury and at their clearance visit using inertial measurement units. During dual-task walking trials, the medial-lateral motion of the center of mass and gait velocity were measured. Postural sway complexity and jerk index were measured during both eyes-open and eyes-closed balance trials.ResultsPaired samples t-tests and Wilcoxon signed rank tests were used to determine whether statistically significant changes occurred for the gait and balance variables, respectively. Medial-lateral sway decreased (4.4 ± 1.3 cm to 4.0 ± 1.2 cm, p = 0.018) and gait velocity increased (0.78 ± 0.23 m/s to 0.91 ± 0.18 m/s, p < 0.001) from initial to clearance testing. Jerk index decreased (6.41 ± 11.06 m²/s⁵ to 5.73 ± 4.28 m²/s⁵, p = 0.031) and (11.87 ± 26.42 m²/s⁵ to 7.87 ± 8.38 m²/s⁵, p = 0.003) from initial to clearance testing for the eyes-open and eyes-closed conditions, respectively. Complexity index increased (2.38 ± 1.08–2.86 ± 0.72, p = 0.010) from initial to clearance testing for the eyes-closed condition. There was no change in complexity index for the eyes-open condition.SignificanceThese preliminary results support the potential use of measures of gait and postural control to assess recovery following a concussion in a clinical setting.     

Fast or slow start? The role of running strategies in triathlon

ObjectivesTo investigate the impact of fast-start, steady or slow-start strategies of the running fraction in sprint triathlon on oxygen consumption, perception of fatigue and blood lactate.DesignThirteen male triathletes (age; 36.4 ± 10.8 yy, height 174.8 ± 7.9 cm, body mass 70.6 ± 11.1 kg; V’O_2max 62.4 ± 8.9 ml min^?1 kg^?1; mean ± SD) attended the laboratory five times in order to complete two incremental tests and three subsequent cycle-run sessions.MethodsThree experimental randomized sessions with different effort distribution were compared. The intensities of the 1st running kilometer were set at 95%, 100% and 105% of the second ventilatory threshold for slow, continuous and fast start protocol respectively. Measurement of ventilatory variables, blood lactate and ratings of perceived exertion were collected throughout all sessions.ResultsA meaningful difference was found between the slow versus fast start protocol in V’O₂ (SE = 0.58, P = 0.0005), BLa^? (SE = 0.21, P = 0.0097), HR (SE = 1.23, P = 0.0011) and RPE (SE = 2.83, P = 0.0047) values. No differences in-between protocols were found at the end of the running bout whatever the condition.ConclusionsDifferences in physiological parameters were found between protocols during the first kilometer, not at the end of exercise. The fast start appears to be more correct and useful for performance in racing setting and may be used as a strategy without impacting the remaining running bout in ecological setting.     

The relation between sprint power and road time trial performance in elite para-cyclists

ObjectivesWhilst cycling performance has been studied extensively, very little is known about the performance of para-cyclists. This study assessed the relation between sprint power and road time trial performance in elite para-cyclists, and whether this relation differed based on impairment type and type of bike used.DesignCross-sectional.MethodsDuring international para-cycling events, 168 athletes (88 bicycles, 17 tricycles, 56 recumbent handbikes and 7 kneeling handbikes) performed 20-s sport-specific sprint tests (mean power output (POmean) W), and their road time trial performance (average speed (km/h)) was taken from the official results. Multilevel regression models to assess the relation of sprint with time trial performance were composed for i. leg-cyclists: bicycle and tricycle and ii. arm-cyclists: recumbent- and kneeling handbike, adjusted for identified confounders. Furthermore, impairment type (categorized as i) muscle power/range of motion, ii) limb deficiency/leg length difference, and iii) coordination) and bike type were tested as effect modifiers.ResultsPOmean ranged from 303 ± 12 W for recumbent handcyclists to 482 ± 156 W for bicyclists. POmean was significantly related to time trial performance, for both leg-cyclists (β = 0.010, SE = 0.003, p < 0.01) and arm-cyclists (β = 0.029; SE = 0.005, p < 0.01), and impairment type and bike type were not found to be effect modifiers.ConclusionsSprint power was related to road time trial performance in all para-cyclists, with no differences found in this relation based on impairment type nor bike type. For those competing on a bicycle, tricycle, recumbent- or kneeling handbike, sprint tests might therefore be useful to predict or monitor time trial performance.     

The effects of pre- and per-cooling interventions used in isolation and combination on subsequent 15-minute time-trial cycling performance in the heat

ObjectivesTo investigate the effects of pre- and per-cooling interventions on subsequent 15-min time-trial (TT) cycling performance in the heat.DesignRandomized cross-over design.MethodsNine male athletes completed four experimental trials in the heat (40 °C, 50% rh): no-cooling (CON); warm-up per-cooling (PER: neck-cooling collar applied during the preload); pre-cooling (PRE: 30 min of cold water (22 °C) immersion [CWI]); and pre- and per-cooling combined (PRE + PER). In each trial, participants completed a 45-min preload exercise (50% V̇O_2peak), followed by a 15-min TT. Physiological (rectal [T_re], skin [T_sk], and neck [T_neck] temperature, and heart rate [HR]) and perceptual data (ratings of perceived exertion [RPE], thermal comfort [TC] and thermal sensation [TS]) were measured throughout.ResultsT_re and T_sk were lower in PRE and PRE + PER at the start of the preload (p < 0.001). T_re remained lower throughout the preload following CWI although these differences were no longer present at the start of the TT (p = 0.22). T_neck was lowered throughout in PER and PRE + PER (p < 0.001). No other physiological or perceptual differences were observed at the start or end of the preload or TT. Participants covered a similar TT distance in all trials (15.7–15.9 km, p = 0.77).ConclusionsPre-cooling induced thermoregulatory benefits for ~45 min and perceptual benefits for the same duration when supplemented with per-cooling. Neck per-cooling offered no such benefits when used in isolation. Neither pre- nor per-cooling, in isolation or combination, improved subsequent 15-min cycling time-trial performance in well-trained participants in the heat (40 °C).     

Morning resistance exercise and cricket-specific repeated sprinting each improve indices of afternoon physical and cognitive performance in professional male cricketers

ObjectivesTo compare two modes (general and cricket-specific) of morning priming exercise on afternoon physical and cognitive performance, and subjective readiness to perform in professional male cricketers.DesignRandomised, crossover, counterbalanced.MethodsOn three occasions, 16 professional men's cricketers completed afternoon tests of countermovement jump height, cricket-specific sprint performance (running between the wickets, two runs), cognitive function (Stroop test, time taken), and subjective readiness to perform. Control (CON; passive rest), lower-body resistance exercise priming (LIFT; trap bar deadlifts, 6 × 4 repetitions up to 85% of one repetition maximum), or cricket-specific running priming (RUN; 6 × 35.36 m sprints including a 180° change of direction) interventions were implemented 5.5 h before testing.ResultsAfternoon sprint times were faster in RUN (?0.04 s, p = 0.013) and LIFT (?0.07 s, p < 0.001) versus CON, and faster in LIFT than RUN (?0.03 s, p = 0.032). Jump height (+1.1 cm, p = 0.021) and cognitive function (?3.83 s, p = 0.003) were greater in LIFT than CON, whilst RUN outperformed CON for cognition (?2.52 s, p = 0.023). Although perceived readiness was not influenced by trial (p > 0.05), players reported favourable responses on the “aggression” subscale in LIFT relative to CON (+1 arbitrary unit, p = 0.022).ConclusionsBoth general (lower-body resistance exercise) and cricket-specific (simulated running between wickets) morning priming are effective match-day strategies to improve afternoon markers of physical and cognitive performance in professional men's cricketers. Practitioners may thus be afforded flexibility in situations where resistance exercise is not feasible on the morning of a match.     

Fluid balance,thermoregulation and sprint and passing skill performance in female soccer players

Ten females performed 90 min of the Loughborough Intermittent Shuttle Test (LIST) on two occasions separated by 7 days. Water [3 mL/kg body mass (BM)] was provided every 15 min during exercise (FL); no fluid was given in the other trial (NF). Participants performed the Loughborough Soccer Passing Test (LSPT) before and every 15 min during the LIST. Core temperature (T_c) was measured throughout using ingestible temperature sensors. Heart rate (HR), blood lactate ([La^?]) and ratings of perceived exertion (RPE) were collected at regular intervals during exercise. Participants experienced greater BM loss in NF (2.2 ± 0.4%) than FL (1.0 ± 0.4%; P<0.001). Sprint performance deteriorated by 2.7% during exercise (P<0.001) but there was no difference between trials (P=0.294). No significant differences in LSPT performance were detected between trials (P=0.31). T_c was higher during exercise in NF and was 38.6 ± 0.3 °C (NF) and 38.3 ± 0.3 °C (FL; P<0.01) after 90 min. HR (P<0.001), [La^?] (P<0.01) and RPE (P=0.009) were higher during exercise in NF. Ingesting water during a 90‐min match simulation reduces the mild dehydration seen in female soccer players when no fluid is consumed. However, there was no effect of fluid ingestion on soccer passing skill or sprint performance.     

Dosimetric comparison of TomoDirect,helical tomotherapy,VMAT, and ff-IMRT for upper thoracic esophageal carcinoma

BackgroundThe new TomoDirect (TD) modality offers a nonrotational option with discrete beam angles. We aim to compare dosimetric parameters of TD, helical tomotherapy (HT), volumetric-modulated arc therapy (VMAT), and fixed-field intensity-modulated radiotherapy (ff-IMRT) for upper thoracic esophageal carcinoma (EC).MethodsTwenty patients with cT2-4N0-1M0 upper thoracic esophageal squamous cell carcinoma (ESCC) were enrolled. Four plans were generated using the same dose objectives for each patient: TD, HT, VMAT with a single arc, and ff-IMRT with 5 fields (5F). The prescribed doses were used to deliver 50.4 Gy/28F to the planning target volume (PTV50.4) and then provided a 9 Gy/5F boost to PTV59.4. Dose-volume histogram (DVH) statistics, dose uniformity, and dose homogeneity were analyzed to compare treatment plans.ResultsFor PTV59.4, the D₂, D₉₈, D_mean, and V_100% values in HT were significantly lower than other plans (all p < 0.05), and those in TD were significantly lower than VMAT and ff-IMRT (all p < 0.05). However, there was no significant difference in the D₂ and D_mean values between VMAT and ff-IMRT techniques (p > 0.05). The homogeneity index (HI) differed significantly for the 4 techniques of TD, HT, VMAT, and ff-IMRT (0.03 ± 0.01, 0.02 ± 0.01, 0.06 ± 0.02, and 0.05 ± 0.01, respectively; p < 0.001). The HI for TD was similar to HT (p = 0.166), and had statistically significant improvement compared to VMAT (p < 0.001) and ff-IMRT (p = 0.003). In comparison with the 4 conformity indices (CIs), there was no significant difference (p > 0.05). For PTV50.4, the D₂ and D_mean values in HT were significantly lower than other plans (all p < 0.05), and those in TD were significantly lower than VMAT and ff-IMRT (all p < 0.05). However, there was no significant difference in the D₂ and D_mean values between VMAT and ff-IMRT techniques (p > 0.05). No D₉₈ and V_100% parameters differed significantly among the 4 treatment types (p > 0.05). HT plans were provided for statistically significant improvement in HI (0.03 ± 0.01) compared to TD plans (0.05 ± 0.01, p = 0.003), VMAT (0.08 ± 0.03, p < 0.001), ff-IMRT (0.08 ± 0.01, p < 0.001). The HI revealed that TD was superior to VMAT and ff-IMRT (p < 0.05). The CI differed significantly for the 4 techniques of TD, HT, VMAT, and ff-IMRT (0.59 ± 0.10, 0.69 ± 0.11, 0.64 ± 0.09, and 0.64 ± 0.11, respectively; p = 0.035). The best CI was yielded by HT. We found no significant difference for the V₅, V₁₀, V₁₅, V₃₀, and the mean lung dose (MLD) among the 4 techniques (all p > 0.05). However, the V₂₀ differed significantly among TD, HT, VMAT, and ff-IMRT (21.50 ± 7.20%, 19.50 ± 5.55%, 17.65 ± 5.45%, and 16.35 ± 5.70%, respectively; p = 0.047). Average V₂₀ for the lungs was significantly improved by the TD plans compared to VMAT (p = 0.047), and ff-IMRT (p = 0.008). The V₅ value of the lung in TD was 49.30 ± 13.01%, lower than other plans, but there was no significant difference (p > 0.05). The D₁ of the spinal cord showed no significant difference among the 4 techniques (p = 0.056).ConclusionsAll techniques are able to provide a homogeneous and highly conformal dose distribution. The TD technique is a good option for treating upper thoracic EC involvement. It could achieve optimal low dose to the lungs and spinal cord with acceptable PTV coverage. HT is a good option as it could achieve quality dose conformality and uniformity, while TD generated superior conformality.