The effect of pre-cooling or per-cooling in athletes with a spinal cord injury: A systematic review and meta-analysis

ObjectivesFor individuals with a spinal cord injury, thermoregulatory challenges presented by the environment are amplified, increasing the risk of exertional heat illness. Thus, this systematic review and meta-analysis aims to quantify the effects of pre- and per-cooling on core temperature (T_c), skin temperature (T_sk) and thermal sensation in participants with spinal cord injury and assess the influence of lesion level on the effects of cooling.DesignSystematic review with meta-analysis.MethodsOut of 2107 potential studies, 17 were identified via the inclusion criteria for a total of 145 research participants. A total of 12 studies were included in the primary analysis of T_c; 9 included in the analysis of T_sk; and 9 included in the analysis of thermal perceptions. 15 experimental conditions were included in the secondary analysis of lesion level on the effects of cooling.ResultsCooling reduced T_c (Hedges' g = 0.44; 95% confidence intervals 0.16, 0.72; p < 0.001), T_sk (Hedges' g = 1.11; 95% confidence intervals 0.56, 1.66; p < 0.002) and thermal sensation (Hedges' g = 0.60; 95% confidence intervals 0.27, 0.93; p < 0.001). Subgroup analysis revealed pre-cooling (Hedges' g = 0.92), reduced T_c to a greater extent than per-cooling (Hedges' g = 0.25; p = 0.020). The effect of lesion level on the effectiveness of cooling on T_c had a moderate, positive association (r = 0.518, p = 0.048).ConclusionPre-cooling may reduce T_c to a greater extent than per-cooling during subsequent exercise. Pre- and per-cooling can attenuate the increase in thermal strain in athletes with a spinal cord injury. The beneficial effects of cooling are greater in tetraplegic individuals.     

A comparison of heat acclimation by post-exercise hot water immersion and exercise in the heat

ObjectivesTo compare heat acclimation adaptations after three and six days of either post-exercise hot water immersion (HWI) or exercise-heat-acclimation (EHA) in recreationally active individuals.DesignRandomised, mixed model, repeated measures.MethodsPost-exercise HWI involved a daily 40-min treadmill-run at 65% V̇O_2peak in temperate conditions (19 °C, 45% RH) followed by HWI (≤40 min, 40 °C water; n = 9). Daily EHA involved a ≤60-min treadmill-run in the heat (65% V̇O_2peak; 33 °C, 40% RH; n = 9), chosen to elicit a similar endogenous thermal stimulus to HWI. A thermoneutral exercise intervention (TNE, 19 °C, 45% RH; n = 9), work-matched to EHA, was also included to determine thermoregulatory adaptations to daily exercise in temperate conditions. An exercise-heat-stress-test was performed before and after three and six intervention days and involved a 40-min treadmill-run and time-to-exhaustion (TTE) at 65% V̇O_2peak in the heat (33 °C, 40% RH).ResultsANCOVA, using baseline values as the covariate, revealed no interaction effects but significant group effects demonstrated that compared to EHA, HWI elicited larger reductions in resting rectal temperature (T_re; p = 0.021), T_re at sweating onset (p = 0.011), and end-exercise T_re during exercise-heat-stress (−0.47 °C; p = 0.042). Despite a similar endogenous thermal stimulus to HWI, EHA elicited a modest reduction in end-exercise T_re (−0.26 °C), which was not different from TNE (−0.25 °C, p = 1.000). There were no main effects or interaction effects for end-exercise T_sk, heart rate, physiological strain index, RPE, thermal sensation, plasma volume, or TTE (all p ≥ 0.154).ConclusionsCompared with conventional short-term exercise heat acclimation, short-term post-exercise hot water immersion elicited larger thermal adaptations.     

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.     

Does exertional heat stress impact gastrointestinal function and symptoms?

ObjectivesExertional-heat stress generates a thermoregulatory strain that exacerbates splanchnic hypoperfusion and sympathetic drive, but the effects on gastrointestinal function are poorly defined. The study aimed to determine the effects of exertional-heat stress on gastric myoelectrical activity, orocecal transit time (OCTT), and gastrointestinal symptoms (GIS).DesignRandomised cross-over study.MethodsEndurance runners (n = 16) completed 2 h of running at 60 % V?O_2max in 35 °C (HOT) and 22 °C (TEMP) ambient conditions. Surface electrogastrography (cEGG) was recorded pre- and post-exercise to determine gastric myoelectrical activity, a lactulose challenge was used to determine OCTT, and GIS were recorded using a modified visual analogue scale tool.ResultsPost-exercise T_re [HOT:38.8(38.5 to 39.0)°C and TEMP:38.1(37.8 to 38.4)°C] and Δ T_re [HOT:2.2(2.0 to 2.4)°C and TEMP:1.5(1.2 to 1.8)°C] was higher on HOT compared to TEMP (p < 0.001). Normal gastric myoelectrical cycle frequency reduced (p = 0.010) on HOT [? 11.7(? 20.8 to ? 2.6)%], but this decrease did not differ (p = 0.058) from TEMP [? 2.7(? 8.3 to 3.0)%]. Bradygastria increased post-exercise on both trials (HOT:11.3(2.3 to 20.4)%, p = 0.030; and TEMP:7.4(2.1 to 12.6)%, p = 0.009). OCTT did not differ between trials (p = 0.864) with transit response classified as very slow on both HOT (99(68 to 131)min) and TEMP (98(74 to 121)min). GIS incidence was higher on HOT (88 %) compared to TEMP (81 %), in accordance with greater total-GIS and upper-GIS severity (p = 0.005 and p = 0.033, respectively).ConclusionsRunning for 2 h at 60 % V?O_2max in either hot or temperate ambient conditions instigates perturbations in myoelectrical activity and OCTT, with GIS incidence and severity greater in hot conditions.     

The effect of warm-up on intermittent sprint performance and selected thermoregulatory parameters

ObjectivesTo investigate the effect of various warm-up intensities based upon individual lactate thresholds on subsequent intermittent sprint performance, as well as to determine which temperature (muscle; T_mu, rectal; T_re or body; T_b) best correlated with performance (total work, work and power output of the first sprint, and % work decrement).DesignNine male team-sport participants performed five 10-min warm-up protocols consisting of different exercise intensities on five separate occasions, separated by a week.MethodsEach warm-up protocol was followed by a 6 × 4-s intermittent sprint test performed on a cycle ergometer with 21-s of recovery between sprints. T_mu, T_re and T_b were monitored throughout the test.ResultsThere were no differences between warm-up conditions for total work (J kg^?1; P = 0.442), first sprint work (J kg^?1; P = 0.769), power output of the first sprint (W kg^?1; P = 0.189), or % work decrement (P = 0.136), respectively. Moderate to large effect sizes (>0.5; Cohen's d) suggested a tendency for improvement in every performance variable assessed following a warm-up performed at an intensity midway between lactate inflection and lactate threshold. While T_mu, T_re, T_b, heart rate, ratings of perceived exertion and plasma lactate increased significantly during the exercise protocols (P < 0.05), there were no significant correlations between T_mu, T_re, and T_b assessed immediately after each warm-up condition and any performance variable assessed.ConclusionsWarm-up performed at an intensity midway between lactate inflection and lactate threshold resulted in optimal intermittent sprint performance. Significant increases in T_mu, T_re and T_b during the sprint test did not affect exercise performance between warm-up conditions.     

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.     

A 2.5 min cold water immersion improves prolonged intermittent sprint performance

ObjectivesWe investigated if cold water immersion (CWI) affects exercise performance during a prolonged intermittent sprint test (IST), designed to mimic activity patterns of team-sports.DesignRandomized-crossover design.MethodsTen male team-sport players completed 3 IST protocols (two 40-min “halves” of repeated 2-min blocks consisting of a 8-s “all-out” sprint, 100-s active recovery and 12-s rest) on a cycle ergometer at normothermic conditions. Each “half” was separated by a 15 min recovery period of either: (i) passive rest, (ii) 5-min CWI at 8 °C (CWI-5) or (iii) 2.5-min CWI at 8 °C (CWI-2.5), in a random counterbalanced order.ResultsPhysical performance, core temperature (T_core) and heart rate were not different among conditions in the first half. In the passive rest trial, total work (TW) and peak power (PP) were lower during the second half (TW: 5.04 ± 1.11 kJ; PP: 929 ± 286 W) than the first half (TW: 5.66 ± 1.02 kJ; PP: 1009 ± 266 W); while TW and PP were not different between halves following CWI-5 (first half, TW: 5.34 ± 1.02 kJ, PP: 1016 ± 283 W; second half, TW: 5.19 ± 1.38 kJ; PP: 996 ± 318 W) and CWI-2.5 (first half, TW: 5.47 ± 1.19 kJ, PP: 966 ± 261 W; second half, TW: 5.25 ± 1.17 kJ; PP: 952 ± 231 W). T_core was lower until the 20^th minute of the second half after CWI-5 and CWI-2.5 compared with passive rest.ConclusionsA post-exercise 2.5–5-min CWI attenuates the reductions in prolonged sprint performance that occur in the second half of team sports, due, at least partly, to reductions in core temperature and associated increase in heat storage.     

Optimal cooling strategies for players in Australian Tennis Open conditions

Objectives

We compared the utility of four cooling interventions for reducing heat strain during simulated tennis match-play in an environment representative of the peak conditions possible at the Australian Open (45 °C, <10% RH, 475 W/m² solar radiation).

Usefulness of two-point Dixon T2-weighted imaging in thyroid-associated ophthalmopathy: comparison with conventional fat saturation imaging in fat suppression quality and staging performance

Objective:To compare the two-point Dixon T ₂ weighted imaging (T ₂WI) with conventional fat-sat T ₂WI in fat suppression (FS) quality and staging performance for patients with TAO.Methods:We enrolled 37 thyroid-associated ophthalmopathy (TAO) patients and 15 healthy controls who underwent both coronal two-point Dixon and fat-sat T ₂WI. Qualitative (overall imaging quality, FS uniformity) and quantitative [signal intensity ratio of extraocular muscle (EOM-SIR)] parameters were assessed between the two-point Dixon T ₂WI and fat-sat T ₂WI. Additionally, water fraction of intraorbital fat (IF-WF) was measured on Dixon image. Dixon-EOM-SIR, Fat-sat-EOM-SIR and Dixon-IF-WF values were compared between active and inactive TAO groups, and the diagnostic efficiency for the active phase were evaluated.Results:Two-point Dixon T ₂WI showed significantly higher overall image quality score, FS uniformity score as well as EOM-SIR value than fat-sat T ₂WI in both TAO and control groups (all p < 0.05). Active TAOs had significantly higher Dixon-EOM-SIR (p < 0.001), Fat-sat-EOM-SIR (p < 0.001) and Dixon-IF-WF (p = 0.001) than inactive TAOs. ROC curves analyses indicated that Dixon-EOM-SIR ≥3.32 alone demonstrated the highest staging sensitivity (75.0%). When integrating Dixon-EOM-SIR ≥3.32 and Dixon-IF-WF ≥0.09, improved staging efficiency and specificity could be achieved (area under the curve, 0.872; specificity, 97.1%).Conclusion:Compared with conventional fat-sat technique, two-point Dixon T ₂WI offers better image quality, as well as improved staging sensitivity and specificity for TAO. Dixon T ₂WI is suggested to be used to evaluate the patients with TAO in clinical practice.Advances in knowledge:Two-point Dixon T ₂WI offers better image quality than fat-sat T ₂WI. Dixon-EOM-SIR alone demonstrated the highest staging sensitivity. Combining with Dixon-IF-WF showed improved staging efficiency and specificity. Dixon T ₂WI is suggested to be used to evaluate TAO patients in clinical practice.     

Progressive hyperthermia elicits distinct responses in maximum and rapid torque production

ObjectivesTo investigate the effect of progressive whole-body hyperthermia on maximal, and rapid voluntary torque production, and their neuromuscular determinants.DesignRepeated measures, randomised.MethodsNine participants performed sets of neuromuscular assessments in HOT conditions (∼50 °C, ∼35% relative humidity) at rectal temperatures (T_re) of 37, 38.5 and 39.5 °C and in CON conditions (∼22 °C, ∼35% relative humidity) at a T_re of ∼37 °C and pre-determined comparative time-points. Electrically evoked twitch (single impulse) and octet (8 impulses at 300 Hz) responses were measured at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were measured during 3−5 s isometric maximal voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary isometric contractions from rest.ResultsAll neuromuscular variables were unaffected by time in CON. In HOT, MVT, normalised EMG at MVT and VA were lower at 39.5 °C compared to 37 °C (p < 0.05). Early- (0−50 ms) and middle- (50−100 ms) phase voluntary RTD were unaffected by increased T_re (p > 0.05), despite lower normalised EMG at T_re 39.5 °C (p < 0.05) in rapid contractions. In contrast, late-phase (100−150 ms) voluntary RTD was lower at 38.5 °C and 39.5 °C compared to 37 °C (p < 0.05) in HOT. Evoked twitch and octet RTD increased with increased T_re (p < 0.05).ConclusionsHyperthermia reduced late-phase voluntary RTD, likely due to reduced neural drive and the reduction in MVT. In contrast, early- and middle-phase voluntary RTD were unaffected by hyperthermia, likely due to the conflicting effects of reduced neural drive but faster intrinsic contractile properties.     

Quadriceps strength changes across the continuum of care in adolescent male and female athletes with anterior cruciate ligament injury and reconstruction

ObjectivesTo examine the quadriceps strength (QUADS) on the surgical (SURG) and non-surgical (Non-SURG) limbs in adolescent male and female athletes at pre-operative (PRE), 12 weeks post-operative (12WK), and return to sport (RTS) time points following ACL injury and reconstruction.DesignProspective cohort study design.SettingClinical Research Laboratory.Participants66 adolescent athletes.Main outcome measuresIsokinetic QUADS of the SURG and Non-SURG limbs at the PRE, 12WK, and RTS time points were assessed and compared between each time point.ResultsBoth male and female participants had significantly lower 12 WK QUADS in the SURG limb than the PRE QUADS, but the RTS QUADS was significantly greater than the 12WK QUAD (p < 0.05). However, only female participants had greater RTS QUADS as compared to the PRE QUADS (p < 0.001). For the Non-SURG limb, only male participants had a significant improvement over time (PRE vs RTS; p < 0.001).ConclusionAdolescent males and females differ in their QUADS recovery across the continuum of care following ACLR. Clinicians should consider this pattern of recovery when treating adolescent males and females.     

Comparison of the acute perceptual and blood pressure response to heavy load and light load blood flow restriction resistance exercise in anterior cruciate ligament reconstruction patients and non-injured populations

ObjectivesTo compare the acute perceptual and blood pressure responses to: 1) light load blood flow restriction resistance exercise (BFR-RE) in non-injured individuals and anterior cruciate ligament reconstruction (ACLR) patients; and 2) light load BFR-RE and heavy load RE (HL-RE) in ACLR patients.DesignBetween-subjects, partially-randomised.MethodsThis study comprised 3 groups: non-injured BFR-RE (NI-BFR); ACLR patients BFR-RE (ACLR-BFR); ACLR patients HL-RE (ACLR-HL). NI-BFR and ACLR-BFR performed 4 sets (30, 15, 15, 15 reps, total = 75 reps, 30s inter-set rest) of unilateral leg press exercise at 30% 1RM with continuous BFR at 80% limb occlusive pressure. ACLR-HL performed 3 × 10 reps (Total = 30 reps, 30s inter-set rest) of unilateral leg press exercise at 70% 1RM. Perceived exertion (RPE), muscle pain, knee pain and pre- and 5-min post-exercise blood pressure were measured.ResultsRPE was higher in ACLR-BFR compared to NI-BFR (p < 0.05). Muscle pain was higher in NI-BFR and ACLR-BFR compared to ACLR-HL (p < 0.05). Knee pain was lower in ACLR-BFR compared to ACLR-HL (p < 0.01). There were no differences in blood pressure.ConclusionThese responses to BFR exercise may not limit application and favourably influence knee pain throughout ACLR rehabilitation training programmes. These findings can help inform practitioners' decisions to utilise this tool.     

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.     

Effect of heat exposure on thermoregulation and hockey-specific response time in field hockey goalkeepers

This study examined the thermoregulatory responses in field hockey goalkeepers during games (Part A), and assessed the effect of heat stress on hockey-specific response time (Part B). In Part A, core temperature (T_c), skin temperature (T_sk), body mass, fluid consumption and heart rate (HR) responses of six goalkeepers during two premier level club games in the Western Australian (winter) hockey season were recorded. Part B assessed the same measures, plus a response time test on four goalkeepers playing a simulated game inside a climate chamber in cool (COOL: 20 °C, 40% RH) and hot (HOT: 35 °C, 40% RH) conditions. In Part A, the mean (±SD) T_c and T_sk measured in games was 38.49 ± 0.20 °C and 34.99 ± 0.99 °C, with increases from baseline of 1.34 ± 0.19 °C and 1.08 ± 0.30 °C, respectively. Most of the increase in T_c resulted from the pre-game warm-up. In Part B, T_c and T_sk only increased significantly (p < 0.05) from baseline in the HOT condition (0.62 ± 0.18 °C and 1.61 ± 0.82 °C, respectively). Response time was significantly slower (0.87 ± 0.14 s, p < 0.01) after heat exposure, compared to COOL (0.75 ± 0.15 s), but the number of correct responses was not affected. For optimal performance, careful attention should be given to strategies to limit T_c increases in field hockey goalkeepers during matches.     

The effects of hydration status and ice-water dousing on physiological and performance indices during a simulated soccer match in the heat

ObjectivesTo assess the effects of hydration status and ice-water dousing on physiological and performance parameters.DesignRandomized, crossover.MethodsTwelve athletes (mean[M] ± standard deviation[SD]; age, 20 ± 1 years; height, 174 ± 8 cm; body mass, 72.1 ± 11.0 kg; VO_2max 53.9 ± 7.3 mL⋅kg⁻¹⋅min⁻¹) completed four trials (euhydrated without dousing, hypohydrated without dousing, euhydrated with dousing, and hypohydrated with dousing), which involved intermittent treadmill running (five 15-minute bouts) in the heat (M ± SD; ambient temperature, 34.7 ± 2.1 °C; relative humidity, 46 ± 3%; wet-bulb globe temperature, 28.0 ± 0.4 °C). Participants also completed four cognitive, power, agility, reaction time, and repeated sprint performance tests throughout each trial. Heart rate (HR) and rectal temperature (T_rec) were measured continuously. Repeated measures ANOVAs were performed to assess differences between physiological and performance variables. Alpha was set at ≤0.05, a priori. Data are reported as mean difference ± standard error (MD ± SE).ResultsHR was significantly lower in euhydrated trials compared to hypohydrated trials, irrespective of dousing (8 ± 2 bpm; p = 0.001). Dousing did not significantly impact HR (p = 0.455) and there was no interaction between hydration and dousing (p = 0.893). T_rec was significantly lower in euhydrated trials compared to hypohydrated trials (0.39 ± 0.05 °C, p < 0.001), with no effect from dousing alone (p = 0.113) or the interaction of hydration and dousing (p = 0.848). Dousing resulted in improved sprint performance (11 ± 3 belt rotations, p = 0.007), while hydration status did not (p = 0.235).ConclusionsAthletes should aim to maintain euhydration during exercise in the heat for improved physiological function and cooling with ice-water dousing elicits additional performance benefits.     

The effect of ambient temperature on the reliability of a preloaded treadmill time-trial

The purpose of this study was to investigate the reliability of a 90-min treadmill-based preloaded time-trial (TT (pre)) in hot (HOT) and moderate (MOD) temperatures. Nine well-trained males completed six 90-min TT (pre), three in HOT (30.5 +/- 0.1 degrees C) and three in MOD (14.4 +/- 0.1 degrees C) conditions, separated by 7 - 14 days conducted on a motorised treadmill. The TT (pre) consisted of 75 min at approximately 60 % V O (2max) followed by a self-paced 15-min time-trial (TT). Subjects ran significantly further in MOD compared to HOT during the 15-minute TT phase (p < 0.01). The CV for the 15-min TTs calculated between trials 1 and 2 were 3.3 % (MOD) and 5.8 % (HOT). This improved to 2.4 % (MOD) (p > 0.05) and significantly improved to 2.7 % (HOT) (p < 0.05) when classifying trial 1 as a familiarisation and calculating the CV between trials 2 and 3. There was no significant difference between the CV calculated between trials 2 and 3 for the 15-min TT section between conditions (p > 0.05) There were no significant differences in any physiological response between conditions or within trials of the same condition (p > 0.05). The 90-min TT (pre) is a reliable test for the assessment of endurance performance in prolonged treadmill running in familiarised males in HOT and MOD conditions.     

The determinants of thermal comfort in cool water

Water‐based activities may result in the loss of thermal comfort (TC). We hypothesized that in cooling water, the hands and feet would be responsible. Supine immersions were conducted in up to five clothing conditions (exposing various regions), as well as investigations to determine if a “reference” skin temperature (T_sk) distribution in thermoneutral air would help interpret our findings. After 10 min in 34.5 °C water, the temperature was decreased to 19.5 °C over 20 min; eight resting or exercising volunteers reported when they no longer felt comfortable and which region was responsible. TC, rectal temperature, and T_sk were measured. Rather than the extremities, the lower back and chest caused the loss of overall TC. At this point, mean (SD) chest T_sk was 3.3 (1.7) °C lower than the reference temperature (P = 0.005), and 3.8 (1.5) °C lower for the back (P = 0.002). Finger T_sk was 3.1 (2.7) °C higher than the reference temperature (P = 0.037). In cool and cooling water, hands and feet, already adapted to colder air temperatures, will not cause discomfort. Contrarily, more discomfort may arise from the chest and lower back, as these regions cool by more than normal. Thus, T_sk distribution in thermoneutral air may help understand variations in TC responses across the body.     

Comparison of lumbar degenerative disc disease using conventional fast spin echo T2W MRI and T2 fast spin echo dixon sequences

Objectives:To compare the grading of lumbar degenerative disc disease (DDD), Modic end-plate changes (MEPC) and identification of high intensity zones (HIZ) on a combination of sagittal T₁weighted turbo spin echo (T₁W TSE), T₂weighted fast spin echo (T₂W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T₂W FSE Dixon MRI sequence which provides in-phase, opposed-phase, water only and fat only images in a single acquisition (Dixon protocol).Methods:50 patients underwent lumbar spine MRI using the routine protocol with the addition of a T₂W FSE Dixon sequence. DDD grade, MEPC and HIZ for each disc level were assessed on the routine and Dixon protocols. Each protocol was reviewed independently by three readers (consultant musculoskeletal radiologists with 26-, 8- and 4 years’ experience), allowing assessment of inter-reader agreement and inter protocol agreement for each assessed variable.Results:The study included 17 males and 33 females (mean age 51 years; range 8–82 years). Inter-reader agreement for DDD grade on the routine protocol was 0.57 and for the Dixon protocol was 0.63 (p = 0.08). Inter-reader agreement for MEPC on the routine protocol was 0.45 and for the Dixon protocol was 0.53 (p = 0.02), and inter-reader agreement for identification of the HIZ on the routine protocol was 0.52 and for the Dixon protocol was 0.46 (p = 0.27). Intersequence agreement for DDD grade ranged from 0.61 to 0.97, for MEPC 0.46–0.62 and for HIZ 0.39–0.5.Conclusion:A single sagittal T₂W FSE Dixon MRI sequence could potentially replace the routine three sagittal sequence protocol for assessment of lumbar DDD, MEPC and HIZ resulting in ~60% time saving.Advances in knowledge:Grading of lumbar DDD, presence of Modic changes and high intensity zones were compared on sagittal T₁W TSE, T₂W FSE and STIR sequences with a T₂W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.     

Optimal break structures and cooling strategies to mitigate heat stress during a Rugby League match simulation

ObjectivesTo examine, 1) optimal structure of break periods to mitigate physiological heat strain during rugby league play (Stage 1); and ii) effectiveness of three different cooling strategies applied during breaks (Stage 2).DesignCounter-balanced crossover design.MethodsIn 37 °C, 50% RH, 11 males completed six simulated 80-min (two 40-min halves) rugby league matches on a treadmill with different break structures: regular game (RG) (12-min halftime), 1-min or 3-min “quarter-time” breaks halfway through each half with a 12-min halftime break (R1C and R3C), a 20-min halftime break (EH), or 1-min or 3-min quarter-time breaks with a 20-min halftime break (E1C and E3C) [Stage 1]. Nine participants completed Stage 2, which assessed the application of either ice towels (ICE), an electric fan (FAN) or a misting fan (MST) during breaks in the E3C protocol which, in Stage 1, prevailed as the optimal break structure.ResultsStage 1: Irrespective of quarter-time break duration, reductions in rectal temperature (−0.24 °C ± 0.24) and heart rate (−61 ± 10 bpm) during the halftime break were greater with a 20-min compared to a 12-min break (−0.08 ± 0.13 °C, p = 0.005; −55 ± −9 bpm, p = 0.021). Stage 2: End-game rises in rectal temperature were smaller (p < 0.006) in MST (1.41 ± 0.22 °C), FAN (1.55 ± 0.36 °C) and ICE (1.60 ± 0.21 °C) than in CON (1.80 ± 0.39 °C). The end-halftime heart rate was lower (p < 0.001) in ICE (89 ± 13 bpm), MST (90 ± 10 bpm) and FAN (92 ± 13 bpm) than in CON (99 ± 18 bpm).ConclusionsCombining an extended halftime period and quarter-time breaks with MST application is the optimal cooling strategy for rugby league players in hot, humid conditions.