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.     

Repeated‐sprint performance and vastus lateralis oxygenation: Effect of limited O2 availability

This study examined the influence of muscle deoxygenation and reoxygenation on repeated‐sprint performance via manipulation of O₂ delivery. Fourteen team‐sport players performed 10 10‐s sprints (30‐s recovery) under normoxic (NM: F_IO₂ 0.21) and acute hypoxic (HY: F_IO₂ 0.13) conditions in a randomized, single‐blind fashion and crossover design. Mechanical work was calculated and arterial O₂ saturation (S_pO₂) was estimated via pulse oximetry for every sprint. Muscle deoxyhemoglobin concentration ([HHb]) was monitored continuously by near‐infrared spectroscopy. Differences between NM and HY data were analyzed for practical significance using magnitude‐based inferences. HY reduced S_pO₂ (–10.7 ± 1.9%, with chances to observe a higher/similar/lower value in HY of 0/0/100%) and mechanical work (–8.2 ± 2.1%; 0/0/100%). Muscle deoxygenation increased during sprints in both environments, but was almost certainly higher in HY (12.5 ± 3.1%, 100/0/0%). Between‐sprint muscle reoxygenation was likely more attenuated in HY (–11.1 ± 11.9%; 2/7/91%). The impairment in mechanical work in HY was very largely correlated with HY‐induced attenuation in muscle reoxygenation (r = 0.78, 90% confidence limits: 0.49; 0.91). Repeated‐sprint performance is related, in part, to muscle reoxygenation capacity during recovery periods. These results extend previous findings that muscle O₂ availability is important for prolonged repeated‐sprint performance, in particular when the exercise is taken in hypoxia.     

Does restricting arm motion compromise short sprint running performance?

BackgroundSynchronized arm and leg motion are characteristic of human running. Leg motion is an obvious gait requirement, but arm motion is not, and its functional contribution to running performance is not known. Because arm-leg coupling serves to reduce rotation about the body’s vertical axis, arm motion may be necessary to achieve the body positions that optimize ground force application and performance.Research questionDoes restricting arm motion compromise performance in short sprints?MethodsSprint performance was measured in 17 athletes during normal and restricted arm motion conditions. Restriction was self-imposed via arm folding across the chest with each hand on the opposite shoulder. Track and field (TF, n = 7) and team sport (TS, n = 10) athletes completed habituation and performance test sessions that included six counterbalanced 30 m sprints: three each in normal and restricted arm conditions. TS participants performed standing starts in both conditions. TF participants performed block starts with extended arms for the normal condition and elevated platform support of the elbows for the crossed-arm, restricted condition. Instantaneous velocity was measured throughout each trial using a radar device. Average sprint performance times were compared using a Repeated Measures ANOVA with Tukey post-hoc tests for the entire group and for the TF and TS subgroups.ResultsThe 30 m times were faster for normal vs. restricted arm conditions, but the between-condition difference was only 1.6% overall and < 0.10 s for the entire group (4.82 ± 0.46 s vs. 4.90 ± 0.46 s, respectively; p < 0.001) and both TF (4.55 ± 0.34 vs. 4.63 ± 0.32 s; p < 0.001) and TS subgroups (5.01 ± 0.46 vs. 5.08 ± 0.47 s; p < 0.001).SignificanceOur findings suggest that when arm motion is restricted, compensatory upper body motions can provide the rotational forces needed to offset the lower body angular momentum generated by the swinging legs. We conclude that restricting arm motion compromised short sprint running performance, but only marginally.     

Relationships between unilateral horizontal and vertical drop jumps and 20 m sprint performance

ObjectivesThe purpose of this study was to compare the relationships between horizontal (HDJ) and vertical drop jumps (VDJ) to sprint performance.DesignExploratory Study.SettingLaboratory.ParticipantsNineteen male collegiate participants (22.5 ± 3.2 years, 181.1 ± 6.7 cm, 80.3 ± 9.6 kg).Main outcome measuresAll participants performed VDJ and HDJ from a 20 cm height onto an AMTI force platform sampling at 1200 Hz before performing three 20 m sprints. Sprint times (5, 10, 15, 20, 5–10, 10–15, 15–20 m) were measured using a LAVEG speed gun.ResultsAll jump and sprint measures showed excellent within session reliability (ICC: 0.954 to 0.99). Pearson's and Spearman's correlations revealed significant (p < 0.01) moderate to high correlations between jump measures and sprint times (R: −0.665 to −0.769). Stepwise multiple regression revealed jump distance normalised by body height (HDJ) was the best predictor for 10, 20, 5–10, 10–15 and 15–20 m sprint times (R² = 41%–48%).ConclusionsHDJ performance measures provide stronger relationships to sprint performance than VDJ's. Thus, HDJ's should be considered in test batteries to monitor training and rehabilitation for athletes in sprint related sports.     

The influence of youth soccer players’ sprint performance on the different sided games’ external load using GPS devices

ABSTRACT

The aims of this study are 1) to compare sided games’ (SGs) external responses encountered by players according to pitch size and to 2) examine the relationships between sprint performance and SGs’ external physical responses. Twenty soccer players under 15 years of age (U-15) participated in this study. Each player performed a sprinting test (10 m and 30 m sprints) and played a SG on two different pitch sizes (small at 100 [SSG] and large at 200 [LSG] m² per player). Higher external responses (p < 0.01, ES = ?6.41–1.22) were found in LSG in comparison to SSG, except to distance accelerating and decelerating (p > 0.05, ES = ?0.26–0.27). Players who were faster over 10 and 30 m covered higher distances cruising and sprinting (r = ?0.47/-0.66; ± 0.23/± 0.30, respectively, p < 0.05), performed a greater number of sprints, achieved higher maximum velocity (Vel_max) during LSG and covered a greater distance at high-intensity accelerating (r = ?0.50/-0.70; ±0.21/±0.29, respectively, p < 0.05) during both SG. LSG demanded a higher external load in comparison with SSG. In addition, the improved sprint capacity could allow players to perform greater running activities and short-term actions at high-intensities during SG.     

The effects of hyperoxia on repeated sprint cycling performance & muscle fatigue

ObjectivesHyperoxia (>21% oxygen) can evoke performance improvements in aerobic and anaerobic exercise. The aims of the current study were to determine the effects of breathing hyperoxic gas (fraction of inspired oxygen [F_iO₂] 1.00) on repeated cycle performance, and to assess the nature and extent of fatigue after intermittent sprinting.Design & methodsTesting (n = 14 males) comprised two visits to the laboratory. Each session involved 10 × 15 s repeated cycle sprints breathing FiO₂ 1.00 (hyperoxia) or FiO₂ 0.21 (normoxia). Muscle fatigue was measured pre and post sprints using Maximal Voluntary Contraction (MVC), voluntary activation (VA) and potentiated doublet twitch (PTF). Blood lactate (BLa) was taken between sprints.Paired samples t-tests were used to examine difference between conditions in power output (peak and mean Watts) and BLa. Two-way ANOVA was used to examine fatigue variables pre and post sprints according to condition.ResultsMean power output was 4% greater in hyperoxia (p < 0.01), with no difference in peak power (p > 0.05). There was a significant increase in BLa in hyperoxia compared with normoxia (p < 0.01) in sprints 4 and 8, as well as meaningful difference in sprints 4–10. There was no significant difference in fatigue factors (MVC, VA and PTF) (p > 0.05) in response to the cycling, although a large drop in PTF occurred in both conditions.ConclusionHyperoxia can elicit improvements in mean cycling power, with no significant change in post exercise muscle fatigue. Hyperoxia as a training aid may provide performance enhancing effects during repeated sprint cycling by reducing concurrent muscle fatigue, primarily via peripheral factors.     

Influence of nitrate supplementation on VO2 kinetics and endurance of elite cyclists

The present study examined if an elevated nitrate intake would improve VO₂ kinetics, endurance, and repeated sprint capacity in elite endurance athletes. Ten highly trained cyclists (72 ± 4 mL O₂/kg/min, mean ± standard deviation) underwent testing for VO₂ kinetics (3 × 6 min at 298 ± 28 W), endurance (120 min preload followed by a 400‐kcal time trial), and repeated sprint capacity (6 × 20 s sprints, recovery 100 s) during two 6‐day periods in randomized order with a daily ingestion of either 0.5 L beetroot (BR) juice to increase nitrate levels or a 0.5 L placebo (PLA) drink with blackcurrant juice. Plasma NOx (nitrate + nitrite) levels were higher (P < 0.01) in BR (147 ± 102 and 159 ± 103 μM after 4 and 6 days of beverage intake, respectively) compared with PLA (41 ± 10 and 40 ± 7 μM). VO₂ kinetics and exercise economy were the same in BR and PLA. Time‐trial performance was similar with an average completion time of 18:20 and 18:37 min:s in BR and PLA, respectively, with average power outputs of 290 ± 43 W in BR and 285 ± 44 W in PLA. Peak and mean power during repeated sprinting were similar in BR and PLA. In contrast to observations in moderately trained subjects intake of BR juice had no effect on VO₂ kinetics and performance in elite cyclists.     

Repeated sprints alter mechanical work done by hip and knee,but not ankle,sagittal moments

ObjectivesTo quantify the changes in work done by lower limb joint moments during maximal speed running following a sports-specific repeated running protocol.DesignObservational with repeated-measures.MethodsRecreational athletes (n = 18 (9 females), aged = 26.2 ± 6.2 years) performed 12 maximal 30-m sprints on a non-motorised treadmill. Three-dimensional kinematics and ground reaction forces were subsequently recorded during a 10-m maximal overground sprint before and immediately after the repeated running protocol, from which we calculated work done by sagittal plane hip, knee, and ankle moments. Relative work (J/kg) was reported as a percentage of positive and negative work done by the sum of joint moments.ResultsFollowing the repeated running protocol, maximal sprint speed decreased by 19% and was accompanied by reductions in total positive (−1.47 J/kg) and negative (−0.92 J/kg) work, in addition to work done by hip (−0.43 to −0.82 J/kg) and knee (−0.28 J/kg) moments during swing. Compared to before the repeated running protocol, less relative work was done by hip (−9%) and knee (−3%) extension moments during swing. Reductions in work done by hip and knee joint moments during swing were significantly correlated with reductions in maximum running speed (r = 0.61−0.89, p < 0.05).ConclusionsA sports-specific repeated running protocol resulted in reductions in mechanical work done by sagittal plane hip and knee joint moments during maximal overground sprinting. Interventions focused on maintaining positive work done by the hip flexors/extensors and negative work done by knee flexors/extensors during the swing phase of running may help prevent reductions in speed following repeated sprinting.     

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.     

Sprint mechanics in world‐class athletes: a new insight into the limits of human locomotion

The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high‐level athletes. Four elite (100‐m best time 9.95–10.29 s) and five sub‐elite (10.40–10.60 s) sprinters performed seven sprints in overground conditions. A single virtual 40‐m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (F_Y), power (P_Y), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). F_Y‐V, RF‐V, and P_Y‐V relationships were well described by significant linear (mean R² of 0.892 ± 0.049 and 0.950 ± 0.023) and quadratic (mean R² = 0.732 ± 0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world‐class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion.     

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.     

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.     

Cardiac autonomic response to aerobic exercise with different levels of blood flow restriction in pre-hypertensive men

Purpose

Cardiovascular safety of aerobic exercise with blood flow restriction (BFR) has been little studied in clinical populations. This study investigated the effects of different levels of BFR on cardiac autonomic response during and after walking tasks in pre-hypertensive men.

Methods

Twelve pre-hypertensive men performed three randomly assigned experimental sessions: (1) 20 min of walking at 40% of peak running velocity (V_peak) without BFR (CON); (2) 20 min of walking at 40% of V_peak with BFR sets at 40% of the maximum cuff pressure that fully interrupted blood flow (BFR40); and (3) 20 min of walking at 40% of V_peak with BFR sets at 80% of the maximum cuff pressure that fully interrupted blood flow (BFR80). The HR and HRV measurements were taken at rest, during exercise, and during the recovery period after constant load sessions.

Results

Heart rate was higher throughout the BFR80 session when compared to the CON condition (p?<?0.05). The time constant of heart rate recovery was higher in both BFR80 (73.2?±?28.8 s) and BFR40 (49.8?±?16.1 s) compared to CON (24.3?±?7.8 s; p?<?0.01). In addition, the cardiac vagal modulation during recovery was lower in the BFR80 than CON (p?<?0.05), but there was no significant difference between BFR40 and CON or between BFR80 and BFR40 (p?>?0.05).

Conclusions

Restricting blood flow imposes additional cardiovascular stress during and after exercise in pre-hypertensive men, with apparently greater stress as the level of BFR increases.

     

Relation entre la force isocinétique,le saut et le sprint chez le footballeur de haut niveau

Purpose – The aim of this study is to appreciate the relation between sprint, jump and knee isokinetic torque in high-level soccer players.Methods – Twenty soccer players (first french national division) were evaluated by sprint and jump tests. Extensors and flexors isokinetic torque was measured by a Cybex Norm dynamometer. Relations between sprints, jumps and isokinetic peak torque were appreciated after correlation analysis.Results – Jumps are correlated with the extensors concentric peak torque at the speed of 180° s⁻¹ when values were corrected by weight (Squat Jump: r = 0.507; Countermovement Jump: r = 0.649; Vertical Jump: r = 0.496). Sprints are correlated with the extensors concentric peak torque at the speed of 180° s⁻¹ when values were corrected by weight (10 and 20 m fixed departure sprint: r = −0.427 and −0.548; 10 and 20 m thrown departure sprint: r = −0.406 and −0.480). Furthermore, sprints with fixed departure are conversely correlated with the flexors eccentric peak torque at the speed of 60° s⁻¹ (r = 0.546 and 0.478) doubtless because a mechanism of knees protection.Conclusions – According to these causal relations, knee extensors and flexors strengthening is recommended for high-level soccer players with the aim of improving sprints and jumps.     

Idarubicin-Loaded ONCOZENE Drug-Eluting Bead Chemoembolization in a Rabbit Liver Tumor Model: Investigating Safety,Therapeutic Efficacy,and Effects on Tumor Microenvironment

PurposeTo investigate toxicity, efficacy, and microenvironmental effects of idarubicin-loaded 40-μm and 100-μm drug-eluting embolic (DEE) transarterial chemoembolization in a rabbit liver tumor model.Materials and MethodsTwelve male New Zealand White rabbits with orthotopically implanted VX2 liver tumors were assigned to DEE chemoembolization with 40-μm (n = 5) or 100-μm (n = 4) ONCOZENE microspheres or no treatment (control; n = 3). At 24–72 hours postprocedurally, multiparametric magnetic resonance (MR) imaging including dynamic contrast-enhanced (DCE), diffusion-weighted imaging (DWI), and biosensor imaging of redundant deviation in shifts (BIRDS) was performed to assess extracellular pH (pHe), followed by immediate euthanasia. Laboratory parameters and histopathologic ex vivo analysis included fluorescence confocal microscopy and immunohistochemistry.ResultsDCE MR imaging demonstrated a similar degree of devascularization of embolized tumors for both microsphere sizes (mean arterial enhancement, 8% ± 12 vs 36% ± 51 in controls; P = .07). Similarly, DWI showed postprocedural increases in diffusion across the entire lesion (apparent diffusion coefficient, 1.89 × 10⁻³ mm²/s ± 0.18 vs 2.34 × 10⁻³ mm²/s ± 0.18 in liver; P = .002). BIRDS demonstrated profound tumor acidosis at baseline (mean pHe, 6.79 ± 0.08 in tumor vs 7.13 ± 0.08 in liver; P = .02) and after chemoembolization (6.8 ± 0.06 in tumor vs 7.1 ± 0.04 in liver; P = .007). Laboratory and ex vivo analyses showed central tumor core penetration and greater increase in liver enzymes for 40-μm vs 100-μm microspheres. Inhibition of cell proliferation, intratumoral hypoxia, and limited idarubicin elution were equally observed with both sphere sizes.ConclusionsNoninvasive multiparametric MR imaging visualized chemoembolic effects in tumor and tumor microenvironment following DEE chemoembolization. Devascularization, increased hypoxia, coagulative necrosis, tumor acidosis, and limited idarubicin elution suggest ischemia as the predominant therapeutic mechanism. Substantial size-dependent differences indicate greater toxicity with the smaller microsphere diameter.     

The validity and reliability of a global positioning satellite system device to assess speed and repeated sprint ability (RSA) in athletes

There is a limited understanding of the validity and reliability of commercially available global positioning satellite (GPS) devices for assessing repeated sprint performance in athletes. The aims of this study were to assess the convergent validity and the test–retest reliability of a GPS device for measuring repeated sprint ability test (RSAT) variables. Two groups participated in this study, a group of 21 physical education students (age: 20.2 ± 2.3 years, stature: 1.75 ± 0.42 m, body mass: 68.0 ± 6.8 kg) and a second group 14 elite junior soccer players (age: 14.5 ± 1.2 years, stature: 1.60 ± 0.09 m, body mass: 57.7 ± 3.8 kg) volunteered to participate in this study. Convergent validity was assessed as the correlation between sprint performance (15 and 30-m) using both timing lights and a portable GPS device during a RSAT (7 × 30-m sprints with 30-s of active recovery). The 7 × 30-m RSAT test–retest reliability using GPS device was assessed in elite junior soccer players repeating the test 1 week apart and expressing reliability as a coefficient of variation. Results showed a strong correlation between peak speed measures with the GPS device and RSAT performance measured with timing lights for the 15-m (r² = 0.87, p < 0.001, N = 147) and 30-m (r² = 0.94, p < 0.001, N = 147) splits, respectively. There was a low coefficient of variation for summated maximal speed (1.7%) and peak speed (1.2%) during the 7 × 30-m RSAT, but high variation for the percentage decrement score (36.2%). These results provide evidence to support the use of the GPS device as an alternative measure to assess repeated sprint performance but suggest a percentage decrement score is not a reliable measure of RSAT performance.     

Test design and individual analysis in wheelchair rugby

Objectives

Use a task vehicle of sprint testing in wheelchair rugby (WCR) to explore the impact of small changes to test design using both group and individual analysis.

Thermographic assessment of the immediate and short term-effects of blood flow restriction exercise on Achilles tendon skin temperature

ObjectivesTo determine the thermal patterning of the Achilles tendon following bodyweight resistance exercise with and without blood-flow restriction (BFR).DesignCross-sectional.SettingResearch laboratory.ParticipantsTwelve asymptomatic recreational runners (Age: 37 ± 10, Height: 169 ± 20, Mass: 73.8 ± 13.4).Main outcome measuresThermograms were taken pre and post exercise with and without a BFR cuff on separate legs. BFR cuff pressure was set at 80% maximal arterial occlusion pressure determined using doppler via the tibial artery. Linear mixed-effects models were used to assess the effect of BFR and time post-exercise on skin-temperature (Tskin).ResultsA lower Tskin was seen following BFR exercise at the tendon insertion (P = 0.002), but not at the free tendon (P = 0.234), or the musculotendinous junction (P = 0.933). A significant effect of time upon changes in Tskin was observed in both BFR and non-BFR groups (P = 0.002). No interaction of time and BFR were observed on changes in Tskin (P = 0.726).ConclusionRegion specific changes in Tskin were found, with greater and longer reductions observed at the insertion of the Achilles following BFR exercise before returning to baseline. These findings could have implications for the programming of BFR exercise on tendon health. Future research should observe for differences between symptomatic and healthy tendons.     

Tissue flossing on ankle range of motion,jump and sprint performance: A follow-up study

ObjectivesPrevious results from our laboratory suggest that band flossing results in increased ankle range of motion (ROM) and jump performance 5-min following application. However, the time-course of such benefits is yet to be examined.DesignParallel group design.SettingUniversity laboratory.Participants69 recreational athletes (32 male/37 female).Main outcome measuresParticipants performed a weight-bearing lunge test (WBLT), a counter-movement jump (CMJ) and a 15 m sprint test (SPRINT) pre and up to 45-min post application of a floss band to both ankles (FLOSS) or without flossing of the ankle joints (CON).ResultsThere was a significant intervention × time interaction in favour of FLOSS when compared to CON for the WBLT (p < 0.05). These results were associated with trivial to small effect sizes at all time points. Small, but non-significant (p > 0.05) benefits were seen for FLOSS when compared to CON for CMJ force (mean ± 90%CI: 89 ± 101 N) and 15 m SPRINT times (−0.06 ± 0.04 s) at 45-min post.ConclusionThere is a trend towards a benefit for the use of floss bands applied to the ankle joint to improve ROM, jump and sprint performance in recreational athletes for up to 45-min following their application.     

The effects of a combined static-dynamic stretching protocol on athletic performance in elite Gaelic footballers: A randomised controlled crossover trial

ObjectivesTo determine the effect of three different static-dynamic stretching protocols on sprint and jump performance in Gaelic footballers.DesignDouble-blind, controlled, crossover trial.SettingSports Institute research environment.ParticipantsSeventeen male elite level Gaelic footballers, aged 18–30 years, completed three stretching protocols.Main Outcome MeasuresAthletic performance was measured by countermovement jump height and power, and timed 10 m, 20 m, and 40 m sprints.ResultsStatic stretching reduced sprint speed by 1.1% over 40 m and 1.0% over 20 m. Static stretching also reduced countermovement jump height by 10.6% and jump power by 6.4%. When static stretching was followed by dynamic stretching, sprint speed improved by 1.0% over 20 m and 0.7% over 40 m (p < 0.05). The static - dynamic stretching protocol also improved countermovement jump height by 8.7% (p < 0.01) and power by 6.7% (p < 0.01).ConclusionsStatic stretching reduces sprint speed and jump performance. Static stretching should be followed by dynamic stretching during warm-up to nullify any performance deficits caused by static stretching.