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Matt B. Brearley and James P. Finn

Background:

Despite the thermal challenge of demanding workloads performed in high cabin temperatures while wearing heavy heat-retardant clothing, information on physiological responses to racing V8 Supercars in hot conditions is not readily available.

Purpose:

To describe the thermal, cardiovascular, and perceptual strain on V8 Supercar drivers competing in hot conditions.

Methods:

Thermal strain was indicated by body-core temperature using an ingested thermosensitive pill. Cardiovascular strain was assessed from heart rate, hydration status, and sweat rate. Perceptual strain was estimated from self-rated thermal sensation, thermal discomfort (modified Gagge scales), perceived exertion (Borg scale), and perceptual strain index.

Results:

Prerace body-core temperatures were (mean ± SD) 37.7°C ± 0.4°C (range 37.0°C to 38.2°C), rising to 39.0°C ± 0.4°C (range 38.4°C to 39.7°C) postrace. Driver heart rates were >160 and >170 beats/min for 85.3% and 46.7% of racing, respectively. Sweat rates were 1.06 ± 0.12 L/h or 13.4 ± 1.2 mL · kg−1 · h−1, and postrace dehydration was 0.6% ± 0.6% of prerace body mass. Drivers rated thermal sensation as hot (10.3 ± 0.9), thermal discomfort as uncomfortable (3.1 ± 1.0), and perceived exertion as very hard to very, very hard (8.7 ± 1.7) after the races. Overall physiological and perceptual strain were 7.4 ± 1.0 and 7.1 ± 1.2, respectively.

Conclusions:

Despite the use of cooling, V8 Supercar drivers endure thermal, cardiovascular, and perceptual strain during brief driving bouts in hot conditions.

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Paola Zamparo, Ivan Zadro, Stefano Lazzer, Marco Beato and Luigino Sepulcri

Shuttle runs can be used to study the physiological responses in sports (such as basketball) characterized by sprints (accelerations/decelerations) and changes of direction.

Purpose:

To determine the energy cost (C) of shuttle runs with different turning angles and over different distances (with different acceleration/deceleration patterns).

Methods:

Nine basketball players were asked to complete 6 intermittent tests over different distances (5, 10, 25 m) and with different changes of direction (180° at 5 and 25 m; 0°, 45°, 90°, and 180° at 10 m) at maximal speed (v ≍ 4.5 m/s), each composed by 10 shuttle runs of 10-s duration and 30-s recovery; during these runs oxygen uptake (VO2), blood lactate (Lab), and C were determined.

Results:

For a given shuttle distance (10 m) no major differences where observed in VO2 (~33 mL · min−1 · kg−1), Lab (~3.75 mM), and C (~21.2 J · m−1 · kg−1) when the shuttle runs were performed with different turning angles. For a given turning angle (180°), VO2 and Lab were found to increase with the distance covered (VO2 from 26 to 35 mL · min−1 · kg−1; Lab from 0.7 to 7.6 mM) while C was found to decrease with it (from 29.9 to 10.6 J · m−1 · kg−1); the relationship between C and d (m) is well described by C = 92.99 × d 0.656, R 2 = .971.

Conclusions:

The metabolic demands of shuttle tests run at maximal speeds can be estimated based on the running distance, while the turning angle plays a minor role in determining C.

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Martin Buchheit, Bachar Haydar, Karim Hader, Pierre Ufland and Said Ahmaidi

Purpose:

To examine physiological responses to submaximal feld running with changes of direction (COD), and to compare two approaches to assess running economy (RE) with COD, ie, during square-wave (SW) and incremental (INC) exercises.

Methods:

Ten male team-sport athletes performed, in straight-line or over 20 m shuttles, one maximal INC and four submaximal SW (45, 60, 75 and 90% of the velocity associated with maximal pulmonary O2 uptake [vVO2pmax]). Pulmonary (VO2p) and gastrocnemius (VO2m) O2 uptake were computed for all tests. For both running mode, RE was estimated as the O2 cost per kilogram of bodyweight, per meter of running during all SW and INC.

Results:

Compared with straight-line runs, shuttle runs were associated with higher VO2p (eg, 33 ± 6 vs 37 ± 5 mL O2·min–1·kg–1 at 60%, P < .01) and VO2m (eg, 1.1 ± 0.5 vs 1.3 ± 0.8 mL O2·min–1·100 g–1 at 60%, P = .18, Cohen’s d = 0.32). With COD, RE was impaired during SW (0.26 ± 0.02 vs 0.24 ± 0.03 mL O2·kg–1·m–1, P < .01) and INC (0.23 ± 0.04 vs 0.16 ± 0.03 mL O2·kg–1·m–1, P < .001). For both SW and INC tests, the changes in RE with COD were related to height (eg, r = .56 [90%CL, 0.01;0.85] for SW) and weekly training/competitive volume (eg, r = –0.58 [–0.86;–0.04] for SW). For both running modes, RE calculated from INC was better than that from SW (both P < .001).

Conclusion:

Although RE is impaired during feld running with COD, team-sport players of shorter stature and/or presenting greater training/competitive volumes may present a lower RE deterioration with COD. Present results do not support the use of INC to assess RE in the feld, irrespective of running mode.

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Mohamed Ali Nabli, Nidhal Ben Abdelkrim, Imed Jabri, Tahar Batikh, Carlo Castagna and Karim Chamari

Purpose:

To examine the relation between game performance, physiological responses, and field-test results in Tunisian basketball referees.

Methods:

Computerized time–motion analysis, heart rate (HR), and blood lactate concentration [La] were measured in 15 referees during 8 competitive games (under-19-y-old Tunisian league). Referees also performed a repeated-sprint test (RSA), Yo-Yo Intermittent Recovery Test level 1 (YYIRTL1), agility T-test, and 30-m sprint with 10-m lap time. Computerized video analysis determined the time spent in 5 locomotor activities (standing, walking, jogging, running, and sprint), then grouped in high-, moderate-, and low-intensity activities (HIAs, MIAs, and LIAs, respectively).

Results:

YYIRTL1 performance correlated with (1) total distance covered during the 4th quarter (r = .52, P = .04) and (2) distance covered in LIA during all game periods (P < .05). Both distance covered and time spent in MIA during the 1st quarter were negatively correlated with the YYIRTL1 performance (r = –.53, P = .035; r = –.67, P = .004, respectively). A negative correlation was found between distance covered at HIA during the 2nd half (3rd quarter + 4th quarter) and fatigue index of the RSA test (r = –.54, P = .029). Mean HR (expressed as %HRpeak) during all game periods was correlated with YYIRTL1 performance (.61 ≤ r < .67, P < .01).

Conclusions:

This study showed that (1) the YYIRTL1 performance is a moderate predictor of game physical performance in U-19 basketball referees and (2) referees’ RSA correlates with the amount of HIA performed during the 2nd half, which represents the ability to keep up with play.

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Alexandre Dellal, Carlos Lago-Penas, Del P. Wong and Karim Chamari

Purpose:

The aim of this study was to examine the influence of the number of ball touches authorized per possession on the physical demands, technical performances and physiological responses throughout the bouts within 4 vs. 4 soccer small-sided games (SSGs).

Methods:

Twenty international soccer players (27.4 ± 1.5 y, 180.6 ± 2.3 cm, 79.2 ± 4.2 kg, body fat 12.7 ± 1.2%) performed three different 4 vs. 4 SSGs (4 × 4 min) in which the number of ball touches authorized per possession was manipulated (1 touch = 1T; 2 touches = 2T; Free Play = FP). The SSGs were divided in 4 bouts (B1, B2, B3 and B4) separated by 3 min of passive recovery. The physical performances, technical activities, heart rate responses, blood lactate and RPE were analyzed.

Results:

The FP rule presented greater number of duels, induced the lowest decreases of the sprint and high-intensity performances, and affected less the technical actions (successful passes and number of ball losses) from B1 to B4 as compared with 1T and 2T forms. Moreover, the SSG played in 1T form led to reach higher solicitation of the high-intensity actions while players presented more difficulty to perform a correct technical action.

Conclusions:

The modification of the number of ball touches authorized per possession affects the soccer player activity from the first to the last bout of SSG, indicating that the determination of this rule has to be precisely planned by the coach according to the objectives of the training.

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Thomas W. Buford, Douglas B. Smith, Matthew S. O’Brien, Aric J. Warren and Stephen J. Rossi

Purpose:

The purpose of the present investigation was to examine the physiological response of collegiate wrestlers to their competitive season.

Methods:

Eleven Division I collegiate wrestlers (mean ± SD; 19.45 ± 1.13 y) volunteered and completed 4 testing sessions throughout the course of the collegiate wrestling season. Testing sessions were conducted pre-, mid-, and postseason, as well as before the national tournament. Testing consisted of weigh-in, skinfold body composition testing, and a 50-rep concentric, isokinetic leg extension muscle endurance test (180°/s). Muscular performance variables measured included peak torque, peak torque at fatigue, percent decline, and peak torque/body mass ratio.

Results:

A significant increase (P < .05) of 2.9% was observed for body mass between midseason and postseason (2.38 kg). From pre- to postseason, a mean increase of 3.8% (3.1 kg) was observed for body mass. An increase (P < .05) in BF% of 2.9% was observed between prenationals and postseason. No significant differences (P > .05) were observed between consecutive time points for quadriceps peak torque; however, there was a significant increase (P < .05) between preseason and prenationals (23.39 N·m). Peak torque at fatigue was greater (P < .05) at midseason than preseason, representing an increase of 9.82 N·m. Between midseason and prenationals testing, we observed an 11% increase (P < .05) in %DCLN. Finally, we noted an increase (P < .05) from 0.6 to 0.69 in peak torque/body mass ratio between preseason and prenationals.

Conclusions:

Our results indicate that while force values seem to suffer at midseason, the wrestlers compensated and were strongest just before their national competition.

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Maria Konstantaki, Edward Winter and Ian Swaine

Context:

Forward propulsion in freestyle swimming is predominantly achieved through arm action. Few studies have assessed the effects of arm training on arm power and swimming performance, yet there have not been any investigations on the effects of arms-only swimming training on swimming performance and physiological responses to arm exercise.

Purpose:

To investigate the changes in arms-only and full-stroke swimming performance, movement economy and aerobic power after an arms-only swimming training program.

Methods:

Fifteen male county level swimmers were assigned either to an experimental (ES, n = 8) or control group (CS, n = 7). For six weeks ES performed arms-only freestyle swimming exercises for 20% of their weekly training distance three times per week, whereas CS performed their usual swimming training. Before and after the training program, both groups performed a) two time trials, 186 m using arms-only (186ARMS) and 372 m using full-stroke (372FULL) freestyle swimming, and b) an incremental arm-pulling exercise test. The time to complete the trials was recorded. Peak oxygen uptake (VO2peak), peak exercise intensity (EIpeak) submaximal oxygen uptake at 60 W (VO2−60) and exercise intensity at ventilatory threshold (VTW) were determined from the exercise test.

Results:

After training, ES had improved in 186ARMS (−14.2 ± 3.6%, P = .03), VO2−60 (−22.5 ± 2.3%, P = .04), EIpeak (+17.8 ± 4.2%, P = .03), and VTW (+18.9 ± 2.3%, P = .02), but not in VO2peak (P = .09) or in 372FULL (P = .07). None of the measures changed in CS (P > .05).

Conclusion:

Arms-only swimming training at 20% of the weekly training distance is an effective method to improve arm conditioning during the preparatory phase of the annual training cycle.

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Michael J. Hartman, Brandon Clark, Debra A. Bemben, J. Lon Kilgore and Michael G. Bemben

Context:

Many elite athletes use increased daily training frequencies as a means to increase training load without substantial published literature to support this practice.

Purpose:

To compare the physiological responses to twice- and once-daily training sessions with similar training volumes.

Methods:

Ten nationally competitive male weightlifters (age 20.5 ± 1.2 y, body mass 92.9 ± 23.6 kg, training history 5.5 ± 1.5 y) were matched on body mass and training experience, then randomly assigned to train either once or twice daily for 3 wk. Isometric knee-extension strength (ISO), muscle cross-sectional area, vertical-jump peak power, resting hormone concentrations, neuromuscular activation (EMG), and weightlifting performance were obtained before and after the experimental training period.

Results:

All dependent measures before the training intervention were similar for both groups. A 2-way repeated-measures ANOVA did not reveal any significant main effects (group or trial) or interaction effects (group × trial) for any of the dependent variables. There were also no significant group differences when parameters were expressed as percentage change, but the twice-daily training group had a greater percentage change in ISO (+5.1% vs +3.2%), EMG (+20.3% vs +9.1%), testosterone (+10.5% vs +6.4%), and testosterone:cortisol ratio (−10.5% vs +1.3%) than did the once-daily training group.

Conclusions:

There were no additional benefits from increased daily training frequency in national-level male weightlifters, but the increase in ISO and EMG activity for the twice-daily group might provide some rationale for dividing training load in an attempt to reduce the risk of overtraining.

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Rob Duffield, Monique King and Melissa Skein

Purpose:

This study investigated the effects of hot conditions on the acute recovery of voluntary and evoked muscle performance and physiological responses following intermittent exercise.

Methods:

Seven youth male and six female team-sport athletes performed two sessions separated by 7 d, involving a 30-min exercise protocol and 60-min passive recovery in either 22°C or 33°C and 40% relative humidity. The exercise protocol involved a 20-s maximal sprint every 5 min, separated by constant-intensity exercise at 100 W on a cycle ergometer. Maximal voluntary contraction (MVC) and a resting evoked twitch (Pf) of the right knee extensors were assessed before and immediately following exercise and again 15, 30, and 60 min post exercise, and capillary blood was obtained at the same time points to measure lactate, pH, and HCO3. During and following exercise, core temperature, heart rate and rating of perceived exertion (RPE) were also measured.

Results:

No differences (P = 0.73 to 0.95) in peak power during repeated sprints were present between conditions. Post exercise MVC was reduced (P < .05) in both conditions and a moderate effect size (d = 0.60) indicated a slower percentage MVC recovered by 60 min in the heat (83 ± 10 vs 74 ± 11% recovered). Both heart rate and core temperature were significantly higher (P < .05) during recovery in the heat. Capillary blood values did not differ between conditions at any time point, whereas sessional RPE was higher 60 min post exercise in the heat.

Conclusions:

The current data suggests that passive recovery in warm temperatures not only delays cardiovascular and thermal recovery, but may also slow the recovery of MVC and RPE.

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Sonya L. Cameron, Rebecca T. McLay-Cooke, Rachel C. Brown, Andrew R. Gray and Kirsty A. Fairbairn

Purpose:

This study investigated the effect of ingesting 0.3 g/kg body weight (BW) of sodium bicarbonate (NaHCO3) on physiological responses, gastrointestinal (GI) tolerability, and sprint performance in elite rugby union players.

Methods:

Twenty-five male rugby players, age 21.6 (2.6) yr, participated in a randomized, double-blind, placebo-controlled crossover trial. Sixty-five minutes after consuming 0.3 g/kg BW of either NaHCO3 or placebo, participants completed a 25-min warm-up followed by 9 min of high-intensity rugby-specific training followed by a rugby-specific repeated-sprint test (RSRST). Whole-blood samples were collected to determine lactate and bicarbonate concentrations and pH at baseline, after supplement ingestion, and immediately after the RSRST. Acute GI discomfort was assessed by questionnaire throughout the trials, and chronic GI discomfort was assessed during the 24 hr postingestion.

Results:

After supplement ingestion and immediately after the RSRST, blood HCO3 concentration and pH were higher for the NaHCO3 condition than for the placebo condition (p < .001). After the RSRST, blood lactate concentrations were significantly higher for the NaHCO3 than for the placebo condition (p < .001). There was no difference in performance on the RSRST between the 2 conditions. The incidence of belching, stomachache, diarrhea, stomach bloating, and nausea was higher after ingestion of NaHCO3 than with placebo (all p < .050). The severity of stomach cramps, belching, stomachache, bowel urgency, diarrhea, vomiting, stomach bloating, and flatulence was rated worse after ingestion of NaHCO3 than with placebo (p < .050).

Conclusions:

NaHCO3 supplementation increased blood HCO3 concentration and attenuated the decline in blood pH compared with placebo during high-intensity exercise in well-trained rugby players but did not significantly improve exercise performance. The higher incidence and greater severity of GI symptoms after ingestion of NaHCO3 may negatively affect physical performance, and the authors strongly recommend testing this supplement during training before use in competitive situations.