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Fabrice Vercruyssen, Mathieu Gruet, Serge S. Colson, Sabine Ehrstrom and Jeanick Brisswalter

Background:

Physiological mechanisms behind the use of compression garments (CGs) during off-road running are unknown.

Purpose:

To investigate the influence of wearing CGs vs conventional running clothing (CON) on muscle contractile function and running economy before and after short-distance trail running.

Methods:

Knee-extensor neuromuscular function and running economy assessed from two 5-min treadmill runs (11 and 14 km/h) were evaluated before and after an 18.6-km short-distance trail run in 12 trained athletes wearing either CGs (stocking + short-tight) or CON. Quadriceps neuromuscular function was assessed from mechanical and EMG recording after maximal percutaneous electrical femoral-nerve stimulations (single-twitch doublets at 10 [Db10] and 100 Hz [Db100] delivered at rest and during maximal quadriceps voluntary contraction [MVC]).

Results:

Running economy (in mL O2 · km–1 · kg–1) increased after trail running independent of the clothing condition and treadmill speeds (P < .001). Similarly, MVC decreased after CON and CGs conditions (–11% and –13%, respectively, P < .001). For both clothing conditions, a significant decrease in quadriceps voluntary activation, Db10, Db100, and the low-to-high frequency doublet ratio were observed after trail running (time effect, all P < .01), without any changes in rectus femoris maximal M-wave.

Conclusions:

Wearing CGs does not reduce physiological alterations induced during short-distance trail running. Further studies should determine whether higher intensity of compression pressure during exercises of longer duration may be effective to induce any physiological benefits in experienced trail runners.

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Gary S. Krahenbuhl, Robert P. Pangrazi, William J. Stone, Don W. Morgan and Tracy Williams

Untrained 6- to 8-year-old children (N = 80) served as subjects in a cross sectional study of the fractional utilization of maximal aerobic power during submaximal running. Using the open-circuit method, the absolute oxygen demands of submaximal running were found to increase with age. When expressed relative to body weight, oxygen demands of submaximal running showed no statistically significant changes over the 3-year span. VO2max increased 36.2%, which was proportionally greater than the percentage increase for either body weight (28.4%) or the absolute oxygen demands of submaximal running (22.9%). Thus, during the span of years studied there was a significant reduction in the fractional utilization of maximal aerobic power required to run at a fixed submaximal speed.

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Viswanath B. Unnithan and Roger G. Eston

Previous studies have consistently shown that the body mass/relative oxygen cost of submaximal treadmill running is greater in children than in young adults. It has been suggested that the obligatory increased stride frequency in children might be at least partly responsible. This hypothesis was investigated by examining the association between stride frequency and oxygen demand characteristics in 10 aerobically fit prepubescent boys (ages 9-10 yrs) and 10 fit young men (ages 18-25 yrs) while running at fixed submaximal speeds on an electronically driven treadmill. The oxygen demand was higher at all running speeds in the boys’ group. To compensate for a shorter stride length, the boys demonstrated higher stride frequency at all speeds. To determine if the inferior running economy in the boys was partly due to the greater stride frequency, the relative oxygen demand per stride was compared between groups at all speeds. This value was similar in both groups. It is concluded that the apparently greater oxygen demand of running in boys may be due in part to the greater stride frequency required to maintain similar running speeds.

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Paul G. Montgomery, David B. Pyne and Clare L. Minahan

Purpose:

To characterize the physical and physiological responses during different basketball practice drills and games.

Methods:

Male basketball players (n = 11; 19.1 ± 2.1 y, 1.91 ± 0.09 m, 87.9 ± 15.1 kg; mean ± SD) completed offensive and defensive practice drills, half court 5on5 scrimmage play, and competitive games. Heart rate, VO2 and triaxial accelerometer data (physical demand) were normalized for individual participation time. Data were log-transformed and differences between drills and games standardized for interpretation of magnitudes and reported with the effect size (ES) statistic.

Results:

There was no substantial difference in the physical or physiological variables between offensive and defensive drills; physical load (9.5%; 90% confidence limits ±45); mean heart rate (-2.4%; ±4.2); peak heart rate (-0.9%; ±3.4); and VO2 (–5.7%; ±9.1). Physical load was moderately greater in game play compared with a 5on5 scrimmage (85.2%; ±40.5); with a higher mean heart rate (12.4%; ±5.4). The oxygen demand for live play was substantially larger than 5on5 (30.6%; ±15.6).

Conclusions:

Defensive and offensive drills during basketball practice have similar physiological responses and physical demand. Live play is substantially more demanding than a 5on5 scrimmage in both physical and physiological attributes. Accelerometers and predicted oxygen cost from heart rate monitoring systems are useful for differentiating the practice and competition demands of basketball.

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Franziska Onasch, Anthony Killick and Walter Herzog

 al. argued that the thrust phase duration is the key parameter in successful double poling performance. The use of short poles, they argued, requires more effort and an increased force per poling cycle to maintain a certain speed, leading to less economic skiing, hence an increase in oxygen demand. 12 Our

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Ted Polglaze and Matthias W. Hoppe

can also be expressed as a rate of oxygen demand. Assuming a respiratory quotient of 0.96 for intermittent activity and corresponding energy equivalent of 20.9 kJ per liter of O 2 , 1 W·kg −1 converts to 2.87 mL·kg −1 ·min −1 . 10 Theoretically, mechanical power could be derived from instantaneous

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Matthew J. Barlow, Antonis Elia, Oliver M. Shannon, Angeliki Zacharogianni and Angelica Lodin-Sundstrom

apneic durations that can be achieved by an individual. However, further research is required to elucidate whether NO 3 − spares oxygen demand or increases it by blunting the diving reflex. Splenic contractions have also been reported to occur, following a series of repeated apneas ( Schagatay, 2009

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Rory Warnock, Owen Jeffries, Stephen Patterson and Mark Waldron

pressure]). Rate pressure product (RPP) was also reported (systolic pressure × HR) as an indication of myocardial oxygen demand. A lancet was used to extract a capillary blood sample from the lobe of the ear to measure B[La], which was measured using a calibrated analyzer (Biosen C Line; EKF diagnostic

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Brandon R. Rigby, Ronald W. Davis, Marco A. Avalos, Nicholas A. Levine, Kevin A. Becker and David L. Nichols

measured at rest and once during steady-state exercise at each stage. Modified ratings of perceived exertion (RPE) on a 0–10 scale were also recorded during steady-state exercise at each stage. Rate pressure product (RPP), a clinical indicator of myocardial oxygen demand calculated using the product of HR

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Maria C. Madueno, Vincent J. Dalbo, Joshua H. Guy, Kate E. Giamarelos, Tania Spiteri and Aaron T. Scanlan

recovery to improve physiological and performance outcomes compared with active recovery. 1 , 5 , 6 It has been theorized active recovery promotes greater workloads than passive recovery, increasing oxygen demands, and limiting PCr resynthesis to incur deleterious effects on repeated-sprint performance. 5