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  • Author: Jason Siegler x
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Paul W.M. Marshall, Ric Lovell and Jason C. Siegler

Purpose:

Passive muscle tension is increased after damaging eccentric exercise. Hamstring-strain injury is associated with damaging eccentric muscle actions, but no research has examined changes in hamstring passive muscle tension throughout a simulated sport activity. The authors measured hamstring passive tension throughout a 90-min simulated soccer match (SAFT90), including the warm-up period and every 15 min throughout the 90-min simulation.

Methods:

Passive hamstring tension of 15 amateur male soccer players was measured using the instrumented straight-leg-raise test. Absolute torque (Nm) and slope (Nm/°) of the recorded torque-angular position curve were used for data analysis, in addition to total leg range of motion (ROM). Players performed a 15-min prematch warm-up, then performed the SAFT90 including a 15-min halftime rest period.

Results:

Reductions in passive stiffness of 20–50° of passive hip flexion of 22.1−29.2% (P < .05) were observed after the warm-up period. During the SAFT90, passive tension increased in the latter 20% of the range of motion of 10.1−10.9% (P < .05) concomitant to a 4.5% increase in total hamstring ROM (P = .0009).

Conclusions:

The findings of this study imply that hamstring passive tension is reduced after an active warm-up that includes dynamic stretching but does not increase in a pattern suggestive of eccentric induced muscle damage during soccer-specific intermittent exercise. Hamstring ROM and passive tension increases are best explained by improved stretch tolerance.

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Robert Robergs, Keith Hutchinson, Shonn Hendee, Sean Madden and Jason Siegler

The purpose of this study was to measure the recovery kinetics of pH and lactate for the conditions of pre-exercise acidosis, alkalosis, and placebo states. Twelve trained male cyclists completed 3 exercise trials (110% workload at VO2max), ingesting either 0.3 g/kg of NH4Cl (ACD), 0.2 g/kg of Na+HCO3 - and 0.2 g/kg of sodium citrate (ALK), or a placebo (calcium carbonate) (PLAC). Blood samples (heated dorsal hand vein) were drawn before, during, and after exercise. Exercise-induced acidosis was more severe in the ACD and PLAC trials (7.15 ± 0.06, 7.21 ± 0.07, 7.16 ± 0.06, P < 0.05, for ACD, ALK, PLAC, respectively). Recovery kinetics for blood pH and lactate, as assessed by the monoexponential slope constant, were not different between trials (0.057 ± 0.01, 0.050 ± 0.01, 0.080 ± 0.02, for ACD, ALK, PLAC, respectively). Complete recovery of blood pH from metabolic acidosis can take longer than 45 min. Such a recovery profile is nonlinear, with 50% recovery occurring in approximately 12 min. Complete recovery of blood lactate can take longer than 60 min, with 50% recovery occurring in approximately 30 min. Induced alkalosis decreases metabolic acidosis and improves pH recovery compared to acidodic and placebo conditions. Although blood pH and lactate are highly correlated during recovery from acidosis, they recover at significantly different rates.

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Dean Norris, David Joyce, Jason Siegler, James Clock and Ric Lovell

Purpose: This study assessed the utility of force–time characteristics from the isometric midthigh pull (IMTP) as a measure of neuromuscular function after elite-level Australian rules football matches. It was hypothesized that rate characteristics of force development would demonstrate a different response magnitude and recovery time course than peak force measurements. Methods: Force–time characteristics of the IMTP (peak force, 0- to 50-ms rate of force development [RFD], 100- to 200-ms RFD) were collected at 48 (G+2), 72 (G+3), and 96 h (G+4) after 3 competitive Australian rules football matches. Results: Meaningful reductions (>75% of the smallest worthwhile change) were observed at G+2, G+3, and G+4 for RFD 0–50 milliseconds (−25.8%, −17.5%, and −16.9%) and at G+2 and G+3 for RFD 100–200 milliseconds (−15.7% and −11.7%). No meaningful reductions were observed for peak force at any time point (G+2 −4.0%, G+3 −3.9%, G+4 −2.7%). Higher week-to-week variation was observed for RFD 0–50 milliseconds (G+2 17.1%, G+3 27.2%, G+4 19.3%) vs both RFD 100–200 milliseconds (G+2 11.3%, G+3 11.5%, G+4 7.2%) and peak force (G+2 4.8%, G+3 4.4%, G+4 8.4%). Conclusions: These findings highlight the potential use of rate characteristics from the IMTP as measures of neuromuscular function in elite sport settings, and in particular RFD 100–200 milliseconds due to its higher reliability. Interestingly, peak force collected from the IMTP was not meaningfully suppressed at any time point after elite Australian rules football match play. This suggests that rate characteristics from IMTP may provide more sensitive and valuable insight regarding neuromuscular function recovery kinetics than peak measures.

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Lars R. McNaughton, Steve Kenney, Jason Siegler, Adrian W. Midgley, Ric J. Lovell and David J. Bentley

Context:

Recently, superoxygenated-water beverages have emerged as a new purported ergogenic substance.

Purpose:

This study aimed to determine the effects of superoxygenated water on submaximal endurance performance.

Methods:

Eleven active male subjects, VO2max 52.6 ± 4.8 mL · kg−1 · min−1, height 180.0 ± 2.0 cm, weight 76.0 ± 7.0 kg, age 24 ± 1.0 y (mean ± SD), completed a 45-min cycle-ergometry exercise test at 70% of their previously predicted maximal power output with a 10-min rest period, followed by a 15-min time trial (TT). Thirty minutes before the exercise test subjects consumed 15 mL of either superoxygenated water (E) or placebo (P; water mixed with low-chlorine solution). Subjects then completed the test again a week later for the other condition (double-blind, randomized). The physiological variables measured during exercise were VO2, VCO2, respiratory-exchange ratio (RER), VE, PO2, PCO2, blood lactate (bLa–), and heart rate (HR). Mean distance covered and the average power output for the 15-min TT were also measured as performance indicators.

Results:

There were no significant differences in VO2, VCO2, RER, VE, bLa, PO2, and HR (P > .05) during the exercise tests. Neither were there any significant improvements in the total distance covered (P 9.01 ± 0.74 km vs E 8.96 ± 0.68 km, P > .05) or the average power output (P 186.7 ± 35.8 W vs E 179.0 ± 25.9 W, P > .05) during the 15-min TT.

Conclusion:

Based on these results the authors conclude that consuming 15 mL of superoxygenated water does not enhance submaximal or maximal TT cycling performance.