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Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m.

ABSTRACT: Backstroke starts involve the athlete starting from a flexed position with their feet against the pool wall and then extending their ankles, knees, hips and back to push off; however, swimmers can start in different positions. The purpose of this study was to evaluate the performance impact of different knee extension angles in the setup position for a backstroke start. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees maximally flexed, and one with the knees less flexed. The start handles and touchpad were instrumented with multi-axial force sensors. Activity of major hip and knee extensors was measured using surface electromyography. Body position in the sagittal plane was recorded using high-speed cameras. There was no overall difference in time to 10 m between the two conditions (p = 0.36, dz = 0.12), but some participants showed differences as large as 0.12 s in time to 10 m between start conditions. We observed that starts performed from a setup position with less knee flexion had an average 0.07 m greater head entry distance (p = 0.07, dz = 0.53), while starts from a setup position with maximal knee flexion had an average 0.2 m/s greater takeoff velocity (p = 0.02, dz = 0.78). Both head entry distance and takeoff velocity are related to start performance, suggesting each position may optimize different aspects of the backstroke start. Coaches should assess athletes individually to determine which position is optimal.

SUBMITTER: Barkwell GE

PROVIDER: S-EPMC7240410 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m.

Barkwell Gordon E GE Dickey James P JP

Sports (Basel, Switzerland) 20200331 4

Backstroke starts involve the athlete starting from a flexed position with their feet against the pool wall and then extending their ankles, knees, hips and back to push off; however, swimmers can start in different positions. The purpose of this study was to evaluate the performance impact of different knee extension angles in the setup position for a backstroke start. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees maximally flexed, an ...[more]

PMID: 32244452

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Project description:Short, intermittent episodes of disuse muscle atrophy (DMA) may have negative impact on age related muscle loss. There is evidence of variability in rate of DMA between muscles and over the duration of immobilization. As yet, this is poorly characterized. This review aims to establish and compare the time-course of DMA in immobilized human lower limb muscles in both healthy and critically ill individuals, exploring evidence for an acute phase of DMA and differential rates of atrophy between and muscle groups. MEDLINE, Embase, CINHAL and CENTRAL databases were searched from inception to April 2021 for any study of human lower limb immobilization reporting muscle volume, cross-sectional area (CSA), architecture or lean leg mass over multiple post-immobilization timepoints. Risk of bias was assessed using ROBINS-I. Where possible meta-analysis was performed using a DerSimonian and Laird random effects model with effect sizes reported as mean differences (MD) with 95% confidence intervals (95% CI) at various time-points and a narrative review when meta-analysis was not possible. Twenty-nine studies were included, 12 in healthy volunteers (total n = 140), 18 in patients on an Intensive Therapy Unit (ITU) (total n = 516) and 3 in patients with ankle fracture (total n = 39). The majority of included studies are at moderate risk of bias. Rate of quadriceps atrophy over the first 14 days was significantly greater in the ITU patients (MD -1.01 95% CI -1.32, -0.69), than healthy cohorts (MD -0.12 95% CI -0.49, 0.24) (P < 0.001). Rates of atrophy appeared to vary between muscle groups (greatest in triceps surae (-11.2% day 28), followed by quadriceps (-9.2% day 28), then hamstrings (-6.5% day 28), then foot dorsiflexors (-3.2% day 28)). Rates of atrophy appear to decrease over time in healthy quadriceps (-6.5% day 14 vs. -9.1% day 28) and triceps surae (-7.8% day 14 vs. -11.2% day 28), and ITU quadriceps (-13.2% day 7 vs. -28.2% day 14). There appears to be variability in the rate of DMA between muscle groups, and more rapid atrophy during the earliest period of immobilization, indicating different mechanisms being dominant at different timepoints. Rates of atrophy are greater amongst critically unwell patients. Overall evidence is limited, and existing data has wide variability in the measures reported. Further work is required to fully characterize the time course of DMA in both health and disease.

Dataset Information

Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m.

Publications

Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m.

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