54 research outputs found
Attractive Gait Training: Applying Dynamical Systems Theory to the Improvement of Locomotor Performance Across the Lifespan
Attractive Gait Training: Applying Dynamical Systems Theory to the Improvement of Locomotor Performance Across the Lifespan
The Difference Between Countermovement and Squat Jump Performances:A Review of Underlying Mechanisms With Practical Applications
Single-Leg Roman Chair Hold Is More Effective Than the Nordic Hamstring Curl in Improving Hamstring Strength-Endurance in Gaelic Footballers With Previous Hamstring Injury
The role of pennation angle and architectural gearing to rate of force development in dynamic and isometric muscle contractions
Background: Associations between muscle architecture and rate of force development (RFD) have been largely studied during fixed-end (isometric) contractions. Fixed-end contractions may, however, limit muscle shape changes and thus alter the relationship between muscle architecture an RFD. Aim: We compared the correlation between muscle architecture and architectural gearing and knee extensor RFD when assessed during dynamic versus fixed-end contractions. Methods: Twenty-two recreationally active male runners performed dynamic knee extensions at constant acceleration (2000°s−2) and isometric contractions at a fixed knee joint angle (fixed-end contractions). Torque, RFD, vastus lateralis muscle thickness, and fascicle dynamics were compared during 0–75 and 75–150 ms after contraction onset. Results: Resting fascicle angle was moderately and positively correlated with RFD during fixed-end contractions (r = 0.42 and 0.46 from 0–75 and 75–150 ms, respectively; p \u3c 0.05), while more strongly (p \u3c 0.05) correlated with RFD during dynamic contractions (r = 0.69 and 0.73 at 0–75 and 75–150 ms, respectively; p \u3c 0.05). Resting fascicle angle was (very) strongly correlated with architectural gearing (r = 0.51 and 0.73 at 0–75 ms and 0.50 and 0.70 at 75–150 ms; p \u3c 0.05), with gearing in turn also being moderately to strongly correlated with RFD in both contraction conditions (r = 0.38–0.68). Conclusion: Resting fascicle angle was positively correlated with RFD, with a stronger relationship observed in dynamic than isometric contraction conditions. The stronger relationships observed during dynamic muscle actions likely result from different restrictions on the acute changes in muscle shape and architectural gearing imposed by isometric versus dynamic muscle contractions
Sample size justifications in Gait & Posture
BACKGROUND: Context regarding how researchers determine the sample size of their experiments is important for interpreting the results and determining their value and meaning. Between 2018 and 2019, the journal Gait & Posture introduced a requirement for sample size justification in their author guidelines. RESEARCH QUESTION: How frequently and in what ways are sample sizes justified in Gait & Posture research articles and was the inclusion of a guideline requiring sample size justification associated with a change in practice? METHODS: The guideline was not in place prior to May 2018 and was in place from 25th July 2019. All articles in the three most recent volumes of the journal (84-86) and the three most recent, pre-guideline volumes (60-62) at time of preregistration were included in this analysis. This provided an initial sample of 324 articles (176 pre-guideline and 148 post-guideline). Articles were screened by two authors to extract author data, article metadata and sample size justification data. Specifically, screeners identified if (yes or no) and how sample sizes were justified. Six potential justification types (Measure Entire Population, Resource Constraints, Accuracy, A priori Power Analysis, Heuristics, No Justification) and an additional option of Other/Unsure/Unclear were used. RESULTS: In most cases, authors of Gait & Posture articles did not provide a justification for their study's sample size. The inclusion of the guideline was associated with a modest increase in the percentage of articles providing a justification (16.6-28.1%). A priori power calculations were the dominant type of justification, but many were not reported in enough detail to allow replication. SIGNIFICANCE: Gait & Posture researchers should be more transparent in how they determine their sample sizes and carefully consider if they are suitable. Editors and journals may consider adding a similar guideline as a low-resource way to improve sample size justification reporting
Can Resistance Training Enhance the Rapid Force Development in Unloaded Dynamic Isoinertial Multi-Joint Movements?:A Systematic Review
Sprint performance and force-velocity profiling does not differ between artificial turf and concrete
Purpose: Force-velocity-power (F-v-P) profiling can illustrate an individual’s sprinting capabilities, but no study has
explored the effect of different running surfaces on F-v-P outcomes.
Method: Twelve elite youth football players (age 16.3 0.5 years, mass 67.3 5.4 kg, height 176.2 4.6 cm) performed
two 30 m sprints on concrete and artificial turf in a randomised order on two testing days. Differences between surfaces
were determined using repeated-measures ANOVA (P < 0.05), whilst the coefficient of variation (CV), smallest worthwhile change and standard error of measurement were calculated to quantify reliability.
Results: No significant differences were found between surfaces over the average of two days. High reliability was
evident for 30 m sprint time, theoretical maximum horizontal velocity and ratio of force on both surfaces (CV 5%),
while the remaining outputs were not reliable (CV >10%).
Conclusion: These findings show that F-v-P profiling does not differ between concrete and artificial turf. However,
higher variability on the more unfamiliar concrete surface suggests that the testing surface should match the playing
surface. Since the standard error of measurement is larger than the smallest worthwhile change, the ability of this
method to monitor seasonal changes may be limited in youth elite soccer players
The effects of the Nordic hamstring exercise on sprint performance and eccentric knee flexor strength: A systematic review and meta-analysis of intervention studies among team sport players
The primary aim of this study was to investigate the effects of the Nordic hamstring exercise
(NH E ) on sprint performance (i.e., 5, 10 and 20 m) and explore associations between study characteristics
and sprint outcomes in team sport players. Secondary aims were to (1) investigate the effects of the NH E on
eccentric strength of the knee flexors (ES KF ) with categorical subgroup analysis to determine differences
between recreationally, well-trained individuals and young athletes, (2) determine the relation between
ES KF and sprint performance in team sport players, and (3) explore the effect of study characteristics (i.e.,
weekly volume, time duration and body mass) on ES KF .Medicin
A Systematic Review and Meta-Analysis of Crossover Studies Comparing Physiological, Perceptual and Performance Measures Between Treadmill and Overground Running
Background Treadmills are routinely used to assess running performance and training parameters related to physiological or perceived effort. These measurements are presumed to replicate overground running but there has been no systematic review comparing performance, physiology and perceived effort between treadmill and overground running. Objective The objective of this systematic review was to compare physiological, perceptual and performance measures between treadmill and overground running in healthy adults.MethodsAMED (Allied and Contemporary Medicine), CINAHL (Cumulative Index to Nursing and Allied Health), EMBASE, MEDLINE, SCOPUS, SPORTDiscus and Web of Science databases were searched from inception until May 2018. Included studies used a crossover study design to compare physiological (oxygen uptake [VO-2], heart rate [HR], blood lactate concentration [La]), perceptual (rating of perceived exertion [RPE] and preferred speed) or running endurance and sprint performance (i.e. time trial duration or sprint speed) outcomes between treadmill (motorised or non-motorised) and overground running. Physiological outcomes were considered across submaximal, near-maximal and maximal running intensity subgroups. Meta-analyses were used to determine mean difference (MD) or standardised MD (SMD) 95% confidence intervals. Results Thirty-four studies were included. Twelve studies used a 1% grade for the treadmill condition and three used grades >1%. Similar (V) over dotO(2) but lower La occurred during submaximal motorised treadmill running at 0% ((V) over dot O-2 MD: -0.55 0.93mL/kg/min; La MD: -1.26 +/- 0.71mmol/L) and 1% ((V) over dotO(2) MD: 0.37 +/- 1.12mL/kg/min; La MD: -0.52 +/- 0.50mmol/L) grade than during overground running. HR and RPE during motorised treadmill running were higher at faster submaximal speeds and lower at slower submaximal speeds than during overground running. (V) over dotO(2) (MD: -1.25 +/- 2.09mL/kg/min) and La (MD: -0.54 +/- 0.63mmol/L) tended to be lower, but HR (MD: 0 +/- 1bpm), and RPE (MD: -0.4 +/- 2.0units [6-20 scale]) were similar during near-maximal motorised treadmill running to during overground running. Maximal motorised treadmill running caused similar (V) over dotO(2) (MD: 0.78 +/- 1.55mL/kg/min) and HR (MD: -1 +/- 2bpm) to overground running. Endurance performance was poorer (SMD: -0.50 +/- 0.36) on a motorised treadmill than overground but sprint performance varied considerably and was not significantly different (MD: -1.4 +/- 5.8km/h). Conclusions Some, but not all, variables differ between treadmill and overground running, and may be dependent on the running speed at which they are assessed. Protocol registration (PROSPERO International Prospective Register of Systematic Reviews)
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