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The reliability and usefulness of biomechanical measures of countermovement jump performance in elite rowers
Objective: This study aimed to define sit-to-walk (STW) movement without phase overlap. In addition, the intrasubject and test-retest repeatability of movement events were measured. Material and Methods: Fifteen healthy children aged between 7 and 12 years old participated in the study. A threedimensional motion analysis system was used to gather and process the kinematic and kinetic data. Two sessions of STW movement were performed with a one-week interval. The intraclass correlation coefficient (ICC) with 95.0% confidence interval (CI) was calculated to determine the repeatability of the new proposed phases at each point of a movement event. The adjusted coefficient of multiple correlation (CMC) was used to evaluate the similarities of the entire STW waveforms. Results: Nine phases of STW were identified by the demands of movement performance. The ICC values indicated poor to excellent intrasubject (0.36-0.97) and test-retest repeatability (0.30-0.96). Poor repeatability was observed at the hip (0.30-0.44), knee (0.36), and ankle (0.47 and 0.49) joints only during the gait cycle. The CMC values demonstrated high to excellent (>0.75) intrasubject and test-retest repeatability, indicating the similarities of STW waveforms. Conclusion: Additional phase definitions of STW demonstrated an acceptable level of repeatability in the childhood population. Variations in the lower extremities could be related to the fluidity with which these children performed at the point of gait initiation. Thus, variability in joint angles could be produced by the different fluidities of initial walking.
Objectives
The primary objective of this meta-analysis was to compare countermovement jump (CMJ) performance in studies that reported the highest value as opposed to average value for the purposes of monitoring neuromuscular status (i.e. fatigue and supercompensation). The secondary aim was to determine the sensitivity of the dependent variables.
Methods
The meta-analysis was conducted on the highest or average of a number of CMJ variables. Multiple literature searches were undertaken in Pubmed, Scopus, and Web of Science to identify articles utilizing CMJ to monitor training status. Effect sizes (ES) with 95% confidence interval (95% CI) were calculated using the mean and standard deviation of the pre- and post-testing data. The coefficient of variation (CV) with 95% CI was also calculated to assess the level of instability of each variable. Heterogeneity was assessed using a random-effects model.
Results
151 articles were included providing a total of 531 ESs for the meta-analyses; 85.4% of articles used highest CMJ height, 13.2% used average and 1.3% used both when reporting changes in CMJ performance. Based on the meta-analysis, average CMJ height was more sensitive than highest CMJ height in detecting CMJ fatigue and supercompensation. Furthermore, other CMJ variables such as peak power, mean power, peak velocity, peak force, mean impulse, and power were sensitive in tracking the supercompensation effects of training.
Conclusions
The average CMJ height was more sensitive than highest CMJ height in monitoring neuromuscular status; however, further investigation is needed to determine the sensitivity of other CMJ performance variables.
The purposes of this study included examining the reliability of reactive strength index-modified
(RSImod), the relationships between RSImod and force-time variables, and the
differences in RSImod between male and female collegiate athletes. 106 Division I collegiate
athletes performed unloaded and loaded countermovement jumps. Intraclass correlation
coefficients and typical error expressed as a coefficient of variation were used to establish the
relative and absolute reliability of RSImod, respectively. Pearson zero order product-moment
correlation coefficients were used to examine the relationships between RSImod and rate of
force development, peak force, and peak power during unloaded and loaded jumping
conditions. Finally, independent samples t-tests were used to examine the sex differences in
RSImod between male and female athletes. Intraclass correlation coefficient values for
RSImod ranged 0.96 – 0.98 and typical error values ranged 7.5 – 9.3% during all jumping
conditions. Statistically significant correlations existed between RSImod and all force-time
variables examined for male and female athletes during both jumping conditions (p < 0.05).
Statistically significant differences in RSImod existed between males and females during
both unloaded and loaded CMJs (p < 0.001). RSImod appears to be a reliable performance
measurement in male and female athletes. RSImod may be described and used as a measure
of explosiveness. Stronger relationships between RSImod, peak force, and peak power
existed in female athletes as compared to male athletes; however, further evidence
investigating these relationships is needed before conclusive statements can be made. Male
athletes produced greater RSImod values as compared to female athletes.
Purpose:
To examine the reliability and magnitude of change after fatiguing exercise in the countermovement-jump (CMJ) test and determine its suitability for the assessment of fatigue-induced changes in neuromuscular (NM) function. A secondary aim was to examine the usefulness of a set of alternative CMJ variables (CMJ-ALT) related to CMJ mechanics.
Methods:
Eleven male college-level team-sport athletes performed 6 CMJ trials on 6 occasions. A total of 22 variables, 16 typical (CMJ-TYP) and 6 CMJ-ALT, were examined. CMJ reproducibility (coefficient of variation; CV) was examined on participants' first 3 visits. The next 3 visits (at 0, 24, and 72 h postexercise) followed a fatiguing high-intensity intermittent-exercise running protocol. Meaningful differences in CMJ performance were examined through effect sizes (ES) and comparisons to interday CV.
Results:
Most CMJ variables exhibited intraday (n = 20) and interday (n = 21) CVs of <10%. ESs ranging from trivial to moderate were observed in 18 variables at 0 h (immediately postfatigue). Mean power, peak velocity, flight time, force at zero velocity, and area under the force-velocity trace showed changes greater than the CV in most individuals. At 24 h, most variables displayed trends toward a return to baseline. At 72 h, small increases were observed in time-related CMJ variables, with mean changes also greater than the CV.
Conclusions:
The CMJ test appears a suitable athlete-monitoring method for NM-fatigue detection. However, the current approach (ie, CMJ-TYP) may overlook a number of key fatigue-related changes, and so practitioners are advised to also adopt variables that reflect the NM strategy used.
Between-days reliability and sensitivity of common fatigue measures in rugby players
- G Roe
- J Darrall-Jones
- K Till
- P Phibbs
- D Read
- J Weakley
- B Jones
Roe, G., Darrall-Jones, J., Till, K., Phibbs, P., Read, D., Weakley, J., Jones, B. (2016). Between-days
reliability and sensitivity of common fatigue measures in rugby players. International Journal of Sports
Physiology and Performance, 11(5), 581-586.