scholarly journals Eccentric Force-Velocity Characteristics during a Novel Squat Protocol in Trained Rugby Union Athletes—Pilot Study

2021 ◽  
Vol 6 (2) ◽  
pp. 32
Author(s):  
Conor McNeill ◽  
C. Martyn Beaven ◽  
Daniel T. McMaster ◽  
Nicholas Gill
Keyword(s):  
Pilot Study ◽  
Dynamic Performance ◽  
Intraclass Correlation ◽  
Rugby Union ◽  
Mean Velocity ◽  
Force Development ◽  
Back Squat ◽  
Force Velocity ◽  
Force Time ◽  
Change In Mean

Eccentric strength characteristics have been shown to be important factors in physical performance. Many eccentric tests have been performed in isolation or with supramaximal loading. The purpose of this study was to investigate within- and between- session reliability of an incremental eccentric back squat protocol. Force plates and a linear position transducer captured force-time-displacement data across six loading conditions, separated by at least seven days. The reliability of eccentric specific measurements was assessed using coefficient of variation (CV), change in mean, and intraclass correlation coefficient (ICC). Eccentric peak force demonstrated good ICC (≥0.82) and TE (≤7.3%) for each load. Variables based on mean data were generally less reliable (e.g., mean rate of force development, mean force, mean velocity). This novel protocol meets acceptable levels of reliability for different eccentric-specific measurements although the extent to which these variables affect dynamic performance requires further research.

The Reliability of Individualized Load–Velocity Profiles

2018 ◽  
Vol 13 (6) ◽  
pp. 763-769 ◽  
Author(s):  
Harry G. Banyard ◽  
Kazunori Nosaka ◽  
Alex D. Vernon ◽  
G. Gregory Haff
Keyword(s):  
Linear Regression ◽  
Peak Velocity ◽  
Intraclass Correlation ◽  
Velocity Profiles ◽  
Mean Velocity ◽  
Movement Velocity ◽  
Repetition Maximum ◽  
Back Squat ◽  
Free Weight ◽  
Order Polynomial

Purpose: To examine the reliability of peak velocity (PV), mean propulsive velocity (MPV), and mean velocity (MV) in the development of load–velocity profiles (LVP) in the full-depth free-weight back squat performed with maximal concentric effort. Methods: Eighteen resistance-trained men performed a baseline 1-repetition maximum (1-RM) back-squat trial and 3 subsequent 1-RM trials used for reliability analyses, with 48-h intervals between trials. 1-RM trials comprised lifts from 6 relative loads including 20%, 40%, 60%, 80%, 90%, and 100% 1-RM. Individualized LVPs for PV, MPV, or MV were derived from loads that were highly reliable based on the following criteria: intraclass correlation coefficient (ICC) >.70, coefficient of variation (CV) ≤10%, and Cohen d effect size (ES) <0.60. Results: PV was highly reliable at all 6 loads. MPV and MV were highly reliable at 20%, 40%, 60%, 80%, and 90% but not 100% 1-RM (MPV: ICC = .66, CV = 18.0%, ES = 0.10, SEM = 0.04 m·s−1; MV: ICC = .55, CV = 19.4%, ES = 0.08, SEM = 0.04 m·s−1). When considering the reliable ranges, almost perfect correlations were observed for LVPs derived from PV20–100% (r = .91–.93), MPV20–90% (r = .92–.94), and MV20–90% (r = .94–.95). Furthermore, the LVPs were not significantly different (P > .05) between trials or movement velocities or between linear regression versus 2nd-order polynomial fits. Conclusions: PV20–100%, MPV20–90%, and MV20–90% are reliable and can be utilized to develop LVPs using linear regression. Conceptually, LVPs can be used to monitor changes in movement velocity and employed as a method for adjusting sessional training loads according to daily readiness.

scholarly journals Squat Jump Movement Onset Thresholds Influence on Kinetics and Kinematics

2021 ◽  
Vol 9 (3) ◽  
pp. 1
Author(s):  
Paul T Donahue ◽  
Christopher M Hill ◽  
Samuel J Wilson ◽  
Charles C Williams ◽  
John C Garner
Keyword(s):  
Intraclass Correlation ◽  
Force Platform ◽  
Vertical Force ◽  
Time Data ◽  
Movement Onset ◽  
Time Curve ◽  
Squat Jump ◽  
Force Velocity ◽  
Force Time ◽  
The Impact

Background of Study: Differing movement onset thresholds have been used when analyzing the squat jump movement from force-time data obtained from a force platform. This makes comparisons difficult between investigations as this will impact the amount of the force-time curve that is analyzed. Objective: Thus, study examined the effect onset threshold had on kinetic and kinematic variables used in the assessment of the squat jump. Methods: Using a within-subject study design, fifteen recreational trained males performed three trials of squat jumps on a force platform. Each trial was analyzed using one of five different onset thresholds (2.5% SW, 5% SW, 10% SW, 20N, 5SD). Force, velocity, and power, as well as time to peak force, velocity, power and jump height were calculated using the vertical force data obtain from the force plate. Reliability was assessed using intraclass correlation coefficients and coefficients of variation. A one-way ANOVA was used to examine the impact of onset thresholds on all variables of interest. Results: The use of 10% SW and 5SD met minimum reliability criteria for all variables. Temporal related variables were impact to the greatest extent by differing thresholds with large (d > 1.20) significant differences. 10% SW showed the highest mean values of force, velocity, and power. Conclusions: The use of 5SD of the weighting phase is recommended as this showed high level of both absolute and relative reliability in addition to preserving a large portion of the force – time curve to be used in the analysis.

scholarly journals The Inter-Session Reliability of Isometric Force-Time Variables and the Effects of Filtering and Starting Force

2019 ◽  
Vol 66 (1) ◽  
pp. 43-55 ◽  
Author(s):  
Gavin L. Moir ◽  
Aaron Getz ◽  
Shala E. Davis ◽  
Mário Marques ◽  
Chad A. Witmer
Keyword(s):  
Body Mass ◽  
Isometric Force ◽  
Intraclass Correlation ◽  
Time Signal ◽  
Time Intervals ◽  
Temporal Shift ◽  
Back Squat ◽  
Time Variables ◽  
Force Time

AbstractThe purposes of the present study were to assess the inter-session reliability of force-time variables recorded during isometric back squats and also to assess the effects of applying a filter to the data prior to analysis and assess the effects of different starting force thresholds on the force-time variables. Eleven resistance trained men (age: 22.5 ± 1.9 years; body mass: 90.3 ± 13.5 kg) attended two sessions where they performed isometric squats on force plates allowing the determination of force-time variables of maximal isometric force (Fmax) and different measures of the rate of force development (RFD). The force-time variables were calculated from both raw and filtered force signals. The start of the force application was determined using force thresholds of 1% or 5% of body mass (BM). Inter-session reliability for the force-time measures was assessed by calculating the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) of the measures. The ICC and CV ranged from 0.03 to 0.96 and 4.6 to 168%, respectively. The application of the filter significantly reduced Fmax and peak RFD (p < 0.004) and increased the reliability of the peak RFD. The use of the 5% BM threshold increased the magnitude of many of the RFD measures (p < 0.004) and resulted in slight improvements in the reliability of these measures although the resulting temporal shift in the force-time signal would preclude accurate assessment of the early phase of the RFD (< 100 ms). The use of a 1% BM starting force threshold without a filter is recommended when using the isometric back squat protocol presented here. Furthermore, the RFD calculated within specific time intervals is recommended

Reliability and validity of a new accelerometer (Wimu®) system for measuring velocity during resistance exercises

2017 ◽  
Vol 232 (3) ◽  
pp. 218-224 ◽  
Author(s):  
José M Muyor ◽  
Paulino Granero-Gil ◽  
José Pino-Ortega
Keyword(s):  
Standard Error ◽  
Intraclass Correlation ◽  
Maximum Velocity ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Back Squat ◽  
Intraclass Correlations ◽  
Resistance Exercises ◽  
Linear Encoder ◽  
Systematic Biases

This study had two main goals. The first was to determine the reliability of the Wimu® system (accelerometer) for mean velocity measurements during resistance exercises at 40% and 80% 1 repetition maximum (1RM). The second was to compare the results for the Wimu system to a linear encoder (gold standard) for mean velocity measurements when clipped to the bar during back squat exercises using the Smith machine. In all, 23 trained men (aged 22.3 ± 3.2 years) participated in this study. At maximum velocity in the concentric phase, they performed 10 repetitions with 40% 1RM and eight repetitions with 80% 1RM while using the Wimu system and T-Force linear encoder simultaneously to record data. Reliability was analysed using intraclass correlation, standard error of measurement and coefficient of variation. The validity was assessed using R2, intraclass correlation and Bland-Altman plots. The differences in test–retest reliability of both systems and systematic biases were non-significant ( p = 0.08–0.85) and very close to 0. The random errors averaged ±0.010 m/s. All the calculated coefficient of variations were less than 5% and all measurements had high intraclass correlations (mean: 0.936). Least-square linear regression and intraclass correlations for validity were very close to 1. Significant systematic biases were observed between the linear encoder and the Wimu system ( p < 0.001), although the effect sizes were small (0.21–0.44) and standard error of the estimate in concentric and eccentric phases at both intensities was less than 0.030. In conclusion, the findings of this study suggest that the Wimu system is a reliable and valid tool for the assessment of mean velocity during the back squat exercise using the Smith machine. These findings could help coaches and sport researchers evaluate athletes performing resistance exercises similar to squats with a reliable, valid and portable tool.

scholarly journals A Comparison of Ballistic and Nonballistic Lower-Body Resistance Exercise and the Methods Used to Identify Their Positive Lifting Phases

2012 ◽  
Vol 28 (4) ◽  
pp. 431-437 ◽  
Author(s):  
Jason Lake ◽  
Mike Lauder ◽  
Neal Smith ◽  
Kathleen Shorter
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
Lower Body ◽  
Power Development ◽  
Mean Power ◽  
Mean Velocity ◽  
Back Squat ◽  
Relative Acceleration ◽  
Body Resistance ◽  
Force Velocity

This study compared differences between ballistic jump squat (B) and nonballistic back squat (NB) force, velocity, power, and relative acceleration duration, and the effect that the method used to identify the positive lifting phase had on these parameters. Ground reaction force and barbell kinematics were recorded from 30 resistance trained men during B and NB performance with 45% 1RM. Force, velocity, and power was averaged over positive lifting phases identified using the traditional peak barbell displacement (PD) and positive impulse method. No significant differences were found between B and NB mean force, and mean power, but B mean velocity was 14% greater than the NB equivalent. Positive impulse mean force was 24% greater than PD mean force, and B relative acceleration duration was 8.6% greater than the NB equivalent when PD was used to identify the end of the positive lifting phase. These results challenge common perceptions of B superiority for power development.

scholarly journals The role of local impedance drop in the acute lesion efficacy during pulmonary vein isolation performed with a new contact force sensing catheter—A pilot study

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257050
Author(s):  
Nándor Szegedi ◽  
Zoltán Salló ◽  
Péter Perge ◽  
Katalin Piros ◽  
Vivien Klaudia Nagy ◽  
...  
Keyword(s):  
Pilot Study ◽  
Pulmonary Vein ◽  
Pulmonary Vein Isolation ◽  
Contact Force ◽  
Posterior Wall ◽  
Anterior Wall ◽  
Force Sensing ◽  
Lesion Formation ◽  
Force Time

Introduction Our pilot study aimed to evaluate the role of local impedance drop in lesion formation during pulmonary vein isolation with a novel contact force sensing ablation catheter that records local impedance as well and to find a local impedance cut-off value that predicts successful lesion formation. Materials and methods After completing point-by-point radiofrequency pulmonary vein isolation, the success of the applications was evaluated by pacing along the ablation line at 10 mA, 2 ms pulse width. Lesions were considered successful if loss of local capture was achieved. Results Out of 645 applications, 561 were successful and 84 were unsuccessful. Compared to the unsuccessful ablation points, the successful applications were shorter (p = 0.0429) and had a larger local impedance drop (p<0.0001). There was no difference between successful and unsuccessful applications in terms of mean contact force (p = 0.8571), force-time integral (p = 0.0699) and contact force range (p = 0.0519). The optimal cut-point for the local impedance drop indicating successful lesion formation was 21.80 Ohms on the anterior wall [AUC = 0.80 (0.75–0.86), p<0.0001], and 18.30 Ohms on the posterior wall [AUC = 0.77 (0.72–0.83), p<0.0001]. A local impedance drop larger than 21.80 Ohms on the anterior wall and 18.30 Ohms on the posterior wall was associated with an increased probability of effective lesion creation [OR = 11.21, 95%CI 4.22–29.81, p<0.0001; and OR = 7.91, 95%CI 3.77–16.57, p<0.0001, respectively]. Conclusion The measurement of the local impedance may predict optimal lesion formation. A local impedance drop > 21.80 Ohms on the anterior wall and > 18.30 Ohms on the posterior wall significantly increases the probability of creating a successful lesion.

scholarly journals Pushing up or pushing out—an initial investigation into horizontal- versus vertical-force training on swimming start performance: a pilot study

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10937
Author(s):  
Shiqi Thng ◽  
Simon Pearson ◽  
Justin W.L. Keogh
Keyword(s):  
Pilot Study ◽  
Resistance Training ◽  
Body Mass ◽  
Deliberate Practice ◽  
Training Programme ◽  
Concurrent Training ◽  
Training Intervention ◽  
Vertical Force ◽  
Squat Jump ◽  
Force Time

Background The block phase in the swimming start requires a quick reaction to the starting signal and a large take-off velocity that is primarily horizontal in direction. Due to the principle of specificity of training, there is a potential benefit of performing a greater proportion of horizontal force production exercises in a swimmers’ dry-land resistance training sessions. Therefore, the purpose of this pilot study was to provide an insight into the effects of a horizontal- (HF) vs vertical-force (VF) training intervention on swim start performance. Methods Eleven competitive swimmers (six males (age 20.9 ± 1.8 years, body mass 77.3 ± 9.7 kg, height 1.78 ± 0.05 m) and five females (age 21.4 ± 2.0 years, body mass 67.5 ± 7.4 kg, height 1.69 ± 0.05 m)) completed 2 weekly sessions of either a horizontal- or vertical-force focused resistance training programme for 8 weeks. Squat jump force-time characteristics and swim start kinetic and kinematic parameters were collected pre- and post-intervention. Results Across the study duration, the swimmers completed an average of nine swimming sessions per week with an average weekly swim volume of 45.5 ± 17.7 km (HF group) and 53 ± 20.0 km (VF group), but little practice of the swim start per week (n = 9). Within-group analyses indicated a significant increase in predicted one repetition maximum (1RM) hip thrust strength in the HF group, as well as significant increases in grab resultant peak force but reductions in resultant peak force of the block phase for the VF group. No significant between-group differences in predicted 1RM hip thrust and back squat strength, squat jump force-time and swim start performance measures were observed after 8 weeks of training. Significant correlations in the change scores of five block kinetic variables to time to 5 m were observed, whereby increased block kinetic outputs were associated with a reduced time to 5 m. This may be indicative of individual responses to the different training programmes. Discussion The results of this current study have been unable to determine whether a horizontal- or vertical-force training programme enhances swim start performance after an 8-week training intervention. Some reasons for the lack of within and between group effects may reflect the large volume of concurrent training and the relative lack of any deliberate practice of the swim start. Larger samples and longer training duration may be required to determine whether significant differences occur between these training approaches. Such research should also look to investigate how a reduction in the concurrent training loads and/or an increase in the deliberate practice of the swim start may influence the potential changes in swim start performance.

scholarly journals Cardiac Energetics Before, During and After Anthracycline-based Chemotherapy in Breast Cancer Patients Using 31P Magnetic Resonance Spectroscopy: A Pilot Study

2020 ◽  
Author(s):  
Gillian Macnaught ◽  
Olga Oikonomidou ◽  
Christopher T. Rodgers ◽  
William Clarke ◽  
Annette Cooper ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Pilot Study ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Resonance Spectroscopy ◽  
Ventricular Ejection Fraction ◽  
Time Points ◽  
Change In Mean

Abstract PURPOSETo explore the utility of phosphorus magnetic resonance spectroscopy (31P MRS) in identifying anthracycline-induced cardiac toxicity in patients with breast cancer.METHODS20 patients with newly diagnosed breast cancer receiving anthracycline-based chemotherapy had cardiac magnetic resonance assessment of left ventricular ejection fraction (LVEF) and 31P MRS to determine myocardial Phosphocreatine/Adenosine Triphosphate ratio (PCr/ATP) at three time points: pre, mid and end-chemotherapy. Plasma high sensitivity cardiac troponin-I (cTn-I) tests and electrocardiograms were also performed at these same time points. RESULTS PCr/ATP ratio did not change significantly between pre- and mid-chemo (2.16±0.46 v 2.00±0.56, p=0.80) and pre- and end-chemo (2.16±0.46 v 2.17±0.86, p=0.99). Mean LVEF reduced significantly by 5.1% between pre- and end-chemo (61.4±4.4 vs 56.3±8.1 %, p=0.02). Change in PCr/ATP ratios from pre- to end-chemo correlated inversely with changes in LVEF over the same period (r=-0.65, p=0.006). Plasma cTn-I increased progressively during chemotherapy from pre- to mid-chemo (1.35±0.81 to 4.40±2.64 ng/L; p=0.01) and from mid to end-chemo (4.40±2.64 to 18.33±13.23 ng/L; p=0.001). CONCLUSIONSIn this small cohort pilot study, we did not observe a clear change in mean PCr/ATP values during chemotherapy despite evidence of increased plasma cardiac biomarkers and reduced LVEF. Future similar studies should be adequately powered to take account of patient drop-out and variable changes in PCr/ATP.

Should We Base Training Prescription on the Force–Velocity Profile? Exploratory Study of Its Between-Day Reliability and Differences Between Methods

2020 ◽  
pp. 1-7
Author(s):  
Pedro L. Valenzuela ◽  
Guillermo Sánchez-Martínez ◽  
Elaia Torrontegi ◽  
Javier Vázquez-Carrión ◽  
Zigor Montalvo ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Intraclass Correlation ◽  
Reliability Coefficient ◽  
Power Coefficient ◽  
Squat Jump ◽  
Jump Test ◽  
Force Velocity ◽  
Constrained Conditions ◽  
Vertical Jumps ◽  
Good Agreement

Purpose: To analyze the differences in the force–velocity (F–v) profile assessed under unconstrained (ie, using free weights) and constrained (ie, on a Smith machine) vertical jumps, as well as to determine the between-day reliability. Methods: A total of 23 trained participants (18 [1] y) performed an incremental load squat jump test (with ∼35%, 45%, 60%, and 70% of the subjects’ body mass) on 2 different days using free weights and a Smith machine. Nine of these participants repeated the tests on 2 other days for an exploratory analysis of between-day reliability. F–v variables (ie, maximum theoretical force [F0], velocity [v0], and power, and the imbalance between the actual and the theoretically optimal F–v profile) were computed from jump height. Results: A poor agreement was observed between the F–v variables assessed under constrained and unconstrained conditions (intraclass correlation coefficient [ICC] < .50 for all). The height attained during each single jump performed under both constrained and unconstrained conditions showed an acceptable reliability (coefficient of variation < 10%, ICC > .70). The F–v variables computed under constrained conditions showed an overall good agreement (ICC = .75–.95 for all variables) and no significant differences between days (P > .05), but a high variability for v0, the imbalance between the actual and the theoretically optimal F–v profile, and maximal theoretical power (coefficient of variation = 17.0%–27.4%). No between-day differences were observed for any F–v variable assessed under unconstrained conditions (P > .05), but all of the variables presented a low between-day reliability (coefficient of variation > 10% and ICC < .70 for all). Conclusions: F–v variables differed meaningfully when obtained from constrained and unconstrained loaded jumps, and most importantly seemed to present a low between-day reliability.

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