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Christopher Thomas, Paul A. Jones and Paul Comfort

Purpose:

To determine the reliability of the Dynamic Strength Index (DSI) in college athletes.

Method:

Nineteen male college athletes performed the squat jump (SJ) and isometric midthigh pull (IMTP) to determine peak force, on 2 separate days. Reliability was assessed by intraclass correlation coefficient (ICC), typical error (TE), percentage change in the mean, smallest worthwhile change (SWC), and coefficient of variation (%CV).

Results:

Peak force for the SJ was 2137 ± 499 N and 2781 ± 435 N for the IMTP, resulting in a mean DSI of 0.78 ± 0.19. Peak forces in the SJ (ICC = .99, TE = 57.22 N, change in mean = 0.2%, SWC = 4.7%, CV = 2.6%) and IMTP (ICC = .95, TE = 104.22 N, change in mean = 0.5%, SWC = 3.1%, CV = 3.8%) were considered highly reliable between sessions. However, IMTP peak force was the only variable with an overall TE < SWC. The DSI was also highly reliable (ICC = .97, TE = 0.03, change in mean = −0.3%, SWC = 5.1%, CV = 4.6%) between sessions.

Conclusion:

This study demonstrates that peak force in the SJ and IMTP are reliable, resulting in a reliable assessment of dynamic-force-production capabilities via the DSI. The DSI may be used to guide individualized training interventions and monitor specific adaptations to training. Changes in SJ peak force, IMTP peak force, and DSI were >4.67%, 3.13%, and 5.13%, respectively, identifying meaningful changes in response to training or competition.

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Christopher Thomas, Thomas Dos’Santos, Paul A. Jones and Paul Comfort

Purpose:

The purpose of this investigation was to determine the reliability of the 30-15 Intermittent Fitness Test (30-15IFT) in semiprofessional soccer players.

Methods:

Fourteen male semiprofessional soccer players performed the 30-15IFT on 2 occasions separated by 7 d. Reliability was assessed by intraclass correlation coefficient (ICC), typical error of measurement expressed as a coefficient of variation (CV), and smallest worthwhile change (SWC) to determine any significant difference between testing sessions.

Results:

Maximal intermittent running velocity (VIFT) demonstrated good reliability (ICC = .80) for between-sessions reliability. The CV was 2.5% for between-sessions reliability of the 30-15IFT. As the SWC (0.70 km/h) falls within the range in which the individual’s true score is likely to lie (1.0 km/h), the usefulness of the VIFT was rated as marginal. Despite the usefulness of the 30-15IFT being deemed marginal, a change in performance as small as 1.0 km/h (2 stages) in VIFT could be considered substantial or real.

Conclusion:

This study demonstrates that VIFT in the 30-15IFT is reliable, resulting in a reliable assessment of team-sport-specific cardiorespiratory fitness, with changes as small as 1.0 km/h (2 stages) in VIFT considered meaningful.

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Christopher Thomas, Paul Comfort, Paul A. Jones and Thomas Dos’Santos

Purpose:

To investigate the relationships between maximal isometric strength, vertical jump (VJ), sprint speed, and change-of-direction speed (CoDS) in academy netball players and determine whether players who have high performance in isometric strength testing would demonstrate superior performance in VJ, sprint speed, and CoDS measures.

Method:

Twenty-six young female netball players (age 16.1 ± 1.2 y, height 173.9 ± 5.7 cm, body mass 66.0 ± 7.2 kg) from a regional netball academy performed isometric midthigh pull (IMTP), squat jumps (SJs), countermovement jumps (CMJs), 10-m sprints, and CoDS (505).

Results:

IMTP measures displayed moderate to strong correlations with sprint and CoDS performance (r = –.41 to –.66). The VJs, which included SJs and CMJs, demonstrated strong correlations with 10-m sprint times (r = –.60 to –.65; P < .01) and CoDS (r = –.60 to –.71; P = .01). Stronger players displayed significantly faster sprint (ES = 1.1–1.2) and CoDS times (ES = 1.2–1.7) and greater VJ height (ES = 0.9–1.0) than weaker players.

Conclusion:

The results of this study illustrate the importance of developing high levels of lower-body strength to enhance VJ, sprint, and CoDS performance in youth netball players, with stronger athletes demonstrating superior VJ, sprint, and CoDS performances.

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Thomas Dos’Santos, Christopher Thomas, Paul A. Jones and Paul Comfort

Purpose:

To investigate the within-session reliability of bilateral- and unilateral-stance isometric midthigh-pull (IMTP) force–time characteristics including peak force (PF), relative PF, and impulse at time bands (0–100, 0–200, 0–250, and 0–300 milliseconds) and to compare isometric force–time characteristics between right and left and dominant (D) and nondominant (ND) limbs.

Methods:

Professional male rugby league and multisport male college athletes (N = 54; age, 23.4 ± 4.2 y; height, 1.80 ± 0.05 m; mass, 88.9 ± 12.9 kg) performed 3 bilateral IMTP trials and 6 unilateral-stance IMTP trials (3 per leg) on a force plate sampling at 600 Hz.

Results:

Intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) demonstrated high within-session reliability for bilateral and unilateral IMTP PF (ICC = .94, CV = 4.7–5.5%). Lower reliability measures and greater variability were observed for bilateral and unilateral IMTP impulse at time bands (ICC = .81–.88, CV = 7.7–11.8%). Paired-sample t tests and Cohen d effect sizes revealed no significant differences for all isometric force–time characteristics between right and left limbs in male college athletes (P >.05, d ≤ 0.32) and professional rugby league players (P > .05, d ≤ 0.11); however, significant differences were found between D and ND limbs in male college athletes (P < .001, d = 0.43–0.91) and professional rugby league players (P < .001, d = 0.27–0.46).

Conclusion:

This study demonstrated high within-session reliability for unilateral-stance IMTP PF, revealing significant differences in isometric force–time characteristics between D and ND limbs in male athletes.

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Christopher A. Knight

Column-editor : Thomas W. Kaminski

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Daohang Sha, Christopher R. France and James S. Thomas

The effect of target location, speed, and handedness on the average total mechanical energy and movement efficiency is studied in 15 healthy subjects (7 males and 8 females with age 22.9 ± 1.79 years old) performing full body reaching movements. The average total mechanical energy is measured as the time average of integration of joint power, potential energy, and kinetic energy respectively. Movement efficiency is calculated as the ratio of total kinetic energy to the total joint power and potential energy. Results show that speed and target location have significant effects on total mechanical energy and movement efficiency, but reaching hand only effects kinetic energy. From our findings we conclude that (1) efficiency in whole body reaching is dependent on whether the height of the body center of mass is raised or lowered during the task; (2) efficiency is increased as movement speed is increased, in part because of greater changes in potential energy; and (3) the CNS does not appear to use movement efficiency as a primary planning variable in full body reaching. It may be dependent on a combination of other factors or constraints.

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Christopher Kuenze, Moataz Eltouhky, Abbey Thomas, Mark Sutherlin and Joseph Hart

Context:

Collecting torque data using a multimode dynamometer is common in sports-medicine research. The error in torque measurements across multiple sites and dynamometers has not been established.

Objective:

To assess the validity of 2 calibration protocols across 3 dynamometers and the error associated with torque measurement for each system.

Design:

Observational study.

Setting:

3 university laboratories at separate institutions.

Equipment:

2 Biodex System 3 dynamometers and 1 Biodex System 4 dynamometer.

Interventions:

System calibration was completed using the manufacturer-recommended single-weight method and an experimental calibration method using a series of progressive weights. Both calibration methods were compared with a manually calculated theoretical torque across a range of applied weights.

Main Outcome Measures:

Relative error, absolute error, and percent error were calculated at each weight. Each outcome variable was compared between systems using 95% confidence intervals across low (0–65 Nm), moderate (66–110 Nm), and high (111–165 Nm) torque categorizations.

Results:

Calibration coefficients were established for each system using both calibration protocols. However, within each system the calibration coefficients generated using the single-weight (System 4 = 2.42 [0.90], System 3a = 1.37 [1.11], System 3b = –0.96 [1.45]) and experimental calibration protocols (System 4 = 3.95 [1.08], System 3a = –0.79 [1.23], System 3b = 2.31 [1.66]) were similar and displayed acceptable mean relative error compared with calculated theoretical torque values. Overall, percent error was greatest for all 3 systems in low-torque conditions (System 4 = 11.66% [6.39], System 3a = 6.82% [11.98], System 3b = 4.35% [9.49]). The System 4 significantly overestimated torque across all 3 weight increments, and the System 3b overestimated torque over the moderate-torque increment.

Conclusions:

Conversion of raw voltage to torque values using the single-calibration-weight method is valid and comparable to a more complex multiweight calibration process; however, it is clear that calibration must be done for each individual system to ensure accurate data collection.

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Thomas Curran, Andrew P. Hill and Christopher P. Niemiec

The potential benefits of children’s engagement in sport for their psychological, social, and physical health are well established. Yet children may also experience psychological and social impairments due, in part, to a variety of detrimental coach behaviors. In the current study, we proposed and tested a conditional process model of children’s self-reported behavioral engagement and behavioral disaffection in sport based on self-determination theory. Results from a sample of 245 youth soccer players suggested that structure from coaches related positively to behavioral engagement and negatively to behavioral disaffection, and that these relations were mediated by athletes’ basic psychological need satisfaction. Importantly, and in line with our hypotheses, these indirect effects were moderated by autonomy support from coaches, such that the mediation was evident only among those who reported higher levels of autonomy support. These findings underscore the importance of coaches’ providing guidance, expectations, and feedback (i.e., structure) in a way that respects athletes’ volition (i.e., autonomy support).

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Paul F. Greene, Christopher J. Durall and Thomas W. Kernozek

Context:

A torso-elevated side support (TESS) has previously been described for measuring endurance of the lateral trunk muscles. In some individuals, however, TESS performance may be hindered by upper extremity pain or fatigue. For this reason a novel test, the feet-elevated side-support test (FESS), was examined.

Objective:

To determine intersession reliability of a FESS and a TESS on the left and right sides using a single examiner, to evaluate the relationship between tests, and to compare reasons for test termination.

Design:

Nonexperimental prospective repeated measures.

Setting:

University laboratory.

Participants:

A convenience sample of 60 healthy participants from a university community (17 men, 43 women; age 21.1 ± 2.2 y; height 169.9 ± 9.5 cm; weight 67.1 ± 11.9 kg).

Results:

Intraclass correlation coefficient between 3 testing sessions = .87 with right FESS, .86 with left FESS, .78 with right TESS, and .91 with left TESS. Pearson correlation coefficients ranged from .59 (between left FESS and left TESS in women) to .75 (between left FESS and left TESS in men). Upper extremity pain or fatigue was the reason given for test termination in 42.5% of participants during the TESS and 5.0% during the FESS (P = .000, Fisher exact test).

Conclusions:

FESS and TESS had comparable intersession reliability by the same evaluator. Moderate to high correlations were found between FESS and TESS scores, suggesting that the tests assess similar qualities. Far fewer participants terminated the FESS because of upper extremity pain or fatigue. Thus, the FESS may be a suitable alternative to the previously validated TESS, particularly for individuals with upper extremity pain or weakness.

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Christopher D. Brown, Christine A. lauber and Thomas Cappaert

Clinical Scenario:

Iontophoresis is a method of local transfer of ionized medicated and nonmedicated substances through the skin and into the target tissues using magnetic polarization. The anti-inflammatory properties exhibited by dexamethasone sodium phosphate (DEX) combined with iontophoresis make it a potentially desirable treatment for clinicians wishing to administer a noninvasive localized drug concentration without having a large systemic concentration of that drug. Since concurrent treatments are commonly used in clinical practice, many of the published studies that included the use of DEX also used concurrent treatments. However, this may make it difficult for clinicians to determine the individual effectiveness of DEX iontophoresis in treating musculoskeletal conditions.

Focused Clinical Question:

Does DEX iontophoresis, alone, decrease pain and improve function in patients with musculoskeletal conditions when compared with placebo or control?