The reliability and precision of measurement in sports medicine are of concern in both research and clinical practice. The validity of conclusions drawn from a research project and the rationale for decisions made about the care of an injured athlete are directly related to the precision of measurement. Through analysis of variance, estimates of reliability and precision of measurement can be quantified. The purpose of this manuscript is to introduce the concepts of intraclass correlation as an estimate of reliability and standard error of measurement as an estimate of precision. The need for a standardized set of formulas for intraclass correlation is demonstrated, and it is urged that the standard error of measurement be included when estimates of reliability are reported. In addition, three examples are provided to illustrate important concepts and familiarize the reader with the process of calculating these estimates of reliability and precision of measurement.
Craig R. Denegar and Donald W. Ball
Niell G. Elvin, Alex A. Elvin and Steven P. Arnoczky
Modern electronics allow for the unobtrusive measurement of accelerations outside the laboratory using wireless sensor nodes. The ability to accurately measure joint accelerations under unrestricted conditions, and to correlate them with jump height and landing force, could provide important data to better understand joint mechanics subject to real-life conditions. This study investigates the correlation between peak vertical ground reaction forces, as measured by a force plate, and tibial axial accelerations during free vertical jumping. The jump heights calculated from force-plate data and accelerometer measurements are also compared. For six male subjects participating in this study, the average coefficient of determination between peak ground reaction force and peak tibial axial acceleration is found to be 0.81. The coefficient of determination between jump height calculated using force plate and accelerometer data is 0.88. Data show that the landing forces could be as high as 8 body weights of the jumper. The measured peak tibial accelerations ranged up to 42 g. Jump heights calculated from force plate and accelerometer sensors data differed by less than 2.5 cm. It is found that both impact accelerations and landing forces are only weakly correlated with jump height (the average coefficient of determination is 0.12). This study shows that unobtrusive accelerometers can be used to determine the ground reaction forces experienced in a jump landing. Whereas the device also permitted an accurate determination of jump height, there was no correlation between peak ground reaction force and jump height.
Stefan Koehn, Alan J. Pearce and Tony Morris
The main purpose of the study was to examine crucial parts of Vealey’s (2001) integrated framework hypothesizing that sport confidence is a mediating variable between sources of sport confidence (including achievement, self-regulation, and social climate) and athletes’ affect in competition. The sample consisted of 386 athletes, who completed the Sources of Sport Confidence Questionnaire, Trait Sport Confidence Inventory, and Dispositional Flow Scale-2. Canonical correlation analysis revealed a confidence-achievement dimension underlying flow. Bias-corrected bootstrap confidence intervals in AMOS 20.0 were used in examining mediation effects between source domains and dispositional flow. Results showed that sport confidence partially mediated the relationship between achievement and self-regulation domains and flow, whereas no significant mediation was found for social climate. On a subscale level, full mediation models emerged for achievement and flow dimensions of challenge–skills balance, clear goals, and concentration on the task at hand.
Stephen J. Pearson, Tim Ritchings and Ahmad S.A. Mohamed
The work describes an automated method of tracking dynamic ultrasound images using a normalized cross-correlation algorithm, applied to the patellar and gastrocnemius tendon. Displacement was examined during active and passive tendon excursions using B-mode ultrasonography. In the passive test where two regions of interest (2-ROI) were tracked, the automated tracking algorithm showed insignificant deviations from relative zero displacement for the knee (0.01 ± 0.04 mm) and ankle (–0.02 ± 0.04 mm) (P > .05). Similarly, when tracking 1-ROI the passive tests showed no significant differences (P > .05) between automatic and manual methods, 7.50 ± 0.60 vs 7.66 ± 0.63 mm for the patellar and 11.28 ± 1.36 vs 11.17 ± 1.35 mm for the gastrocnemius tests. The active tests gave no significant differences (P > .05) between automatic and manual methods with differences of 0.29 ± 0.04 mm for the patellar and 0.26 ± 0.01 mm for the gastrocnemius. This study showed that automatic tracking of in vivo displacement of tendon during dynamic excursion under load is possible and valid when compared with the standardized method. This approach will save time during analysis and enable discrete areas of the tendon to be examined.
Denine Ellis, Ervin Sejdic, Karl Zabjek and Tom Chau
The strength of time-dependent correlations known as stride interval (SI) dynamics has been proposed as an indicator of neurologically healthy gait. Most recently, it has been hypothesized that these dynamics may be necessary for gait efficiency although the supporting evidence to date is scant. The current study examines over-ground SI dynamics, and their relationship with the cost of walking and physical activity levels in neurologically healthy children aged nine to 15 years. Twenty participants completed a single experimental session consisting of three phases: 10 min resting, 15 min walking and 10 min recovery. The scaling exponent (α) was used to characterize SI dynamics while net energy cost was measured using a portable metabolic cart, and physical activity levels were determined based on a 7-day recall questionnaire. No significant linear relationships were found between a and the net energy cost measures (r < .07; p > .25) or between α and physical activity levels (r = .01, p = .62). However, there was a marked reduction in the variance of α as activity levels increased. Over-ground stride dynamics do not appear to directly reflect energy conservation of gait in neurologically healthy youth. However, the reduction in the variance of α with increasing physical activity suggests a potential exercise-moderated convergence toward a level of stride interval persistence for able-bodied youth reported in the literature. This latter finding warrants further investigation.
Olaf Hoos, Tobias Boeselt, Martin Steiner, Kuno Hottenrott and Ralph Beneke
To analyze time-domain, spectral, and fractal properties of speed regulation during half-marathon racing.
In 21 male experienced runners, high-resolution data on speed (V), stride frequency (SF), and stride length (SL) were assessed during half-marathon competition (21,098 m). Performance times, timeand frequency-domain variability, spectral-scaling exponent (beta), and fractal dimension (FD) of V, SF, and SL were analyzed.
V of 3.65 ± 0.41 m/s, SF of 1.41 ± 0.05 Hz, and SL of 2.58 ± 0.25 m occurred with higher (P < .05) individual variability in V and SL than in SF. Beta and FD were always 1.04–1.88 and 1.56–1.99, respectively. Beta and FD differed (P < .05) in SF and SL compared with V and were correlated in V and SL (r = .91, P < .05). Spectral peaks of V, SF, and SL occurred at wavelengths of 3–35 min, and those of V and SL were interrelated (r = .56, P < .05). Mean SF and mean SL were significantly correlated with performance (r = .59 and r = .95, P < .05). SL accounted for 84% ± 6% and SF for 16% ± 6% of speed variability.
The observed nonrandom fluctuations in V, SF, and SL correspond to nonstationary fractional Brownian motion with inherent long-range correlations. This indicates a similar complex regulation process in experienced runners that is primarily mediated via SL.
Mohamed Ali Nabli, Nidhal Ben Abdelkrim, Imed Jabri, Tahar Batikh, Carlo Castagna and Karim Chamari
To examine the relation between game performance, physiological responses, and field-test results in Tunisian basketball referees.
Computerized time–motion analysis, heart rate (HR), and blood lactate concentration [La–] were measured in 15 referees during 8 competitive games (under-19-y-old Tunisian league). Referees also performed a repeated-sprint test (RSA), Yo-Yo Intermittent Recovery Test level 1 (YYIRTL1), agility T-test, and 30-m sprint with 10-m lap time. Computerized video analysis determined the time spent in 5 locomotor activities (standing, walking, jogging, running, and sprint), then grouped in high-, moderate-, and low-intensity activities (HIAs, MIAs, and LIAs, respectively).
YYIRTL1 performance correlated with (1) total distance covered during the 4th quarter (r = .52, P = .04) and (2) distance covered in LIA during all game periods (P < .05). Both distance covered and time spent in MIA during the 1st quarter were negatively correlated with the YYIRTL1 performance (r = –.53, P = .035; r = –.67, P = .004, respectively). A negative correlation was found between distance covered at HIA during the 2nd half (3rd quarter + 4th quarter) and fatigue index of the RSA test (r = –.54, P = .029). Mean HR (expressed as %HRpeak) during all game periods was correlated with YYIRTL1 performance (.61 ≤ r < .67, P < .01).
This study showed that (1) the YYIRTL1 performance is a moderate predictor of game physical performance in U-19 basketball referees and (2) referees’ RSA correlates with the amount of HIA performed during the 2nd half, which represents the ability to keep up with play.
Jacob J. Janicki, Craig L. Switzler, Bradley T. Hayes and Charlie A. Hicks-Little
Functional movement screening (FMS) has been gaining popularity in the fields of sports medicine and performance. Currently, limited research has examined whether FMS screening that identifies low FMS scores is attributed primarily to limits in range of motion (ROM).
To compare scores from the FMS hurdle-step movement with ROM measurements for ankle dorsiflexion and hip flexion (HF).
Correlational research design.
Sports medicine research laboratory.
20 healthy active male (age 21.2 ± 2.4 y, weight 77.8 ± 10.2 kg, height 180.8 ± 6.8 cm) and 20 healthy active female (21.3 ± 2.0 y, 67.3 ± 8.9 kg, 167.4 ± 6.6 cm) volunteers.
All 40 participants completed 3 trials of the hurdle-step exercise bilaterally and goniometric ROM measurements for active ankle dorsiflexion and HF.
Main Outcome Measures:
Correlations were determined between ROM and FMS scores for right and left legs. In addition, mean data were compared between FMS scores, gender, and dominant and nondominant limbs.
There were no significant correlations present when all participants were grouped. However, when separated by gender significant correlations were identified. There was a weak correlation with HF and both hurdle-step (HS) and average hurdle-step (AHS) scores on both left (r = .536, P = .015 and r = .512, P = .012) and right (r = .445, P = .049 and r = .565, P = .009) legs for women. For men, there was a poor negative correlation of HF and both HS and AHS on the left leg (r = –.452, P = .045 and r = .451, P = .046).
Our findings suggest that although hip and ankle ROMs do not have a strong relationship with FMS hurdle-step scores, they are a contributing factor. More research should be conducted to identify other biomechanical factors that contribute to individual FMS test scores.
Kevin Laudner, Jose Vazquez, Noelle Selkow and Keith Meister
Baseball players, specifically pitchers, with symptomatic neurovascular occlusion often initially complain of arm fatigue and loss of ball control and velocity. As the compression continues complaints may manifest in dull pain, paresthesia, and decreased grip strength.
To determine the correlation between upper-extremity blood-flow volume and grip strength among baseball pitchers.
Athletic training room.
66 professional baseball pitchers (age 21.6 ± 2.0 y, height 186.9 ± 5.7 cm, mass 91.3 ± 10.9 kg) before the start of spring training.
Main Outcome Measures:
Diagnostic ultrasound was used to measure upper-extremity blood-flow volume with the throwing shoulder in a resting position and in a provocative position. Grip strength was measured with participants seated and their throwing-arm elbow flexed to 90°. Pearson product–moment correlation coefficients were used to determine the strength of the relationships between blood-flow volume in the 2 arm positions and grip strength (P < .05).
No significant relationship was found between blood-flow volume in the resting position and grip strength (r = .03, P = .81); however, a strong positive correlation was found in the 2nd provocative position (r = .67, P = .001). This relationship indicates that as blood-flow volume tested in a provocative shoulder position decreases, so does grip strength.
A strong positive relationship was found in pitchers, demonstrating that as upper-extremity blood-flow volume while in the provocative shoulder position decreases, so does grip strength.
Aleksandar Sovtic, Predrag Minic, Jovan Kosutic, Gordana Markovic-Sovtic and Milan Gajic
The modified Chrispin-Norman radiography score (CNS) is used in evaluation of radiographic changes in children with cystic fibrosis (CF). We evaluated the correlation of modified CNS with peak exercise capacity (Wpeak) and ventilatory efficiency (reflected by breathing reserve index—BRI) during progressive cardiopulmonary exercise testing (CPET). Thirty-six children aged 8–17 years were stratified according to their CNS into 3 groups: mild (<10), moderate (10–15), and severe (>15). CPET was performed on a cycle ergometer. Lung function tests included spirometry and whole-body plethysmography. Patients with higher CNS had lower FEV1 (p < .001), Wpeak predicted (%; p = .01) and lower mean peak oxygen consumption (VO2peak/kg; p = .014). The BRI at the anaerobic threshold and at Wpeak was elevated in patients with the highest CNS values (p < .001). The modified CNS correlates moderately with Wpeak (R = −0.443; p = .007) and BRI (R = −0.419; p = .011). Stepwise multiple linear regression showed that RV/TLC was the best predictor of Wpeak/pred (%; B = −0.165; b = −0.494; R2 = .244; p = .002). Children with CF who have high modified CNS exhibit decreased exercise tolerance and ventilatory inefficacy during progressive effort.