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Kathryn Mills, Aula Idris, Thu-An Pham, John Porte, Mark Wiggins and Manolya Kavakli

Objectives: To determine the validity and reliability of the peak frontal plane knee angle evaluated by a virtual reality (VR) netball game when landing from a drop vertical jump. Study Design: Laboratory. Methods: Forty participants performed 3 drop vertical jumps evaluated by 3-dimensional motion analysis and 3 drop vertical jumps evaluated by the VR game. Limits of agreement for the peak projected frontal plane knee angle and peak knee abduction were determined. Participants were given a consensus category of “above threshold” or “below threshold” based on a prespecified threshold angle of 9° during landing. Classification agreement was determined using kappa coefficient, and accuracy was determined using specificity and sensitivity. Ten participants returned 1 week later to determine intrarater reliability, standard error of the measure, and typical error. Results: The mean difference in detected frontal plane knee angle was 3.39° (95% confidence interval [CI], 1.03° to 5.74°). Limits of agreement were −10.27° (95% CI, −14.36° to −6.19°) to 17.05° (95% CI, 12.97° to 21.14°). Substantial agreement, specificity, and sensitivity were observed for the threshold classification (κ = .66; 95% CI, .42 to .88; specificity = 0.96; 95% CI, 0.78 to 1.0; and sensitivity = 0.75; 95% CI, 0.43 to 0.95). The game exhibited acceptable reliability over time (intraclass correlation coefficient, ICC3,1 = .844), and error was approximately 2°. Conclusion: The VR game reliably evaluated a projected frontal plane knee angle. Although the knee angle detected by the VR game is strongly related to peak knee abduction, the accuracy of detecting the exact angle was limited. A threshold approach may be a more accurate approach for gaming technology to evaluate frontal plane knee angles when landing from a jump.

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Amy Brightmore, John O’Hara, Kevin Till, Steve Cobley, Tate Hubka, Stacey Emmonds and Carlton Cooke

Purpose:

To evaluate the movement and physiological demands of Australasian National Rugby League (NRL) referees, officiating with a 2-referee (ie, lead and pocket) system, and to compare the demands of the lead and pocket referees.

Methods:

Global positioning system devices (10 Hz) were used to obtain 86 data sets (lead, n = 41; pocket, n = 45) on 19 NRL referees. Total distance, relative distance covered, and heart rate per half and across match play were examined within and between referees using t tests. Distance, time, and number of movement “efforts” were examined in 6 velocity classifications (ie, standing <0.5, walking 0.51–2.0, jogging 2.01–4.0, running 4.01–5.5, high-speed running 5.51–7.0, and sprinting >7.0 m/s) using analysis of variance. Cohen d effect sizes are reported.

Results:

There were no significant differences between the lead and pocket referees for any movement or physiological variable. There was an overall significant (large, very large) effect for distance (% distance) and time (% time) (P < .001) between velocity classifications for both the lead and pocket referees. Both roles covered the largest distance and number of efforts at velocities of 0.51–2.0 m/s and 2.01–4.0 m/s, which were interspersed with efforts >5.51 m/s.

Conclusions:

Findings highlight the intermittent nature of rugby league refereeing but show that there were no differences in the movement and physiological demands of the 2 refereeing roles. Findings are valuable for those responsible for the preparation, training, and conditioning of NRL referees and to ensure that training prepares for and simulates match demands.

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Rebecca J. Guthrie, Terry L. Grindstaff, Theodore Croy, Christopher D. Ingersoll and Susan A. Saliba

Context:

Individuals with low back pain (LBP) are thought to benefit from interventions that improve motor control of the lumbopelvic region. It is unknown if therapeutic exercise can acutely facilitate activation of lateral abdominal musculature.

Objective:

To investigate the ability of 2 types of bridging-exercise progressions to facilitate lateral abdominal muscles during an abdominal drawing-in maneuver (ADIM) in individuals with LBP.

Design:

Randomized control trial.

Setting:

University research laboratory.

Participants:

51 adults (mean ± SD age 23.1 ± 6.0 y, height 173.6 ± 10.5 cm, mass 74.7 ± 14.5 kg, and 64.7% female) with LBP. All participants met 3 of 4 criteria for stabilization-classification LBP or at least 6 best-fit criteria for stabilization classification.

Interventions:

Participants were randomly assigned to either traditional-bridge progression or suspension-exercise-bridge progression, each with 4 levels of progressive difficulty. They performed 5 repetitions at each level and were progressed based on specific criteria.

Main Outcome Measures:

Muscle thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) was measured during an ADIM using ultrasound imaging preintervention and postintervention. A contraction ratio (contracted thickness:resting thickness) of the EO, IO, and TrA was used to quantify changes in muscle thickness.

Results:

There was not a significant increase in EO (F 1,47 = 0.44, P = .51) or IO (F 1,47 = .30, P = .59) contraction ratios after the exercise progression. There was a significant (F 1,47 = 4.05, P = .05) group-by-time interaction wherein the traditional-bridge progression (pre = 1.55 ± 0.22; post = 1.65 ± 0.21) resulted in greater (P = .03) TrA contraction ratio after exercise than the suspension-exercise-bridge progression (pre = 1.61 ± 0.31; post = 1.58 ± 0.28).

Conclusion:

A single exercise progression did not acutely improve muscle thickness of the EO and IO. The magnitude of change in TrA muscle thickness after the traditional-bridging progression was less than the minimal detectable change, thus not clinically significant.

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Tom Kempton, Anita Claire Sirotic, Ermanno Rampinini and Aaron James Coutts

Purpose:

To describe the metabolic demands of rugby league match play for positional groups and compare match distances obtained from high-speed-running classifications with those derived from high metabolic power.

Methods:

Global positioning system (GPS) data were collected from 25 players from a team competing in the National Rugby League competition over 39 matches. Players were classified into positional groups (adjustables, outside backs, hit-up forwards, and wide-running forwards). The GPS devices provided instantaneous raw velocity data at 5 Hz, which were exported to a customized spreadsheet. The spreadsheet provided calculations for speed-based distances (eg, total distance; high-speed running, >14.4 km/h; and very-highspeed running, >18.1 km/h) and metabolic-power variables (eg, energy expenditure; average metabolic power; and high-power distance, >20 W/kg).

Results:

The data show that speed-based distances and metabolic power varied between positional groups, although this was largely related to differences in time spent on field. The distance covered at high running speed was lower than that obtained from high-power thresholds for all positional groups; however, the difference between the 2 methods was greatest for hit-up forwards and adjustables.

Conclusions:

Positional differences existed for all metabolic parameters, although these are at least partially related to time spent on the field. Higher-speed running may underestimate the demands of match play when compared with high-power distance—although the degree of difference between the measures varied by position. The analysis of metabolic power may complement traditional speed-based classifications and improve our understanding of the demands of rugby league match play.

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Abdulla S. Al-Mohannadi, Abdulaziz Farooq, Angus Burnett, Mercia Van Der Walt and Mohamed Ghaith Al-Kuwari

Background:

Little is known about the effects that climatic conditions, especially extreme heat, have on physical activity (PA) levels. The aim of this 2-year cohort analysis undertaken in the Arabian Gulf region was to assess changes in objectively-assessed PA as a result of changes in climatic conditions.

Methods:

A total of 2088 adults (1390 men and 698 women) from many regions of the world were enrolled in a community health program in Qatar, were included in this study. For 2 years participants recorded daily step count using an Omron HJ-720 ITC pedometer. Daily climate parameters included temperature, relative humidity and other conditions.

Results:

From linear mixed model analysis it was evident that higher average temperature and humidity, and the Wet bulb Globe Temperature (WbGT), resulted in a reduction of the number of steps taken per day. Analysis of interaction effects also revealed that the effects of heat stress were equivalent across gender, age, and the region participants came from according to a World Health Organization classification scheme.

Conclusions:

Increased temperature and humidity are associated with a reduction in the number of steps taken per day. Community-based PA programs in hot hot/humid climates should consider novel approaches to increase PA levels.

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Edward McAuley and John B. Gross

One of the more problematic methodological issues in attributional research has been the accurate classification, by researchers, of causal attributions made by respondents along causal dimensions. Closed-ended and open-ended approaches have been logical but limiting solutions to assessing attributions. Russell (1982) has the Causal Dimension Scale, a measure that allows the respondent to record a causal statement and indicate how he or she perceives that causal attribution in terms of causal dimensions. The present study examined the effects of winning and losing at table-tennis upon causal attributions using the Causal Dimension Scale. Reliability of the measure was assessed in a sport setting and the relationship between respondents' perceptions of attributions in terms of causal dimensions and judges' perception of the same were examined. The Causal Dimension Scale was found to be a reliable measure of how individuals perceive attributions in terms of causal dimensions. Winners' attributions were more internal, stable, and controllable than those of losers but attributions were of an internal, unstable, and controllable nature for both winners and losers.

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Gail M. Dummer, Martha E. Ewing, Rochelle V. Habeck and Sara R. Overton

The attributions of 147 athletes with cerebral palsy who participated in the 1985 National Cerebral Palsy/Les Autres Games were investigated following competition relative to their reactions to objectively and subjectively defined success or failure. Attributions were the dependent variable in a 2 × 2 (More-Disabled/Less-Disabled × Win/Loss) MANOVA. Attributions were also analyzed in a 2 × 4 (More-Disabled/Less-Disabled × Satisfied/Dissatisfied, Winner/Loser) MANOVA designed to determine the influence of perceived success or failure upon causal explanations of performance. There were no significant differences in the use of attributions by gender; however, there were differences in the use of attributions across disability classifications. Disabled winners used both internal and external explanations to a greater degree than losers, which was inconsistent with previous literature. Previous results linking persistence in sport to the use of internal and stable attributions were supported. Subjective outcome, defined in terms of satisfaction with performance, was a more powerful explanation of achievement behavior for the disabled athletes in this study than objective outcome. Satisfaction was associated with demonstration of positive qualities such as using the right strategy and ability, with realistic assessment of ability, and with enjoying competition.

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George Antonogeorgos, Anastasios Papadimitriou, Demosthenes B. Panagiotakos, Kostas N. Priftis and Polyxeni Nikolaidou

Background:

Childhood obesity has become a modern epidemic with escalating rates. The aim of our study was to identify physical activity patterns among Greek schoolchildren and to examine their relationship with obesity.

Methods:

700 adolescents age 10 to 12 years were evaluated through a standardized questionnaire. Several demographic, socioeconomic, and physical activity characteristics were recorded. Physical activity was assessed and adolescents were characterized as active and nonactive. Body height and weight were measured and body mass index was calculated in order to to classify subjects as overweight or obese (IOTF classification). Multiple logistic regression and multivariate techniques (principal components analysis) were performed.

Results:

Eight physical activity patterns were identified, including increased physical activity in weekdays and weekends, sports physical activity, vigorous, moderate, and low physical activity. Increased physical activity on weekends and vigorous physical activity in boys were negatively associated with being overweight or obese (OR: 0.65; 95% CI: 0.48−0.90 and OR: 0.66; 95% CI: 0.49−0.88, correspondingly) and moderate physical activity was marginally positively associated in girls (OR: 1.28; 95% CI: 0.97−1.69), after adjusting for several confounders.

Conclusions:

Our findings demonstrate the important role of vigorous physical activity in the maintenance of normal weight of adolescents

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Heather M. Hayes, Joey C. Eisenmann, Karin Pfeiffer and Joseph J. Carlson

Background:

The purpose of this study was to determine the independent and joint association of weight status and physical activity on resting blood pressure and C-reactive protein in children.

Methods:

Participants were 174 (71 males, 103 females) children (mean age = 10.5 ± 0.4 yrs). Physical activity was self-reported, body mass index was calculated from measured height and body mass, and blood pressure was measured according to standard procedures. A subset of 91 children had C-reactive protein measured by fingerstick blood sample. Four weight/physical activity groups were created by cross tabulation of weight status classification and physical activity level.

Results:

The prevalence of low physical activity (< 5 days/wk moderate-vigorous activity) did not differ between overweight and normal weight children (50%). Physical activity was not correlated with C-reactive protein (r = 0.01; P = 0.91) and C-reactive protein was not significantly different between physical activity groups (P = 0.87). Physical activity did not modify the difference in blood pressure or C-reactive protein within weight categories.

Conclusions:

Fatness (specifically overweight and obesity), but not physical activity, was shown to be associated with blood pressure and C-reactive protein levels in children. Physical activity did not attenuate blood pressure or C-reactive protein in overweight and obese children.

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David Diggin, Ross Anderson and Andrew J. Harrison

Evidence suggests reports describing the reliability of leg-spring (kleg) and joint stiffness (kjoint) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of kleg and kjoint requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of kleg and kjoint. Thirty-two participants completed 2 trials of single-legged hopping at 1.5, 2.2, and 3.0 Hz at the same time of day across 3 days. On the final test day a fourth experimental bout took place 6 hours before or after participants’ typical testing time. Kinematic and kinetic data were collected throughout. Stiffness was calculated using models of kleg and kjoint. Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that kleg and kankle exhibited strong agreement. In contrast, kknee and khip demonstrated weak-to-moderate consistency. Results suggest limits in kjoint reliability persist despite employment of appropriate filtering procedures. Furthermore, diurnal fluctuations in lower-limb muscle-tendon stiffness exhibit little effect on intraday reliability. The present findings support the existence of kleg as an attractor state during hopping, achieved through fluctuations in kjoint variables. Limits to kjoint reliability appear to represent biological function rather than measurement artifact.