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Tishya A. L. Wren and Jack R. Engsberg

The traditional method for normalizing quantitative strength data is to divide force or torque by body mass. We have previously shown that this method is not appropriate for able-bodied children and young adults and that normalization using allometric scaling is more effective. The purpose of the current study was to evaluate the effectiveness of applying existing normalization equations for lower extremity strength to children, adolescents, and young adults with cerebral palsy (CP) and, if appropriate, to develop CP-specific normalization equations using allometric scaling. We measured the maximum torque generated during hip abduction/adduction, knee extension/flexion, and ankle dorsiflexion/plantar flexion in 96 subjects with spastic diplegia CP ages 4–23 years. Traditional mass normalization (Torque/Mass1.0) and allometric scaling equations from children without disability (Torque/Mass1.6 for hip and knee; Torque/Mass1.4 for ankle) were not effective in eliminating the influence of body mass. Normalization using CP-specific allometric scaling equations was effective using both muscle-specific and common (Torque/Mass0.8 for ankle plantar flexors; Torque/Mass1.4 for all others) scaling relationships. For the first time, normalization equations have been presented with demonstrated effectiveness in adjusting strength measures for body size in a group of children, adolescents, and young adults with CP.

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David R. Mullineaux, Hilary M. Clayton and Lauren M. Gnagey

This study assessed the effect of offset normalizations on variability in kinematic data. The tarsal angles for 12 elderly horses, with mild lameness of the tarsal joint, were measured at the trot pre and post 2 weeks administration of a dietary supplement intended to promote joint health (Corta-Flx, Nature's Own, Aiken, SC). For five strides, pre- and postsupplement, the tarsal angles measured on the flexor side (full exten. = 180°) were smoothed, normalized to 101 data points, and averaged. Four offset normalizations were applied: minus standing tarsal angle (Tarsal); minus impact angle (Impact); minus mean angle (Average); multiplicative scatter correction (MSC). For 11 angle variables across the stride there were no significant differences pre- and postsupplement, p > 0.05. Normalization had no effect on the timing of variables or magnitude of angles, but generally the variability in the angles was reduced. Least to greatest reduction occurred with the Tarsal, Impact, Average, then MSC normalizations. The Average and MSC techniques resulted in two and three variables, respectively, becoming significantly different. These differences were small, emphasizing that significant findings should be interpreted for meaningfulness. Normalizations based on the data gave the largest reductions in variability, but these may introduce biases into the data. Thus, normalization with respect to measurements external to data capture may be preferable, but their theoretical and statistical relationship to the kinematic variables should be confirmed. MSC altered the shape of the kinematic trace, which may be misleading. Offset normalizations should be used with care, but they can reduce variability in kinematic data to increase statistical power in biomechanical studies.

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Wendy J. Hurd, Bernard F. Morrey and Kenton R. Kaufman

Context:

Muscle force must be normalized for between-subjects comparisons of strength to be valid. The most effective method for normalizing muscle strength has not, however, been systematically evaluated.

Objective:

To evaluate the effects of normalizing muscle strength using a spectrum of anthropometric parameters.

Design:

Cross-sectional.

Setting:

Laboratory.

Participants:

50 uninjured high-school-age baseball pitchers.

Interventions:

Shoulder-rotation strength was tested at 0° and 90° abduction with a handheld dynamometer. Muscle force was normalized to parameters including subject height, weight, height × weight, body-mass index (BMI), forearm length, and forearm length × height.

Outcome Measures:

Statistical analysis included evaluating the coefficient of variation, skewness, and kurtosis of the nonnormalized and normalized muscle force. The most effective normalization method was determined based on the scaling factor that yielded the lowest variability for the data set and promoted the most normal distribution of the data set.

Results:

Using body weight to scale muscle force was the most effective anthropometric parameter for normalizing strength values based on the group of statistical measures of variability. BMI, height × weight, and forearm length × weight as scaling factors also yielded less variable values for muscle strength compared with nonnormalized strength, but less consistently than body weight. Height and forearm length were least effective in reducing the variability of the data set relative to nonnormalized muscle force.

Conclusion:

This study provides objective support for scaling muscle strength to subject body weight. This approach to normalizing muscle strength uses methods readily accessible to clinicians and researchers and may facilitate the identification of differences in strength between individuals with diverse physical characteristics.

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Martin Švehlík, Kryštof Slabý, Tomáš Trc̆ and Jir̆í Radvanský

The aim of the study is to investigate whether the net nondimensional oxygen utilization scheme is able to detect postoperative improvement in the energy cost of walking in children with cerebral palsy and to compare it with a body mass normalization scheme. We evaluated 10 children with spastic cerebral palsy before and 9 months after equinus deformity surgery. Participants walked at a given speed of 2 km/hr and 3 km/hr on a treadmill. Oxygen utilization was measured, and mass relative VO2 and net nondimensional VO2 were calculated. Coefficient of variation was used for the description of variability among subjects. Postoperatively, gait kinematics normalized and the mass relative VO2 and net nondimensional VO2 showed significant improvement. Net nondimensional VO2 is able to detect postoperative improvement with smaller variability among subjects than body mass related normalization in children with cerebral palsy.

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Jane Lee Sinden

The present study examines Foucault’s (1977) concept of normalization as it applies to the emotions of female elite amateur rowers. Specifically, this study sought to understand how beliefs about emotion, developed through the normalization process, may coerce athletes to continue to train even when physically unhealthy. Interviews were conducted with 11 retired elite amateur female rowers who suffered health problems while training but continued training despite these health problems. Interpretation of the data suggests that the rowers suppressed emotions to avoid appearing mentally weak, negative, or irrational, despite needing to express their concerns about training volumes and health issues to minimize deleterious effects that continued training eventually had on their health.

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Timothy J. Curry and Richard H. Strauss

This visual study explores the social conditions that promote the normalization of injuries in sport. Photographs taken at a university wrestling team’s meets and practices, and in a hospital operating room, convey some of the details and social ambience of today’s approach to collegiate sports medicine. Quotations drawn from photo-elicitation interviews with the coaches and athletes express the views of the participants. This study suggests that the normalization of injuries in sport—illustrated when universities make medical care immediately available and coaches and athletes minimize the significance of injury—encourages continued participation. Such continuation may be questioned by those concerned with the long-term effects of “playing with pain.”

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Jin H. Yan, Richard N. Hinrichs, V. Gregory Payne and Jerry R. Thomas

This study was designed to examine Ihe developmental differences in the speed and smoothness of arm movement during overarm throwing. The second purpose of this investigation was to evaluate whether jerk is a useful measure in understanding children's overarm throwing. Fifty-one girls, aged 3 to 6 years, voluntarily participated in the study. Each subject threw tennis balls as hard as she could toward a large target on the wall. A 2-camera video system was used to obtain 3-D coordinates of the hand and ball using the DLT algorithm. The variables of velocity and jerk (for the hand and ball) served as the movement outcome measures. The age-associated differences in velocity and normalized jerk (absolute jerk standardized relative to movement time and distance) were examined by ANOVAs. The results supported the hypothesis that the older subjects demonstrated faster and smoother hand movements than their younger counterparts during the forward acceleration phase (from the beginning of forward motion to ball release). In addition, the correlation results indicated thai increased hand movement speed was associated with decreased movement jerk in older subjects, whereas increased hand speed was associated with increased jerk in younger subjects. The findings suggest that examining the jerk parameter (normalized or absolute jerk) is a useful and alternative approach to capture the variance of hand movement execution for children's overarm throwing.

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Nicholas M. Brisson, Paul W. Stratford, Saara Totterman, José G. Tamez-Peña, Karen A. Beattie, Jonathan D. Adachi and Monica R. Maly

Investigations of joint loading in knee osteoarthritis (OA) typically normalize the knee adduction moment to global measures of body size (eg, body mass, height) to allow comparison between individuals. However, such measurements may not reflect knee size. This study used a morphometric measurement of the cartilage surface area on the medial tibial plateau, which better represents medial knee size. This study aimed to determine whether normalizing the peak knee adduction moment and knee adduction moment impulse during gait to the medial tibial bone–cartilage interface could classify radiographic knee OA severity more accurately than traditional normalization techniques. Individuals with mild (N = 22) and severe (N = 17) radiographic knee OA participated. The medial tibial bone–cartilage interface was quantified from magnetic resonance imaging scans. Gait analysis was performed, and the peak knee adduction moment and knee adduction moment impulse were calculated in nonnormalized units and normalized to body mass, body weight × height, and the medial tibial bone–cartilage interface. Receiver operating characteristic curves compared the ability of each knee adduction moment normalization technique to classify participants according to radiographic disease severity. No normalization technique was superior at distinguishing between OA severities. Knee adduction moments normalized to medial knee size were not more sensitive to OA severity.

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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.

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Paul Comfort, Thomas Dos’Santos, Paul A. Jones, John J. McMahon, Timothy J. Suchomel, Caleb Bazyler and Michael H. Stone

 al 14 demonstrated that changes in early force production and early RFD are influenced by increases in fascicle length in response to training, which may partly explain these differential adaptations in early and late force development. When comparing RFD normalized to isometric PF between athletes and