Biomedical subjects

David R Mullineaux

Publications and source records attributed to David R Mullineaux.

6 recordsLinked to original sources

PubMed2006

Normalization of ground reaction forces.

The appropriateness of normalizing data, as one method to reduce the effects of a covariate on a dependent variable, should be evaluated. Using ratio, 0.67-nonlinear, and fitted normalizations, the aim of this study was to investigate the relationship between ground reaction force variables and body mass (BM). Ground reaction forces were recorded for 40 female subjects running at 3.7 +/- 0.18 m x s(-1) (mass = 58 +/- 6 kg). The explained variance for mass to forces (peak-impact-vertical = 70%; propulsive-vertical = 27%; braking = 40%) was reduced to <0.1% for mass to ratio normalized forces (i.e., forces/BM1) with statistically significantly different power exponents (p < 0.05). The smaller covariate effect of mass on loading rate variables of 2-16% was better removed through fitted normalization (e.g., vertical-instantaneous-loading rate/ BM(0.69+/-0.93); +/-95% CI) with nonlinear power exponents ranging from 0.51 to 1.13. Generally, these were similar to 0.67 as predicted through dimensionality theory, but, owing to the large confidence intervals, these power exponents were not statistically significantly different from absolute or ratio normalized data (p > 0.05). Further work is warranted to identify the appropriate method to normalize loading rates either to mass or to another covariate. Ratio normalization of forces to mass, as predicted through Newtonian mechanics, is recommended for comparing subjects of different masses.

Adult↗

PubMed2006

Locomotor mechanics of the tölt in Icelandic horses.

OBJECTIVE: To evaluate the locomotor mechanics of the tölt in Icelandic horses. ANIMALS: 10 adult Icelandic horses with no history of lameness. PROCEDURES: Force platform data were captured for 27 trials for horses ridden at a tölt in a lateral sequence single-foot gait at a steady speed from 0.89 to 5.98 m/s. Simultaneous kinematic data were obtained by tracking retroflective markers overlying the right fore- and hind limbs. These kinetic and kinematic data were combined to evaluate 3 mechanical approaches, duty factor, Froude number, and center of mass (COM) mechanics, and to evaluate the capacity to recover mechanical energies during tölting via inverse pendulum and spring-mass (bouncing) mechanics. RESULTS: Tölting horses had in-phase fluctuations of gravitational potential and kinetic energies of their COM and a capacity to recover mechanical energy through elastic recoil of spring elements in their limbs. These characteristics, along with Froude numbers exceeding values expected for the walk-run transition, are indicative of bouncing mechanics and, hence, most strongly ally tölting with running. Only the footfall pattern of a lateral sequence single-foot gait and low vertical excursions of the COM are more commonly associated with walking. CONCLUSIONS AND CLINICAL RELEVANCE: At the tölt, horses have unique mechanical characteristics that should be understood for veterinary care. Differences in interlimb coordination between tölting and trotting mask the overall similarities in most other aspects of their locomotor dynamics.

Animals↗

PubMed2005

Criterion validity of an isokinetic dynamometer to assess shoulder function in tennis players.

Isokinetic dynamometry is used in the assessment and rehabilitation of shoulder function in tennis players. The aim of this study was to validate a newly installed Biodex III Isokinetic Dynamometer for internal and external shoulder rotation. A non-injured male performed this movement which replicates an integral section of the tennis service action (Cohen et al., 1994). Three maximal trials were performed at six randomly assigned angular velocities (0.52, 1.05, 1.57, 2.09, 2.62 and 3.14 rad x s(-1)) with 90 s rest between each set. Trials were recorded using an on-line motion analysis system and kinematic data were obtained. Kinematic angular displacement of the lever arm was slightly greater (> or = 0.01 rad x s(-1)) than for the isokinetic dynamometer at all test angular velocities. Mean angular velocities from the kinematic data were almost identical to those from the isokinetic dynamometer but less than the target values, and this difference (e.g. 2.55 rad x s(-1) at 3.14 rad x s(-1)) was greater at higher angular velocities owing to the greater acceleration phases required. Peak angular velocity was similar on the isokinetic dynamometer to the target values, but substantially less than those from the kinematic data (e.g. 0.68 rad x s(-1) at 0.52 rad x s(-1)). This suggests that the isokinetic data are over-smoothed and may mask important information. In summary, criterion validity of this isokinetic dynamometer is supported for displacement and mean angular velocity, but not for peak angular velocity. Shoulder rotations in tennis are often at angular velocities greater than the Biodex can reproduce, but for the purpose of monitoring the shoulder strength and range of motion of tennis players and providing safe functional rehabilitation, the use of slower angular velocities is acceptable.

Adult↗

PubMed2004

The effect of four anesthetic protocols on splenic size in dogs.

OBJECTIVE: To characterize the effects of four anesthetic protocols on the size of the spleen during surgery in dogs. STUDY DESIGN: Prospective experimental trial. ANIMALS: Twenty-four beagle dogs, 1.1 +/- 0.3 years of age and weighing 10.9 +/- 2.7 kg. METHODS: Dogs were allocated to receive one of four anesthetic protocols: 1 - pre-medication with acepromazine and butorphanol, induction with thiopental; 2 - pre-medication with acepromazine and butorphanol, induction with propofol; 3 - pre-medication with medetomidine and butorphanol, induction with propofol; and 4 - pre-medication with medetomidine and butorphanol, induction with ketamine and diazepam. Anesthesia was then maintained with halothane. At laparotomy, the spleen length, width, and height were measured, these were measured again just prior to closure of the abdomen. Splenic area and volume were calculated. Hematocrit and total serum protein (TSP) were measured before and after induction and during laparotomy. RESULTS: Splenic volume was greatest after protocol 4 (161.2 +/- 40.2 cm(3); p < 0.05) and was least after protocol 2. The differences in volume were because of differences in length, width, and height between groups. There was no significant change in area, length, or width over the study period. Hematocrit decreased significantly in all dogs but at different times. The decrease occurred after pre-medication if acepromazine was administered, at induction following protocol 3 and during surgery following protocol 4. CONCLUSIONS: If splenic volume is to be minimized during surgery, then acepromazine and propofol should be used in the anesthetic protocol. The administration of medetomidine, diazepam, and ketamine will produce a greater splenic volume. Lack of correlation between hematocrit and spleen size following the anesthetic protocols studied suggests sequestration of red blood cells in nonsplenic sites.

Acepromazine↗

PubMed2003

Assessment of the reliability of a technique to measure postural sway in horses.

OBJECTIVE: To assess the reliability of the center-of-pressure (COP) values obtained from a force platform for analysis of postural sway in horses. ANIMALS: Six 2-year-old horses that were free from lameness and neurologic disease. PROCEDURE: Horses stood stationary with all 4 hooves on a force platform; COP data were collected at 1,000 Hz and 3-dimensional kinematics collected at 60 Hz for 10 seconds. Five trials were recorded at each of 3 time periods (15-minute intervals) or at 1 time period on 3 separate days. Mean values for each set of 5 trials and actual, normalized, and relative COP variables were calculated. The reliability was quantified by use of agreement boundary. RESULTS: The COP results within and across days were similar and provided small agreement boundary limits (eg, across days, in order of least relative reliability: area, +/- 62 mm2; mediolateral range, +/- 8 mm; radius, +/- 2 mm; craniocaudal range, +/- 4 mm; and velocity, +/- 3 mm/s). Head height possessed the greatest relative intraday reliability (12%) but a high agreement boundary limit (+/- 0.15 m). CONCLUSIONS AND CLINICAL RELEVANCE; The use of a force platform to analyze postural sway in a group of young healthy horses was found to produce reliable results and may provide a simple and sensitive measure for assessing balance deficiencies in horses. Agreement boundaries provide 95% confidence intervals for use as limits of error and variability in measurements that, if exceeded, may signify meaningful effects.

Animals↗

PubMedDate not supplied

Investigation of the immediate analgesic effects of extracorporeal shock wave therapy for treatment of navicular disease in horses.

OBJECTIVES: To measure the acute analgesic properties of extracorporeal shock wave therapy (ESWT) in horses with navicular disease using objective ground reaction forces (GRF). STUDY DESIGN: Prospective study. ANIMALS: Nine client-owned horses with unilateral forelimb lameness caused by navicular disease. METHODS: Horses were trotted at 3 m/s over a force plate to record pre-treatment GRF of the lame and contra-lateral forelimbs. After ESWT of the lame limb, applied with a radial unit to each of the frog and heel bulb areas with 1500 pulses at 4 bar and 10 Hz, GRF measurements were repeated at 15 minutes and 24-hour intervals for 7 days. From the 5 trials recorded at each time, peak vertical force (PVF) was calculated and averaged. Data were compared between limbs and over time using a 2-way repeated-measures ANOVA. RESULTS: Mean (+/-SD) PVF was significantly different between lame (day 1; 4339+/-626 N) and contra-lateral (day 1; 5236+/-515 N) limbs pre-treatment (P<.05). After ESWT treatment, this difference remained unchanged at 15 minutes and from days 1 to 7. To confirm navicular disease, palmar digital analgesia significantly reduced the lameness (lame 5144+/-430 N; contralateral 5082+/-586 N; P>.05). CONCLUSIONS: Single ESWT treatment applied in this manner does not influence lameness in horses with navicular disease. CLINICAL RELEVANCE: Although many equine regulatory commissions currently ban the use of ESWT before competition, our results suggest that such regulations may be unfounded. Further research is required to determine the long-term analgesic properties of this frequently used treatment modality in equine athletes.

Analgesia↗