Biomedical subjects

K N Magee

Publications and source records attributed to K N Magee.

5 recordsLinked to original sources

PubMed1999

Comparison of upper limb muscle activity in four walking canes: a preliminary study.

It is hypothesized that the cane and forearm can be aligned to reduce muscular activity needed during ambulation. In this prospective study, 10 nonimpaired control subjects were tested both in stationary and dynamic weight-bearing states while using different cane prototypes and the platform cane (PC) as compared to the standard cane (SC). The outcome measures were: 1) root mean square (RMS) voltage (µV) of electromyographic (EMG) signal as a measure of muscle power and 2) distance of ambulation. Results of stationary cane use showed that Prototype 1 decreased RMS output by 19 percent (p=0.01), Prototype 2 with wrist splint decreased it by 23 percent (p=0.003), and the PC decreased it by 68 percent (p<0.0001) as compared to the SC (ANOVA, posthoc LSM). In conclusion, the two prototypes and the PC significantly decrease RMS voltage muscle output in the upper limb, compared to the SC.

Aged↗

PubMed1992

Directional baseline differences and type I error probabilities in randomized clinical trials.

Adequate correction for baseline differences that occur in the same or opposite direction from inferred treatment effects in a simple randomized experimental design is addressed by Monte Carlo simulation. Results confirm that the analysis of covariance (ANOVA) can provide appropriate correction whether baseline means differ significantly by chance in the same or opposite direction from the inferred treatment effect. The results from analysis of simple pre-post difference scores are highly dependent on the direction of chance baseline deviations in relation to the directional treatment effect that would be inferred from rejection of the null hypothesis. The attempt to correct for baseline differences by expressing outcome as percentage of baseline entails directional bias that depends on the location of the zero point, the direction of change, and the level of correlation between baseline and follow-up measurements.

Analysis of Variance↗

PubMed1992

Baseline correction in a two-way randomized blocks design.

Randomized blocks designs are used in clinical psychopharmacology research to test the hypothesis that relative effectiveness of different drug treatments depends on the type of patient being treated. Monte Carlo methods were used to evaluate the adequacies of different approaches to statistical control over baseline differences in such a design with special concern for the treatments x blocks interaction effect. Given the usual assumptions, analysis of covariance (ANCOVA) was shown to provide adequate baseline correction with consequent unbiased tests for the treatments x blocks interaction, as well as the main effect for the randomized treatments. Tests relying on simple pre-post difference scores and percentage change scores evidenced seriously conservative or nonconservative bias in the test for treatments x blocks interaction effect, a bias that depended on the direction of the corresponding interaction effect observed in the baseline measurements alone. This is discussed as a serious matter because the interaction effect in a randomized blocks design is a common basis for the claim of specific indications of drug treatments for particular types of patients.

Humans↗

PubMedDate not supplied

Augmented sensory nerve action potentials during distant muscle contraction.

We previously reported that the median sensory nerve action potentials (SNAP) increased in amplitude during ipsilateral abductor pollicis brevis contraction. The objectives of the present project were to study the timing and origin of this phenomenon and to eliminate the possibility of local artifact. Ten normal subjects were recruited. The baseline was established using ten threshold stimuli, which were delivered to the median nerve at the wrist at 0.2 Hz. Using the same stimulus strength, the SNAP was recorded while the tibialis anterior was contracted at 25, 50, 75, and 100% of maximum force. Responses were signal-averaged. Results showed an increase in ipsilateral SNAP amplitude between baseline and maximum contraction of 6 +/- 2 microV (standard error, P = 0.004) and contralateral amplitude of 8 +/- 2 microV (standard error, P = 0.01). Statistical analysis was performed with analysis of variance for repeated measures and paired t test. The effect peaked between 0 and 10 min after contraction and lasted from 1.5 to more than 20 min after muscle relaxation. In conclusion, SNAP appear to be enhanced during and after muscle contraction. Theories concerning underlying causes for this event are discussed.

Adult↗

PubMedDate not supplied

Electromyographic localization of the palmaris brevis muscle.

The palmaris brevis (PB) is the only muscle frequently innervated by the superficial branch of the ulnar nerve. It is clinically involved in patients with sensory impairment of the ulnar nerve sparing the deep branch as seen in mild cases of cyclist or crutch palsy. It is also involved in palmaris brevis spasm syndrome. A technique is described that makes it possible to localize the PB distinctly from its neighbors by electromyographic (EMG) pin examination. Methods include prospective (1) anatomic measurement in 10 cadavers and (2) EMG pin examination in 12 normal subjects measuring rise time (ms) and RMS voltage output (microV). Results showed (1) the area of the PB in elderly cadavers was 2.1+/-0.7 x 2.1+/-0.3 cm with a thickness of 0.2+/-.01 cm and (2) in the live subjects, the muscle could be located with identification of motor unit potentials having a rise time <1 ms 100% of the time. In conclusion, the PB can be localized for EMG analysis by using an approach parallel to surface of the palm. Clinically, it could be a useful complement to diagnose neuropathy involving the superficial fibers of the ulnar nerve.

Adult↗