Biomedical subjects

Z Dvir

Publications and source records attributed to Z Dvir.

11 recordsLinked to original sources

PubMed1996

Suboptimal muscular performance: measuring isokinetic strength of knee extensors with new testing protocol.

OBJECTIVE: To analyze the relevance of several isokinetics-based variables for the differentiation of suboptimal from optimal knee extension efforts. DESIGN: Three experimental conditions using 4 intermittent-reciprocal concentric (Con) and eccentric (Ecc) efforts at 30/sec and 180/sec. The first condition (MAX) served as the baseline; subjects were instructed to exert maximal Con and Ecc effort. In the second condition (50%MAX), subjects were asked to exert 50% of the strength measured in the first condition based on the initial use of visual feedback. In the third condition (BREP), subjects repeated the second condition but were asked to exert what they thought was a reproducible level of strength. SETTING: A motor performance laboratory in rehabilitation department of a major hospital. PARTICIPANTS: 16 healthy men, ages 21 to 30. RESULTS: Among several parameters that included variability of results and Ecc/Con strength ratios, the one with the highest differentiating power among MAX, 50%MAX, and BREP was the difference between the Ecc/Con ratios at high and low velocities (P < .0006). CONCLUSIONS: Suboptimal knee extension effort can effectively be differentiated from optimal effort in healthy subjects using this protocol.

Adult↗

PubMed1995

Variations in several mechanical parameters associated with elbow flexion during practice under different load criteria.

The purpose of this study was to analyze variations in the accuracy of the moment produced by the elbow flexors during feedback-assisted acquisition of a motor skill. The task consisted of minimizing the error around three criterional levels: 20%, 30%, or 50% of the maximal isokinetic concentric moment of these muscles measured at 90 degrees/sec. Healthy women, aged 22 to 30 years, were divided into three groups (nA = 6, nB = 6, nC = 4) corresponding to the above criteria. They were asked to perform 10 sets of 10 right-elbow flexions per day over a period of three consecutive days. The results indicated a significant difference among the groups mainly in terms of overshooting (Group A) or undershooting (Group C) the criterion. On the other hand, Group B subjects performed optimally as indicated both by a significant convergence to the criterion (30%) and a comparatively small number of repetitions required for achievements. These findings demonstrate the existence of an optimal performance point which is located at about 30% of the maximal isokinetic concentric moment.

Adult↗

PubMed1993

The relationship between short-term antibiotic treatments and fatigue in healthy individuals.

Antibiotic treatment tends sometimes to result in sensations of fatigue and decreased physical performance. The effects of antibiotics were therefore studied in 50 healthy, male trainees, aged 18-25 years, assigned in a random, double-blind fashion to one of the following treatments: tetracycline, ampicillin, trimethoprim/sulphamethoxazole, placebo I and placebo II. Duration of treatment was five times the half-life of each agent and the placebo was matched accordingly. Muscle enzyme activity (serum glutamine oxaloacetate transaminase, lactate dehydrogenase, creatine phosphokinase), maximal aerobic capacity (VO2max), muscle strength (MS), and rating of subjective sensation of fatigue were assessed prior to and upon conclusion of treatment. Compared to pretreatment values, plasma enzymes activity was elevated in all five groups (P < 0.005). No differences in VO2max or in MS were found among the subjects treated with either one of the antibiotics or those given a placebo. A significant difference in VO2max was found between the groups treated for 1 day (antibiotic and placebo) and the groups treated for 3 days (antibiotic and placebo) (P < 0.0001). The rating of subjective sensation was not affected by any of the agents. We concluded that in healthy individuals, a short-term antibiotic treatment had no deleterious effect on aerobic capacity or on muscle strength and was not associated with subjective side effects. The time interval between the two maximal tests could, however, have affected the aerobic capacity. Physiological disturbances associated with a sensation of fatigue following a longer period of antibiotics cannot be excluded.

Adolescent↗

PubMed1990