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Biomedical subjects

S Garner

Publications and source records attributed to S Garner.

10 recordsLinked to original sources
PubMed1991

Abnormal M-wave responses during exercise in myotonic muscular dystrophy: a Na(+)--K+ pump defect?

Maximum M-waves (muscle compound action potentials) were studied in the abductor pollicis brevis (APB), extensor digitorum brevis (EDB), and tibialis anterior (TA) muscles of 12 patients with myotonic muscular dystrophy (MMD) and in the same number of control subjects, matched for age and sex. The peak-to-peak amplitudes and voltage-time areas of the responses were measured at rest, between 40 maximum voluntary contractions (each lasting 3 s) and also during a 2-min recovery period. In 34 of the 36 control muscles the M-waves potentiated during the period of intermittent voluntary contractions. In the MMD patients, however, the M waves exhibited initial declines in 25 of 30 muscles. In the APB and EDB muscles the normalized mean values for the smallest M-waves, recorded during the 350 s total observation periods, differed significantly between the 2 groups of subjects. It is suggested that the sarcolemmal Na(+)-K+ pump has a raised threshold for activation in MMD patients.

Adult↗
PubMed1990

Interaction between concurrent strength and endurance training.

To assess the effects of concurrent strength (S) and endurance (E) training on S and E development, one group (4 young men and 4 young women) trained one leg for S and the other leg for S and E (S+E). A second group (4 men, 4 women) trained one leg for E and the other leg for E and S (E+S). E training consisted of five 3-min bouts on a cycle ergometer at a power output corresponding to that requiring 90-100% of oxygen uptake during maximal exercise (VO2 max). S training consisted of six sets of 15-20 repetitions with the heaviest possible weight on a leg press (combined hip and knee extension) weight machine. Training was done 3 days/wk for 22 wk. Needle biopsy samples from vastus lateralis were taken before and after training and were examined for histochemical, biochemical, and ultrastructural adaptations. The nominal S and E training programs were "hybrids", having more similarities as training stimuli than differences; thus S made increases (P less than 0.05) similar to those of S+E in E-related measures of VO2max (S, S+E: 8%, 8%), repetitions with the pretraining maximal single leg press lift [1 repetition maximum (RM)] (27%, 24%), and percent of slow-twitch fibers (15%, 8%); and S made significant, although smaller, increases in repetitions with 80% 1 RM (81%, 152%) and citrate synthase (CS) activity (22%, 51%). Similarly, E increased knee extensor area [computed tomography (CT) scans] as much as E+S (14%, 21%) and made significant, although smaller, increases in leg press 1 RM (20%, 34%) and thigh girth (3.4%, 4.8%). When a presumably stronger stimulus for an adaptation was added to a weaker one, some additive effects occurred (i.e., increases in 1 RM and thigh girth that were greater in E+S than E; increases in CS activity and repetitions with 80% 1 RM that were greater in S+E than S). When a weaker, although effective, stimulus was added to a stronger one, addition generally did not occur. Concurrent S and E training did not interfere with S or E development in comparison to S or E training alone.

Adult↗
PubMed1990

Strength training effects in prepubescent boys.

Possible changes in muscle size and function due to resistance training were examined in prepubertal boys. Thirteen boys (9-11 yr) volunteered for each of the training and control groups. Progressive resistance training was performed three times weekly for 20 wk. Measurements consisted of the following: 1 repetition maximum (RM) bench press and leg press; maximal voluntary isometric and isokinetic elbow flexion and knee extension strength; evoked isometric contractile properties of the right elbow flexors and knee extensors; muscle cross-sectional area (CSA) by computerized tomography at the mid-right upper arm and thigh; and motor unit activation (MUA) by the interpolated twitch procedure. Training significantly increased 1 RM bench press (35%) and leg press (22%), isometric elbow flexion (37%) and knee extension strength (25% and 13% at 90 degrees and 120 degrees, respectively), isokinetic elbow flexion (26%) and knee extension (21%) strength, and evoked twitch torque of the elbow flexors (30%) and knee extensors (30%). There were no significant effects of training on the time-related contractile properties (time to peak torque, half-relaxation time), CSA, or %MUA of the elbow flexors or knee extensors. There was, however, a trend toward increased MUA for the elbow flexors and knee extensors in the trained group. Strength gains were independent of changes in muscle CSA, and the increases in twitch torque suggest possible adaptations in muscle excitation-contraction coupling. Improved motor skill coordination (especially during the early phase of training), a tendency toward increased MUA, and other undetermined neurological adaptations, including better coordination of the involved muscle groups, are likely the major determinants of the strength gains in this study.

Anthropometry↗
PubMed1990

Comparison of two regimens of concurrent strength and endurance training.

To compare the responses to doing strength (S) training on alternate days with endurance (E) training vs doing both types of training on the same days per week, seven young men (group A-2 d) did S and E training together in single sessions 2 d.wk-1 for 20 wk. A second group (B-4 d, N = 8) did the S training on 2 d.wk-1 and E training on 2 other d.wk-1. S training was six to eight sets of 15-20 RM on a leg press weight machine. E training was six to eight 3-min bouts of cycle ergometer exercise at 90-100% VO2max. B-4 d (25%) increased leg press 1 RM more (P less than 0.05) than A-2 d (13%), but the groups increased similarly (A-2 d, B-4 d) in knee extensor (31%, 34%) and flexor (12%, 14%) cross-sectional area and vastus lateralis mean fiber area (33%, 25%). Increases in VO2max (7%, 6%), repetitions with 80% 1 RM (39%, 64%), repetitions with the pre-training 1 RM (33, 55), and PFK (19%, 10%) and LDH (15%, 23%) activity did not differ (P greater than 0.05) between groups. CS activity increased significantly only in A-2 d (26%; B-4 d, 6%). It is concluded that same day (vs different day) concurrent strength and endurance training may impede strength development without impeding hypertrophy. On the other hand, same day training may enhance increases in CS activity but not VO2max or weight lifting endurance.

Citrate (si)-Synthase↗
PubMed1989

M wave potentiation during and after muscle activity.

The M wave (muscle compound action potential) has been shown to enlarge between successive 3-s voluntary contractions of the human thenar and extensor digitorum brevis (EDB) muscles. The changes, which affected both the amplitude and the area of the M wave, were more obvious in the thenar than in the EDB muscles. In the thenar muscles the mean amplitude was already significantly enlarged after the first voluntary contraction and close to the maximal value by the third (mean maximal increase 23.6 +/- 12.6% of control). The increase in mean M wave area was more gradual, reaching a maximum of 29.3 +/- 14.1% at 100 s. After the voluntary thenar contractions ceased, the amplitude of the M wave subsided more rapidly than the area and had regained the control value within 50 s. The magnitude and time course of the increase in EDB M wave area (maximum change 25.9 +/- 15.2%) were similar to those of the thenar muscles; however, the subsequent decline was slower. The amplitude of the EDB M wave showed the least change, and the maximum increase (11.4 +/- 9.6%) occurred early in the postcontraction period. In both muscles the changes in M wave amplitude and area were significantly different from the control values.

Action Potentials↗
PubMed1988

Spontaneous pregnancies and pregnancies as a result of treatment on an in vitro fertilization program terminating in ectopic pregnancies or spontaneous abortions.

Five hundred three patients were accepted for the in vitro fertilization (IVF) program from 1983 to 1986. Two hundred ninety-nine patients had a total of 678 IVF treatment cycles during this period. Eighty-one clinical pregnancies resulted, of which 8 were ectopic pregnancies and 19 spontaneous abortions (group A). During this period 82 patients accepted for IVF became pregnant spontaneously: 44 before treatment and 38 after a failed IVF treatment cycle (group B). Of these, 14 were ectopic pregnancies and 8 were miscarriages. The main indications for acceptance on the IVF program were similar in the two groups if those patients who had a bilateral salpingectomy are excluded from group A. Causative factors for the high ectopic pregnancy rate are discussed. The authors suggest that after embryo transfer, migration of the embryo or embryos into the fallopian tubes occurs more frequently than realized, and the diseased tube is less likely than a normal tube to propel the embryo back into the uterus. The abortion rate in group B was similar to the rate in the general population.

Abortion, Spontaneous↗