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Biomedical subjects

M D Hoffman

Publications and source records attributed to M D Hoffman.

At least 19 recordsLinked to original sources
PubMed1992

Effect of age and coronary artery disease on response to snow shoveling.

OBJECTIVES: The objective of this study was to evaluate the effect of age and coronary artery disease on responses to snow shoveling. BACKGROUND: Little information is available on the hemodynamic and metabolic responses to snow shoveling. METHODS: Sixteen men with asymptomatic coronary artery disease and relatively good functional work capacity, 13 older normal men and 12 younger normal men shoveled snow at a self-paced rate. Oxygen consumption, heart rate and blood pressure were determined. In nine men with coronary artery disease left ventricular ejection fraction was evaluated with an ambulatory radionuclide recorder. RESULTS: Oxygen consumption during snow shoveling differed (p < 0.05) among groups; it was lowest (18.5 +/- 0.8 ml/kg per min) in those with coronary artery disease, intermediate (22.2 +/- 0.9 ml/kg/min) in older normal men and highest (25.6 +/- 1.3 ml/kg/min) in younger normal men. Percent peak treadmill oxygen consumption and heart rate with shoveling in the three groups ranged from 60% to 68% and 75% to 78%, respectively. Left ventricular ejection fraction and frequency of arrhythmias during shoveling were similar to those during treadmill testing. CONCLUSIONS: During snow shoveling 1) the rate of energy expenditure selected varied in relation to each man's peak oxygen consumption; 2) older and younger normal men and asymptomatic men with coronary artery disease paced themselves at similar relative work intensities; 3) the work intensity selected represented hard work but was within commonly recommended criteria for aerobic exercise training; and 4) arrhythmias and left ventricular ejection fraction were similar to those associated with dynamic exercise.

Adult↗
PubMed1992

In-line skating: physiological responses and comparison with roller skiing.

The use of in-line skates has become popular in recent years for recreational and conditioning purposes. This investigation evaluated the physiological responses of ten subjects during in-line skating on a flat track with three different in-line skating techniques. The double pole technique demonstrated the greatest economy with oxygen uptake requirements that were approximately 12% lower (p less than 0.05) than conventional skating (without poles) or the V1 skate technique. Across the investigated velocity spectrum of 14.6 to 18.0 km.h-1, individuals with an average fitness level of 40 ml.kg-1.min-1 will achieve exercise intensities of 68-90% of maximum oxygen uptake using the conventional skating and V1 skate techniques on flat terrain. These exercise intensities are appropriate for cardiorespiratory training. However, high fit individuals who are attempting to elicit a cardiorespiratory training effect using in-line skates with rolling resistances similar to those tested may need to perform uphill interval work or skate at higher velocities which may be technically difficult and may be unsafe in some training environments. Comparison of the present data with previously published data on roller skiing demonstrates that differences in physiological responses for the two modes of exercise are the result of differences in rolling resistances between the devices. Measurements of rolling resistance and comparison of the oxygen uptake requirements for double polling on both devices allow for the mechanical efficiency to be estimated at approximately 18% for this mode of locomotion.

Analysis of Variance↗
PubMed1992

Biathlon shooting performance after exercise of different intensities.

Biathletes commonly reduce their skiing intensity as they approach the firing line. However, it is not clear how the intensity of the previous exercise affects their shooting results. The purpose of this investigation was to assess shooting performance among elite American biathletes immediately after exercise of various intensities. Shooting performance was assessed from measures of shooting accuracy, shooting precision, and stability of hold. It was found that exercise intensity had minimal effect on shooting accuracy and precision for prone shooting, but did affect these measures for shooting in the standing position. In addition, stability of hold was affected more by exercise intensity for shooting in the standing position compared with prone shooting. If these results can be transferred to competitive biathlon, it is suggested that the intensity of exertion immediately prior to biathlon shooting has minimal influence on prone shooting performance, but does affect shooting in the standing position by altering the stability of the hold.

Exercise↗
PubMed1992

Characterization of the heart rate response during biathlon.

Continuous heart rate recordings were obtained on elite American bi-athletes during competitions to provide a better understanding of the physiological demands of biathlon and the strategies used in approaching the shooting range. The findings demonstrate that the average age heart rate during skiing was approximately 90% of maximum heart rate. Heart rates decreased 10-12 bpm over a time period of approximately 50-60 sec during the approach to the firing line. At arrival to the firing line, heart rates were similar for prone and standing shooting averaging 85-87% of maximum heart rate. Mean minimum heart rates while at the firing line dropped to 61-73% of maximum heart rate and averaged approximately 20 bpm lower for prone shooting. The lower minimum heart rates during prone shooting were accounted for by the bi-athletes spending a longer time at the firing line and having a more rapid decrease in heart rate while in the prone position.

Heart Rate↗
PubMed1992

Physiological aspects of competitive cross-country skiing.

The physiological demands of cross-country skiing require competitive skiers to have high maximal oxygen uptakes and anaerobic thresholds. Anaerobic capacity has a relatively less important role, but may be of greater importance today with the faster race velocities resulting from the new skiing techniques of ski skating. Although use of the ski skating techniques results in faster race velocities than the classical techniques, it has been found that under some conditions the double-pole technique is more economical than other skiing techniques. It is suggested that this results from a more effective storage and recovery of elastic energy, a greater proportion of the forces being directed along the line of travel, and a lower air resistance due to greater trunk and hip flexion with the double-pole technique. The greater economy of the double-pole technique suggests that this may be advantageous in certain race conditions if the upper body is adequately prepared. The greater propulsive forces generated with the upper body with ski skating also suggest that training of the upper body should receive more emphasis. The potential cardiovascular adaptations from cross-country ski training appear to be similar for the classical and skating techniques, yet training specificity is important for optimal performance.

Biomechanical Phenomena↗
PubMed1992

A clinical trial of strengthening and aerobic exercise to improve gait and balance in elderly male nursing home residents.

The purpose of this study was to determine whether a moderate to high intensity strengthening and aerobic exercise program can improve the strength, exercise capacity, gait and balance of deconditioned male nursing home residents. Ambulatory subjects who scored 30 or less on the modified Tinetti gait and balance assessment scale, who demonstrated less than 80% of age-matched lower extremity strength on isokinetic muscle testing and who gave informed consent were enrolled. Subjects were randomized to either an exercise (n = 8) or a control (n = 6) group. All participants underwent an exercise test to determine maximal oxygen uptake (VO2max) and received quantitative gait and balance measurements. The subjects assigned to the exercise group than completed a 12-wk program of weight training for the lower extremities and stationary cycling. Both the exercise and control groups were then retested. Ten outcome variables were assessed: Tinetti mobility scores, VO2max, isokinetic-tested lower extremity strength and endurance, stride length, gait velocity, stance time, gait duration, cadence and balance. The exercise group, after completion of the program, demonstrated significant improvements in Tinetti mobility scores (P < 0.05), combined right and left quadricep muscle strength (P < 0.01), right and left lower extremity muscular endurance (P < 0.01), left stride length and gait velocity (P < 0.05), although other outcome variables changed insignificantly. The control group revealed no changes of significance with the exception of improvement of the combined right and left hamstring muscle strength (P < 0.05). Nevertheless, for those outcome variables that had improved significantly in the exercise group, the changes amounted to only a 5 to 10% increase over the baseline measurements. These findings showed that an appropriately designed high intensity exercise program can result in significant although limited improvements for clinical mobility scores, strength, muscular endurance and certain gait parameters.

Aged↗
PubMed1992

Linkage analysis of GLUT1 (HepG2) and GLUT2 (liver/islet) genes in familial NIDDM.

Familial NIDDM probably results from combined inherited defects of insulin secretion and action. Members of the facilitative glucose transporter family are strong candidates for both defects, and RFLPs for both GLUT1 (erythrocyte) and GLUT2 (liver/islet) genes have been associated with NIDDM in some populations. To test the hypothesis that GLUT1 and GLUT2 mutations contribute to the inherited predisposition to NIDDM, we examined linkage of these loci with NIDDM in 18 large Utah white pedigrees (two and three generation) ascertained for > or = 2 NIDDM siblings. We used two RFLPs detected with Xba1 and Stu1 for the GLUT1 transporter. For the GLUT2 (liver/beta-cell) transporter gene, we used an RFLP detected with EcoR1 and a highly polymorphic (6-allele) dinucleotide (microsatellite) repeat. Analysis was performed with the MLINK program of the LINKAGE package. We tested four models for each locus: dominant and recessive, with IGT alternately considered as unknown affection status, or affected if IGT was diagnosed < or = 45 yr of age and unknown if > 45 yr. Disease gene frequencies were chosen to give approximate disease prevalence in American whites (q = 0.03, dominant; q = 0.25, recessive). Linkage of GLUT1 and NIDDM was strongly and significantly rejected under all models, with total (pooled) LOD scores of -5.7 to -8.9, indicating > 500,000:1 odds against linkage. Pooled LOD scores were significantly negative (< -2.0, or 100:1 odds against linkage) to a recombination fraction of > 5%. No heterogeneity was apparent. Analysis of GLUT2 gave similar results, with LOD scores of < -4.0 under each model, indicating at least 10,000:1 odds against linkage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Physiological comparisons of cross-country skiing techniques.

Since the popularization of ski skating, several investigations have compared the physiological responses of various cross-country skiing techniques. While this work is incomplete in fully characterizing the relative physiological demands of the different skiing techniques, some conclusions can be made. The diagonal stride technique is the least economical technique for skiing on flat ground. The magnitude of the difference in economy between the diagonal stride and skating techniques for skiing on flat terrain compares well with the 10-30% faster race velocities with the skating techniques. Nevertheless, it appears that the heart rates, blood lactate concentrations and perceived efforts elicited at a given oxygen uptake are similar between the diagonal stride and skating techniques. Therefore, the cardiorespiratory training benefits from classical skiing and ski skating should be similar if performed at the same heart rates or perceived efforts. Several studies have demonstrated that the double pole technique is the most economical cross-country skiing technique on flat terrain. Extended use of the double pole technique, however is probably limited by its greater anaerobic demands.

Friction↗
PubMed1991

Inhibition of human neutrophil activation by the allergic mediator release inhibitor, CI-949.

The allergic mediator release inhibitor Cl-949 [5-methoxy-3-(1-methylethoxy)-1-phenyl-N-1H-tetrazol-5-yl-1H -indole-2-carboxamide, L-arginine salt] was evaluated for its effects on human neutrophil functions. Cl-949 (100 microM) inhibited spontaneous migration and chemotaxis toward f-met-leu-phe (FMLP) by 49.1% and 45.8%, respectively. At the same concentration, Cl-949 inhibited the phagocytosis of serum-opsonized zymosan (SOZ) by 39.0%. Cl-949 inhibited leukotriene B4 and thromboxane B2 release in response to SOZ with IC50s of 2.0 microM and 3.3 microM, while inhibiting the response to FMLP with IC50s of 1.7 and 2.0 microM. Cl-949 also inhibited myeloperoxidase release from primary lysosomal granules in response to the following stimuli with the respective IC50s (microM): C5a (40.3); FMLP (34.4): SOZ (21.4); concanavalin A (Con A) 3.9); and calcium ionophore A23187 (91.2). In contrast, Cl-949 inhibited lysozyme release from secondary granules in response to SOZ and Con A with IC50s of 99.3 and 56.1 microM, while inhibiting the response to C5a, FMLP, and A23187 by 41.2%, 52.4%, and 10.0%, respectively, at 100 microM. Cl-949 (100 microM) had no inhibitory effect against lysozyme release in response to L-alpha-1,2 dioctanoylglycerol (DiC8), or phorbol 12-myristate 13-acetate (PMA). Cl-949 inhibited superoxide anion generation stimulated by FMLP and Con A with IC50s of 33.9 and 25.8 microM, while inhibiting the response to C5a, SOZ, and A23187 by 36.6%, 24.8%, and 14.1% and having no effect on the response to DiC8 or PMA at 100 microM. These results demonstrate preferential inhibition of arachidonic acid metabolism and degranulation of primary lysosomal granules by Cl-949 with selectivity for stimuli which promote intracellular calcium mobilization or calcium influx.

Arachidonic Acid↗
PubMed1990

Inhibition of human neutrophil activation by the allergic mediator release inhibitor, CI-949: mechanism of inhibitory activity.

CI-949 [5-methyl-3-(1-methylethoxy)-1-phenyl-N-1H-tetrazol-5-yl-1H- indole-2- carboxamide, L-arginine salt] inhibits human neutrophil activation in response to stimuli which promote calcium mobilization or calcium influx. This report further examines the effect of CI-949 on phosphoinositide-dependent stimulus-response coupling. At 100 microM, CI-949 had no inhibitory effect on human neutrophil phospholipase C or protein kinase C. In contrast, CI-949 inhibited FMLP-stimulated intracellular calcium mobilization with an IC50 of 8.4 microM. The compound was also a potent calmodulin antagonist, inhibiting calmodulin-dependent phosphodiesterase activity with an IC50 of 31.0 microM. The calmodulin antagonist activity of CI-949 was confirmed by fluorescence spectroscopy. These results demonstrate that CI-949 may function through inhibition of calcium- and calmodulin-dependent signal transduction processes.

Azoles↗
PubMed1990

Effect of increased central blood volume with water immersion on plasma catecholamines during exercise.

To examine the influence of an increase in central blood volume with head-out water immersion (WI) on the sympathoadrenal response to graded dynamic exercise, nine healthy men underwent upright leg cycle exercise on land and with WI. Plasma norepinephrine and epinephrine concentrations were used as indexes of overall sympathoadrenal activity. Oxygen consumption (VO2), heart rate, systolic blood pressure, and plasma concentrations of norepinephrine, epinephrine, and lactate were determined at work loads corresponding to approximately 40, 60, 80, and 100% peak VO2. Peak VO2 did not differ on land and with WI. Plasma norepinephrine concentration was reduced (P less than 0.05) at 80 and 100% peak VO2 with WI and on land, respectively. Plasma epinephrine and lactate concentrations were similar on land and with WI at the three submaximal work stages, but both were reduced (P less than 0.05) at peak exertion with WI. Heart rate was lower (P less than 0.05) at the three highest work intensities with WI. These results suggest that the central shift in blood volume with WI reduces the sympathoadrenal response to high-intensity dynamic exercise.

Adrenal Glands↗
PubMed1990

Physiological responses to different cross country skiing techniques on level terrain.

This study compared the physiological responses and ratings of perceived exertion elicited by several of the most common currently used cross country skiing techniques. The comparison included two classical techniques (kick double pole and diagonal stride), two ski skating techniques (V1 skate and marathon skate), and the double pole technique on both classical and skating skis. Eight male cross country ski racers skied each technique for three laps around a 420 m flat, professionally groomed and tracked oval surface at a mean (+/- SD) velocity of 14.2 +/- 0.6 km.h-1. Heart rate was recorded by telemetry and expired gases were collected for determination of minute ventilation and oxygen consumption during the final minute of each bout. Rating of perceived exertion was requested immediately after each bout. It was found that the diagonal stride technique required the highest oxygen consumption, with the V1 skate, marathon skate, and kick double pole techniques inducing a 16% lower (P less than 0.01) oxygen cost, and the double pole technique inducing a 26% lower (P less than 0.01) oxygen cost. Heart rate was also highest (P less than 0.01) with the diagonal stride technique and lowest with the double pole technique. The rating of perceived exertion was greatest (P less than 0.05) for the diagonal stride technique and lowest (P less than 0.05) for the V1 skate technique. These results indicate that the double pole technique has the greatest economy, the diagonal stride technique elicits the greatest physiological demands and has the highest perceived effort, and the V1 skate technique is associated with the lowest perceived effort under the conditions of this study.

Adult↗
PubMed1990

Physiological responses to different roller skiing techniques.

This study compared the physiological responses during roller skiing with the V1 skate, kick double pole, and double pole techniques. Eight male nordic ski racers roller skied over a flat one-mile track at 14 and 18 km.h-1 using each of the three techniques under study. Heart rates and oxygen uptakes were measured during the last minute of each bout, ratings of perceived exertion were requested immediately after each bout, and capillary blood lactate concentrations were determined 3 min after each bout. The double pole technique was found to be significantly more economical (P less than 0.05) than the other techniques, as demonstrated by a 12% lower oxygen consumption. No differences were found between the V1 skate and the kick double pole techniques for any of the variables studied. The findings of similar physiological responses with the V1 skate and kick double pole techniques suggest that these techniques should induce similar cardiovascular adaptations when roller skiing at the same speed on flat terrain.

Adult↗
PubMed1989

Weight carrying versus handgrip exercise testing in men with coronary artery disease.

The clinical merits of handgrip and weight carrying tests were compared in 30 patients with documented coronary artery disease. The static loads in the 2 tests were matched by percentage of maximal static effort and corresponded to 25 and 45% of maximal voluntary handgrip contraction and 25 and 45% of maximal 1-hand lift capacity. Each static load in both tests was continued for less than or equal to 3 minutes. At the 25% maximal effort stage, 93 and 90% of patients were able to complete 3 minutes of handgrip and weight carrying, respectively. Only 13 and 10% were able to complete 3 minutes at the 45% maximal effort stage with handgrip and weight carrying, respectively. Arm fatigue and an increase in diastolic blood pressure greater than 120 mm Hg were the predominant endpoints. Weight carrying resulted in significantly higher (p less than 0.05) heart rate, systolic blood pressure, pressure-rate product, ventilation and oxygen consumption compared to handgrip. Diastolic blood pressure responses did not differ between the tests. None of the patients demonstrated ischemic responses to either handgrip or weight carrying and the incidence of arrhythmias was rare. The diastolic blood pressure response to static effort is equally evaluated by handgrip and weight carrying tests. However, the greater myocardial oxygen demand, reflected by the pressure-rate product, in addition to the greater total body oxygen consumption, imposed by weight carrying, enhances the clinical application of the weight carrying test.

Adult↗
PubMed1989

High school football injuries: field conditions and other factors.

This study was conducted to identify factors that were associated with injuries during 59 varsity high school football games in 1987. For each injury, medical personnel recorded data on the type and body location of each injury, player position, specific player activity at the time of injury, the quarter of the game, the week of the season, playing field conditions, and ambient air temperature. We found injury frequencies, types, body locations and seasonal and game quarter distributions similar to previous reports. This study demonstrated a previously unreported association between playing field condition and injury rate.

Contusions↗
PubMed1988

Ventilatory and PaCO2 responses to voluntary and electrically induced leg exercise.

We studied the role of central command mediation of exercise hyperpnea by comparing the ventilatory and arterial CO2 partial pressure (PaCO2) responses to voluntary (ExV) and electrically induced (ExE) muscle contractions in normal, awake human subjects. We hypothesized that if central command signals are critical to a normal ventilatory response, then ExE should cause a slower ventilatory response resulting in hypercapnia at the onset of exercise. ExE was induced through surface electrodes placed over the quadriceps and hamstring muscles. ExE and ExV produced leg extension (40/min) against a spring load that increased CO2 production (VCO2) 100-1,000 ml/min above resting level. PaCO2 and arterial pH during work transitions and in the steady state did not differ significantly from rest (P greater than 0.05) or between ExE and ExV. The temporal pattern of ventilation, tidal volume, breathing frequency, and inspired and expired times, and the ventilation-VCO2 relationship were similar between ExE and ExV. We conclude that since central command was reduced and/or eliminated by ExE, central command is not requisite for the precise matching of alveolar ventilation to increases in VCO2 during low-intensity muscle contractions.

Adult↗
PubMed1988

Is the hyperpnea of muscular contractions critically dependent on spinal afferents?

We studied the role of spinal afferent pathways in the hyperpnea of electrically induced muscle contractions (ExE). The ventilatory (VE) and arterial CO2 partial pressure (PaCO2) responses were measured at rest and during two levels of ExE in awake human paraplegic subjects with clinically complete lesions of the spinal cord (range T4-T11). We hypothesized that if peripheral neural drive is critical to a normal ventilatory response, then ExE in the absence of intact pathways should cause a lower ventilatory response resulting in hypercapnia at the onset of ExE. ExE was induced by stimulation of the quadriceps and hamstring muscles that approximately doubled the resting level of CO2 production (VCO2). PaCO2 during work transitions and in the latter stages of ExE did not differ significantly from that at rest. Arterial pH progressively declined over time during ExE (P less than 0.01) as a result of increased lactate concentration (P less than 0.01). The linear relationship between VE and VCO2 was similar to that found for normal human subjects during ExE (P = 0.73). These data suggest that VE and presumably alveolar ventilation (VA) can be appropriately matched to VCO2 during low-intensity muscle contractions of the lower extremities in the absence of intact spinal afferent pathways. Moreover, since it is unlikely that postulated "central command" mechanisms were initiated during ExE in these paraplegic subjects, the data provide support for our previous conclusion that central command is not obligatory for matching VA to VCO2 (J. Appl. Physiol. 64: 218-225, 1988).

Adult↗