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Biomedical subjects

M L Pollock

Publications and source records attributed to M L Pollock.

At least 55 records · Page 3Linked to original sources
PubMed1994

Using the exercise test to develop the exercise prescription in health and disease.

The objective of an exercise program for persons with or without disease should be the development or maintenance of cardiorespiratory fitness, strength and muscular endurance, and flexibility. The basic principles of prescribing exercise--frequency, intensity, and duration of training--and the mode of activity as recommended by the ACSM for healthy adults are also appropriate for persons with disease. The difference in the exercise prescription for persons with disease is the manner in which these principles are applied. Usually, the more fragile the patient, the lower the intensity of exercise and the slower the progression of training. The role of cardiopulmonary exercise testing is to determine a safe and effective level of exercise for healthy persons as well as those with disease. GXT is useful in identifying individuals with disease and in providing information regarding the level of supervision needed during exercise training. In addition, exercise testing can be used to clear a person for participation in a resistance training program. Resistance training should be integrated as part of a well-rounded program, because of the importance of maintaining strength, muscle mass, and bone mineral density. Generally, the starting intensity for persons with disease is lower, the frequency and duration higher, and the progression of exercise slower to allow a more gradual adaptation to exercise training.

Exercise↗
PubMed1993

Frequency and volume of resistance training: effect on cervical extension strength.

Quantification of cervical extension (CERV EXT) strength is complicated by the inability to stabilize the torso and isolate the CERV EXT muscles. A newly developed machine designed to stabilize the torso and isolate the CERV EXT muscles was used to evaluate the effect of frequency and volume of resistance training on CERV EXT strength. Fifty men (age, 26 +/- 9 years; height, 174 +/- 16 cm; weight, 74 +/- 9 kg) and 28 women (age, 30 +/- 9 years; height, 152 +/- 32 cm; weight, 62 +/- 7 kg) volunteered to participate. Subjects were randomly stratified to one of four training groups or a control group (CONT, n = 19) that did not train. Each training group exercised for 12 weeks as follows; once per week using one set of dynamic exercise (DYN 1x/wk, n = 14), once per week using one set of DYN and one set of maximal isometric (IM) exercise at eight angles through a 126 degrees-range of CERV EXT (DYN-IM 1x/wk, n = 16), DYN 2x/wk (n = 19), or DYN-IM 2x/wk (n = 10). Maximal IM torque was measured at eight angles initially and after 12 weeks of training. All training groups improved CERV EXT strength (p < or = 0.05) at all angles tested compared to the CONT except for DYN once per week at 0 degree of CERV flexion. A greater increase in strength was found when the groups that trained two times a week were compared to those that trained once per week.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Exercise-induced hypoxemia in heart transplant recipients.

OBJECTIVES: The purpose of this study was to determine whether heart transplantation has an adverse effect on pulmonary diffusion and to investigate the potentially deleterious effects of impaired pulmonary diffusion on arterial blood gas dynamics during exercise in heart transplant recipients. BACKGROUND: Abnormal pulmonary diffusing capacity is reported in patients after orthotopic heart transplantation. Abnormal diffusion may be caused by cyclosporine or by the persistence of preexisting conditions known to adversely affect diffusion, such as congestive heart failure and chronic obstructive pulmonary disease. METHODS: Eleven patients (mean age 50 +/- 14 years) performed pulmonary function tests 3 +/- 1 months before and 18 +/- 12 (mean +/- SD) months after heart transplantation. Transplant patients were assigned to groups with diffusion > 70% (n = 5) or diffusion < 70% of predicted values (n = 5). The control group and both subsets of patients performed 10 min of cycle exercise at 40% and 70% of peak power output. Arterial blood gases were drawn every 30 s during the 1st 5 min and at 6, 8 and 10 min. RESULTS: Significant improvements in forced vital capacity (17.4%), forced expiratory volume in 1 s (11.7%) and diffusion capacity (6.6%) occurred in the patients; however, posttransplantation vital capacity, forced expiratory volume and diffusion were lower (p < or = 0.05) compared with values in 11 matched control subjects. Changes in blood gases were similar among groups at 40% of peak power output. At 70% of peak power output, arterial blood gases and pH were significantly (p < or = 0.05) lower in transplant patients with low diffusion (arterial oxygen pressure 15 to 38 mm Hg below baseline) than in patients with normal diffusion and control subjects. Cardiac index did not differ (p > or = 0.05) between transplant patients with normal and low diffusion at rest or during exercise. Posttransplantation mean pulmonary artery pressure was significantly related to exercise-induced hypoxemia (r = 0.71; p = 0.03). CONCLUSIONS: Abnormal pulmonary diffusion observed in patients before heart transplantation persists after transplantation with or without restrictive or obstructive ventilatory defects. Heart transplant recipients experience exercise-induced hypoxemia when diffusion at rest is < 70% of predicted. Our data also suggest that abnormal pulmonary gas exchange possibly contributes to diminished peak oxygen consumption in some heart transplant recipients; however, direct testing of this hypothesis was beyond the scope of the present study. This possibility needs to be investigated further.

Adult↗
PubMed1993

Effect of training on the relationship between maximal and submaximal strength.

The purpose of this study was to evaluate the validity of a dynamic seven to 10 repetition maximum (7-10 RM) test to estimate maximal knee extension strength (1-RM) in untrained and trained subjects. Thirty-three men and 25 women (25 +/- 5 yr) were randomly assigned to a group that trained two or three times.wk-1 for 18 wk (N = 47) or a control group (N = 11). Training included one set of 7-10 repetitions to volitional fatigue on a Nautilus knee extension machine. Prior to (T1) and after training (T2) dynamic strength was evaluated by 1-RM and 7-10 RM tests. The 7-10 RM test consisted of one set of variable resistance knee extension exercise performed to volitional fatigue with a weight that allowed 7-10 repetitions. The training group improved their 1-RM and 7-10 RM strength (by 31.7 and 51.4%, respectively) (P < or = 0.01) while the control group did not change. Training increased relative 7-10 RM strength (68.4% of 1-RM at T1 and 79.1% of 1-RM at T2) (P < or = 0.01). The relationship between the 7-10 RM weight and 1-RM at T1 was linear: 1-RM = 1.554 (7-10 RM weight)-5.181; R2 = 0.89; SEE = 9.3 kg. Application of this equation following training resulted in a systematic overprediction (p < or = 0.01) of 1-RM (21.2 kg) in trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Blood gas dynamics at the onset of exercise in heart transplant recipients.

One hypothesis to explain the rapid neural component of exercise hyperpnea contends that afferent stimuli originating in the ventricles of the heart act reflexly on the respiratory center at the onset of exercise, ie, "cardiodynamic hyperpnea." Orthotopic cardiac transplantation (Tx) results in the loss of afferent information from the ventricles. Thus, Tx possibly results in transient hypercapnia and hypoxemia in deafferented heart transplant recipients (HTR) at the onset of exercise due to hypoventilation. To examine the cardiodynamic hypothesis, we collected serial arterial blood gas (ABG) samples during both the transient and the steady-state responses to moderate cycle exercise in 5 HTRs (55 +/- 7 years) 14 +/- 7 months post-Tx and 5 control subjects matched with respect to gender, age, and body composition. Forced vital capacity, forced expiratory volume in 1 s, total lung capacity, and diffusion capacity did not differ (p > or = 0.05) between groups. Resting arterial PO2, PCO2, and pH did not differ between groups (p > or = 0.05). The ABGs were drawn every 30 s during the first 5 min and at 6, 8, and 10 min of constant load square wave cycle exercise at 40 percent of the peak power output (watts). Absolute and relative changes in arterial PO2, PCO2, and pH were similar (p > or = 0.05) between HTR and the control group at all measurement periods during exercise. Heart rate (%HRmax reserve), rating of perceived exertion, and reductions in plasma volume (% delta from baseline) did not differ between HTR and control during exercise at 40 percent of peak power output (p > or = 0.05). Our results demonstrate that there is no discernible abnormality in ABG dynamics during the transient response to exercise at 40 percent of peak power output in patients with known cardiac denervation. These data do not support the cardiodynamic hyperpnea hypothesis of ventilatory control in humans. The absence of hypercapnia in HTRs is further evidence for the existence of redundant mechanisms capable of stimulating exercise hyperpnea.

Adult↗
PubMed1993

Lumbar strengthening in chronic low back pain patients. Physiologic and psychological benefits.

The effects of exercise for isolated lumbar extensor muscles were examined in 54 chronic low-back pain patients. Subjects were randomly assigned to a 10-week exercise program (N = 31) or a wait-list control group (N = 23). Results indicated a significant increase in isometric lumbar extension strength for the treatment group and a significant reduction in reported pain compared with the control group (P 0.05). Treated subjects reported less physical and psychosocial dysfunction whereas the control group increased in pain, and physical and psychosocial dysfunction. There were no concomitant changes in reported daily activity levels. These results show that lumbar extension exercise is beneficial for strengthening the lumbar extensors and results in decreased pain and improved perceptions of physical and psychosocial functioning in chronic back pain patients. However, these improvements were not related to changes in activities or psychological distress.

Adult↗
PubMed1993

Exercise testing in cardiac rehabilitation. Role in prescribing exercise.

Graded exercise tests provide useful information for the prescription of exercise for cardiac patients. The responses to graded exercise depend on the mode of testing. The observed heart rate and electrocardiographic responses during graded exercise are used to establish an appropriate level or intensity of exercise at which the patient may participate safely. This article specifically addresses the role of exercise testing for the prescription of exercise in cardiac rehabilitation.

Adult↗
PubMed1992

Incidence of injury during moderate- and high-intensity walking training in the elderly.

To evaluate the effect of 26 weeks of moderate- and high-intensity walking training on injury rates in the elderly, 68 healthy volunteers (31 men, 37 women) were assigned to moderate intensity (MOD, n = 26) or high-intensity (HI, n = 24) training, or to a control (CONT, n = 18) group. To achieve prescribed training intensity, many subjects walked uphill on a treadmill. Seven of 50 subjects who trained (14%) suffered a training-related orthopedic injury; one subject was injured during treadmill testing. Four training injuries (lower leg and foot) occurred during weeks 1-13; three training injuries (leg and groin) occurred during weeks 14-26. Six of the injuries were to women. Because only one training injury occurred during uphill treadmill walking, injuries appeared related to fast walking and not exercise intensity. The higher incidence of injury in females is consistent with our earlier work, indicating the importance of further research to determine the underlying cause.

Aged↗
PubMed1992

Effect of reduced frequency of training and detraining on lumbar extension strength.

To investigate the effect of reduced frequency of training and detraining on lumbar extension strength, 50 subjects (34 men, aged 34 +/- 11 yrs; and 16 women, aged 33 +/- 11 yrs) were recruited from ongoing strength training programs. Initial training consisted of 10 or 12 weeks of variable resistance lumbar extension strength exercise to volitional fatigue 1, 2, or 3 times a week. After the initial training, subjects reduced the frequency of training to once every 2 weeks (n = 18) or once every 4 weeks (n = 22) for 12 weeks. Only the frequency of training was changed; the mode, volume, and intensity of exercise remained constant for both reduced frequency of training groups. An additional ten subjects terminated training and acted as controls (detraining group). Isometric lumbar extension strength was evaluated at seven angles through a 72 degree range-of-motion before training, after training, and after reduced frequency of training or detraining. Analysis of variance with repeated measures indicated that lumbar extension strength improved (P < or = 0.05) for all groups after the initial 10 or 12 weeks of training. After 12 weeks of reduced training, the once every 2 weeks and once every 4 weeks groups showed no significant reduction in lumbar extension strength at any angle tested, whereas the detraining group demonstrated an average 55% reduction in strength. These findings indicate that isometric lumbar extension strength can be maintained for up to 12 weeks with a reduced frequency of training as low as once every 4 weeks when the intensity and the volume of exercise are maintained.

Adult↗
PubMed1992

Abnormal neuroendocrine responses during exercise in heart transplant recipients.

BACKGROUND: Osmotic and neural factors stimulate neuroendocrine activity during exercise. In contrast to excitatory mechanisms, afferent information from cardiac mechanoreceptors inhibits integrative centers in the hypothalamus and medula oblongata, which serves to buffer neuroendocrine activity. Orthotopic cardiac transplantation results in the loss of afferent information from cardiac mechanoreceptors. Thus, transplantation possibly results in exaggerated neuroendocrine responses when patients are physically active. METHODS AND RESULTS: We measured the neuroendocrine response to moderate and strenuous exercise performed at the same relative intensity in 11 heart transplant recipients (50 +/- 14 years old) 18 +/- 12 months after transplantation and 11 control subjects matched with respect to sex, age, and body size. Plasma levels of norepinephrine, vasopressin, renin activity, atrial natriuretic peptide, angiotensin II, and aldosterone were measured at rest, during a maximal graded exercise test, and during submaximal exercise at 40% and 70% of peak power output on a cycle ergometer (W). Plasma renin activity and atrial natriuretic peptide were elevated at rest in heart transplant recipients (p < or = 0.05). Heart rate (%HRmax reserve), rating of perceived exertion, and reductions in plasma volume (% delta from rest) at the conclusion of the three exercise conditions did not differ between heart transplant recipients and control (p > or = 0.05). Relative changes in neuroendocrine hormones were similar (p > or = 0.05) in heart transplant recipients and control during exercise at 40% of peak power output. Relative changes in plasma norepinephrine, vasopressin, atrial natriuretic peptide, and plasma renin activity were greater (p < or = 0.05) in heart transplant recipients during exercise at 70% of peak power output and the graded exercise test. CONCLUSIONS: We interpret these data as a possible indication of ablation of cardiac mechanoreceptor afferents and unopposed neuroendocrine stimulation in heart transplant recipients. Furthermore, chronic neuroendocrine hyperactivity is likely in ambulatory heart transplant recipients. Although cyclosporine nephrotoxicity is implicated in the development of hypertension, our data suggest that chronic neuroendocrine hyperactivity, which alters renal volume regulation, also contributes to the incidence and severity of hypertension in heart transplant recipients.

Afferent Pathways↗
PubMed1992

[A comparison of fat and muscle thickness in Japanese and American women].

The purpose of this study was to investigate the ethnic differences in the body composition, thickness of subcutaneous fat and muscle between Japanese and American white females. Thirty-six Japanese (aged 20-30 years) and 42 American white females (aged 20-29 years) served as subjects. Percentage of fat weight (%fat) and fat free weight (FFW) were assessed by hydrostatic weighing. Subcutaneous fat and muscle thickness were measured by using B-scan ultrasound equipment with a 5MHz transducer at eight sites: forearm, biceps, triceps, subscapular, abdomen, quadriceps, hamstrings and posterior calf. There were no significant differences in %fat between Japanese and American subjects. However, American subjects had significantly higher values in FFW compared to Japanese. The Americans showed higher muscle thickness than Japanese at every site and higher fat thickness of biceps, triceps and hamstrings compared to Japanese subjects. For fat thickness at the abdomen, however, Japanese indicated significantly higher values than American. In both Japanese and Americans, relative values of fat weight (FW) and FFW per unit of height were significantly related to each of the sum of fat and muscle thicknesses obtained from every measurement site respectively. There were no differences in fat thickness at a given FW/height between Japanese and Americans.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

Limited range-of-motion lumbar extension strength training.

The purpose of this study was to evaluate the effect of limited range-of-motion (ROM) resistance training on the development of lumbar extension strength through a 72 degrees ROM. Thirty-three men and 25 women (age = 30 +/- 11 yr) were randomly assigned to one of three training groups or a control group (C; n = 10) that did not train. Training was conducted once per week for 12 wk and consisted of one set of 8-12 repetitions of variable resistance lumbar extensions until volitional fatigue. Group A (n = 18) trained from 72 degrees to 36 degrees of lumbar flexion; group B (n = 14) from 36 degrees to 0 degree of lumbar flexion; and group AB (n = 16) from 72 degrees to 0 degree of lumbar flexion. Prior to and after training, isometric lumbar extension torque was assessed at 72 degrees, 60 degrees, 48 degrees, 36 degrees, 24 degrees, 12 degrees, and 0 degree of lumbar flexion. Analysis of covariance showed that groups A, B, and AB increased lumbar extension torque (P less than or equal to 0.05) at all angles measured when compared with C. The greatest gains in torque were noted for groups A and B in their respective ranges of training but A and B did not differ from AB (P greater than 0.05) at any angle. These data indicate that limited ROM lumbar extension training through a 36 degrees ROM is effective for developing strength through 72 degrees of lumbar extension.

Adult↗
PubMed1992

Rehabilitation and life-style modification in the elderly.

The projected growth of the elderly population in the United States in the coming years underlines the importance of assuring that the quality of life for older persons is maintained. Because CHD is prevalent in this population, measures for preventing disease as well as for optimizing the abilities of those with disease will assume greater significance. Exercise training is a key component in achieving and maintaining optimal capacities in the elderly cardiac and noncardiac populations. These groups can safely undergo exercise training with proper screening and program design. Modifications in the components of the exercise prescription (i.e., frequency, intensity, duration, and activity mode) must be individualized according to the abilities, needs, and goals of each person. Risk factors for CHD still prevail in the elderly, although the predictive value of some risk factors may change with age. For this reason, efforts to control risk factors in older individuals should still be effective in reducing risk from CHD. Dietary modification, weight control, blood pressure control, smoking cessation, and endurance exercise training are several of the interventions used in concert to control risk for CHD.

Aged↗
PubMed1991

Effect of 12 and 20 weeks of resistance training on lumbar extension torque production.

This study compared the effect of varied training frequencies on the development of isometric lumbar extension torque (strength) over 12- and 20-week training periods. Fifty-six subjects were randomly assigned to training once every other week (training group 1, n = 10), once per week (training group 2, n = 12), twice per week (training group 3, n = 12), or three times per week (training group 4, n = 7) or to a nontraining control group (n = 15). Training consisted of one set of 8 to 12 variable-resistance lumbar extensions to volitional muscular fatigue. Prior to and following 12 and 20 weeks of training, subjects were given a test that evaluated isolated isometric lumbar extension torque in a seated position at seven positions (angles) through a 72-degree range of motion. The control group showed no change in isometric torque. All training groups showed significant increases in lumbar extension torque at 12 and 20 weeks of training, whereas no significant differences were found among the groups with respect to the magnitude of torque gained. Pooled training showed a significant time x angle interaction at 12 weeks and a continuing trend at 20 weeks, indicating that the shape of the isometric torque-angle curve changed as a result of training. This effect was due to greater increases in isometric torque at the fully extended position than at the fully flexed position at 12 weeks (92% versus 16%, respectively) and at 20 weeks (123% versus 17%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Injuries and adherence to walk/jog and resistance training programs in the elderly.

To evaluate the effects of 26 wk of aerobic and resistance training on the incidence of injury and program adherence in 70- to 79-yr-old men and women, 57 healthy volunteers (25 males, 32 females) were randomly assigned to a walk/jog (W/J, N = 21), strength (STREN, N = 23), or control (CONT, N = 13) group. Walk/jog training was for 30-45 min, 3 d.wk-1 with intensity equal to 40-70% heart rate max reserve (HRmax reserve) during the first 13 wk, and 75-85% HRmax reserve for weeks 14-26. STREN training consisted of one set (10-12 repetitions) each of 10 variable resistance exercises performed to volitional fatigue. Forty-nine of the original participants completed the training program. Walk/jog training increased VO2max from 22.5 to 27.1 ml.kg-1.min-1 (P less than or equal to 0.05) while STREN and CONT showed no change. STREN improved significantly in chest press and leg extension strength (P less than or equal to 0.05) while W/J and CONT showed no change. Adherence to training was 20/23 (87%) and 17/21 (81%) in STREN and W/J, respectively. One repetition maximum (1-RM) strength testing resulted in 11 injuries in the 57 subjects (19.3%) while STREN training resulted in only two injuries in 23 subjects (8.7%). Walk training during weeks 1-13 resulted in one injury in 21 subjects (4.8%). Eight of 14 subjects (57%) who began jogging intervals at week 14 incurred an injury: two of eight (25%) of the men and all of the women (6 of 6). All W/J training injuries were to the lower extremity.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Effect of exercise training on blood pressure in 70- to 79-yr-old men and women.

Men and women 70-79 yr of age (N = 49) were studied to assess the effect of 6 months of resistance or endurance exercise training on their blood pressure, hemodynamic parameters, and pressor hormone levels. Resistance training consisted of one set of 8-12 repetitions on ten Nautilus machines three times per week. The endurance training group progressed to training at 75-85% VO2max for 35-45 min three times per week for the last 2 months of training. No changes in body weight or estimated lean body mass occurred; however, the sum of seven skinfolds, as an index of percent body fat, decreased in both exercise groups. Upper and lower body strength increased with resistance training, while VO2max increased by 20% in the endurance training group. Blood pressure did not change with resistance training in individuals with normal or somewhat elevated blood pressures. Diastolic and mean blood pressure decreased significantly, by 5 and 4 mm Hg, with endurance training. Subjects with blood pressure greater than 140/90 reduced their systolic, diastolic, and mean blood pressure by 8, 9, and 8 mm Hg, respectively, with endurance exercise training. Cardiac output, peripheral vascular resistance, and plasma levels of angiotensin I and II and epi- and norepinephrine did not change in any of the groups. Thus, resistance exercise training does not adversely affect, or reduce, blood pressure, while endurance exercise training produces modest reductions in blood pressure in 70-79-yr-old individuals with somewhat elevated blood pressures.

Aged↗
PubMed1990

Effect of aerobic and resistance training on fractionated reaction time and speed of movement.

To evaluate the effect of aerobic and variable resistance exercise training on fractionated reaction time (RT) and speed of movement (SM) in elderly individuals, premotor time (PMT), motor time (MT), total RT, and SM were measured in 49 healthy, untrained men and women, 70 to 79 years of age, before and after 6 months of training. Subjects were randomized into either a walk/jog (n = 17), a strength training (n = 20), or a control group (n = 12). Improvements in aerobic capacity were only weakly related to reduced total RT (r = 0.30, p less than .05). Analysis of covariance revealed that there were no differences (p greater than .05) among the three groups after training with respect to PMT, MT, total RT, and SM. These findings indicate that 6 months of aerobic and strength training did not induce significant changes in RT or SM in this group.

Aged↗