Biomedical subjects

S H Leggett

Publications and source records attributed to S H Leggett.

At least 19 recordsLinked to original sources

PubMed1996

Relative heart rate, heart rate reserve, and VO2 during submaximal exercise in the elderly.

BACKGROUND: The purpose of this study was to examine the relationships among relative maximal heart rate (%HRmax), maximal heart rate reserve (%HRmax reserve), and maximal oxygen uptake (%VO2max) during submaximal exercise by elderly subjects. METHODS: VO2max and HRmax were determined on 36 women and 19 men, 60 to 80 yrs of age, by a maximal treadmill test to volitional exhaustion. On a separate day, subjects underwent a submaximal treadmill protocol consisting of three 6-min exercise stages at treadmill speeds and grades estimated to elicit 40%, 60%, and 80% of HRmax reserve. Cardiorespiratory responses were determined during mins 4-5 and 5-6 of each stage. RESULTS: Measured exercise intensities expressed by the three methods were: %HRmax reserve = 36, 55, and 79%; %HRmax = 65, 75, and 88%; %VO2max = 53, 69, and 88%. %HRmax was greater (p < .05) than %VO2max at 53 and 69% of VO2max. %HRmax reserve was less (p < .05) than %VO2max for all three intensities. Slopes and intercepts for the linear regression equations relating %VO2max with %HRmax and with %HRmax reserve differed between men and women (p < .05). The regression equation relating %VO2max and %HRmax was y = -22.8 + 1.2 (%HRmax) -13.0 (Gender) + 0.2 (%HRmax x Gender): standard error of the estimate (SEE) = 9.7% and R2 = .71. The regression equation relating %VO2max and %HRmax reserve was y = 32.4 + 0.7 (%HRmax reserve) -10.9 (Gender) + 0.2 (%HRmax reserve x Gender): SEE = 9.8% and R2 = .70 (Gender: F = 0; M = 1). CONCLUSIONS: The data indicate that there is considerable variability among methods of expressing exercise intensity and that %HRmax more closely represents %VO2max than does %HRmax reserve (p < .05) in older adults. These results are in contrast to what has been shown with younger subjects and with American College of Sports Medicine guidelines for exercise prescription.

Aged↗

PubMed1996

Applied physiology of water-skiing.

Water-skiing is a physically demanding sport involving highly coordinated movements, extreme upper body torques, sustained isometric contractions and near maximal stresses on the anaerobic system. Due to the physical demands of the sport, elite skiers have developed physiological characteristics similar to other elite athletes. However, until recently little research has focused on the kinesiology, physiology and physical conditioning of water-skiing.

Exercise Therapy↗

PubMed1995

The effect of lumbar belts on isolated lumbar muscle. Strength and dynamic capacity.

STUDY DESIGN: This study analyzed the effect of lumbar support belts on functional performance. OBJECTIVE: To compare lumbar muscle strength and lifting capacity with and without a lumbar belt. SUMMARY OF BACKGROUND DATA: Industrialized settings have begun to encourage the use of lumbar support belts for their employees. It is believed that the belts may decrease the risk of injury and enhance the functional performance of the individual. METHODS: Twenty-two subjects (average age, 27.5 years) were tested on four separate days to evaluate the effect of a commercially available belt on isolated lumbar isometric strength and functional dynamic lifting capacity. All subjects had no history of low back problems. The order of testing with and without a belt was randomized for both conditions. On the first 2 days, subjects performed a seven-angle isometric lumbar extension strength test, 1 day with and 1 day without a lumbar belt. On the following 2 days, subjects were tested to evaluate functional capacity with and without a lumbar belt. The functional capacity evaluation was performed by progressively lifting weighted canisters from various levels. Heart rates were monitored to ensure that a maximum effort was achieved over the different days. RESULTS: T tests revealed that isometric lumbar strength and functional lifting capacity was not significantly affected by the belt. CONCLUSION: The use of a lumbar belt does not enhance isometric lumbar muscle strength or dynamic lifting capacity.

Adult↗

PubMed1995

Body fat and muscle thickness distributions in untrained young females.

Brightness-mode (B-mode) ultrasound was used to measure fat and muscle thicknesses on 44 untrained females (age = 18-29 yr, body density = 1.050 +/- 0.009 (SD)g.ml-1, %fat = 21.5 +/- 4.1%) at eight sites (triceps, biceps, forearm, subscapular, abdomen, quadriceps, hamstrings, and posterior calf). The correlation coefficients between fat and muscle thickness were not significant at any measurement site except for the triceps (r = -0.32, P < 0.05). Intercorrelation analyses among the eight sites were significant (P < 0.05) in almost all cases for fat thickness, while mainly between adjoining sites for muscle thickness. However, both tissues had a low degree of generality in thickness among sites. Fat thickness at all measurement sites was significantly correlated with body density except for the posterior calf; the best correlation was found with the quadriceps (r = -0.73). On the other hand, for muscle thickness, only the forearm and triceps were significantly correlated with body density. These results show 1) the extent of muscled and fat thicknesses are independent each of other within the same region, 2) fat and muscle thicknesses have a high degree of specificity in site distribution, and 3) fat thickness measurements determined from B-mode ultrasound may be of significant value assessing total body composition.

Adipose Tissue↗

PubMed1994

Pelvic stabilization during resistance training: its effect on the development of lumbar extension strength.

The purpose of this study was to evaluate and compare resistance exercise training with and without pelvic stabilization on the development of isolated lumbar extension strength. Isometric torque of the isolated lumbar extensor muscles was measured at seven positions through a 72 degree range-of-motion on 47 men and 30 women before and after 12 weeks of variable resistance lumbar extension training. Subjects were assigned to either a group that trained with pelvic stabilization (P-STAB, n = 21), a group that trained without pelvic stabilization (NO-STAB, n = 41), or a control group that did not train (n = 15). Subjects trained once a week with 8 to 12 repetitions to volitional exhaustion. The P-STAB and NO-STAB groups showed significant (p < or = 0.05) and similar increases in the weight load used for training (P-STAB = 24.1 +/- 9.4kg; NO-STAB = 19.4 +/- 11.0kg) during the 12-week training period. In contrast, posttraining isometric torque values describing isolated lumbar extension strength improved only for the P-STAB group (23.5%, p < or = 0.05) and not for the NO-STAB group (-1.2%, p > 0.05) relative to controls. These data indicate that pelvic stabilization is required to effectively train the lumbar extensor muscles. The increased training load for the NO-STAB group is probably the result of exercising the muscles involved in pelvic rotation (hamstring and buttock muscles).

Adult↗

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

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↗

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

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↗

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↗

PubMed1990

Quantitative assessment of full range-of-motion isometric lumbar extension strength.

The purpose of this study was to evaluate the reliability and variability of repeated measurements of isometric (IM) lumbar extension (LB EXT) strength made at different joint angles. Fifty-six men (age, 29.4 +/- 10.7 years) and 80 women (age, 24.3 +/- 9.1 years) completed IM LB EXT strength tests on 3 separate days (D1, D2, and D3). On D1 and D2, subjects completed two tests (T1 and T2) separated by a 20- to 30-minute rest interval. For each test, IM LB EXT strength was measured at 72, 60, 48, 36, 24, 12, and 0 degrees of lumbar extension. Mean IM strength values, within-day reliability coefficients, and test variability over the seven angles improved from D1 to D2 (D1: mean, 160.0 to 304.1 N.m, r = 0.78 to 0.96, SEE = 37.6 to 46.9 N.m; D2: mean, 176.3 to 329.1 N.m, r = 0.94 to 0.98, SEE = 29.0 to 34.4 N.m). Mean strength values leveled off by D3 (174.5 to 317.0 N.m). The most reliable test results showed that the IM LB EXT strength curves were linear and descending from flexion to extension and ranged from 235.8 +/- 85.2 to 464.9 +/- 150.7 N.m for men (extension to flexion) and from 134.6 +/- 53.2 to 237.3 +/- 71.9 N.m for women. Lumbar extension strength was clearly greatest in full flexion, which is in contrast to previously reported results. One practice test was required to attain the most accurate and reliable results. These data indicate that repeated measures of IM LB EXT strength are highly reliable and can be used for the quantification of IM LB EXT strength through a range of motion.

Adult↗

PubMed1990

Effect of training frequency and specificity on isometric lumbar extension strength.

To investigate the effects of training frequency and specificity of training on isolated lumbar extension strength, 72 men (age = 31 +/- 9 years) and 42 women (age = 28 +/- 9 years) were tested before and after 12 weeks of training. Each test involved the measurement of maximum voluntary isometric torque at 72 degrees, 60 degrees, 48 degrees, 36 degrees, 24 degrees, 12 degrees, and 0 degrees of lumbar flexion. After the pretraining tests, subjects were randomly stratified to groups that trained with variable resistance dynamic exercise every other week (1X/2 weeks, n = 19), once per week (1X/week, n = 22), twice per week (2X/week, n = 23) or three times per week (3X/week, n = 21); a group that trained isometrically once per week (n = 14); or a control group that did not train (n = 15). Analysis of covariance showed that all training groups improved their ability to generate isometric torque at each angle measured when compared with controls (P less than 0.05). There was no statistical difference in adjusted posttraining isometric torques among the groups that trained (P greater than 0.05), but dynamic training weight increased to a lesser extent (P less than 0.08) for the 1X/2 weeks group (26.6%) than for the groups that trained 1X/week, 2X/week, and 3X/week (37.2 to 41.4%). These data indicate that a training frequency as low as 1X/week provides an effective training stimulus for the development of lumbar extension strength. Improvements in strength noted after isometric training suggest that isometric exercise provides an effective alternative for developing lumbar strength.

Adult↗

PubMed1990

Constant vs variable resistance knee extension training.

To compare the effect of constant resistance (CR) and variable resistance (VR) training on full range-of-motion (ROM) strength development, 22 men and 27 women (age = 26 +/- 5 yr) were randomly assigned to either a CR training group (N = 17), a VR training group (N = 17), or a control group (N = 15) that did not train. The CR and VR groups trained 2 to 3 d.wk-1 for 10 wk. Subjects completed one set of full ROM (120 to 0 degrees of flexion) bilateral knee extensions with an amount of weight that allowed 8 to 12 repetitions during each training session. For the VR group, resistance was varied with a cam supplied by the manufacturer (Nautilus). For the CR group, the cam was removed and replaced with a round sprocket. Prior to and after training, maximal voluntary isometric torque was measured at 9, 20, 35, 50, 65, 80, 95, and 110 degrees of knee flexion. Analysis of covariance indicated that the VR and CR groups gained strength at all angles (P less than or equal to 0.05) when compared to the control. [table: see text] There was no difference (P greater than 0.05) between the CR and VR groups at any angle, and the magnitude of strength gained was similar (P greater than 0.05) among angles for both groups. These data indicate that both CR and VR knee extension training elicit full ROM strength development.

Adult↗

PubMed1989

Cardiovascular responses of 70- to 79-yr-old men and women to exercise training.

This study determined the effects of endurance or resistance exercise training on maximal O2 consumption (VO2max) and the cardiovascular responses to exercise of 70- to 79-yr-old men and women. Healthy untrained subjects were randomly assigned to a control group (n = 12) or to an endurance (n = 16) or resistance training group (n = 19). Training consisted of three sessions per week for 26 wk. Resistance training consisted of one set of 8-12 repetitions on 10 Nautilus machines. Endurance training consisted of 40 min at 50-70% VO2max and at 75-85% VO2max for the first and last 13 wk of training, respectively. The endurance training group increased its VO2max by 16% during the first 13 wk of training and by a total of 22% after 26 wk of training; this group also increased its maximal O2 pulse, systolic blood pressure, and ventilation, and decreased its heart rate and perceived exertion during submaximal exercise. The resistance training group did not elicit significant changes in VO2max or in other maximal or submaximal cardiovascular responses despite eliciting 9 and 18% increases in lower and upper body strength, respectively. Thus healthy men and women in their 70s can respond to prolonged endurance exercise training with adaptations similar to those of younger individuals. Resistance training in older individuals has no effect on cardiovascular responses to submaximal or maximal treadmill exercise.

Aged↗