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Biomedical subjects

William G Herbert

Publications and source records attributed to William G Herbert.

8 recordsLinked to original sources
PubMed2006

Knee extensor and flexor torque development with concentric and eccentric isokinetic training.

This study assessed muscular torque and rate of torque development following concentric (CON) or eccentric (ECC) isokinetic training. Thirty-eight women were randomly assigned to either CON or ECC training groups. Training consisted of knee extension and flexion of the nondominant leg three times per week for 20 weeks (SD = 1). Eccentric training increased ECC knee extension and flexion peak torque more than CON training. The ECC group improved acceleration time and time to peak torque with ECC movements versus the CON group. Slow-velocity ECC isokinetic training yielded greater ECC and similar CON torque development gains versus CON training over the course of 20 weeks in young women.

Adolescent↗
PubMed2006

Hypertension research in sleep apnea.

Obstructive sleep apnea (OSA) is characterized by repetitive partial and total collapse of the upper airway that induces stressful arousals throughout sleep to reestablish breathing. Although estimates vary, prevalence has been reported as high as 20% in the adult population. OSA is common in several chronic diseases, the most common of which is obesity. Evidence is strong that OSA increases the risk of hypertension and both fatal and nonfatal cardiovascular events. Several mechanisms linking OSA to hypertension have been proposed, with increased sympathetic activation implicated as the prime mediator. This review summarizes recent data on the influence of OSA on blood pressure, the effect of standard OSA therapy on improving blood pressure, and the potential of lifestyle modification for further decreasing hypertension risk. Challenges confronting the investigation of blood pressure outcomes in response to treatment in OSA patients are discussed.

Blood Pressure↗
PubMed2005

Distal tibia areal bone mineral density: use in detecting low aBMD of the hip in young women.

Dual-energy X-ray absorptiometry (DXA) is a primary clinical tool for identification of adults with low areal bone mineral density (aBMD) and who are at increased risk for future osteoporosis and fragility fractures. Procedures for several aBMD scans of clinical interest might be limited by artifact, inaccessible anatomical regions, and positioning errors. Sites for scanning that overcome these limitations need further investigation for application to large-scale screening and relevance to clinical decisions regarding diagnosis and treatment. In this study, 146 women (mean +/- SE age = 20.1 +/- 0.1 yr, height = 163.3 +/- 0.2 cm, weight = 60.0 +/- 0.2 kg) underwent DXA of the total body (TB) and right and left total proximal femurs (TPF), total forearms (TF), and distal tibiae (DT). Osteopenia was identified in 24 women. Areal BMD was positively related among all measurement sites (r = 0.55-0.81, all p < 0.001). Total body, TF, and DT aBMD each displayed low sensitivity (0.29-0.33) and high specificity (0.95-0.98) to detect osteopenia of the TPF. Addition of TB fat-free mass slightly enhanced the predictive value of DT aBMD. Overall, DT aBMD can discriminate between osteopenic and normal subjects with comparable accuracy to TB or TF aBMD.

Absorptiometry, Photon↗
PubMed2003

Effects of low volume resistance and cardiovascular training on strength and aerobic capacity in unfit men and women: a demonstration of a threshold model.

A threshold model postulates that prescriptively applying the appropriate cardiorespiratory and strength stimulus at a designated threshold of intensity for a brief time results in the targeted adaptations. A randomized control group design was used with 17 unfit males and females (mean age = 37.1 +/- 6.5 year) assigned to an exercise group (n = 9) who performed a progressive cardiovascular graded exercise protocol and resistance training twice a week for 12 weeks or a nonexercising control group (n = 8). The intervention included a graded exercise protocol involving a 3-min warm-up, exercising 3-4 min at 70-80% of maximum heart rate, and a 3-min cooldown. Progressive resistance exercise consisted of one set of six repetitions on each of six resistance machines. Results showed that the exercise group increased predicted aerobic capacity by 13.4% (p < 0.05), decreased submaximal rate pressure product by 17.2% (p < 0.05), and increased strength by 34% (p < 0.01). The results support a threshold model and show that time for effective exercise can be substantially reduced.

Adaptation, Physiological↗
PubMed2003

Recovery of self-reported functional capacity after coronary artery bypass surgery.

STUDY OBJECTIVES: This study was conducted to determine the effects of age, gender, comorbid conditions, and exercise on the recovery of self-reported functional capacity after coronary artery surgery, and to identify predictors of 1-year functional capacity. PATIENTS: One hundred ninety-eight patients undergoing coronary artery bypass graft surgery. MEASUREMENTS AND RESULTS: Self-reported functional capacity was evaluated before surgery, and 3 months and 1 year postoperatively using the Veterans Specific Activity Questionnaire (VSAQ). Patients were classified into groups based on age, gender, comorbid conditions, and postoperative exercise. Repeated-measures analysis of variance was used to determine if groups differed with respect to functional capacity recovery and multiple linear regression was used to identify predictors of 1-year VSAQ score. A significant time by age interaction was found (p = 0.0001), with a more protracted recovery for older patients. There were significant group effects for gender (p = 0.0001), and presence of comorbid conditions (p = 0.0009); however, there were no time/group interactions for these variables. A significant group effect was found for postoperative exercise (p = 0.0001), with a trend toward group/time interaction (p = 0.096). Predictors of 1-year functional capacity were VSAQ score in the year prior to surgery and performance of regular aerobic exercise in the postoperative period. CONCLUSIONS: This study suggests that older patients attain good self-reported functional outcomes after surgery; however, the time course for recovery is more protracted than for younger patients. Functional capacity in the year prior to surgery and postoperative exercise are key predictors of 1-year functional capacity.

Activities of Daily Living↗
PubMed2003

Adaptation of pulmonary oxygen consumption slow component following 6 weeks of exercise training above and below the lactate threshold in untrained men.

STUDY OBJECTIVES: To examine the effects of 6 weeks of exercise training above or below the lactate threshold (LT) on the slow component (SC) of pulmonary oxygen consumption (.VO(2)). DESIGN: Randomized controlled trial. SETTING: University human performance laboratory. PARTICIPANTS: Apparently healthy, untrained men (n = 18). INTERVENTIONS: Subjects were randomized to one of three groups: high-intensity exercise training (HI) [above the LT], moderate-intensity exercise training (MOD) [below the LT], or no exercise training (CON). Exercise groups performed cycle ergometry 4 d/wk for 6 weeks. Total work throughout training was constant between groups. MEASUREMENTS AND RESULTS: Maximal cycle ergometry was performed at baseline and after training to assess power output at the LT (WLT), .VO(2) at the LT (.VO(2)LT), and peak .VO(2) (.VO(2)PK). High-intensity, constant-load cycling was performed at baseline and weeks 1, 2, 4, and 6 to assess SC adaptations. WLT, .VO(2)LT, and .VO(2)PK increased after 6 weeks in both exercise groups compared to the CON group (p < 0.05), although there were no differences between the training groups. SC of .VO(2) decreased 44% in the HI group following 1 week of exercise training vs MOD (20%, p < 0.05) and CON (12%, p < 0.01) groups. The SC attenuation was more prominent at all time points in the HI group compared to the MOD group. Total SC attenuation over the 6-week training period did not differ between the HI (71%) and MOD (57%) groups. CONCLUSIONS: Training at HI or MOD produced similar improvements in the LT, .VO(2), and power output at peak exertion when total work output was held constant. Attenuation of the SC with training above and below the LT were similar, although above-LT training promoted faster SC adaptations.

Adult↗
PubMedDate not supplied

Predicting exercise training outcome from cardiac rehabilitation.

PURPOSE: This study was conducted to identify predictors of training effect after 6 months of supervised exercise for cardiac rehabilitation patients. METHODS: Data at baseline and after 6 months of supervised exercise from 60 patients with coronary artery disease were used for this study. All the patients exercised 3 days per week for 5 to 9 months. Attendance exceeded 70%. The training effect was independently evaluated by the change in rate-pressure product at a 5-metabolic equivalent (MET) workload (RPP5), and the change in estimated peak METs (METPK) during treadmill testing. Baseline variables were examined to identify predictors of change in RPP5 and METPK separately using multiple linear regression. RESULTS: A reduction in RPP5 (-23 +/- 33 bpm x mm Hg x 10(2); P<.0001) and an increase in METPK (2.1 +/- 1.7 METs; P<.0001) were found after training. Baseline fitness was the best predictor of training effect. Inverse relations were found between baseline scores and change scores for RPP5 (r=-0.68; P<.001) and METpk (r=-0.39; P=.002). Beta-blocker status also was useful for predicting change in RPP5. No association was found between training effect and age, revascularization status, or exercise-induced ischemia. CONCLUSIONS: Training effect has limited predictability using baseline variables. No baseline patient characteristics other than high initial fitness were related to reduced training effect. Therefore, patients with clinical characteristics similar to those evaluated in this study can achieve a training effect successfully and are eligible for cardiac rehabilitation. The findings of this study support previous research related to this topic.

Coronary Disease↗