Clenbuterol and the horse revisited.

Clenbuterol is a beta(2)-agonist and potent selective bronchodilator that is used to treat bronchospasm in the horse. The drug is normally administered to horses orally as a syrup formulation. Once absorbed into the systemic circulation, clenbuterol has the potential to cause many side effects, including a repartitioning effect and major alterations in cardiac and skeletal muscle function.

Development of nonexercise prediction models of maximal oxygen uptake in healthy Japanese young men.

The present study developed nonexercise models for predicting maximal oxygen uptake (VO2max) using skeletal muscle (SM) mass and cardiac dimensions and to investigate the validity of these equations in healthy Japanese young men. Sixty healthy Japanese men were randomly separated into two groups: 40 in the development group and 20 in the validation group. VO2max during treadmill running was measured using an automated breath-by-breath mass spectrometry system.

Changes in adipopnectin, leptin, and fat mass after clenbuterol treatment in horses.

Introduction: Adipose tissue plays complex role(s) in metabolic and endocrine control. To date, little work has been done in the horse regarding adipocytokines.

Purpose: This study was conducted to determine whether therapeutic levels of chronic beta-agonist administration, exercise, or both could alter their concentrations.

Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training.

Previous studies have shown that low-intensity resistance training with restricted muscular venous blood flow (Kaatsu) causes muscle hypertrophy and strength gain. To investigate the effects of daily physical activity combined with Kaatsu, we examined the acute and chronic effects of walk training with and without Kaatsu on MRI-measured muscle size and maximum dynamic (one repetition maximum) and isometric strength, along with blood hormonal parameters. Nine men performed Kaatsu-walk training, and nine men performed walk training alone (control-walk).

Prediction and validation of total and regional skeletal muscle mass by ultrasound in Japanese adults.

The present study was performed to develop regression-based prediction equations for skeletal muscle (SM) mass by ultrasound and to investigate the validity of these equations in Japanese adults. Seventy-two Japanese men (n=38) and women (n=34) aged 18-61 years participated in this study and were randomly separated into two groups: the model development group (n=48) and the validation group (n=24). The total and regional SM mass were measured using magnetic resonance imaging (MRI) 1.

Adiponectin and leptin are related to fat mass in horses.

Plasma concentrations of adiponectin and leptin were measured in 23 mature Standardbred mares (age: 10+/-3 years) and 12 weanling fillies (10 Quarter Horse/Belgian crossbreds and two Quarter Horses; aged: 4+/-3 months) to test the hypothesis that adipocytokines are proportional to adiposity in horses. Rump fat thickness was measured using B-mode ultrasound and percent body fat (% fat) calculated using a published formula for the estimation of fatness in horses. Plasma adiponectin and leptin were determined using radioimmunoassay.

Peak oxygen uptake during running and arm cranking normalized to total and regional skeletal muscle mass measured by magnetic resonance imaging.

The purposes of our study were to determine the peak oxygen uptake (V(.) >O(2peak)) per total or regional skeletal muscle (SM) mass using magnetic resonance imaging (MRI) and to investigate the relationships between SM mass and V(.) >O(2peak) during running and arm cranking.

Therapeutic clenbuterol treatment does not alter Ca2+ sensitivity of permeabilized fast muscle fibres from exercise trained or untrained horses.

Clenbuterol is a beta2-adrenoceptor agonist primarily used for treating bronchospasm and alleviating the symptoms of chronic obstructive pulmonary disease (COPD) in the horse. In other species (rats, mice, sheep, and cattle), chronic high doses of clenbuterol (typically in the milligram per kilogram body weight range) has been shown to cause a muscle directed protein anabolic response. Clenbuterol can also modify muscle fibre composition and therefore potentially affect muscle function.

Myosin heavy chain profiles and body composition are different in old versus young Standardbred mares.

There are limited data on age-related changes in body composition or skeletal muscle in the horse. Therefore, the purpose of this study was to investigate any differences in muscle myosin heavy chain (MHC) and body composition associated with aging. Twenty-three young (4-8 years) and eight old (20+ years) unfit Standardbred mares were evaluated.

Clenbuterol diminishes aerobic performance in horses.

Purpose: The purpose of this 8-wk study was to examine the effect of therapeutic levels of clenbuterol on aerobic performance and hemodynamics associated with exercise.

Methods: Twenty-three unfit Standardbred mares were divided into four experimental groups, clenbuterol (2.4 microg x kg(-1) body weight twice daily) plus exercise (20 min at 50% O2max; CLENEX; N = 6), clenbuterol only (CLEN; N = 6), exercise only (EX; N = 5), and control (CON; N = 6).

Endothelin response during and after exercise in horses.

The objective of the present study was to measure plasma endothelin-1 (ET-1) at rest and during exercise in the horse. Six healthy, Standardbred and Thoroughbred mares (5.3+/-0.

Chronic clenbuterol administration negatively alters cardiac function.

Purpose: Chronic administration of pharmacological levels of beta2-agonists have been shown to have toxic effects on the heart; however, no data exist on cardiac function after chronic clenbuterol administration. The purpose of this study was to examine the effect of therapeutic levels of clenbuterol on cardiac performance.

Methods: Twenty unfit Standardbred mares were divided into four experimental groups: clenbuterol (2.