Exercise Training and Testosterone Replacement in Heart Failure Patients

Muscle sympathetic nerve activity (MSNA) is recorded directly from the peroneal nerve using the microneurography technique. Multiunit postganglionic muscle sympathetic nerve recordings is made using a tungsten microelectrode. All of the recordings of MSNA met previously established and described criteria. MSNA is quantified as burst frequency (bursts per minute).

Forearm blood flow is measured by venous occlusion plethysmography. The nondominant arm is elevated above heart level to ensure adequate venous drainage. A mercury-filled silastic tube attached to a low-pressure transducer is placed around the forearm and connected to a plethysmography. Forearm blood flow is determined on the basis of a minimum off four separate readings. Forearm vascular conductance is calculated by dividing forearm blood flow by mean arterial pressure times 100 and expressed in arbitrary units.

The maximal cardiopulmonary test is carried out on a bike using a ramp protocol with workload increment every minute with energetic demand of about 1 metabolic equivalent(MET) per minute or 3.5 mL/Kg.min of oxygen uptake.

Body composition and bone mineral density is determined by dual energy x-ray absorptiometry using densitometry equipment (Hologic), at the following regions: lumbar spine, femoral neck, total femur and total body. Appendicular lean mass is calculated as the sum of arms and legs lean soft tissue masses, assuming that all non-fat and non-bone tissue is skeletal muscle. The total body fat is expressed in grams and as a percentage of body weight.

The muscle biopsy is obtained with a single entry into the muscle 5-10 minutes after administering the local anesthetic following an incision through the skin. A portion of the muscle (~10 mg) is processed to evaluate 1) muscle fiber type and 2) cross-sectional area