The role of oxygen in determining phosphocreatine onset kinetics in exercising humans.

31P-magnetic resonance spectroscopy was used to study phosphocreatine (PCr) onset kinetics in exercising human gastrocnemius muscle under varied fractions of inspired O(2) (F(IO(2))). Five male subjects performed three identical work bouts (5 min duration; order randomised) at a submaximal workload while breathing 0.1, 0.

Regulation of free radical outflow from an isolated muscle bed in exercising humans.

Incremental knee extensor (KE) exercise performed at 25, 70, and 100% of single-leg maximal work rate (WR(MAX)) was combined with ex vivo electron paramagnetic resonance (EPR) spectroscopic detection of alpha-phenyl-tert-butylnitrone (PBN) adducts, lipid hydroperoxides (LH), and associated parameters in five males. Blood samples were taken from the femoral arterial and venous circulation that, when combined with measured changes in femoral venous blood flow, permitted a direct examination of oxidant exchange across a functionally isolated contracting muscle bed. KE exercise progressively increased the net outflow of LH and PBN adducts (100% > 70% > 25% WR(MAX), P < 0.

Skeletal muscle oxidative metabolism in sedentary humans: 31P-MRS assessment of O2 supply and demand limitations.

Previously, it was demonstrated in exercise-trained humans that phosphocreatine (PCr) recovery is significantly altered by fraction of inspired O2 (FI(O2)), suggesting that in this population under normoxic conditions, O2 availability limits maximal oxidative rate. Haseler LJ, Hogan ML, and Richardson RS. J Appl Physiol 86: 2013-2018, 1999.

Exercise and nitric oxide prevent bubble formation: a novel approach to the prevention of decompression sickness?

Nitrogen dissolves in the blood during dives, but comes out of solution if divers return to normal pressure too rapidly. Nitrogen bubbles cause a range of effects from skin rashes to seizures, coma and death. It is believed that these bubbles form from bubble precursors (gas nuclei).

Reduced mechanical efficiency in chronic obstructive pulmonary disease but normal peak VO2 with small muscle mass exercise.

We studied six patients with chronic obstructive pulmonary disease (COPD) (FEV1 = 1.1 +/- 0.2 L, 32% of predicted) and six age- and activity level-matched control subjects while performing both maximal bicycle exercise and single leg knee-extensor exercise.

EPR spectroscopic detection of free radical outflow from an isolated muscle bed in exercising humans.

There is no direct evidence to support the contention that contracting skeletal muscle and/or associated vasculature generates free radicals in exercising humans. The unique combination of isolated quadriceps exercise and the measurement of femoral arterial and venous free radical concentrations with the use of electron paramagnetic resonance (EPR) spectroscopy enabled this assumption to be tested in seven healthy men. Application of ex vivo spin trapping using alpha-phenyl-tert-butylnitrone (PBN) resulted in the detection of oxygen- or carbon-centered free radicals (a(N) = 1.

NOS inhibition increases bubble formation and reduces survival in sedentary but not exercised rats.

Previously we have shown that chronic as well as a single bout of exercise 20 h prior to a simulated dive protects rats from severe decompression illness (DCI) and death. However, the mechanism behind this protection is still not known. The present study determines the effect of inhibiting nitric oxide synthase (NOS) on bubble formation in acutely exercised and sedentary rats exposed to hyperbaric pressure.

The sensation of angina can be evoked by stimulation of the human thalamus.

We have performed single-neuron recording and microstimulation in the region of the thalamic principal sensory nucleus (ventrocaudal nucleus, Vc) prior to implantation of a deep brain-stimulating electrode in a patient with pain secondary to arachnoiditis and with a past history of unstable angina. Cells located in the 16 mm lateral plane had cutaneous receptive fields on the chest wall. At and posterior to the location of these cells stimulation coincided precisely with the sensation of angina (stimulation-associated angina).