ABSTRACT
Six healthy subjects rapidly lifted and lowered a small (250 g) weight with the first dorsal interosseous muscle (FDI) of one hand while the work performed was recorded continuously until fatigue (defined as losing the ability to continue lifting). Work was recorded in units of chart recorder trace displacement from baseline (centimeters) as an isotonic transducer followed the movement of the weight. In all experiments, the temperature of the hand was first adjusted by immersion in a controlled-temperature water bath. In the warmest condition, the skin surface temperature over the FDI was 30.5(0.30) degrees C [mean (SE)]. After moderate cooling, this surface temperature was 21.5(0.16) degrees C. Cooling significantly reduced the time taken to reach fatigue and more than halved the work capacity. An intermediate degree of cooling was also used in four subjects, showing that most of the effects seen were changing incrementally. Before work, and at fatigue, intracellular metabolic conditions in the FDI were studied by phosphorus nuclear magnetic resonance (31P-NMR) spectroscopy, with occlusion of the blood flow maintained during measurements. The mean intracellular pH of the FDI was also calculated. The changes observed were all consistent with the fact that intense work requires energy which must be derived largely from intracellular stores of phosphocreatine and glycogen. Less work made less demand upon reserves, and created lower concentrations of waste products and by-products. The observations did not, however, allow us to explain why fatigue occurred at a particular point or why work capacity was reduced by cooling.
Subject(s)
Body Temperature , Hand , Magnetic Resonance Spectroscopy , Muscle, Skeletal/physiology , Physical Exertion/physiology , Adult , Cold Temperature , Female , Hot Temperature , Humans , Hydrogen-Ion Concentration , Immersion , Male , Middle Aged , Muscle Fatigue , Physical Endurance , Skin Temperature , Weight LiftingABSTRACT
Four hundred cases of intra ocular lens implantation of the posterior chamber variety were analysed. Operative and post operative complications were minimal. Testing of visual acuity after surgery produced good results. Visual rehabilitation was readily achieved. The development of the various types of intraocular lens implants is traced and their associated problems discussed. It is concluded that the modern posterior chamber lens provides the most effective mode of treatment. Some contra-indications, however, are emphasized.