Physical training and skeletal muscle in elderly women : a study of muscle mass, composition, fiber charasteristics and isometric strength

Abstract

The relationship between physical training and the properties of skeletal muscle in elderly women was examined by comparing 66-85-year-old female athletes and untrained controls and by investigating the effects of 18 weeks of strength and endurance training in 76-78-year-old women. The strength group trained the thigh and calf muscles on apparatus using compressed air as a resistance and the training of the endurance group included track walking and step aerobics. Quadriceps muscle mass and composition were measured using ultrasonography (US) and computed tomography (CT). Knee flexor muscle mass and composition was measured using CT. A quantitative US was developed for the analysis of muscle composition. In the experimental study, needle biopsies were taken from the vastus lateralis, and the relative proportion of different fiber types and their cross-sectional areas (CSA) were determined. To evaluate muscle strength, maximal isometric knee extension (KE) and flexion force were measured. The athletes had higher quadriceps muscle CSA and KE force and less fat in the thigh muscles than the controls. Strength training increased the CT-measured CSA of the quadriceps and type I fiber CSA of the vastus lateralis. When comparing the baseline and 18-week measurements within the strength group, the mean grey shade of the vastus lateralis, obtained from the US scans, was lower and that of the femur higher after training, suggesting a decreased proportion of fat in the muscle. The effects of endurance training on muscle mass, composition and fiber characteristics were negligible. Both strength and endurance training increased isometric KE force. The results indicate that female athletes preserve superior muscle mass and performance up to old age and that physical training, started in old age, also improves the properties of skeletal muscle. The results also point to the usefulness of quantitative US in studying skeletal muscle composition in elderly women.