Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. A total of eight elderly (E; 76 Ϯ 1 yr) and eight young (Y; 20 Ϯ 1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis in both legs. ATPase staining and a pax7-antibody were used to determine fiber type-specific SC content (i.e., pax7-positive SC) on serial muscle cross sections. In contrast to the type I fibers, the proportion and mean cross-sectional area of the type II fibers were substantially reduced in E vs. Y. The number of SC per type I fiber was similar in E and Y. However, the number of SC per type II fiber was substantially lower in E vs. Y (0.044 Ϯ 0.003 vs. 0.080 Ϯ 0.007; P Ͻ 0.01). In addition, in the type II fibers, the number of SC relative to the total number of nuclei and the number of SC per fiber area were also significantly lower in E. This study is the first to show type II fiber atrophy in the elderly to be associated with a fiber type-specific decline in SC content. The latter is evident when SC content is expressed per fiber or per fiber area. The decline in SC content might be an important factor in the etiology of type II muscle fiber atrophy, which accompanies the loss of skeletal muscle with aging.

With the advent of miniaturised sensing technology, which can be body-worn, it is now possible to collect and store data on different aspects of human movement under the conditions of free-living. This technology has the potential to be used in automated activity profiling systems which produce a continuous record of activity patterns over extended periods of time. Such activity profiling systems are dependent on classification algorithms which can effectively interpret body-worn sensor data and identify different activities. This article reviews the different techniques which have been used to classify normal activities and/or identify falls from body-worn sensor data. The review is structured according to the different analytical techniques and illustrates the variety of approaches which have previously been applied in this field. Although significant progress has been made in this important area, there is still significant scope for further work, particularly in the application of advanced classification techniques to problems involving many different activities.

We determined muscle fiber type-specific hypertrophy and changes in satellite cell (SC) content following a 12-week resistance training program in 13 healthy, elderly men (72 +/- 2 years). Leg strength and body composition (dual-energy X-ray absorptiometry and computed tomography) were assessed, and muscle biopsy samples were collected. Leg strength increased 25%-30% after training (p < .001). Leg lean mass and quadriceps cross-sectional area increased 6%-9% (p < .001). At baseline, mean fiber area and SC content were smaller in the Type II versus Type I muscle fibers (p < .01). Following training, Type II muscle fiber area increased from 5,438 +/- 319 to 6,982 +/- 503 microm(2) (p < .01). Type II muscle fiber SC content increased from 0.048 +/- 0.003 to 0.084 +/- 0.008 SCs per fiber (p < .001). No changes were observed in the Type I muscle fibers. In older adults, skeletal muscle tissue is still capable of inducing SC proliferation and differentiation, resulting in Type II muscle fiber hypertrophy.

Timed protein supplementation immediately before and after exercise does not further augment the increase in skeletal muscle mass and strength after prolonged resistance-type exercise training in healthy elderly men who habitually consume adequate amounts of dietary protein. This trial was registered at clinicaltrials.gov as NCT00744094.

The reproducibility of the 6-min walking test (6MWT) needs to be more solidly studied. This study aimed to investigate the reproducibility of two 6MWTs performed on subsequent days in a large and representative sample of patients with chronic obstructive pulmonary disease (COPD), and to quantify the learning effect between the two tests, as well as its determinants.In a retrospective observational study, 1,514 patients with COPD performed two 6MWTs on subsequent days. Other measurements included body composition (dual X-ray absorptiometry), dyspnoea (Medical Research Council scale) and comorbidity (Charlson index).Although the 6MWT was reproducible (intraclass correlation coefficient50.93), patients walked farther in the second test (391 m, 95% CI 155-585 m versus 418 m, 95% CI 185-605 m; p,0.0001). On average, the second 6MWT increased by 27 m (or 7%), and 82% of patients improved in the second test. Determinants of improvement o42 m in the second test (upper limit of the clinically important change) were as follows: first 6MWT ,350 m, Charlson index ,2 and body mass index ,30 kg?m -2 (OR 2.49, 0.76 and 0.60, respectively).The 6MWT was statistically reproducible in a representative sample of patients with COPD. However, the vast majority of patients improved significantly in the second test by an average learning effect of 27 m.KEYWORDS: Chronic obstructive pulmonary disease, 6-min walking test, reproducibility of results C hronic obstructive pulmonary disease (COPD) is a systemic disease characterised by progressive airflow limitation, exercise intolerance and physical inactivity [1,2]. Although the degree of airflow obstruction is frequently used as a marker of disease severity, it does not adequately reflect extrapulmonary manifestations of COPD [3,4]. Some modalities of field tests are available to assess these patients' exercise capacity [4], which better reflect the extrapulmonary features of the disease.The 6-min walking test (6MWT) is a simple and inexpensive test that provides a global and integrated response of both physical (pulmonary and nonpulmonary factors) and psychological factors [5,6]. The 6MWT is used to assess functional exercise capacity before and after interventions [7,8] and as a predictor of morbidity and mortality in COPD [9].In general, the 6MWT is a reliable test in COPD patients but a learning effect has been suggested [10-15], i.e. patients achieving a considerably higher walked distance when a second test is performed. Indeed, there is controversy about the size of the learning effect, which may range from 2.6% to 22% [10,11,[16][17][18][19][20]. Moreover, the external validity of the previous studies is limited due to the pre-specified inclusion criteria [10,11,13,18]. Furthermore, researchers usually used statistical analysis that did not demonstrate trends and agreement between both 6MWTs, thereby compromising the internal validity of the results [10]. Additionally, the determinants of improvement in walking distance remain unknown. Considering the importance of the 6...