When cells are allowed to age in vitro, or are taken from aged normal donors or subjects with features of accelerated aging (progeria or Werner syndrome), they may be considered 'old'. Such old cells have reduced growth rates in culture compared to early or mid-passage cells from young normal donors. During exponential growth the rate constants for protein synthesis were not significantly different between young and old cells (0.023±0.002 h1 vs. 0.021±0.002 h1, respectively), yet growth rates (i.e. protein accretion) were only 0.013±0.003 h1 in old cells compared to 0.022±0.002 h1 in young cells. Thus, the reduced rate of protein accumulation during growth of old cells compared to young cells was associated with increased protein degradation (0.01+0.002 h1 vs. 0.001±0.002 h1; P<0.05) rather than reduced rates of protein synthesis. When cells entered quiescence from density dependent inhibition of growth, protein synthetic rates decreased in both young and old cells to comparable levels (0.013±0.002 h1) with the result that rates of growth (0.003±0.0003 h1) and degradation (0.01±0.003h1) were not significantly different between the two groups. Thus, a difference in protein turnover between young and old cells was only seen during exponential growth, where degradation was increased in old cells. The causal relationship between increased protein degradation and decreased growth rates in old cells is not known.

The possibility of measuring human activity patterns is discussed in terms of data obtained by attitude assessment, activity questionnaires, personal monitoring devices and fitness assessment. Specific problems are noted in applying these several techniques to elderly populations. Attitude assessments indicate the intention to exercise, and practical barriers may limit the translation of intention into overt behaviour. Questionnaires are open to exaggeration, but nevertheless remain the most practical method of evaluating large populations. Personal monitors can only be applied to small samples, but may nevertheless be helpful in improving questionnaire design. Fitness tests raise concerns of safety, and seem likely to bias population sampling towards the active elderly; scores are also influenced more by inherited factors than by current activity. Activity measurements seem unlikely to yield more than a crude estimate of total dietary needs in a population, but they may nevertheless help to identify a subset of old people where detailed nutritional examination is particularly cost-effective. The accurate determination of activity patterns will also have value as a means of encouraging the elderly to adopt an active lifestyle, maximizing their physical potential.

The purpose of the study was to compare passive joint stiffness in ankles of young and elderly men (21–39, and 64–87 years, respectively). A torque motor system was used to record angular displacement and resistive torque during a slow 6 degree/second ankle rotation from 10 degrees of plantarflexion to 10 degrees of dorsiflexion (DF). Passive torque (Nm) and passive elastic stiffness (Nm/degree) were measured at neutral, 5 and 10 degrees of DF. Passive torque increased nonlinearly as the ankle was rotated into DF. The elderly men had significantly lower passive torque values (p < .05), but there was no age-related difference in passive elastic stiffness. Variability of the two measures was greater in the older group. We concluded that within the range of motion tested, there was no evidence of increased stiffness in the elderly ankle joints.