To our knowledge no literature is available in which research is described to what extent (older) adults who fulfil the recommendation of a minimum of 30 min on five days also meet the recommendation of vigorous intensity aerobic activity for a minimum of 20 min on three days each week. In our study population, 51% complied with the health recommendation. In comparison in the general Dutch population this is 60%. In our study population, 46% complied with both norms, compared to 62% of the Dutch and 49% of the US population (TNO 2008, CDC 2007).

More men than women fulfilled both norms, which is in accordance with data from the general Dutch population. Because AZD6244 solubility dmso 42% of our study population did not fulfil one of the two recommendations, we hypothesise that this group is more prone to health problems, deterioration of their fitness and consequently losing their independence. In view of this, these people should be stimulated to become more physically active. In the latest ACSM recommendations (Franklin et al 2007), it is advised that every older adult should have an activity plan in consultation with a physician or health care provider. With respect to patients after total knee arthroplasty, this means that postoperative therapeutic and preventive recommendations should be integrated into management. With respect

to patients after total knee arthroplasty, regular physical activity is associated with improvement in strength, balance, and co-ordination, which has proven to be an effective

strategy in the prevention of falls. almost In the presence phosphatase inhibitor library of a total knee arthroplasty, falls may result in periprosthetic fracture, implant loosening and/or dislocation of the prosthesis. Furthermore, there are indications that increased bone density due to physical activity improves prosthetic fixation, reducing the risk of loosening. Finally, physical activity might minimise bone loss due to stress shielding, facilitating future revision surgery if needed. On the other hand, preventive recommendations should include not only the stimulation of physical activity but also the education of patients regarding the risks of physical activity associated with a prosthetic knee – in particular the risks of athletic high-impact, high-demand activities (Healy et al 2000.) In general it can be stated that activities with highpeak loading, like running, cause more mechanical loading compared to low- and moderate-impact activities (such as walking, bicycling, and yoga/tai-chi), and may therefore cause more wear of the prosthesis (Stevens et al 2011). In this study 51% of people at least one year after total knee arthroplasty were physically active for a minimum of 30 min on five days a week and 53% undertook activity of vigorous intensity for a minimum of 20 min on three days a week. Although 46% complied with both recommendations, 42% did not fulfil either of the two recommendations. In stimulating physical activity emphasis should be laid on this latter group.