But too much rest may do more harm than good. Once prescribed almost universally for back pain, illness, and discomfort of all kinds, bed rest has been shown in studies to be associated with loss of strength and endurance, changes in soft tissue, bone loss, joint disease, high blood pressure, and weakening of the cardiovascular system. It’s one reason falls are a danger for people over 80: The resulting injuries may heal, but the health complications from staying in bed for weeks can be irreversible.
Selection bias may limit generalizability to other populations of older adults since the included participants in the Generation 100 study were healthier, more educated and more physically active than nonparticipants . However, our study population was diverse and included both healthy as well as older adults with comorbidities, and both inactive and very active older adults were included. The findings in the present study are based on a very large data material, and represent the most comprehensive data material on exercise patterns among older adults to date.
In both groups, men had a significantly higher proportion of sessions at a gym compared to women (Fig. 6). Contrary, women had a higher proportion of sessions at a sports facility compared to men. In the MCT group, men had a significantly higher proportion of sessions outdoors compared to women, while the opposite was observed in the HIIT group (Fig. 6).
The MCT group was prescribed two weekly exercise sessions of 50-min continuous activity at 70% of peak heart rate, or approximately 13 on the Borg 6–20 rating of perceived exertion (RPE) scale . The HIIT group was prescribed two exercise sessions a week with 10-min warm-up followed by 4 × 4 min intervals at 85–95% of peak heart rate, or approximately 16 on the Borg 6–20 RPE scale. The participants were given individual oral and written information about the training methods, including information about frequency, duration, intensity and examples of exercise sessions. The participants were free to exercise individually, with an exercise type and at a location of their own choosing. Every sixth week the participants met for a supervised spinning session where they exercised with a heart rate monitor. These exercise sessions gave the participants an opportunity to control their intensity during exercise. In addition, organized group exercise was offered twice per week for motivational purposes. Attendance to these exercises was voluntary and the activity performed varied between indoor and outdoor activities such as walking, jogging and aerobics . Besides the two prescribed exercise sessions, the participants were free to exercise as desired.
Behind the seemingly uniform acute hormonal response to exercise, explaining the disturbance to the neuroendocrine system caused by OTS is not that simple. There are several similarities with other intensive and chronic stress situations. There is compelling evidence for the involvement of HPA axis abnormalities in chronic stress situations such as post-traumatic stress disorder17 and depression25 and probably also during NFO and OTS. In chronic stress situations, the number of ACTH and cortisol secretion pulses is increased, which is also reflected in elevated urinary cortisol production.25
One way repeated ANOVA was used to compare time to exhaustion between sessions (S1, S2 and S3). Relative reliability was calculated with the intraclass correlation (ICC) model (3, 1) . Absolute reliability was calculated with the typical error of measurement (the standard deviation of the change scores divided by [28, 29]). Bland and Altman’s 95% limits of agreement were also used (calculated for S1 vs S2, S1 vs S3 and S2 vs S3) as an additional representation of measurement error and to identify the presence of heteroscedasticity . As data were heteroscedastic, both raw data and log transformed Bland and Altman’s plots are presented. Limit of agreement ratio (LOA) was also calculated from the log transformed data as follow: LOA = (1.96 × SDdiff / grand mean) × 100; where “SDdiff” represents the SD of the differences between tests (S1 vs S2, S1 vs S3, S2 vs S3) and “grand mean” represents (mean S1 + mean S2 + mean S3)/3. As time to exhaustion data were heteroscedastic, we also calculated the coefficient of variation (CV) for each subject as follow: CV = 100×(SD of the three measurements)/(mean of the three measurements). Mean CV for all subjects were also calculated. We also calculated the smallest worthwhile change (0.2 × between subjects SD) .
Recruiting lasted 6 months starting from September 2013. Participants were recruited by means of family doctors to whom the goal of the study was explained. The recruitment flow chart is shown in Figure 1. Three hundred and fifty people aged ≥ 65 were invited to participate. Of these, 51.4% agreed to be included in the screening list while 48.6% refused to participate, mainly for family reasons such as illness/hospitalization/old age of a family member. Forty people were found eligible to participate in the research protocol. Randomly, twenty were assigned to VE and twenty to the control group. The latter were instructed not to take part in any physical activity throughout the study period. All the selected participants signed an informed consent. The study was performed according to the Declaration of Helsinki and approved by the local ethics committee on September 23, 2013.