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We identified data-driven multidimensional physical activity (PA) profiles using several novel accelerometer-derived metrics. Participants aged 75, 80, and 85 (n = 441) wore triaxial accelerometers for 3–7 days. PA profiles were formed with k-means cluster analysis based on PA minutes, intensity, fragmentation, sit-to-stand transitions, and gait bouts for men and women. Associations with physical capacity and life-space mobility were examined using age-adjusted general linear models. Three profiles emerged: "Exercisers" and "actives" accumulated relatively high PA minutes, with actives engaging in lighter intensity PA. "Inactives" had the highest activity fragmentation and lowest PA volume, intensity, and gait bouts. Inactives showed lower scores in physical capacity and life-space mobility compared with exercisers and actives. Exercisers and actives had similar physical capacity and life-space mobility, except female exercisers had higher walking speed in the 6-min walk test. Our findings demonstrate the importance of assessing PA as multidimensional behavior rather than focusing on a single metric. [ABSTRACT FROM AUTHOR]

This study aimed to compare community-dwelling older adults' physical activity (PA) during the COVID-19 restrictions in 2020 to their PA levels 2 years before and investigate associations between earlier physical performance and PA levels over the follow-up. Participants' (n = 809, initial age 75–85 years) self-reported PA was assessed at baseline in 2017–2018 and May/June 2020 as total weekly minutes of walking and vigorous PA. Physical performance was assessed at baseline using the maximal handgrip strength and Short Physical Performance Battery tests. During the first wave of the COVID-19 pandemic, a median change in total weekly minutes of walking and vigorous PA among all participants was + 20.0 (interquartile range: −60.0 to 120.0, p <.001) min per week compared with 2 years earlier. Higher baseline Short Physical Performance Battery total scores were associated with higher total weekly minutes of walking and vigorous PA over the follow-up in men and women, and better handgrip strength in women. [ABSTRACT FROM AUTHOR]

Purpose: Habitual strength and power-demanding activities of daily life may support the maintenance of adequate lower extremity functioning with aging, but this has been sparingly explored. Hence, we examined whether the characteristics of free-living sit-to-stand (STS) transitions predict a decline in lower extremity functioning over a 4-yr follow-up. Methods: A total of 340 community-dwelling older adults (60% women; age 75, 80, or 85 yr) participated in this prospective cohort study. At baseline, a thigh-worn accelerometer was used continuously (3-7 d) to monitor the number and intensity of free-living STS transitions. A decline in lower extremity functioning was defined as a drop of ≥2 points in the Short Physical Performance Battery (SPPB) from baseline to follow-up. Maximal isometric knee extension strength was measured in the laboratory. Results: Eighty-five participants (75%women) declined in SPPB over 4 yr. After adjusting for age, sex, and baseline SPPB points, higher free-living peak STS angular velocity (odds ratio (OR), 0.70; 95% confidence interval (CI), 0.52-0.92, per 20°⋅s-1 increase) protected against a future decline. When adjusting the model for maximal isometric knee extension strength, the statistical significance was attenuated (OR = 0.72; 95% CI = 0.54-0.96, per 20°⋅s-1 increase). Conclusions: Performing STS transitions at higher velocities in the free-living environment can prevent a future decline in lower extremity function. This indicates that changes in daily STS behavior may be useful in the early identification of functional loss. Free-living peak STS angular velocity may be a factor underlying the longitudinal association of lower extremity strength and performance. [ABSTRACT FROM AUTHOR]

Purpose: Correlations between fatigue-induced changes in exercise performance and maximal rate of heart rate (HR) increase (rHRI) may be affected by exercise intensity during assessment. This study evaluated the sensitivity of rHRI for tracking performance when assessed at varying exercise intensities. Method: Performance (time to complete a 5-km treadmill time-trial [5TTT]) and rHRI were assessed in 15 male runners following 1 week of light training, 2 weeks of heavy training (HT), and a 10-day taper (T). Maximal rate of HR increase (measured in bpm·s[superscript-1]) was the first derivative maximum of a sigmoidal curve fit to HR data recorded during 5 min of running at 8 km·h[superscript -1] (rHRI[subscript 8km·h][superscript -1]), and during subsequent transition to 13 km·h[superscript -1] (rHRI[subscript 8-13km·h][superscript -1]) for a further 5 min. Results: Time to complete a 5-km treadmill time-trial was likely slower following HT (effect size ± 90% confidence interval = 0.16 ± 0.06), and almost certainly faster following T (-0.34 ± 0.08). Maximal rate of HR increase during 5 min of running at 8 km·h[superscript -1] and rHRI[subscript 8-13km·h][superscript -1] were unchanged following HT and likely increased following T (0.77 ± 0.45 and 0.66 ± 0.62, respectively). A moderate within-individual correlation was found between 5TTT and rHRI[subscript 8km·h][superscript -1] (r value ± 90% confidence interval = -0.35 ± 0.32). However, in a subgroup of athletes (n = 7) who were almost certainly slower to complete the 5TTT (4.22 ± 0.88), larger correlations were found between the 5TTT and rHRI[subscript 8km·h][superscript -1] (r = -0.84 ± 0.22) and rHRI[subscript 8-13km·h][superscript -1] (r = -0.52 ± 0.41). Steady-state HR during rHRI assessment in this group was very likely greater than in the faster subgroup (= 1.34 ± 0.86). Conclusion(s): The 5TTT performance was tracked by both rHRI[subscript 8km·h][superscript -1] and rHRI[subscript 8-13km·h][superscript -1]. Correlations between rHRI and performance were stronger in a subgroup of athletes who exhibited a slower 5TTT. Individualized workloads during rHRI assessment may be required to account for varying levels of physical conditioning.

The authors examined whether accelerometer-based free-living walking differs between those reporting walking modifications or perceiving walking difficulty versus those with no difficulty. Community-dwelling 75-, 80-, or 85-year-old people (N = 479) wore accelerometers continuously for 3–7 days, and reported whether they perceived no difficulties, used walking modifications, or perceived difficulties walking 2 km. Daily walking minutes, walking bouts, walking bout intensity and duration, and activity fragmentation were calculated from accelerometer recordings, and cut points for increased risk for perceiving walking difficulties were calculated using receiver operating characteristic analysis. The authors' analyses showed that accumulating ≤83.1 daily walking minutes and walking bouts duration ≤47.8 s increased the likelihood of reporting walking modifications and difficulties. Accumulating walking bouts ≤99.4 per day, having walking bouts ≤0.119 g intensity, and ≥0.257 active to sedentary transition probability fragmented activity pattern were associated only with perceiving walking difficulties. The findings suggest that older people's accelerometer-based free-living walking reflects their self-reported walking capability. [ABSTRACT FROM AUTHOR]

The present study examined the effects of twice weekly total body strength training (ST), endurance cycling (ET), and combined ST and ET (2 + 2 times a week) (SET) training on the load carrying walking test performance on the treadmill (TM) and changes in neuromuscular and endurance performance during a 21-week training period in aging men. Forty healthy men (54.8 [+ or -] 8.0 years) were divided into 3 training groups (ET n = 9, ST n = 11, SET n = 11) and a control group (C, n = 9). Peak oxygen uptake (V[O.sub.2]peak), heart rate, and blood lactate concentration were measured before and after a 21-week training program using a graded TM and maximal incremental bicycle ergometer (BE) tests. Isometric forces, vertical jump, and electromyographic activity of leg extensor and/or forearm flexor (F) muscles were measured before and after training and the TM tests. Increases of 20-21% in strength and of 7-12% in cycling BE V[O.sub.2]peak occurred in the training groups, whereas the changes of C remained minor. V[O.sub.2]peak was associated, both before and after training, with TM exercise time in all groups (from r = 0.65, p = 0.030 to r = 0.93, p < 0.001). Only SET showed a significant training-induced increase (p = 0.011) in exercise time of the TM walking with no significant increase in TM V[O.sub.2]peak. The present data suggest that in older men ET and SET induced specific increases in BE V[O.sub.2]peak and ST and SET in strength. However, only SET increased walking exercise time indicating improved load carrying walking performance because of large individual differences in the magnitude of the development of either strength or endurance capacities. KEY WORDS graded exercise test, walking

Purpose: To compare the effects of a standardized endurance-training program with individualized endurance training modified based on the cumulative training load provided by the Polar training-load feature. Methods: After 12 wk of similar training, 24 recreationally endurance-trained men were matched to a training-load-guided (TL, n = 10) or standardized (ST, n = 14) group and continued training for 12 wk. In TL, training sessions were individually chosen daily based on an estimated cumulative training load, whereas in ST the training was standardized with 4-6 sessions/wk. Endurance performance (shortest 1000-m running time during an incremental field test of 6 x 1000 m) and heart-rate variability (HRV) were measured every 4 wk, and maximal oxygen consumption (VO2max) was measured during an incremental treadmill test every 12 wk. Results: During weeks 1-12, similar changes in VO2max and 1000-m time were observed in TL (+7% ± 4%, P = .004 and -6% ± 4%, P = .069) and ST (+5% ± 7%, P = .019 and -8% ± 5%, P < .001). During wk 13-24, VO2max statistically increased in ST only (3% ± 4%, P = .034). The 1000-m time decreased in TL during wk 13-24 (-9% ± 5%, P = .011), but in ST only during wk 13-20 (-3% ± 2%, P = .003). The overall changes in VO2max and 1000-m time during wk 0-24 were similar in TL (+7% ± 4%, P = .001 and -9% ± 5%, P = .011) and ST (+10% ± 7%, P < .001 and -13% ± 5%, P < .001). No between-groups differences in total training volume and frequency were observed. HRV remained statistically unaltered in both groups. Conclusions: The main finding was that training performed according to the cumulative training load led to improvements in endurance performance similar to those with standardized endurance training in recreational endurance runners. [ABSTRACT FROM AUTHOR]

Background: The usual accelerometry-based measures of physical activity (PA) are dependent on physical performance. We investigated the associations between PA relative to walking performance and the prevalence and incidence of early and advanced walking difficulties compared to generally used measures of PA.Methods: Perceived walking difficulty was evaluated in 994 community-dwelling participants at baseline (age 75, 80, or 85 years) and 2 years later over 2 km (early difficulty) and 500 m (advanced difficulty). We used a thigh-mounted accelerometer to assess moderate-to-vigorous PA, daily mean acceleration, and relative PA as movement beyond the intensity of preferred walking speed in a 6-minute walking test (PArel). Self-reported PA was assessed using questionnaires.Results: The prevalence and incidence were 36.2% and 18.9% for early and 22.4% and 14.9% for advanced walking difficulty, respectively. PArel was lower in participants with prevalent (mean 42 [SD 45] vs 69 [91] min/week, p < .001) but not incident early walking difficulty (53 [75] vs 72 [96] min/week, p = .15) compared to those without difficulty. The associations between absolute measures of PA and incident walking difficulty were attenuated when adjusted for preferred walking speed.Conclusions: The variation in habitual PA may not explain the differences in the development of new walking difficulty. Differences in physical performance explain a meaningful part of the association of PA with incident walking difficulty. Scaling of accelerometry to preferred walking speed demonstrated independence on physical performance and warrants future study as a promising indicator of PA in observational studies among older adults. [ABSTRACT FROM AUTHOR]