Physical Activity in Centenarians beyond Cut-Point-Based Accelerometer Metrics.

This study described and compared physical activity (PA) characteristics at the end of the human lifespan using conventional cut-point-based versus cut-point-free accelerometer metrics. Eighteen institutionalized centenarians (101.5 ± 2.1 years, 72.2% female, 89% frail) wore the wrist GENEActiv accelerometer for 7 days. Conventional metrics, such as time spent in light-intensity PA (LiPA) and moderate-to-vigorous intensity PA (MVPA) were calculated according to published cut-points for adults and older adults. The following cut-point-free metrics were evaluated: average acceleration, intensity gradient and Mx metrics. Depending on the cut-point, centenarians accumulated a median of 15-132 min/day of LiPA and 3-15 min/day of MVPA. The average acceleration was 9.2 mg [Q1: 6.7 mg-Q3: 12.6 mg] and the intensity gradient was -3.19 [-3.34--3.12]. The distribution of Z-values revealed positive skew for MVPA, indicating a potential floor effect, whereas the skew magnitude was attenuated for cut-point-free metrics such as intensity gradient or M5. However, both cut-point-based and cut-point-free metrics were similarly positively associated with functional independence, cognitive and physical capacities. This is the first time that PA has been described in centenarians using cut-point-free metrics. Our results suggest that new analytical approaches could overcome cut-point limitations when studying the oldest-old. Future studies using these new cut-point-free PA metrics are warranted to provide more complete and comparable information across groups and populations.

ECG Ventricular Repolarization Dynamics during Exercise: Temporal Profile, Relation to Heart Rate Variability and Effects of Age and Physical Health.

Periodic repolarization dynamics (PRD) is a novel electrocardiographic marker of cardiac repolarization instability with powerful risk stratification capacity for total mortality and sudden cardiac death. Here, we use a time-frequency analysis approach to continuously quantify PRD at rest and during exercise, assess its dependence on heart rate variability (HRV) and characterize the effects of age (young adults/middle-aged adults/older adults), body mass index (non-overweight/overweight) and cardiorespiratory fitness level (fit/unfit). Sixty-six male volunteers performed an exercise test. RR and dT variabilities (RRV, dTV), as well as the fraction of dT variability unrelated to RR variability, were computed based on time-frequency representations. The instantaneous LF power of dT (PdTV), representing the same concept as PRD, and of its RRV-unrelated component (PdTVuRRV) were quantified. dT angle was found to mostly oscillate in the LF band. Overall, 50-70% of PdTV was linearly unrelated to RRV. The onset of exercise caused a sudden increase in PdTV and PdTVuRRV, which returned to pre-exercise levels during recovery. Clustering analysis identified a group of overweight and unfit individuals with significantly higher PdTV and PdTVuRRV values at rest than the rest of the population. Our findings shed new light on the temporal profile of PRD during exercise, its relationship to HRV and the differences in PRD between subjects according to phenotypic characteristics.

Validity of the Polar H7 Heart Rate Sensor for Heart Rate Variability Analysis during Exercise in Different Age, Body Composition and Fitness Level Groups.

This work aims to validate the Polar H7 heart rate (HR) sensor for heart rate variability (HRV) analysis at rest and during various exercise intensities in a cohort of male volunteers with different age, body composition and fitness level. Cluster analysis was carried out to evaluate how these phenotypic characteristics influenced HR and HRV measurements. For this purpose, sixty-seven volunteers performed a test consisting of the following consecutive segments: sitting rest, three submaximal exercise intensities in cycle-ergometer and sitting recovery. The agreement between HRV indices derived from Polar H7 and a simultaneous electrocardiogram (ECG) was assessed using concordance correlation coefficient (CCC). The percentage of subjects not reaching excellent agreement (CCC > 0.90) was higher for high-frequency power (PHF) than for low-frequency power (PLF) of HRV and increased with exercise intensity. A cluster of unfit and not young volunteers with high trunk fat percentage showed the highest error in HRV indices. This study indicates that Polar H7 and ECG were interchangeable at rest. During exercise, HR and PLF showed excellent agreement between devices. However, during the highest exercise intensity, CCC for PHF was lower than 0.90 in as many as 60% of the volunteers. During recovery, HR but not HRV measurements were accurate. As a conclusion, phenotypic differences between subjects can represent one of the causes for disagreement between HR sensors and ECG devices, which should be considered specifically when using Polar H7 and, generally, in the validation of any HR sensor for HRV analysis.

Estimation of the second ventilatory threshold through ventricular repolarization profile analysis.

Under the hypothesis that sympathetic control of ventricular repolarization may change once the second ventilatory threshold (VT2) has been reached, a novel methodology for non-invasive VT2 estimation based on the analysis of the T wave from the electrocardiogram (ECG) is proposed, and potential underlying physiological mechanisms are suggested. 25 volunteers (33.4 ± 5.2 years) underwent an incremental power cycle ergometer test (25 W/minute). During the test, respiratory gas exchange and multi-lead ECG were acquired. The former was employed to determine VT2, used here as a reference, whereas the latter was used to compute the temporal profiles of an index of ventricular repolarization instability (dT) and its low-frequency (LF) oscillations (LFdT). The sudden increases observed in dT and LFdT profiles above an established heart rate threshold were employed to derive VT2 estimates, referred to as VT2d T and VT2LF d T , respectively. Estimation errors of -4.7 ± 25.2 W were obtained when considering VT2d T . Errors were lower than the one-minute power increment of 25 W in 68% of the subjects and lower than 50 W in 89.5% of them. When using VT2LF d T , estimation error was of 15.3 ± 32.4 W. Most of the subjects shared common characteristic dT and LFdT profiles, which could be reflecting changes in the autonomic control of ventricular repolarization before and after reaching VT2. The analysis of ventricular repolarization dynamics during exercise allows non-invasive ECG-based estimation of VT2, possibly in relation to changes in the autonomic control of ventricular electrical activity when VT2 is reached.

Heart Rate Variability and Exceptional Longevity.

Centenarians are the paradigm of human extreme longevity and healthy aging, because they have postponed, if not avoided, mayor age-related diseases. The purpose of this study was to investigate potential differences in resting heart rate variability (HRV) between young adults, octogenarians, and centenarians and assess whether HRV variables are predictors of all-cause mortality in centenarians. To this end, three groups of participants: young adults (N = 20; 20.6 ± 2.3 years), octogenarians (N = 18; 84.1 ± 2.6 years), and centenarians (N = 17; 101.9 ± 1.9 years) were monitored for 15 min at rest (seated, without moving or talking) to measure RR intervals, from which HRV was evaluated. Our results showed a clear decrease with age in the main parasympathetic HRV variables, as well as in the standard deviation (SD) of the RR series [SD of normal-to-normal interval (SDNN)] and in low frequency (LF) heart rate (HR) oscillations, although differences between octogenarians and centenarians did not reach statistical significance. In 14 centenarians followed until death, only SDNN showed significant correlation (ρ = 0.536; p = 0.048) with survival prognosis. Additionally, SDNN <19 ms was associated with early mortality (≤1 year) in centenarians (Hazard Ratio = 5.72). In conclusion, HRV indices reflecting parasympathetic outflow as well as SDNN and LF all present an age-related reduction, which could be representative of a natural exhaustion of allostatic systems related to age. Moreover, low SDNN values (<19 ms) could be associated with early mortality in centenarians. HRV seems to play a role in exceptional longevity, which could be accounted for by centenarians' exposome.

Physical Activity and Sedentary Behavior at the End of the Human Lifespan.

To objectively assess physical activity levels and sedentary behavior in a cohort of Spanish centenarians and their nonagenarian peers. Physical activity and sedentary behavior patterns were objectively measured by an ActiGraph GT3X accelerometer in centenarians (n = 18; 83% women; 100.8 ± 0.8 [100-103] years) and nonagenarians (n = 11; 91% women; 93.3 ± 2.5 [90-98] years). Centenarians showed less counts per minute (17.6 ± 7.1 vs. 46.1 ± 23.7, p = .003, d = 1.851) and steps per day (455 ± 237 vs. 1,249 ± 776, p = .007, d = 1.587) than nonagenarians. The daily number of sedentary breaks was also lower in the former (5.0 ± 1.5 vs. 6.7 ± 2.0, p = .019, d = 0.971). When observing time distribution, the most active day period in both groups was the morning, with a peak between 10:00 and 11:59. This data suggest that the decline in physical activity levels continues to worsen until the end of the human lifespan.

Is the SenseWear Armband accurate enough to quantify and estimate energy expenditure in healthy adults?

BACKGROUND: The SenseWear Armband (SWA) is a monitor that can be used to estimate energy expenditure (EE); however, it has not been validated in healthy adults. The objective of this paper was to study the validity of the SWA for quantifying EE levels. METHODS: Twenty-three healthy adults (age 40-55 years, mean: 48±3.42 years) performed different types of standardized physical activity (PA) for 10 minutes (rest, walking at 3 and 5 km·h-1, running at 7 and 9 km·h-1, and sitting/standing at a rate of 30 cycle·min-1). Participants wore the SWA on their right arm, and their EE was measured by indirect calorimetry (IC) the gold standard. RESULTS: There were significant differences between the SWA and IC, except in the group that ran at 9 km·h-1 (>9 METs). Bland-Altman analysis showed a BIAS of 1.56 METs (±1.83 METs) and limits of agreement (LOA) at 95% of -2.03 to 5.16 METs. There were indications of heteroscedasticity (R2 =0.03; P<0.05). Analysis of the receiver operating characteristic (ROC) curves showed that the SWA seems to be not sensitive enough to estimate the level of EE at highest intensities. CONCLUSIONS: The SWA is not as precise in estimating EE as IC, but it could be a useful tool to determine levels of EE at low intensities.

Validation study of Polar V800 accelerometer.

BACKGROUND: The correct quantification of physical activity (PA) and energy expenditure (EE) in daily life is an important target for researchers and professionals. The objective of this paper is to study the validity of the Polar V800 for the quantification of PA and the estimation of EE against the ActiGraph (ActiTrainer) in healthy young adults. METHODS: Eighteen Caucasian active people (50% women) aged between 19-23 years wore an ActiTrainer on the right hip and a Polar V800 on the preferred wrist during 7 days. Paired samples t-tests were used to analyze differences in outcomes between devices, and Pearson's correlation coefficients to examine the correlation between outcomes. The agreement was studied using the Bland-Altman method. Also, the association between the difference and the magnitude of the measurement (heteroscedasticity) was examined. Sensitivity, specificity and area under the receiver operating characteristic curve (ROC-AUC value) were calculated to evaluate the ability of the devices to accurately define a person who fulfills the recommendation of 10,000 daily steps. RESULTS: The devices significantly differed from each other on all outcomes (P<0.05), except for Polar V800's alerts vs. ActiTrainer's 1 hour sedentary bouts (P=0.595) and Polar V800's walking time vs. ActiTrainer's lifestyle time (P=0.484). Heteroscedasticity analyses were significant for all outcomes, except for Kcal and sitting time. The ROC-AUC value was fair (0.781±0.048) and the sensitivity and specificity was 98% and 58%, respectively. CONCLUSIONS: The Polar V800 accelerometer has a comparable validity to the accelerometer in free-living conditions, regarding "1 hour sedentary bouts" and "V800's walking time vs. ActiTrainer's lifestyle time" in young adults.