Associations between physical fitness, body composition, and heart rate variability during exercise in older people: exploring mediating factors.

Background: Age-related changes in body composition affect physical fitness in older adults. However, whether the autonomic response is associated with body fat percentage and its implication for physical fitness is not fully understood. Aim: To understand the association between physical fitness, body composition, and heart rate variability in older people and its mediating factors. Methods: A cross-sectional study with 81 older adults was conducted, assessing Short Physical Performance Battery (SPPB), Two-minute Step Test (TMST), body composition, and cardiac autonomic response. Correlation and mediation analyses were performed. Results: Body fat percentage negatively correlated with physical fitness (SPPB: r =  - 0.273, p = 0.015; TMST: r =  - 0.279, p = 0.013) and sympathetic activity (sympathetic nervous system (SNS) index: r =  - 0.252, p = 0.030), yet positively correlated with parasympathetic tone (root mean square of successive differences (RMSSD): r = 0.253, p = 0.029; standard deviation of NN intervals (SDNN): r = 0.269, p = 0.020). Physical fitness associated with sympathetic nervous system index (SPPB: r = 0.313, p = 0.006; TMST: r = 0.265, p = 0.022) and parasympathetic nervous system index (TMST: r =  - 0.344, p = 0.003). Muscle mass mediated body fat's impact on physical fitness, while physical fitness mediated body fat's impact on autonomic response. Conclusion: Body composition and cardiac autonomic response to exercise are associated with physical fitness in older people, highlighting a possible protective effect of muscle mass against the decline in physical fitness associated with increased body fat.

Frailty, Seasonal Sensitivity and Health-related Quality of Life in Older People Living in High Southern Latitudes: a Bayesian Analysis.

Background: In older people, a notable research gap exists regarding the intricate dynamics between frailty, seasonal sensitivity, and health-related quality of life (HRQoL). This study aimed to determine the association between frailty, seasonal sensitivity, and HRQoL in older people from high southern latitudes. Methods: A cross-sectional observational study was conducted. Frailty, seasonal sensitivity, and HRQoL measurements were self-reported by participants through questionnaires. A total of 118 older people were recruited from a local community. The participants were selected through intentional non-probabilistic sampling. Results: The adjusted models showed a trend where lower education was associated with a higher risk of frailty (BF = 0.218). For frailty and HRQoL, we observed a trend suggesting that HRQoL decreases with increasing severity of frailty (BF = 1.76). In addition, we observed a linear effect based on the severity of seasonal sensitivity, meaning that older people with higher perceived severity report a proportional decrease in HRQoL (BF = 6.66). Conclusion: Sociodemographic factors, such as lower education levels, have increased the risk of frailty. At the same time, frailty and seasonal sensitivity perceived severity were associated with a lower HRQoL in older people.

Validity and Reliability of Short-Term Heart Rate Variability Parameters in Older People in Response to Physical Exercise.

BACKGROUND: Currently, and to the best of our knowledge, there is no standardized protocol to measure the effect of low- to moderate-intensity physical exercise on autonomic modulation focused in older people. AIM: Validate a test-retest short-term exercise protocol for measuring the autonomic response through HRV in older people. METHODS: A test-retest study design was used. The participants were selected through intentional non-probabilistic sampling. A total of 105 older people (male: 21.9%; female: 78.1%) were recruited from a local community. The assessment protocol evaluated HRV before and immediately after the 2-min step test. It was performed twice on the same day, considering a time of three chronological hours between the two measurements. RESULTS: The posterior distribution of estimated responses in the Bayesian framework suggests moderate to strong evidence favoring a null effect between measurements. In addition, there was moderate to robust agreement between heart rate variability (HRV) indices and assessments, except for low frequency and very low frequency, which showed weak agreement. CONCLUSIONS: Our results provide moderate to strong evidence for using HRV to measure cardiac autonomic response to moderate exercise, suggesting that it is sufficiently reliable to show similar results to those shown in this test-retest protocol.

Cardiac autonomic regulation in response to functional power threshold testing in elite cyclists / Regulación autonómica cardiaca en respuesta a la prueba de umbral de potencia funcional en ciclistas deélite

Objective: To evaluate the impact of a functional power threshold test (FTP) on cardiac autonomic regulation indicators in high performance cyclists.Methods: A total of 12 male elite cyclists (mean age 36.1 ± 11.2 years) were recruited. Body composition parameters were measured usingbioimpedancemetry and heart rate variability (HRV) before and after the application of the FTP assessment. Results: We observed that a greater sympathetic nervous system (SNS) index and Stress index on baseline were correlated with a smaller decrease in theparasympathetic nervous system (PNS) activity in response to the FTP test (ρ= 0.69, p = 0.013). Concerning morphological parameters, the skeletalmuscle index (SMI) was the only one that was inversely correlated with ∆PNS (ρ= -0.69, p = 0.02) whereas the muscle-bone index (MBI) displayed apositive correlation with ∆SNS (ρ = 0.82, p = 0.001). In fully adjusted models we found that waist-to-hip ratio (β= 7.90, CI95%[4.16, 11.63], t(8) = 4.88, p =0.001) and SMI significantly influenced ∆PNS (β = -1.38, CI95%[-1.84, -0.92], t(8) = -6.94, p < 0.001), whereas MBI (β= 10.26, CI95%[8.10, 12.42], t(8) =10.96, p < 0.001) and the interaction between the latter and Power achieved during FTP influenced ∆SNS (β = -0.05, CI95%[-0.09, -4.99e-03], t(8) = -2.56, p= 0.033). Conclusion: Our findings indicate that the SMI had a negative effect on the ∆PNS, while the MBI was positively correlated with the ∆SNS in cyclists. Thesefindings suggest that a higher SMI and MBI could have a detrimental impact on the cardiac autonomic response to maximal aerobic exercise in high-performance cyclists, such as FTP.(AU)

Objetivo: Evaluar el impacto de una prueba de umbral de potencia funcional (FTP) sobre los indicadores de regulación autonómica cardiaca en ciclistasde alto rendimiento. Métodos: Se reclutó a un total de 12 ciclistas de élite masculinos (edad media 36.1 ± 11.2 años). Se midieron los parámetros de composición corporalmediante bioimpedanciometría y la variabilidad de la frecuencia cardiaca (HRV) antes y después de la aplicación de la evaluación del FTP. Resultados: Observamos que un mayor índice del sistema nervioso simpático (SNS) e índice de estrés basalmente se correlacionaron con una menordisminución de la actividad del sistema nervioso parasimpático (PNS) en respuesta a la prueba FTP (ρ= 0.69, p = 0.013). En cuanto a los parámetrosmorfológicos, el índice músculo esquelético (SMI) fue el único que se correlacionó inversamente con el ∆PNS (ρ= -0.69, p = 0.02) mientras que el índicemúsculo-hueso (MBI) mostró una correlación positiva con ∆SNS (ρ = 0.82, p = 0.001). En los modelos totalmente ajustados encontramos que la relacióncintura-cadera (β= 7.90, CI95%[4.16, 11.63], t(8) = 4.88, p = 0.001) y el SMI influían significativamente en el ∆PNS (β= -1.38, CI95%[-1.84, -0.92], t(8) = -6.94,p < 0.001), mientras que el MBI (β = 10.26, CI95%[8.10, 12.42], t(8) = 10.96, p < 0.001) y la interacción entre este último y la Potencia alcanzada durante elFTP influían en el ∆SNS (β= -0.05, CI95%[-0.09, -4.99e-03], t(8) = -2.56, p = 0.033). Conclusión: Nuestros hallazgos indican que el SMI tuvo un efecto negativo sobre el ∆PNS, mientras que el MBI se correlacionó positivamente con el ∆SNSen ciclistas. Estos hallazgos sugieren que un mayor SMI y MBI podrían tener un impacto perjudicial en la respuesta autonómica cardíaca al ejercicioaeróbico máximo en ciclistas de alto rendimiento, como el FTP.(AU)