Fit elderly men can also stand: orthostatic tolerance and autonomic cardiovascular control in elderly endurance athletes

Orthostatic testing for heart rate and heart rate variability monitoring in exercise science and practice

Orthostatic testing, involving the transition from different body positions (e.g., from lying or sitting position to an upright or standing position), offers valuable insights into the autonomic nervous system (ANS) functioning and cardiovascular regulation reflected through complex adjustments in, e.g., measures of heart rate (HR) and heart rate variability (HRV). This narrative review explores the intricate physiological mechanisms underlying orthostatic stress responses and evaluates its significance for exercise science and sports practice. Into this matter, active orthostatic testing (e.g., active standing up) challenges the cardiovascular autonomic function in a different way than a passive tilt test. It is well documented that there is a transient reduction in blood pressure while standing up, leading to a reflex increase in HR and peripheral vasoconstriction. After that acute response systolic and diastolic blood pressures are usually slightly increased compared to supine lying body position. The ANS response to standing is initiated by instantaneous cardiac vagal withdrawal, followed by sympathetic activation and vagal reactivation over the first 25-30 heartbeats. Thus, HR increases immediately upon standing, peaking after 15-20 beats, and is less marked during passive tilting due to the lack of muscular activity. Standing also decreases vagally related HRV indices compared to the supine position. In overtrained endurance athletes, both parasympathetic and sympathetic activity are attenuated in supine and standing positions. Their response to standing is lower than in non-overtrained athletes, with a tendency for further decreased HRV as a sign of pronounced vagal withdrawal and, in some cases, decreased sympathetic excitability, indicating a potential overtraining state. However, as a significant main characteristic, it could be noted that additional pathophysiological conditions consist in a reduced responsiveness or counter-regulation of neural drive in ANS according to an excitatory stimulus, such as an orthostatic challenge. Hence, especially active orthostatic testing could provide additional information about HR(V) reactivity and recovery giving valuable insights into athletes' training status, fatigue levels, and adaptability to workload. Measuring while standing might also counteract the issue of parasympathetic saturation as a common phenomenon especially in well-trained endurance athletes. Data interpretation should be made within intra-individual data history in trend analysis accounting for inter-individual variations in acute responses during testing due to life and physical training stressors. Therefore, additional measures (e.g., psychometrical scales) are required to provide context for HR and HRV analysis interpretation. However, incidence of orthostatic intolerance should be evaluated on an individual level and must be taken into account when considering to implement orthostatic testing in specific subpopulations. Recommendations for standardized testing procedures and interpretation guidelines are developed with the overall aim of enhancing training and recovery strategies. Despite promising study findings in the above-mentioned applied fields, further research, thorough method comparison studies, and systematic reviews are needed to assess the overall perspective of orthostatic testing for training monitoring and fine-tuning of different populations in exercise science and training.

Rationale and design of the Birkebeiner Ageing Study - a prospective cohort study of older endurance athletes

BACKGROUND

While regular physical activity is associated with reduced mortality and morbidity in general populations, health outcomes and functional capacity related to upholding strenuous endurance exercise beyond the age of 65 years are only sparsely studied. The aim of this study is to assess associations of prolonged strenuous endurance sport practice with ageing, functional decline, morbidity and longevity among older recreational endurance athletes, during long-term follow-up.

METHODS

Prospective cohort study of older recreational endurance athletes in Norway. All skiers aged 65 years and older who participated in a long-distance endurance competition, the annual 54-km Birkebeiner cross-country ski race in 2009 or 2010, were invited. The participants answered an extensive baseline questionnaire about lifestyle habits, including leisure-time physical activity and endurance sport participation, diseases, medication use and physical and mental health, with follow-up questionnaires planned every fifth year until 2029. New participants may be invited with the aim to increase the study size. Endpoints such as all-cause and disease-specific mortality, incidence and cumulative prevalence of diseases, use of medication, physical and mental health and functional decline will be assessed subsequently. Out of 658 invited skiers (51 women), 551(84%) completed the baseline questionnaire and were included in the study. The mean age was 68.8 years (median 68, range 65- 90). At baseline, the participants had completed the Birkebeiner race for an average of 16.6 years and reported an average of 33.4 years of regular endurance exercise, with one out of five reporting at least 50 years of exercise. In all, 479 (90%) reported that they were still practicing leisure-time physical activity of moderate or vigorous intensity at least twice weekly. The prevalence of cardiovascular risk factors and diseases was low.

DISCUSSION

This prospective study of a cohort of recreational athletes exposed to prolonged and strenuous endurance exercise, could complement population-based studies by providing data on associations between life-long endurance sport participation, aging, functional decline and health outcomes during long-term follow-up.

The Physical Capacity of Rowing Athletes Cannot Reverse the Influence of Age on Heart Rate Variability during Orthostatic Stress

The current study was undertaken to test the hypothesis that the high physical capacity of rowing athletes may not reverse the influence of age on cardiac autonomic control decline estimated by heart rate variability (HRV). Forty-four male subjects divided in four groups: 11 young athletes (YA; 18 ±1 year), 11 young non-athletes (YNA; 20 ±1 year), 11 middle age athletes (MAA; 43 ±6 years) and 11 middle age non-athletes (MNA; 44 ±8 years) participated in the study. Heart rate (HR) was recorded beat-by-beat for 10 minutes in supine (SUP) and 10 min in orthostatic (ORT) positions. HRV was analyzed in the frequency domain to obtain the spectral power in the high (HF) and low frequency (LF) bands, and the changes to ORT (%∆HRV) were calculated (ORT - SUP / SUP). During SUP, HF was lower in MNA and MA compared to YA and YNA, while LF was lower in MNA than YA. For %ΔHRV, %ΔHF was higher in YA than YNA, MA and MNA. The %ΔLF was not different among groups. In conclusion, aging seems to overcome the influence of physical fitness on neural regulation of the heart, as highlighted by the HRV response to active standing.

Cardiovascular regulation: associations between exercise and head-up tilt

It was hypothesized that faster cardiorespiratory kinetics during exercise are associated with higher orthostatic tolerance. Cardiorespiratory kinetics of 14 healthy male subjects (30 ± 4 years, 179 ± 8 cm, 79 ± 8 kg) were tested on a cycle ergometer during exercise with changing work rates of 30 and 80 W. Pulmonary oxygen uptake ( ) was measured breath-by-breath and heart rate (HR), mean arterial blood pressure (MAP), and total peripheral resistance (TPR) were measured beat-to-beat. Muscular oxygen uptake ( ) was estimated from HR and . Kinetic parameters were determined by time-series analysis, using cross-correlation functions (CCF_max(x)) between the parameter and the work rate. Cardiovascular regulations of MAP, HR, and TPR during orthostatic stress were measured beat-to-beat on a tilt seat. Changes between the minima and maxima during the 6° head-down tilt and the 90° head-up tilt positions were calculated for each parameter (Δ_tilt-up). correlated significantly with ΔTPR_tilt-up (r = 0.790, p ≤ 0.001). CCF_max(HR) was significantly correlated with ΔHR_tilt-up (r = -0.705, p = 0.002) and the amplitude in HR from 30 to 80 W (r_SP = -0.574, p = 0.016). The observed correlations between cardiorespiratory regulation in response to exercise and orthostatic stress during rest might allow for a more differential analysis of the underlying mechanisms of orthostatic intolerance in, for example, patient groups.

Heart rate variability in middle-aged sprint and endurance athletes

BACKGROUND

Aging is associated with decreased autonomic balance which could be assessed by Heart Rate Variability (HRV). Exercise training improves autonomic balance, but there is a lack in the literature regarding the heart rate variability (HRV) of master sprinters and endurance athletes.

PURPOSE

The effects of lifelong endurance and sprint training on cardiac autonomic balance were assessed in master athletes and compared with age-matched controls and young untrained controls.

METHODS

Participants (n = 81) were 8 master sprinters (MS; 51.8 ± 11.1 yrs), 8 master endurance athletes (EN, n = 8, 53.6 ± 8.6 yrs), 17 age-matched untrained (CON, 47.47 ± 6.00 yrs) and 48 young controls (YC, 25.40 ± 3.87 yrs). For the acquisition of RR intervals (iRR) (Polar RS800X Heart Rate Monitor®) the participants remained seated for 15-min with the final 10-min being considered for analysis. HRV was measured using Kubios software. A one-way ANOVA with repeated measures was applied.

RESULTS

All studied parameters did not differ between MS and EN {Time Domain [HR (bpm) 59.00 ± 6.13 vs. 58.94 ± 12.75], [R-R (ms) 1030.45 ± 107.45 vs. 1068.77 ± 206.17], [SDNN (ms) 57.35 ± 20.07 vs. 80.66 ± 71.07], [RMSSD (ms) 40.88 ± 20.07 vs. 38.93 ± 20.44]; Non-linear domain [SD1 (ms) 28.93 ± 14.20 vs. 27.56 ± 14.46]}, whose demonstrated a reduced HR and elevated mean R-R intervals in comparison to both YC {[HR (bpm) 69.64 ± 9.81]; [R-R (ms) 883.93 ± 124.11]} and age-matched controls {[HR (bpm) 70.06 ± 6.63]; [R-R (ms) 865.11 ± 78.39]}. It was observed a lower HRV for middle-aged CON {[RMSSD (ms) 20.23 ± 5.87], [SDNN (ms) 37.79 ± 10.15] and [SD1 (ms) 14.31 ± 4.15]} compared to YC {[RMSSD (ms) 43.33 ± 26.41], [SDNN (ms) 67.07 ± 28.77] and [SD1 (ms) 30.66 ± 18.69; p < .05]}. These last age-related differences were not observed for MS and EN.

CONCLUSION

For master athletes, regardless of whether they are trained in endurance or sprinters, both training modes revealed to be equally beneficial in attenuating the effects of aging on the autonomic balance.