ECSS Paris 2023: OP-MH34
INTRODUCTION: Cardiorespiratory fitness (CRF) is a key clinical marker in older adults, with low CRF consistently associated with increased premature mortality and adverse health outcomes comparable to traditional cardiovascular disease (CVD) risk factors. Given these implications, accurate assessment is essential. A supramaximal verification phase following a traditional incremental exercise test has been proposed to confirm the attainment of true maximal oxygen uptake (VO2max). This study therefore aimed to 1) assess whether a supramaximal verification phase confirms VO2max attainment in older adults at low and high risk of CVD, and 2) determine the impact of different time-sampling intervals on the interpretation of VO2max results. METHODS: Data from 69 maximal cycle ergometer (Corival, Lode) tests performed by older adults were analyzed (25 females; 44 males; 69.8±5.6 [60-84] yrs; 59.4% with CVD risk factors). Tests were considered maximal if fatigue-limited and associated with respiratory exchange ratio (RER) >1.1. Following at least 5 minutes of recovery, participants completed a supramaximal verification phase at a power output 20% greater than the penultimate stage of the incremental maximal exercise test. VO2max from the incremental exercise test (iVO2max) and verification phase (verVO2max) were calculated using 10-seconds (s), 20-s, and 30-s from breath-by-breath averaging intervals (MCD Medgraphics, MGC Diagnostics). Data were analyzed using repeated measures ANOVA with Bonferroni correction and paired t-tests. RESULTS: Participants achieved a peak power output of 161.0±58.8 Watts, a maximal heart rate of 153±15 bpm, and a peak RER of 1.24±0.06. During the incremental test, 60.8% of participants (n=42) demonstrated a VO2 plateau (increase of <100 mlO2.min-1 with increasing workload). Total exercise time averaged 542.8±149.3s for the iVO2max and 130.8±25.3s for verVO2max tests. Mean iVO2max and verVO2max did not differ significantly across sampling intervals of 10-s (26.73±6.95 vs 26.77±6.97 mlO2.min-1.kg-1), 20-s (26.57±6.92 vs 26.51±6.97 mlO2.min-1.kg-1), and 30-s (26.42±6.91 vs 26.31±6.99 mlO2.min-1.kg-1), respectively (all p>0.05). However, 10-s averages yielded significantly higher VO2max than 30-s averaging for both test phases (p<0.001). Notably, individual analysis revealed that 13 participants (≈19%) increased VO2max by more than 1.5 mlO2.min-1.kg-1 and 24.6% by >3% during the verification phase. CONCLUSION: These findings support the use of a supramaximal verification phase to confirm VO2max attainment in older adults. Sampling interval duration did not influence verification success; however, shorter averaging (10-s) yielded statistically higher, though clinically negligible, VO2max values. Notably, despite stable group means, ≈19% of participants demonstrated a significant increase in their VO2max during the verification phase. This has important implications for intervention studies that use repeated VO2max assessments to detect training-induced changes in CRF.
Read CV Pierre BoulayECSS Paris 2023: OP-MH34
INTRODUCTION: A single bout of exercise decreases blood pressure (BP) transiently, which is called as “post-exercise hypotension (PEH)”. Repetition of PEH contributes to reducing BP chronically. A previous study revealed that endurance exercise reduced markedly systolic BP (SBP) compared to resistance exercise (Ramis et al. 2014). In addition, resistance exercise under hypoxic environment caused greater PEH compared to the same exercise under normoxic condition (Horiuchi et al. 2018). Therefore, combination of “endurance exercise” and “hypoxia” may facilitate PEH. However, PEH after endurance exercise in hypoxia has not been fully elucidated. Therefore, the aim of the present study was to compare PEH between endurance exercise in hypoxia and the same exercise in normoxia. METHODS: Eighteen young men (22 ± 2 years) conducted three trials on different days with a randomized order of trial: (1) pedaling exercise in hypoxia (FiO2: 14.5%; HYP), (2) pedaling exercise in normoxia (FiO2: 20.9%; NOR), and (3) rest in normoxia (REST). Exercise trials (HYP and NOR) consisted of 60 min of pedaling exercise at 55% of maximal oxygen uptake in normoxia. During each trial, heart rate (HR), rating of perceived exertion, and arterial oxygen saturation (SpO2) were determined. Following each intervention (60 min of exercise or rest), BP and cardiac output (CO), stroke volume (SV), total peripheral vascular resistance (TPR) were measured every 15min for 3h. Also, HR variability (HRV) was continuously monitored for 3h. RESULTS: During exercise, HR was significantly higher in HYP compared to NOR and REST (p<0.001). SpO2 was significantly lower in HYP (82.7 ± 3.6%) than in NOR (95.7 ± 1.7%) and REST (97.3 ± 0.5%, p<0.001). During 3 h of post-exercise period, reduction of mean arterial pressure (ΔMAP) was significantly profound in HYP (-4.2 ± 4.8mmHg) and NOR (-3.2 ± 3.2mmHg) compared to REST (1.3 ± 2.7mmHg, p<0.05). Moreover, the duration of PEH was longer in HYP than NOR. However, average ΔMAP did not differ significantly between HYP and NOR (p>0.05). During post-exercise period (NOR, HYP), CO increased until 30 min whereas SV and TPR decreased between 15-165 min after the exercise with no significant difference between the trials (p>0.05). Also, time-domain HRV parameters (i.e., SDNN, RMSSD, NN50, pNN50) returned to baseline levels within approximately 2 h with no significant difference between NOR and HYP. CONCLUSION: Although both HYP and NOR significantly reduced MAP compared to REST, the magnitude of PEH (ΔMAP) did not differ significantly between NOR and HYP. Furthermore, CO was transiently elevated during post-exercise, but the reductions of SV, TPR, and HRV parameters lasted over 2 h. These findings suggest that endurance exercise causes PEH regardless of oxygen concentration during the exercise.
Read CV Miyu KobayashiECSS Paris 2023: OP-MH34
INTRODUCTION: Arterial baroreflex function and respiratory sinus arrhythmia (RSA) constitute two key feedback mechanisms governed by interactions between sympathetic and parasympathetic activity. As respiratory frequency (Rf) increases, vagal efferent mechanisms progressively lose their ability to track respiration-related oscillations, resulting in a reduction in RSA, whereas lower Rf enhances RSA. Slow paced breathing (SPB) is therefore expected to promote health benefits through an increase in RSA; however, previous findings remain inconsistent. The present study aimed to compare a personalized SPB condition with a placebo condition to differentiate the specific effects of SPB from those attributable to breathing awareness or attentional distraction alone. METHODS: Twenty-four healthy young adults completed a six-week intervention consisting of either personalized SPB (n = 12) or a control condition involving spontaneous breathing (CON, n = 12). Baroreflex sensitivity (BRS), pulse waveform (PWF) and heart rate variability (HRV) were assessed under laboratory conditions before and after the intervention (labPRE and labPOST). Additionally, three times per week during the intervention, participants completed an at-home orthostatic test (5 min supine [sup] followed by 5 min standing [stand]) before (hPRE) and after (hPOST) each SPB or CON session. Personalized SPB corresponded to the breathing frequency producing maximal RSA, reflecting optimal synchronization between respiration and heart rate. HRV indices included heart rate (HR), root mean square of successive differences (RMSSD), and spectral power in the low- (LF) and high-frequency (HF) bands; PWF indices include: stiffness index (SI), augmentation index (AI), and systolic/diastolic amplitudes and timings and were interpreted as indicators of combined central and peripheral vascular adaptations to SPB training. RESULTS: From labPRE to labPOST, BRS (12.8 ± 3.2 vs. 15.2 ± 2.8 ms/mmHg p = .030), RMSSDsup (45.9 ± 12.6 vs. 62.9 ± 19.4 ms, p = .014) and HFsup (1062 ± 687 vs. 1469 ± 905 ms2, p = .040) increased only in the SPB group. Large artery SI (161+/-28 vs. 137+/-13 mmHg/s, p = .027) and AI (2.52+/-0.43 vs. 2.15+/-0.28, p = .026) decreased only in the SPB group and were significantly lower than CON at labPOST. From hPRE to hPOST, LFsup decreased more in SPB than in CON, whereas RMSSDstand increased more in CON than in SPB. Toward the end of the intervention, LFstand showed a greater reduction in SPB than in CON, whilst HFstand increased more in SPB. CONCLUSION: Six weeks of personalized SPB training induced greater parasympathetic modulation of cardiac function and improved vascular compliance compared with spontaneous breathing, supporting the health benefits of prolonged SPB practice. Additional research is needed to further elucidate the physiological mechanisms underlying these adaptations.
Read CV Nicolas BourdillonECSS Paris 2023: OP-MH34