ECSS Paris 2023: OP-PN31
INTRODUCTION: Aging leads to significant decrease in aerobic capacity, cardiovascular function (1), muscle strength and power, muscle mitochondrial oxidative capacity and capillarity (2). In older people, muscle fiber atrophy and loss of fiber oxidative capacity (3,4) may counter effect muscle capillary rarefaction (4) and thereby protect O2 diffusive flow into contracting muscle fibers by increasing the capillary supply region (5). We aimed to evaluate age-related differences in muscle oxidative capacity and O2 diffusion in vivo. METHODS: Twelve young (YG; 26±5 y), nine middle-aged (MID; 57±5 y) and twelve old (OLD; 78±5 y) individuals volunteered. They underwent an incremental cycle-ergometry to the limit of tolerance for peak oxygen uptake (V̇O2peak). In a different occasion vastus lateralis V̇O2 recovery rate constant (k) was measured by near-infrared spectroscopy during repeated transient occlusions after moderate exercise. Duration and timing of occlusions were manipulated to keep tissue saturation index (TSI) within 10% bounds of two different O2 availability conditions: not-limiting (HIGH) and limiting (LOW) (6). kHIGH provides an estimate of muscle oxidative capacity, while the difference between kHIGH and kLOW (∆k) is inversely proportional to capillarity (a high ∆k reveals O2 diffusion limitation). One-way ANOVA with Tuckey’s post hoc test was used to test differences among groups and one sample t test was used to test ∆k difference from zero in each group. Linear regression was utilized to analyze correlation of V̇O2peak with kHIGH and ∆k. RESULTS: YG had greater V̇O2peak than MID and OLD (35.7±8.2 vs. 30.1±5.6 and 24.2±4.4 ml*min-1*kg-1 respectively; p<0.05). kHIGH was greater in YG (2.97±0.55 min-1) compared to MID (2.09±0.63 min-1, p<0.05) and OLD (2.04±0.57 min-1, p<0.01), but MID and OLD were not different (p=0.985). ∆k was significantly greater than zero (p<0.05) in YG (1.32±0.70 min-1) and MID (0.62±0.62 min-1), but not in OLD (0.02±0.65 min-1; p=0.941). Linear regression showed V̇O2peak significantly correlated with both kHIGH (r=0.40; p<0.05) and ∆k (r=0.38; p<0.05). CONCLUSION: Age-related differences in maximal aerobic capacity were related to skeletal muscle oxidative capacity and O2 diffusion limitation. Unlike young and middle-aged muscle, diffusive capacity was not limiting to muscle oxidative capacity in the elderly. Thus, our data suggest age-related muscle adaptations help to protect muscle oxidative function in older aging. Future analyses on muscle samples to better characterize muscle structure and function will help to gain insights into age-related differences in limitations to intramuscular O2 flow. [1] Chodzko-Zajko et al, 2009, MSSE [2] Conley et al, 2000, J Physiol [3] Nilwik et al, 2013, Exp Gerontol [4] Proctor et al, 1995, J Appl Physiol [5] Barnouin et al, 2017, J Cachexia Sarcopenia Muscle [6] Pilotto et al, 2022, J Physiol
Read CV Andrea PilottoECSS Paris 2023: OP-PN31
INTRODUCTION: Performing sustained cognitive activities (SCA) can lead to perceived cognitive fatigue as well as changes in motivation, affective valence, arousal, as well as boredom and has been shown to impair endurance performance and motor control during various tasks. However, the temporal recovery dynamics of the perceptual responses and oxygenation of the prefrontal cortex after SCA have rarely been studied. For this reason, temporal recovery dynamics of perceived cognitive fatigue and other perceptual responses as well as prefrontal cortex oxygenation were investigated for 60 min after an SCA METHODS: In a randomised, counterbalanced cross-over design, 30 subjects (females: 15; age: 23 ± 2.9 years; BMI: 20.5 ± 3.1 kg*m-2) completed an SCA task (60min digital Stroop task) and a control task (60 min watching a neutral video). Thereafter, a neutral video was watched for 60 min in both conditions to monitor temporal recovery of variables. Development and recovery of perceived cognitive fatigue and other perceptual responses (e.g., motivation, affective valence, arousal, boredom) during and after SCA were assessed at regular time intervals with visual analogue scales. Furthermore, oxygenation of the prefrontal cortex was measured using functional near-infrared spectroscopy (fNIRS). Data were analysed using repeated measures ANOVAs. RESULTS: No significant interactions of time x condition were observed for perceived cognitive fatigue (p = .834; ηp2 = .013), motivation (p = .132; ηp2 = .061), affective valence (p = .397; ηp2 = .035), arousal (p = .397; ηp2 = .035), boredom (p = .894; ηp2 = .010). For oxygenation of the prefrontal cortex, trends for interactions were found (O2Hb; HHb; tHb; TSI%: p ≥ 0.093; ηp2 ≤ .064). No main effects of condition were shown for all parameters. No time effects were found for perceived cognitive fatigue as well as all other perceptual responses. Time effects were found for O2Hb, tHb and TSI% (p ≤ .011; ηp2 ≥ .100) but not for HHb (p = .096; ηp2 = .064). CONCLUSION: Although no interaction effects were found for the perceptual responses, it appears that the initial level of prefrontal cortex oxygenation (baseline TSI%) is not achieved until 30 min after the SCA, while a full recovery was observed already during the first minute of recovery after the control task. These results indicate distinct temporal recovery dynamics of prefrontal cortex oxygenation but not the perceptual responses and emphasise the need for a multiparametric assessment to explain potential effects of SCA on subsequent cognitive or motor performance.
Read CV Martin GubeECSS Paris 2023: OP-PN31
INTRODUCTION: The inter-individual responses vary from no change to marked reduction in blood pressure (BP) after an acute and chronic aerobic exercise. The physiological background for heterogeneity in BP responses after chronic or acute aerobic exercise is not known. We hypothesized that skeletal muscle fiber type may modify BP responses after an acute aerobic exercise. METHODS: Normotensive participants (12 males and 8 females, age 27±6, maximal oxygen uptake 45±7 ml/kg/min) performed two 30 min aerobic exercises, continuous and interval intensities, by bicycle ergometer on separate days with BP measurements before and 60 min after exercises. BP was measured three times at baseline and 5 min intervals after exercises. Area under the curve after exercises (AUC) was calculated for systolic BP. Continuous aerobic exercise was 30 min at intensity of 60% of maximal exercise capacity. Aerobic interval exercise consisted of 8 x 1 min high intensity intervals (80-90% of maximal exercise capacity) with two min easy cycling between the intervals. The average workload was equal for both exercises (60% of maximal exercise capacity). Muscle biopsy was taken from vastus lateralis on separate day and the proportion of fast and slow fibers was counted. RESULTS: The average proportion of fast type fibers was 55±17% (range 16-84%). The change in systolic BP from baseline to 60 min recovery phase was -9±10 mmHg (range -18 - +8) and -9±8 mmHg (range -10 to +3) in continuous and interval exercises, respectively (time p<0.001, group p=ns, time·group interaction p=ns). AUC for systolic BP was -386±387 mmHg·min (range -591 - +348) and -399±228 mmHg·min (range -347 - +183) after continuous and interval exercises (p=ns), respectively. The change in systolic BP from baseline to 60 min recovery and the AUC for systolic BP were correlated with the proportion of fast muscle fibers after interval exercise (r=-0.53, p=0.023 and r=-0.59, p=0.010, respectively) but not after continuous exercise (r=-0.20, p=0.42 and r=-0.19, p=0.45, respectively). CONCLUSION: Inter-individual differences in post exercise BP responses are associated with skeletal muscle phenotype particularly after interval exercise. Participants with large amount of fast muscle fibers result in superior BP response after interval exercise compared to subjects with a low number of fast muscle fibers.
Read CV Venla YlinenECSS Paris 2023: OP-PN31