Aging effects on prefrontal cortex oxygenation in a posture-cognition dual-task: an fNIRS pilot study

The aging process alters upright posture and locomotion control from an automatically processed to a more cortically controlled one. The present study investigated a postural-cognitive dual-task paradigm in young and older adults using functional Near- Infrared Spectroscopy (fNIRS).Methods: Twenty healthy participants (10 older adults 72 ± 3 y, 10 young adults 23 ± 3 y) performed a cognitive (serial subtractions) and a postural task (tandem stance) as single-tasks (ST) and concurrently as a dual-task (DT) while the oxygenation levels of the dorsolateral prefrontal cortex (DLPFC) were measured.Results: In the cognitive task, young adults performed better than older adults in both conditions (ST and DT) and could further increase the number of correct answers from ST to DT (all ps ≤ 0.027) while no change was found for older adults. No significant effects were found for the postural performance. Cerebral oxygenation values (O2Hb) increased significantly from baseline to the postural ST (p = 0.033), and from baseline to the DT (p = 0.031) whereas no changes were found in deoxygenated hemoglobin (HHb). Finally, the perceived exertion differed between all conditions (p ≤  0.003) except for the postural ST and the DT (p = 0.204).Conclusions: There was a general lack of age-related changes except the better cognitive performance under motor-cognitive conditions in young compared to older adults. However, the current results point out that DLPFC is influenced more strongly by postural than cognitive load. Future studies should assess the different modalities of cognitive as well as postural load

Changes in Skeletal Muscle Oxidative Capacity After a Trail Running Race

Purpose: To evaluate the effects of a trail-running race on muscle oxidative function by measuring pulmonary gas exchange variables and muscle fractional O2 extraction. Methods: Eighteen athletes were evaluated before (PRE) and after (POST) a trail-running competition of 32 or 50 km with 2000 or 3500 m of elevation gain, respectively. During the week before the race, runners performed an incremental uphill running test and an incremental exercise by utilizing a 1-leg knee extension ergometer. The knee extension exercise was repeated after the end of the race. During the knee extension test, the authors measured oxygen uptake (V\u2d9O2) and micromolar changes in deoxygenated hemoglobin (Hb)+myoglobin (Mb) concentrations (\u394[deoxy(Hb+Mb)]) on vastus lateralis with a portable near-infrared spectroscopy. Results: V\u2d9O2peak was lower at POST versus PRE ( 1223.9% [9.0%]; P\u2009<\u2009.001). V\u2d9O2peak at POST was lower than V\u2d9O2 at the same workload at PRE ( 128.4% [15.6%]; P\u2009<\u2009.050). Peak power output and time to exhaustion decreased at POST by 1223.7% (14.3%) and 1218.3% (11.3%), respectively (P\u2009<\u2009.005). At POST, the increase of \u394[deoxy(Hb+Mb)] as a function of work rate, from unloaded to peak, was less pronounced (from 20.2% [10.1%] to 64.5% [21.1%] of limb ischemia at PRE to 16.9% [12.7%] to 44.0% [18.9%] at POST). Peak \u394[deoxy(Hb+Mb)] values were lower at POST (by 1231.2% [20.5%]; P\u2009<\u2009.001). Conclusions: Trail running leads to impairment in skeletal muscle oxidative metabolism, possibly related to muscle damage from repeated eccentric contractions. In association with other mechanisms, the impairment of skeletal muscle oxidative metabolism is likely responsible for the reduced exercise capacity and tolerance during and following these races