Feasibility of superimposed supine cycling and lower body negative pressure as an effective means of prolonging exercise tolerance in individuals experiencing persisting post-concussive symptoms: Preliminary results.

Abstract

To examine the feasibility, utility and safety of superimposed lower body negative pressure (LBNP) and tilt during supine cycling in individuals suffering from persisting post-concussive symptoms (PPCS). Elevenindividuals aged 17-31 (6 females/5 males) participated in two randomized separate visits, 1week apart. A ramp-incremental test was performed during both visits until volitional failure. Visits included no pressure (control) or LBNP at -40Torr (experimental) with head-up tilt at 15degrees (females) or 30degrees (males). Transcranial Doppler ultrasound was utilized to quantify middle cerebral artery velocity (MCAv), while symptom reports were filled out before and 0, 10, and 60min post-exertion. Ratings of exertion and overall condition followed similar trends for participants across both tests. The relative increase in MCAv was blunted during the experimental condition (8%) compared to control (24%), while a greater heart rate (17 beats/min) was achieved during the LBNP condition (P=0.047). Symptom severity at the 0 and 10minpost-exertion time points displayed negligible-to-small effect sizes between conditions (Wilcoxon's r<0.11). Symptom reporting was lower at the 60min post-exertion time point with these displaying a moderate effect size (Wilcoxon's r=0.31). The combination of LBNP and tilt during supine cycling did not change the participants' subjective interpretation of the exertional test but attenuated the hyperpnia-induced vasodilatory MCAv response, while also enabling participants to achieve a higher heart rate during exercise and reduced symptoms 1h later. As this protocol is safe and feasible, further research is warranted in this area for developing PPCS treatment options. HIGHLIGHTS: What is the central question of this study? What are the feasibility, safety and utility of combining head-up tilt with lower body negative pressure during supine cycling for blunting the increase in cerebral blood velocity seen during moderate-intensity exercise in individuals experiencing persisting post-concussion symptoms? What is the main finding and its importance? Although no differences were found in symptoms between conditions within the first 10min following exertion, symptom severity scores showed a clinically meaningful reduction 60min following the experimental condition compared to the non-experimental control condition.