Hemodynamic Response Alterations in Sensorimotor Areas as a Function of Barbell Load Levels during Squatting: An fNIRS Study.

Rouven Kenville,Daniel Carius,Patrick Ragert,Tom Maudrich

doi:10.3389/fnhum.2017.00241

Abstract

Functional near-infrared spectroscopy (fNIRS) serves as a promising tool to examine hemodynamic response alterations in a sports-scientific context. The present study aimed to investigate how brain activity within the human motor system changes its processing in dependency of different barbell load conditions while executing a barbell squat (BS). Additionally, we used different fNIRS probe configurations to identify and subsequently eliminate potential exercise induced systemic confounders such as increases in extracerebral blood flow. Ten healthy, male participants were enrolled in a crossover design. Participants performed a BS task with random barbell load levels (0% 1RM (1 repetition maximum), 20% 1RM and 40% 1RM for a BS) during fNIRS recordings. Initially, we observed global hemodynamic response alterations within and outside the human motor system. However, short distance channel regression of fNIRS data revealed a focalized hemodynamic response alteration within bilateral superior parietal lobe (SPL) for oxygenated hemoglobin (HbO2) and not for deoxygenated hemoglobin (HHb) when comparing different load levels. These findings indicate that the previously observed load/force-brain relationship for simple and isolated movements is also present in complex multi-joint movements such as the BS. Altogether, our results show the feasibility of fNIRS to investigate brain processing in a sports-related context. We suggest for future studies to incorporate short distance channel regression of fNIRS data to reduce the likelihood of false-positive hemodynamic response alterations during complex whole movements.

Highlights

Recent animal and human studies have provided compelling evidence, that the brain modulates its activity as a function of applied load
Based on the aforementioned findings and limitations with respect to Functional near-infrared spectroscopy (fNIRS), the present study aimed to investigate how brain activity within the human motor system changes its processing in dependency of different load conditions while executing a barbell squat (BS)
Post hoc analysis revealed significant hemodynamic response alterations for L20% vs. L0% in bilateral M1, inferior parietal lobe (IPL), supplementary motor area (SMA), and premotor cortex (PMC) for HbO2, while no such effect could be observed for HHb

Summary

Introduction

Recent animal and human studies have provided compelling evidence, that the brain modulates its activity as a function of applied load. A pioneer study, conducted by Evarts (1968) showed that the brain reorganizes itself when exposed to external force requirements These results applied to isolated movements and were later supplemented for more complex motion sequences (Georgopoulos et al, 1982). Ward and Frackowiak (2003) found a high correlation between the height of the blood oxygen level dependent (BOLD) signal (contralateral M1 and S1) and the force applied during a hand grip task. These results were later confirmed by subsequent fMRI studies (Talelli et al, 2008; Ward et al, 2008; Noble et al, 2011). Differences in neural activity between a ‘‘precision grip’’ (compression of the thumb and index finger) and a ‘‘power grip’’ (clenching of the fist) were assessed by Takasawa et al (2003), who found no significant differences in brain activity between ‘‘precision grip’’ and ‘‘power grip’’

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Conclusion