AUTHOR=Caen Kevin , Vermeire Kobe , Pogliaghi Silvia , Moerman Annelies , Niemeijer Victor , Bourgois Jan Gustaaf , Boone Jan 

TITLE=Aerobic Interval Training Impacts Muscle and Brain Oxygenation Responses to Incremental Exercise

JOURNAL=Frontiers in Physiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.01195

DOI=10.3389/fphys.2019.01195

ISSN=1664-042X

ABSTRACT=<p>The purpose of the present study was to assess the effects of aerobic interval training on muscle and brain oxygenation to incremental ramp exercise. Eleven physically active subjects performed a 6-week interval training period, proceeded and followed by an incremental ramp exercise to exhaustion (25 W min<sup>–1</sup>). Throughout the tests pulmonary gas exchange and muscle (Vastus Lateralis) and brain (prefrontal cortex) oxygenation [concentration of deoxygenated and oxygenated hemoglobin, HHb and O<sub>2</sub>Hb, and tissue oxygenation index (TOI)] were continuously recorded. Following the training intervention <inline-formula><mml:math id="INEQ1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula><sub>peak</sub> had increased with 7.8 ± 5.0% (<italic>P</italic> &lt; 0.001). The slope of the decrease in muscle TOI had decreased (<italic>P</italic> = 0.017) 16.6 ± 6.4% and the amplitude of muscle HHb and totHb had increased (<italic>P</italic> &lt; 0.001) 40.4 ± 15.8 and 125.3 ± 43.1%, respectively. The amplitude of brain O<sub>2</sub>Hb and totHb had increased (<italic>P</italic> &lt; 0.05) 40.1 ± 18.7 and 26.8 ± 13.6%, respectively. The training intervention shifted breakpoints in muscle HHb, totHb and TOI, and brain O<sub>2</sub>Hb, HHb, totHb and TOI to a higher absolute work rate and <inline-formula><mml:math id="INEQ2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> (<italic>P</italic> &lt; 0.05). The relative (in %) change in <inline-formula><mml:math id="INEQ3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula><sub>peak</sub> was significantly correlated to relative (in %) change slope of muscle TOI (<italic>r</italic> = 0.69, <italic>P</italic> = 0.011) and amplitude of muscle HHb (<italic>r</italic> = 0.72, <italic>P</italic> = 0.003) and totHb (<italic>r</italic> = 0.52, <italic>P</italic> = 0.021), but not to changes in brain oxygenation. These results indicate that interval training affects both muscle and brain oxygenation, coinciding with an increase in aerobic fitness (i.e., <inline-formula><mml:math id="INEQ4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula><sub>peak</sub>). The relation between the change in <inline-formula><mml:math id="INEQ5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover><mml:mo>⁢</mml:mo><mml:msub><mml:mtext>O</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula><sub>peak</sub> and muscle but not brain oxygenation suggests that brain oxygenation <italic>per se</italic> is not a primary factor limiting exercise tolerance during incremental exercise.</p>