AUTHOR=Robin Adrien , Wang Linjie , Custaud Marc-Antoine , Liu Jiexin , Yuan Min , Li Zhili , Lloret Jean-Christophe , Liu Shujuan , Dai Xiaoqian , Zhang Jianfeng , Lv Ke , Li Wenjiong , Gauquelin-Koch Guillemette , Wang Huijuan , Li Kai , Li Xiaotao , Qu Lina , Navasiolava Nastassia , Li Yinghui 

TITLE=Running vs. resistance exercise to counteract deconditioning induced by 90-day head-down bedrest

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.902983

DOI=10.3389/fphys.2022.902983

ISSN=1664-042X

ABSTRACT=<p>Spaceflight is associated with enhanced inactivity, resulting in muscular and cardiovascular deconditioning. Although physical exercise is commonly used as a countermeasure, separate applications of running and resistive exercise modalities have never been directly compared during long-term bedrest. This study aimed to compare the effectiveness of two exercise countermeasure programs, running and resistance training, applied separately, for counteracting cardiovascular deconditioning induced by 90-day head-down bedrest (HDBR). Maximal oxygen uptake (<inline-formula id="inf53"><mml:math id="m53" 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:mrow></mml:math></inline-formula>O<sub>2</sub>max), orthostatic tolerance, continuous ECG and blood pressure (BP), body composition, and leg circumferences were measured in the control group (CON: <italic>n</italic> = 8), running exercise group (RUN: <italic>n</italic> = 7), and resistive exercise group (RES: <italic>n</italic> = 7). After HDBR, the decrease in <inline-formula id="inf54"><mml:math id="m54" 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:mrow></mml:math></inline-formula>O<sub>2</sub>max was prevented by RUN countermeasure and limited by RES countermeasure (−26% in CON <italic>p</italic> &lt; 0.05, −15% in RES <italic>p</italic> &lt; 0.05, and −4% in RUN <italic>ns</italic>). Subjects demonstrated surprisingly modest orthostatic tolerance decrease for different groups, including controls. Lean mass loss was limited by RES and RUN protocols (−10% in CON vs. −5% to 6% in RES and RUN). Both countermeasures prevented the loss in thigh circumference (−7% in CON <italic>p</italic> &lt; 0.05, −2% in RES <italic>ns</italic>, and −0.6% in RUN <italic>ns</italic>) and limited loss in calf circumference (−10% in CON vs. −7% in RES vs. −5% in RUN). Day–night variations in systolic BP were preserved during HDBR. Decrease in <inline-formula id="inf55"><mml:math id="m55" 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:mrow></mml:math></inline-formula>O<sub>2</sub>max positively correlated with decrease in thigh (<italic>r</italic> = 0.54 and <italic>p</italic> = 0.009) and calf (<italic>r</italic> = 0.52 and <italic>p</italic> = 0.012) circumferences. During this 90-day strict HDBR, running exercise successfully preserved <inline-formula id="inf56"><mml:math id="m56" 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:mrow></mml:math></inline-formula>O<sub>2</sub>max, and resistance exercise limited its decline. Both countermeasures limited loss in global lean mass and leg circumferences. The <inline-formula id="inf57"><mml:math id="m57" 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:mrow></mml:math></inline-formula>O<sub>2</sub>max reduction seems to be conditioned more by muscular than by cardiovascular parameters.</p>