TY - JOUR
T1 - Effect of ischemic preconditioning and changing inspired O2 fractions on neuromuscular function during intense exercise
AU - Halley, Samuel L.
AU - Marshall, Paul
AU - Siegler, Jason C.
N1 - Publisher Copyright:
© 2019 the American Physiological Society.
PY - 2019
Y1 - 2019
N2 - The aim of the present study was to determine whether ischemic preconditioning (IPC)-mediated effects on neuromuscular function are dependent on tissue oxygenation. Eleven resistance-trained males completed four exercise trials (6 sets of 11 repetitions of maximal effort dynamic single-leg extensions) in either normoxic [fraction of inspired oxygen (FIO2 ): 21%) or hypoxic FIO2 : 14%] conditions, preceded by treatments of either IPC (3 × 5 min bilateral leg occlusions at 220 mmHg) or sham (3 × 5 min at 20 mmHg). Femoral nerve stimulation was utilized to assess voluntary activation and potentiated twitch characteristics during maximal voluntary contractions (MVCs). Tissue oxygenation (via near-infrared spectroscopy) and surface electromyography activity were measured throughout the exercise task. MVC and twitch torque declined 62 and 54%, respectively (MVC: 96 ± 24 N•m, Cohen's d = 2.9, P < 0.001; twitch torque: 37 ± 11 N•m, d = 1.6, P < 0.001), between pretrial measurements and the sixth set without reductions in voluntary activation (P > 0.21); there were no differences between conditions. Tissue oxygenation was reduced in both hypoxic conditions compared with normoxia (P < 0.001), with an even further reduction of 3% evident in the hypoxic IPC compared with the sham trial (mean decrease 1.8 ± 0.7%, d = 1.0, P < 0.05). IPC did not affect any measure of neuromuscular function regardless of tissue oxygenation. A reduction in FIO2 did invoke a humoral response and improved muscle O2 extraction during exercise, however, it did not manifest into any performance benefit. NEW & NOTEWORTHY Ischemic preconditioning did not affect any facet of neuromuscular function regardless of the degree of tissue oxygenation. Reducing the fraction of inspired oxygen induced localized tissue deoxygenation, subsequently invoking a humoral response, which improved muscle oxygen extraction during exercise. This physiological response, however, did not manifest into any performance benefits.
AB - The aim of the present study was to determine whether ischemic preconditioning (IPC)-mediated effects on neuromuscular function are dependent on tissue oxygenation. Eleven resistance-trained males completed four exercise trials (6 sets of 11 repetitions of maximal effort dynamic single-leg extensions) in either normoxic [fraction of inspired oxygen (FIO2 ): 21%) or hypoxic FIO2 : 14%] conditions, preceded by treatments of either IPC (3 × 5 min bilateral leg occlusions at 220 mmHg) or sham (3 × 5 min at 20 mmHg). Femoral nerve stimulation was utilized to assess voluntary activation and potentiated twitch characteristics during maximal voluntary contractions (MVCs). Tissue oxygenation (via near-infrared spectroscopy) and surface electromyography activity were measured throughout the exercise task. MVC and twitch torque declined 62 and 54%, respectively (MVC: 96 ± 24 N•m, Cohen's d = 2.9, P < 0.001; twitch torque: 37 ± 11 N•m, d = 1.6, P < 0.001), between pretrial measurements and the sixth set without reductions in voluntary activation (P > 0.21); there were no differences between conditions. Tissue oxygenation was reduced in both hypoxic conditions compared with normoxia (P < 0.001), with an even further reduction of 3% evident in the hypoxic IPC compared with the sham trial (mean decrease 1.8 ± 0.7%, d = 1.0, P < 0.05). IPC did not affect any measure of neuromuscular function regardless of tissue oxygenation. A reduction in FIO2 did invoke a humoral response and improved muscle O2 extraction during exercise, however, it did not manifest into any performance benefit. NEW & NOTEWORTHY Ischemic preconditioning did not affect any facet of neuromuscular function regardless of the degree of tissue oxygenation. Reducing the fraction of inspired oxygen induced localized tissue deoxygenation, subsequently invoking a humoral response, which improved muscle oxygen extraction during exercise. This physiological response, however, did not manifest into any performance benefits.
KW - Blood occlusion
KW - Central drive
KW - Hypoxia
KW - Intense exercise
KW - Peripheral fatigue
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U2 - 10.1152/japplphysiol.00539.2019
DO - 10.1152/japplphysiol.00539.2019
M3 - Article
C2 - 31600099
AN - SCOPUS:85076449565
SN - 8750-7587
VL - 127
SP - 1688
EP - 1697
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -