The effect of IPC on central and peripheral fatiguing mechanisms in humans following maximal single limb isokinetic exercise

Abstract

Ischemic preconditioning ( IPC ) has been suggested to preserve neural drive during fatiguing dynamic exercise, however, it remains unclear as to whether this may be the consequence of IPC ‐enhanced muscle oxygenation. We hypothesized that the IPC ‐enhanced muscle oxygenation during a dynamic exercise task would subsequently attenuate exercise‐induced reductions in voluntary activation. Ten resistance trained males completed three 3 min maximal all‐out tests ( AOT s) via 135 isokinetic leg extensions preceded by treatments of IPC (3 × 5 min bilateral leg occlusions at 220 mmHg), SHAM (3 × 5 min at 20 mmHg) or CON (30 min passive rest). Femoral nerve stimulation was utilized to assess voluntary activation and potentiated twitch torque during maximal voluntary contractions ( MVC s) performed at baseline ( BL ), prior to the AOT (Pre), and then 10 sec post (Post). Tissue oxygenation (via near‐infrared spectroscopy) and sEMG activity was measured throughout the AOT . MVC and twitch torque levels declined ( MVC : −87 ± 23 Nm, 95% CI = −67 to −107 Nm; P < 0.001, twitch: −30 ± 13 Nm; 95% CI = −25 to −35 Nm; P < 0.001) between Pre and Post without reductions in voluntary activation ( P = 0.72); there were no differences between conditions ( MVC : P = 0.75, twitch: P = 0.55). There were no differences in tissue saturation index ( P = 0.27), deoxyhemoglobin concentrations ( P = 0.86) or sEMG activity ( P = 0.92) throughout the AOT . These findings demonstrate that IPC does not preserve neural drive during an all‐out 3 min isokinetic leg extension task.

Sex differences in fatigability after ischemic preconditioning of non-exercising limbs

“…Modulation of central mechanisms associated with fatigability such as voluntary activation and presynaptic inhibition [ 14 , 50 ] were not altered by IPC in the current study. This is in accordance with others who showed no effects of a single session of IPC on voluntary activation or H-reflex amplitude of the quadriceps muscles in men, but its effects in women were not evaluated [ 11 , 12 , 51 , 52 ]. Nonetheless, it is suggested that some individuals seem to respond to the IPC technique but others do not [ 10 , 52 , 53 ] and differences in the populations involved, the intensity of contraction and muscles recruited are some factors that may explain the contradictory findings across studies.…”

“…There was no sex difference in physical activity levels in the current study, and therefore this variable likely does not explain the sex difference in response to IPC in our sample. The current study agrees with others that investigated the effects of IPC during fatiguing tasks at submaximal intensities using different muscle groups [ 6 , 52 ], but it is in contrast with others employing a maximal intensity task (e.g., all out sprint) in men [ 11 , 12 , 51 ] and women [ 55 ], and suggests the effects of IPC may be task dependent.…”

Ischemic Preconditioning Did Not Affect Central and Peripheral Factors of Performance Fatigability After Submaximal Isometric Exercise

“…However, our data on central and peripheral determinants of performance fatigability as well as muscle activity, SmO 2 , and perceptual responses during exercise do not support this conclusion. Our results are in accordance with the outcomes of other studies that have neither found an increased exercise performance nor altered physiological and perceptual responses during and after submaximal and maximal exercise following IPC (Tocco et al, 2015;Sabino-Carvalho et al, 2017;Halley et al, 2018Halley et al, , 2019. Explanations for the discrepant outcomes of our study and that of Tanaka et al (2016) might be that they have not performed a warm-up after the interventions (IPC and the control condition) and before the fatigue protocol.…”

“…Recently, Halley et al (2018Halley et al ( , 2019 have found that IPC does not alter central and peripheral determinants of performance fatigability after maximal voluntary isometric and isokinetic exercise of the knee extensors compared to a sham treatment (SHAM). However, maximal voluntary contractions (MVC) induce complete or near-complete ischemia (Oranchuk et al, 2019), which renders modulations of blood flow due to IPC unlikely.…”

Effect of ischemic preconditioning and changing inspired O2fractions on neuromuscular function during intense exercise

“…However, whereas sEMG can provide an estimate of gross nervous system output, a multitude of unrelated factors contribute to the sEMG signal (18,20,21). In an attempt to address these limitations, we incorporated the interpolated twitch technique into two separate studies (24,25); however, we failed to observe any influence of IPC on sEMG amplitudes, voluntary activation, or any other additional central or peripheral measures of neural drive.…”