Sex-Specific Impact of Ischemic Preconditioning on Tissue Oxygenation and Maximal Concentric Force

Abstract

Prior peripheral hypoxia induced via remote ischemic preconditioning (IPC) can improve physical performance in male athletes through improved O2 delivery and utilization. Since females may have an innate protective mechanism against ischemia-reperfusion injury, and since muscle metabolism during contraction differs between sexes, it is relevant to examine the impact of sex in response to IPC to determine whether it is also ergogenic in females. In a randomized, crossover, single-blind study, we investigated muscle performance, hemodynamic and O2 uptake in strength-trained males (n = 9) and females (n = 8) performing five sets of 5 maximum voluntary knee extensions on an isokinetic dynamometer, preceded by either IPC (3 × 5-min ischemia/5-min reperfusion cycles at 200 mmHg) or SHAM (20 mmHg). Changes in deoxy-hemoglobin (Δ[HHb], expressed in percentage of arterial occlusion and considered an index of O2 extraction), and total hemoglobin (Δ[THb]) concentrations of the vastus lateralis muscle were continuously monitored by near-infrared spectroscopy. The metabolic efficiency of the contractions was calculated as the average force/Δ[HHb]avg ratio. Cohen's effect sizes (ES) ± 90% confidence limits were used to estimate IPC-induced changes and sex differences. IPC increased total muscular force in males only (13.0%, ES 0.64, 0.37;0.90), and this change was greater than in females (10.4% difference, ES 0.40, 0.10;0.70). Percent force decrement was only attenuated in females (−19.8%, ES −0.38, −0.77;0.01), which was clearly different than males (sex difference: ES 0.45, −0.16;1.07). IPC also induced different changes between sexes for average muscle O2 uptake in set 2 (males: 6.4% vs. females: −16.7%, ES 0.21, −0.18;0.60), set 3 (males: 7.0% vs. females: −44.4%, ES 0.56, −0.17;1.29), set 4 (males: 9.1% vs. females: −40.2%, ES 0.51, −0.10;1.13), and set 5 (males: 10.2% vs. females: −40.4%, ES 0.52, −0.04;1.09). However, metabolic efficiency was not meaningfully different between conditions and sexes. IPC increased muscle blood volume (↑[THb]) at rest and during recovery between sets, to the same extent in both sexes. Despite a similar IPC-induced initial increase in O2 delivery in both sexes, males displayed greater peripheral O2 extraction and greater strength enhancement. This ergogenic effect appears to be mediated in part via an up regulated oxidative function in males. We conclude that strength-trained males might benefit more from IPC than their female counterparts during repeated, maximal efforts.

The effect of ischaemic preconditioning on central and peripheral fatiguing mechanisms in humans following sustained maximal isometric exercise

“…This would suggest that IPC induced an increase in oxygen delivery to the exercising muscle. This finding is similar to that of Paradis‐Deschênes, Joanisse, and Billaut (), whereupon IPC increased oxygenation throughout a repeated, maximal voluntary knee‐extension task (16% increase in oxygen delivery; d = 0.36 ± 0.86). This consistent effect of increased oxygen delivery might be attributable, in part, to improved endothelial function resulting from the release of blood‐borne chemical vasodilators induced by IPC (Downey, Davis, & Cohen, ; Jones & Bolli, ; Kimura et al ., ).…”

“…However, sEMG measures are influenced by multiple factors, rendering comparisons between electrical activity within the muscle and neural drive inappropriate (Dimitrova & Dimitrov, ; Farina et al., ). Alternatively, these increases in sEMG signals might in fact be related to humoral benefits induced by IPC enabling an increase in skeletal muscle performance (Bailey et al., ; Lindsay et al., ; Paradis‐Deschênes et al., , ). As such, prior observations of increased sEMG activity might have been a byproduct of IPC‐augmented humoral pathways, rather than a direct neural response.…”

Ischemic preconditioning does not alter muscle sympathetic responses to static handgrip and metaboreflex activation in young healthy men

“…Indeed, IPC has been shown to possess analgesic effects (Pereira et al. ), although not tested specifically in skeletal muscle. Notwithstanding that PECO procedures can also activate central pain pathways (Macefield and Henderson ), SHG at 30% MVC has been shown consistently to increase MSNA during the second minute of contraction coincident with increased metabolite accumulation (a more rapid response as compared to prolonged ischemia), which is maintained during isolation of the metaboreflex with PECO (Mitchell et al.…”

“…Recruitment was confined to men as women have been reported to have blunted ergogenic responses to IPC (Paradis‐Deschênes et al. ) and smaller exercise pressor responses to SHG and PECO (Ettinger et al. ).…”

Ischemic Preconditioning Enhances Performance and Erythrocyte Deformability of Responders

“…But the results are very heterogeneous, showing beneficial [3,9,10,13,19,20,28,31,38,45,51], detrimental [2,48], and no effects [7, 14-16, 23, 34, 42, 43, 55, 56, 61] of IPC on performance. The different performance outcomes might be due to an inconsistency of influencing variables such as gender [50], and training status of the subjects (highly trained [28] or recreationally active [61]), included number of occlusion and reperfusion cycles [2,3], applied body sites (arm [34] or leg [56]), type of exercise (cycling [19], running [55], swimming [13], or resistance [54]), length of exercise (short/sprint [16], long distance [56], or incremental exercise [20]), and time duration between the end of the IPC manoeuvre and start of physical exercise [40]. Studies that used an incremental cycle ergometer test to evaluate performance in response to an IPC intervention also showed inconsistent performance outcomes [7,9,20].…”