Author(s): MCDONALD, T., WU, A.; COLLINS, S.; SOMANI, Y.B, Institution: UNIVERSITY OF LEEDS, Country: UNITED KINGDOM, Abstract-ID: 2283

INTRODUCTION:
Ischaemia–reperfusion (IR) contributes to vascular and cardiac injury in acute cardiovascular events and surgical settings. A single bout of dynamic handgrip exercise performed immediately prior to IR attenuates vascular endothelial injury in young, healthy individuals1 and in older adults with increased cardiovascular risk2. Dynamic handgrip exercise, performed in brief intervals, shares a similar pattern of tissue desaturation to ischaemic preconditioning1. Isometric handgrip exercise (IHG), a shorter protocol performed as sustained contractions, is known to lower blood pressure and improve vascular function with 4−12 weeks of training3, however, whether a single session confers acute protection against IR injury has not been studied. It is also unclear whether a single bout of handgrip exercise can provide short-term protection against vascular injury. Therefore, in this randomised crossover study, we aim to (1) compare the effects of acute isometric to acute dynamic handgrip exercise on endothelial responses to IR injury, and (2) assess these responses 24 hours following each exercise bout.
METHODS:
Seven healthy young adults (M/F: 4/3, age: 26 ± 4 years, BMI: 26.9 ± 3.1, resting BP: 117 ± 12 / 74 ± 10 mmHg) attended the laboratory on five occasions. During visit 1 (control), brachial artery flow-mediated dilation (FMD) was assessed before and after temporary endothelial IR injury, induced in the upper arm (15-minutes ischaemia, 15-minutes reperfusion). During visits 2 and 4, participants performed either dynamic (4 x 5 minutes, 40% maximal voluntary contraction [MVC], 25 contractions per min) or isometric handgrip (4 x 2 minutes, 50% MVC) in a randomised order prior to the IR protocol in the contralateral arm. Participants returned to the laboratory 24 hours after each exercise bout (visits 3 and 5) to repeat the IR protocol. A one-week washout was implemented between the two exercise modes. Data were analysed using general linear models.
RESULTS:
When assessing the acute effects of exercise, we found a significant overall decrease in FMD following IR injury (p<0.001). FMD decreased from pre- to post-IR in the control condition (9.2 ± 3.9% to 5.2 ± 3.8%, p=0.02), acute dynamic (7.1 ± 2.9% to 4.5 ± 2.6%, p=0.03) and acute isometric handgrip condition (8.8 ± 2.5% to 5.0 ± 1.8%, p= 0.01). A similar pre- to post-IR decline in FMD was also observed during the 24-hour follow-up sessions after both exercise modes (p<0.05).
CONCLUSION:
We show that IR injury significantly reduces endothelial function in young healthy individuals, and these responses are not attenuated when preceded by a single bout of dynamic or isometric handgrip exercise, both acutely and 24 hours following exercise. A larger sample may be required to fully interrogate these responses.
1. Bannell et al. Am J Physiol Regul Integr Comp Physiol 324, R329–R335 (2023).
2. Somani et al. Am J Physiol Regul Integr Comp Physiol 326, R79–R87 (2024).
3. Oliveira et al. J Hum Hypertens 37, 844–853 (2023).