Effects of isometric handgrip (IHG) training of one forearm on reactive and exercise hyperaemia in the ipsilateral and contralateral arm of White European Young Men

There is evidence that IHG training reduces arterial blood pressure (ABP), particularly in hypertensive subjects and that it may also enhance reactive hyperaemia in the trained arm. We have tested in normotensive, young men, whether IHG improves reactive and exercise hyperaemia in the contralateral, untrained arm, which would be evidence of remote effects on dilator function. The study was performed on 10 recreationally active, White European men (18–25 years). IHG training comprised 4×3 min contractions at 30% Maximum voluntary contraction (MVC) at 5 min intervals, 4 days/week for 4 weeks, undertaken with the dominant arm. Before and after IHG training, forearm blood flow (FBF) was recorded by venous occlusion plethysmography in the trained arm and non‐trained contralateral arm, at rest and at intervals after 3‐mins arterial occlusion (reactive hyperemia), or 3‐min rhythmic handgrip contractions at 60% Maximum voluntary contraction (MVC; exercise hyperemia). As expected, MVC was increased after IHG training in the trained arm (29.0±1.3, vs 33.5±1.5*Kg, *: P< 0.01, paired t‐test), but not in the untrained arm (27.0±0.9 vs 27.1±0.9Kg). IHG training did not affect resting ABP: 124±1.8/70±1.7 vs 125±1.8/72±1.6 mmHg, or resting FBF: 4–9±0.9 vs 5.1±0.8 ml.min −1 .100ml −1 in dominant arm before vs after IHG training. However, reactive hyperaemia was increased in both the trained arm and non‐trained arm by IHG training: peak FBF increased from 41.4±1.9 to 50.8±2.0* ml.min −1 . 100ml −1 (*: P< 0.01 RMANOVA) in the trained arm, and from 41.3±4.8 to 52.8 ± 1.7* ml.min −1 . 100ml −1 in the non‐trained arm. Further, exercise hyperaemia was increased in both arms by IHG training, peak FBF was increased from 75.6±2.5 to 110.2±2.6* ml.min −1 . 100ml −1 in the trained arm and from 77.8±9.4 to 101.1±2.9* ml.min −1 . 100ml −1 . These results indicate that in healthy young men, IHG training of one arm for 4 weeks improves peak muscle power and induces a parallel increase in exercise hyperaemia associated with submaximal isometric contraction in the trained arm. In addition, our results indicate for the first time, that not only is there a concomitant increase in reactive hyperaemia in the trained arm, but also a substantial increase in reactive hyperaemia and in exercise hyperaemia to submaximal contraction in the contralateral, non‐trained arm, in the absence of a change in muscle power. The mechanisms underlying these changes remain to be determined but we propose that they reflect a generalised beneficial effect of IHG training on endothelial dilator function. Support or Funding Information Alexander S. Onassis Public Benefit Foundation