Impact of Priming Exercise Load in Vascular Occlusion Test Outcomes

Authors

Wonjae Lee, University of North TexasFollow
Elizabeth G. Knoll, University of North TexasFollow
Joshua L. Keller, University of North TexasFollow

Abstract

Near-infrared spectroscopy combined with a vascular occlusion test (NIRS-VOT) assesses microvascular function by analyzing tissue oxygen saturation (StO₂). StO₂-derived outcomes from the NIRS-VOT have been shown to differ across biological sex and fitness and are interpreted as reflecting differences in muscle oxidative capacity, microvascular function, and endothelial health. These differences may be influenced by the accumulation of metabolic byproducts that modulate local oxygen delivery. Exercise performed before a NIRS-VOT can alter metabolic rate, potentially influencing StO₂ responses. However, it is unclear whether different submaximal priming exercise intensities affect NIRS-VOT outcomes, particularly when the magnitude of the ischemic stimulus is standardized. Clarifying this is important for improving the interpretation and mechanistic understanding of NIRS-VOT. PURPOSE: The purpose of this study was to examine changes in StO2-derived outcomes following two distinct submaximal, non-fatiguing handgrip exercise tasks. METHODS: 6 healthy adults (5 men; 27 ± 7 yrs; 76.1 ± 8.0 kg) completed two NIRS-VOT on two separate visits. The NIRS-VOT protocol included a cuff wrapped around the participants’ upper arm and inflated to 250 mmHg. After baseline, the cuff was inflated until StO₂ reached 40% or for up to 5 minutes. A 30-s linear slope coefficient was calculated during the transient ischemia phase and defined as Downslope. Once 40% StO₂ or the 5-min limit was observed, the cuff was deflated, and re-saturation metrics were calculated. These included Upslope (linear slope coefficient across the first 10 seconds of reperfusion) and StO_2max (the greatest StO₂ value observed during reperfusion). Subsequently, maximum handgrip strength (MVIC) was measured to determine exercise loads. Participants were randomized to one of two volume-matched priming exercise protocols: 60 static handgrips at 25% MVIC or 20 static handgrips at 75% MVIC. Following the exercise, NIRS-VOT was immediately repeated. For each outcome, a two-way repeated-measures ANOVA was conducted with Condition (25% vs. 75%) and Time (pre vs post). A p<0.05 was considered significant; values are presented as mean ± standard deviation. RESULTS: For Upslope, there was no significant Condition × Time interaction (p = .250), but there was a significant main effect of Time (p = .007). Pairwise comparisons indicated that upslope (collapsed across condition) increased from pre- to post-exercise (2.19 ± 0.58 vs. 2.95 ± 0.47%· s^-1; p < .001). For Downslope, there was significant interaction or no main effect. For StO_2max, there was no significant Condition × Time interaction (p = .349); however, there was a significant main effect of Time (p = .003), indicating a decrease from pre- to post-exercise (78.2 ± 4.2 vs. 73.3 ± 3.5%; p < .001). CONCLUSION: Handgrips performed prior to a NIRS-VOT augment reactive hyperemia, indicating that upslope is sensitive to exercise-induced metabolic perturbations. Individuals with faster re-saturation may generate greater concentrations of vasoactive metabolites, reflecting higher metabolic rate and superior skeletal muscle health. However, responsive hyperemia, as defined by StO_2max, may be influenced by other mechanisms, such as mechano-signaling. Future studies should leverage this model to examine various interindividual differences in microvascular function.

Recommended Citation

Lee, Wonjae; Knoll, Elizabeth G.; and Keller, Joshua L. (2026) "Impact of Priming Exercise Load in Vascular Occlusion Test Outcomes," International Journal of Exercise Science: Conference Proceedings: Vol. 2: Iss. 18, Article 58.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss18/58