Background: Lack of dystrophin in skeletal muscle leads to disruptions in nitric oxide signaling, potentially reducing blood flow to contracting muscles and contributing to fatigue and muscle damage. The MRI post-contractile blood oxygen level-dependent (BOLD) response has shown promise in evaluating microvascular function in lower extremities of dystrophic muscle. However, its feasibility in upper extremity muscles has been less established. The objective of this study was to to assess the reproducibility of post-contractile BOLD response parameters in the biceps brachii (BB) following arm flexion muscle contractions.
Methods: Six participants (age 23.5±12.9 years) underwent MRI assessments during two separate sessions. Participants performed five brief maximal isometric arm flexion contractions, each separated by one minute, during which dynamic BOLD imaging was acquired. The BOLD response after contractions were analyzed in the BB for peak response, time to peak, and half-recovery time. Reproducibility was evaluated using the coefficient of variation (CV) for inter-session variability.
Results: The MRI protocol with maximal isometric contractions was successfully completed by each participant with adequate image quality. An increase in signal intensity was observed following the contractions in each subject, indicating an increase in oxygen availability relative to utilization. The average peak response after contractions was 6.0±1.3%, with a time to peak of 6.3±1.4 s, and half recovery time of 9.4±3.6 s. There was excellent inter-session reproducibility in peak response (CV: 6.6±4.6%) and time to peak (CV: 6.6±5.0%), with more variability in half recovery time (CV: 23.8±18.0%).
Conclusions: Our findings indicate that the post-contractile BOLD response in the BB muscle demonstrates adequate inter-session reproducibility, supporting its potential as a non-invasive marker of microvascular function. Further research will aim to validate in non-ambulatory individuals with muscular dystrophies. Funding support: DOD/DMDRP, MD230025