P97 Exploring the repeated bout effect in neuromuscular diseases

• Published in: Neuromuscular disorders : NMD 2023-10, Vol.33, p.S169-S169
• Main Authors: Stemmerik, M., Beha, G., Flensted, I., Slipsager, A., Vissing, J.
• Format: Article
• Language: English
• ISSN: 0960-8966; 1873-2364
• DOI: 10.1016/j.nmd.2023.07.404

The repeated bout effect (RBE) is mechanism where a single bout of unaccustomed eccentric exercise protects against muscle damage from subsequent bouts. Though the effect is well described in healthy, it has never been studied in patients with neuromuscular diseases (NMDs). In healthy, the RBE is only described using eccentric exercise, but unlike healthy persons, patients with NMDs can experience significant muscle damage with concentric exercise. This raises the question if patients with NMDs could also show RBE when performing concentric exercise. We are using an established concentric exercise intervention, shown to induce muscle damage in specific NMDs to characterize the RBE in these groups. Patients with either Limb-Girdle Muscular Dystrophy R9 (FKRP), Becker Muscular Dystrophy and McArdle disease underwent two exercise bouts consisting of a high-intensity interval cycling exercise followed by a strength training test with one month in-between. Blood was collected at rest and 0-, 2-, 4- and 24-hours post-exercise for measurement of Creatine Kinase (CK) and Myoglobin. Preliminary results from the first 10 participants show, that the first bout caused an increase from baseline to peak in CK of 5402 U/L SD 7991 U/L, and in Myoglobin of 2200 µg/L SD 2618 µg/L, while the second bout increased CK by 2671 U/L SD 6323 U/L and Myoglobin by 1280 µg/L SD 2769 µg/L. There was no significant difference in the biomarker-response (p-value 0,18 for CK and 0,22 for Myoglobin). Our results have shown a (non-significant) reduction in injury biomarkers between the first and second bout. More participants are planned to properly power the trial and to explore if this mechanism differs between the diseases. As the mechanisms for disease varies among NMDs, it is likely that some patients might experience RBE in a similar fashion to healthy, while others may not. Results from this trial will be important when planning trials involving both exercise and biomarker outcomes.