Delayed-Onset Muscle Soreness Mimics a Tendency Towards a Positive Romberg Test

Delayed-onset muscle soreness (DOMS) is induced by unaccustomed and/or strenuous repetitive eccentric or isometric contractions. However, the exact mechanism of DOMS is far from entirely known for more than 120 years. A recent neurocentric DOMS theory proposes that DOMS is a non-contact acute compression axonopathy initiated on the intrafusal proprioceptive Type Ia terminal, in the form of an autonomously acquired transient Piezo2 channelopathy under eccentric/isometric contractions and allostatic stress. The current study was executed on seventeen young male handball players in the Hungarian National Handball Academy. A dynamometer-based eccentric exercise protocol was used in order to induce DOMS and stabilometry was used to measure postural sway before and right after the aforementioned DOMS inducing exercise protocol. The findings of this DOMS study is in contrast to fatigue related ones, namely it decreased sway with open eyes. Furthermore, closed eyes did not reduce antero-posterior postural sway due to DOMS effect, like it is observed in fatigue, in fact it increased it. Hence, both open and closed eye related DOMS findings are in contrast to the fatigue related ones, where sway was increased when eyes were open and antero-posterior postural sway was reduced when eyes were closed. The closed eye finding due to DOMS effect is an analogous tendency towards a positive Romberg test. Indeed, a positive Romberg test is indicative of impaired proprioceptive signaling in neurology and Piezo2 is the principal mechanosensory ion channel responsible for proprioception. In summary, our study suggests that a reflex-like compensatory postural control enhancement is initiated in response to closed eyes when fatigue is the underlying factor, however this reflex-like compensatory mechanism is impaired due to DOMS effect, resulting in enhanced antero-posterior and left-right postural sway. This observation may have relevance in the higher risk of sport injuries due to DOMS effect, not to mention that stabilometry provides a differential diagnostic method to distinguish between fatigue and DOMS related proprioceptive microdamage.