ORCID Profile
0000-0002-2469-8787
Current Organisation
Università degli Studi di Verona
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Publisher: Elsevier BV
Date: 03-2015
Publisher: Wiley
Date: 29-09-2014
DOI: 10.1113/JPHYSIOL.2014.275438
Abstract: We aimed to elucidate the role of group III/IV locomotor muscle afferents in the development of central fatigue and the responsiveness of the corticospinal tract in relation to an unexercised arm muscle. Intrathecal fentanyl, a μ‐opioid receptor agonist, was employed to attenuate afferent feedback from the leg muscles during intense cycling exercise characterized by either no or severe peripheral locomotor muscle fatigue. In the absence of locomotor muscle fatigue, group III/IV‐mediated leg afferent feedback facilitates the responsiveness of the motor pathway to upper limb flexor muscles. By contrast, in the presence of leg fatigue, group III/IV locomotor muscle afferents facilitate supraspinal fatigue in a remote muscle not involved in the exercise and disfacilitate the responsiveness of associated corticospinal projections. We investigated the influence of group III/IV lower limb muscle afferents on the development of supraspinal fatigue and the responsiveness of corticospinal projections to an arm muscle. Eight males performed constant‐load leg cycling exercise (80% peak power output) for 30 s (non‐fatiguing) and to exhaustion (∼9 min fatiguing) both under control conditions and with lumbar intrathecal fentanyl impairing feedback from μ‐opioid receptor‐sensitive lower limb muscle afferents. Voluntary activation (VA) of elbow flexors was assessed via transcranial magnetic stimulation (TMS) during maximum voluntary contraction (MVC) and corticospinal responsiveness was monitored via TMS‐evoked potentials (MEPs) during a 25% MVC. Accompanied by a significant 5 ± 1% reduction in VA from pre‐ to post‐exercise, elbow flexor MVC progressively decreased during the fatiguing trial ( P 0.05). By contrast, with attenuated feedback from locomotor muscle afferents, MVC and VA remained unchanged during fatiguing exercise ( P 0.3). MEPs decreased by 36 ± 6% ( P 0.05) from the start of exercise to exhaustion under control conditions, but this reduction was prevented with fentanyl blockade. Furthermore, fentanyl blockade prevented the significant increase in elbow flexor MEP observed from rest to non‐fatiguing exercise under control conditions and resulted in a 14% lower corticospinal responsiveness during this short bout ( P 0.05). Taken together, in the absence of locomotor muscle fatigue, group III/IV‐mediated leg muscle afferents facilitate responsiveness of the motor pathway to upper limb flexor muscles. By contrast, in the presence of cycling‐induced leg fatigue, group III/IV locomotor muscle afferents facilitate supraspinal fatigue in remote muscle not involved in the exercise and disfacilitate, or inhibit, the responsiveness of corticospinal projections to upper limb muscles.
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.JSAMS.2011.02.013
Abstract: Soccer is a popular game practiced all around the world by teenagers. However, despite being a relatively safe sport, muscle-strain injuries during competitive matches are common compared to other team-sports. Few studies, to date, have investigated risk factors for soccer injuries using a multivariate survival model (e.g., Cox regression). The aim of this study was to use a multivariate survival model to investigate factors associated with an increased risk of thigh muscle strains, in young soccer players. A multivariate Cox regression was used to evaluate survival probability predictors for thigh muscle strains. 84 young male soccer players (16.4 ± 1.6 years) were followed for a season. Baseline tests were performed for body size, body composition, endurance, flexibility, and jump height from both a static position (SJ), and with a countermovement (CMJ) the percentage difference between the two types of jumps was also calculated (ΔJH). Cox regression result (hazard ratio C.I. 95%) showed that: previous injuries (2.80 1.19-6.54), ΔJH (0.79 0.71-0.87), and stature (1.17 1.06-1.25) were significantly correlated to thigh-strain survival probability. This study confirms that previous injuries are an important risk factor. However, we also report that a negative ΔJH and an elevated stature increased the probability of thigh strain. This could be explained by poor player coordination, influencing jumping ability, which may be even more evident in tall young players.
Publisher: American Physiological Society
Date: 11-2015
DOI: 10.1152/AJPHEART.00433.2015
Abstract: We investigated the influence of aging on the group III/IV muscle afferents in the exercise pressor reflex-mediated cardiovascular response to rhythmic exercise. Nine old (OLD 68 ± 2 yr) and nine young (YNG 24 ± 2 yr) males performed single-leg knee extensor exercise (15 W, 30 W, 80% max) under control conditions and with lumbar intrathecal fentanyl impairing feedback from group III/IV leg muscle afferents. Mean arterial pressure (MAP), cardiac output, leg blood flow (Q L ), systemic (SVC) and leg vascular conductance (LVC) were continuously determined. With no hemodynamic effect at rest, fentanyl blockade during exercise attenuated both cardiac output and Q L ∼17% in YNG, while the decrease in cardiac output in OLD (∼5%) was significantly smaller with no impact on Q L ( P = 0.8). Therefore, in the face of similar significant ∼7% reduction in MAP during exercise with fentanyl blockade in both groups, LVC significantly increased ∼11% in OLD, but decreased ∼8% in YNG. The opposing direction of change was reflected in SVC with a significant ∼5% increase in OLD and a ∼12% decrease in YNG. Thus while cardiac output seems to account for the majority of group III/IV-mediated MAP responses in YNG, the impact of neural feedback on the heart may decrease with age and alterations in SVC become more prominent in mediating the similar exercise pressor reflex in OLD. Interestingly, in terms of peripheral hemodynamics, while group III/IV-mediated feedback plays a clear role in increasing LVC during exercise in the YNG, these afferents seem to actually reduce LVC in OLD. These peripheral findings may help explain the limited exercise-induced peripheral vasodilation often associated with aging.
No related grants have been discovered for Massimo Venturelli.