Neural adaptations in quadriceps muscle after 4 weeks of local vibration training in young versus older subjects

Abstract

This study investigated the effects of a 4-week local vibration training (LVT) on the function of the knee extensors and corticospinal properties in healthy young and older subjects. Seventeen subjects (9 young and 8 older) performed 3 testing sessions: before (PRE) and after (PRE) a 4-week resting period to control the repeatability of the data as well as after the LVT (POST). Jump performance, maximal voluntary contraction (MVC) and electromyographic (EMG) activity on vastus lateralis and rectus femoris muscles were assessed. Single-pulse transcranial magnetic stimulation (TMS) allowed evaluation of cortical voluntary activation (VA), motor evoked potential (MEP) area, and silent period (SP) duration. All training adaptations were similar between young and older subjects (p > 0.05) and the following results reflect the pooled sample of subjects. MVC (+11.9% ± 8.0%, p < 0.001) and VA (+3.6% ± 5.2%, p = 0.004) were significantly increased at POST compared with PRE. Maximal vastus lateralis EMG was significantly increased at POST (+21.9% ± 33.7%, p = 0.03). No changes were reported for MEPs on both muscles (p > 0.05). SPs recorded during maximal and submaximal contractions decreased in both muscles at POST (p < 0.05). Vertical jump performance was increased at POST (p < 0.05). LVT seems as effective in young as in older subjects to improve maximal functional capacities through neural modulations occurring at least partly at the supra-spinal level. Local vibration may be used as an efficient alternative training method to improve muscular performance in both healthy young and older subjects.

Specific motor cortex hypoexcitability and hypoactivation in COPD patients with peripheral muscle weakness

“…In the current study, the mean TMS voluntary activation using a figure-of-eight coil was 89% in the healthy elderly controls and 92% in the patients without muscle weakness. In a previous study using a double-cone coil on the same muscle group and on a similar population (healthy elderly), mean TMS voluntary activation was 90% [61].…”

Intermediate Muscle Length and Tendon Vibration Optimize Corticospinal Excitability During Knee Extensors Local Vibration

“…Various muscle lengths have been used in studies that assessed the acute effects of LV to modulate neuromuscular function, i.e., knee angle of 75° ( Richardson et al, 2006 ), 90° ( Kouzaki et al, 2000 ; Konishi et al, 2002 , 2009 ; Jackson and Turner, 2003 ; Saito et al, 2016b ,a; Souron et al, 2017b ), 120° ( Fry and Folland, 2014 ), and 180° ( Iodice et al, 2011 ). Similarly, studies that investigated the effect of LV as a training method on the KE used various muscle lengths; some have applied LV at shortened muscle length, i.e., knee angle at 180° ( Iodice et al, 2011 ; Tankisheva et al, 2015 ) while others used intermediate muscle length, i.e., knee angle at 90° ( Souron et al, 2017a ). The initial muscle state at which LV is applied is another parameter to consider since it significantly influences muscle spindles sensitivity ( Vallbo, 1974 ; Burke et al, 1976b , 1978 ).…”

“…Therefore, in line with our recent works that investigated the acute ( Souron et al, 2017b ) and chronic effects ( Souron et al, 2017a ) of LV on neuromuscular function of the KE, the present study aimed to investigate the effects of muscle length and vibration site (i.e., muscle vs. tendon) on LV-induced changes in corticospinal excitability of the KE. We hypothesized that the increase in MEPs amplitude during LV would be higher at a knee angle corresponding to a lengthened quadriceps muscle because of the increased responses of Ia afferents at long muscle length ( Burke et al, 1976b ).…”

“…The vibrating device (VB 115, Techno Concept, Mane, France) was locally applied and strapped directly on (i) the right RF muscle (40% of the muscle length from the upper edge of the patella to the anterior superior iliac spine) ( Souron et al, 2017a , b ) and (ii) the mid-portion of the infrapatellar tendon ( Konishi et al, 2002 ; Fry and Folland, 2014 ) ( Figure 1B ). As Ia afferents are sensitive to a small vibration amplitude ( Roll et al, 1989 ) and fire synchronously with vibration frequencies up to 120 Hz ( Roll and Vedel, 1982 ; Roll et al, 1989 ), vibration was set in the present study with a 100-Hz frequency and 1-mm amplitude, as in our previous works on KE ( Souron et al, 2017a , b ). During the control condition (see the Experimental protocol section for further details), the vibrators were turned off but remained strapped to the RF and the infrapatellar tendon.…”

“…Since LV stimuli is a significant neuromuscular workload that induces fatigue, it is not surprising that when repeated, it could trigger long-term adaptations leading to improved neuromuscular function ( Souron et al, 2017c ), as already reported for traditional training that involved a variety of voluntary dynamic exercises, e.g., resistance training or cycling ( Burtin et al, 2012 ; Gathercole et al, 2015 ). Indeed, increased maximal-force generating capacity was recently reported after LV training performed on relaxed muscles over 14 to 180 days ( Lapole and Pérot, 2010 , 2012 ; Iodice et al, 2011 ; Lapole et al, 2013 ; Tankisheva et al, 2015 ; Souron et al, 2017a , d ). However, LV as a modality for neuromuscular conditioning remains relatively under-investigated and, more importantly, studies that have addressed this question have used a wide variety of protocols [see Souron et al (2017c) for a review].…”