The effects of whole-body vibration on the cross-transfer of strength

This study investigated whether the use of superimposed whole-body vibration (WBV) during cross-education strength training would optimise strength transfer compared to conventional cross-education strength training. Twenty-one healthy, dominant right leg volunteers (21&plusmn;3 years) were allocated to a strength training (ST, m = 3, f = 4), a strength training with WBV (ST + V, m = 3, f = 4), or a control group (no training, m = 3, f = 4). Training groups performed 9 sessions over 3 weeks, involving unilateral squats for the right leg, with or without WBV (35 Hz; 2.5mm amplitude). All groups underwent dynamic single leg maximum strength testing (1RM) and single and paired pulse transcranial magnetic stimulation (TMS) prior to and following training. Strength increased in the trained limb for the ST (41%; ES = 1.14) and ST + V (55%; ES = 1.03) groups, which resulted in a 35% (ES = 0.99) strength transfer to the untrained left leg for the ST group and a 52% (ES = 0.97) strength transfer to the untrained leg for the ST + V group, when compared to the control group. No differences in strength transfer between training groups were observed (P = 0.15). For the untrained leg, no differences in the peak height of recruitment curves or SICI were observed between ST and ST + V groups (P = 1.00). Strength training with WBV does not appear to modulate the cross-transfer of strength to a greater magnitude when compared to conventional cross-education strength training.<br /

Does the longer application of anodal-transcranial direct current stimulaton increase corticomotor excitability further? A pilot study

Introduction: Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) has been shown to be effective in increasing corticomotor excitability.　Methods: We investigated whether longer applications of a-tDCS coincide with greater increases in corticomotor excitability compared to shorter application of a-tDCS. Ten right-handed healthy participants received one session of a-tDCS (1mA current) with shorter (10 min) and longer (10+10 min) stimulation durations applied to the left M1 of extensor carpi radialis muscle (ECR). Corticomotor excitability following application of a-tDCS was assessed at rest with transcranial magnetic stimulation (TMS) elicited motor evoked potentials (MEP) and compared with baseline data for each participant.　Results: MEP amplitudes were increased following 10 min of a-tDCS by 67% (p = 0.001) with a further increase (32%) after the second 10 min of a-tDCS (p = 0.005). MEP amplitudes remained elevated at 15 min post stimulation compared to baseline values by 65% (p = 0.02).　Discussion: The results demonstrate that longer application of a-tDCS within the recommended safety limits, increases corticomotor excitability with after effects of up to 15 minutes post stimulation.<br /

Strength Training with Superimposed Whole Body Vibration Does Not Preferentially Modulate Cortical Plasticity

Paired-pulse transcranial magnetic stimulation (TMS) was used to investigate 4 wks of leg strength training with and without whole body vibration (WBV) on corticospinal excitability and short-latency intracortical inhibition (SICI). Participants (n = 12) were randomly allocated to either a control or experimental (WBV) group. All participants completed 12 squat training sessions either with (WBV group) or without (control group) exposure to WBV (f = 35 Hz, A = 2.5 mm). There were significant (P < 0.05) increases in squat strength and corticospinal excitability and significant (P < 0.05) reductions in SICI for both groups following the 4 wk intervention. There were no differences detected between groups for any dependant variable (P > 0.05). It appears that WBV training does not augment the increase in strength or corticospinal excitability induced by strength training alone

Corticospinal excitability following short-term motor imagery training of a strength task

Motor imagery and actual movement engage similar neural structures, however, whether they produce similar training-related corticospinal adaptations has yet to be established. The aim of this study was to compare changes in strength and corticospinal excitability following short-term motor imagery strength training and short-term strength training. Transcranial magnetic stimulation (TMS) was applied over the contralateral motor cortex (M1) to elicit motor-evoked potentials in the dominant biceps brachii muscle prior to and following 3-week strength training using actual bicep curls or motor imagery of bicep curls. The strength training (n = 6) and motor imagery (n = 6) groups underwent three supervised training sessions per week for 3 weeks. Participants completed four sets of six to eight repetitions (actual or imagined) at a training load of 80% of their one-repetition maximum. The control group (n = 6) were required to maintain their current level of physical activity. Both training groups exhibited large performance gains in strength (p &lt; 0.001; strength training 39% improvement, imagery 16% improvement), which were significantly different between groups (p = 0.027). TMS revealed that the performance improvements observed in both imagery and strength training were accompanied by increases in corticospinal excitability (p &lt; 0.001), however, these differences were not significantly different between groups (p = 0.920). Our findings suggest that both strength training and motor imagery training utilised similar neural substrates within the primary M1, however, strength training resulted in greater gains in strength than motor imagery strength training. This difference in strength increases may be attributed to adaptations during strength training that are not confined to the primary M1. These findings have theoretical implications for functional equivalent views of motor imagery as well as important therapeutic implications

High volume versus low volume balance training on postural sway in adults with previous ankle inversion injury

Balance training is commonly used in the rehabilitation process of ankle injuries; however, the exercise prescription guidelines for prescribing balance training are poorly understood. The aim of the present study was to determine if high or low volume balance training is more effective in improving postural sway after an 8 week balance training program utilising the same exercises. Seventeen subjects (14 male, 3 female) with a mean age of 24.06 &plusmn; 5.6 years were randomly allocated into a control group (CG), low volume training (LVT) or high volume training (HVT). All subjects had sustained at least two inversion ankle injuries within the last 18 months. Subjects completed 8 weeks of balance training of up to 30 mins duration, 3 times per week. LVT consisted of 40 repetitions for week 1, progressing to 90 repetitions by week 8. HVT consisted of 60 repetitions for week 1, progressing to 130 repetitions by week 8. The maximum centre of pressure (COP) excursion was obtained from the porce plate in the medial-lateral (ML) direction and subsequently used for pre-test and post-test analysis. After the 8 week training intervention, there was a significant (P&lt;0.001) difference in postural sway between pre and post testing for both the LVT (pre = 88.69mm &plusmn; 25.08mm, post = 72.17mm &plusmn; 27.53mm) and HVT (pre = 77.47mm &plusmn;10.57mm, post = 58.54mm &plusmn; 7.01mm) groups. There was no significant (P&gt;0.01) difference detected for improvements between the LVT and HVT, however reported effect sizes (ES) showed large effect size chances in the high volume training (ES = 1.7) whereas low volume training showed medium effect sizes changes (ES = 0.6). This preliminary study demonstrates the importance of training volume in the rehabilitation of ankle injuries, with the HVT being superior to LVT.<br /

The Effect of Task Complexity Influencing Bilateral Transfer.

International Journal of Exercise Science 10(8): 1174-1183, 2017. Bilateral transfer is a well-known phenomenon whereby training one limb results in improvement in the untrained homologous limb. However, despite evidence across a range of motor skill paradigms, the influence of motor skill complexity on the magnitude of bilateral transfer has not yet been fully explored. The aim of this preliminary study was to compare bilateral transfer effects between three dexterity tasks with the hypothesis that the complexity of the task, the volume of time training, and the amount of improvement in the trained hand would positively influence bilateral transfer. Using a randomized cross-over design, 14 young healthy participants (mean age of 22.6 ± 6.6 years; eight female) completed three finger dexterity tasks (O’Connor dexterity, Purdue pegboard, and Mirror Purdue pegboard tasks) with one week rest between each task. Each task required training with the participant’s dominant hand with pre and post testing in both the dominant and non-dominant hands. The Mirrored Purdue pegboard task showed the greatest rate of improvement in the dominant hand. Similarly, the greatest bilateral transfer effect was found in the Mirrored Purdue task. Interestingly, the amount of time training was not a factor associated with bilateral transfer. In conclusion, this study has demonstrated that the value of task complexity, but not the volume of practice, correlated with the magnitude of bilateral transfer to the non-dominant hand

Corticomotor excitability during precision motor tasks

The aim of this preliminary study was to investigate motor cortex (cortical) excitability between a similar fine visuomotor task of varying difficulty. Ten healthy adults (three female, seven male; 20—45 years of age) participated in the study. Participants were instructed to perform a fine visuomotor task by statically abducting their first index finger against a force transducer which displayed the level of force (represented as a marker) on a computer monitor. This marker was to be maintained between two stationary bars, also displayed on the computer monitor. The level of difficulty was increased by amplifying the position of the marker, making the task more difficult to control. Cortical measures of motor evoked potential (MEP) and silent period (SP) duration in first dorsal interosseous (FDI) muscle were obtained using transcranial magnetic stimulation (TMS) while the participant maintained the ‘‘easy’’ or ‘‘difficult’’ static task. An 11.8% increase in MEP amplitude was observed when subjects undertook the ‘‘difficult’’ task, but no differences in MEP latency or SP duration. The results from this preliminary study suggest that cortical excitability increases reflect the demand required to perform tasks requiring greater precision with suggestions for further research discussed

Game and training load differences in elite junior Australian football

Game demands and training practices within team sports such as Australian football (AF) have changed considerably over recent decades, including the requirement of coaching staff to effectively control, manipulate and monitor training and competition loads. The purpose of this investigation was to assess the differences in external and internal physical load measures between game and training in elite junior AF. Twenty five male, adolescent players (mean &plusmn;SD: age 17.6 &plusmn; 0.5 y) recruited from three elite under 18 AF clubs participated. Global positioning system (GPS), heart rate (HR) and rating of perceived exertion (RPE) data were obtained from 32 game files during four games, and 84 training files during 19 training sessions. Matched-pairs statistics along with Cohen\u27s d effect size and percent difference were used to compare game and training events. Players were exposed to a higher physical load in the game environment, for both external (GPS) and internal (HR, Session-RPE) load parameters, compared to in-season training. Session time (d = 1.23; percent difference = 31.4% (95% confidence intervals = 17.4 - 45.4)), total distance (3.5; 63.5% (17.4 - 45.4)), distance per minute (1.93; 33.0% (25.8 - 40.1)), high speed distance (2.24; 77.3% (60.3 - 94.2)), number of sprints (0.94; 43.6% (18.9 - 68.6)), mean HR (1.83; 14.3% (10.5 - 18.1)), minutes spent above 80% of predicted HRmax (2.65; 103.7% (89.9 - 117.6)) and Session-RPE (1.22; 48.1% (22.1 - 74.1)) were all higher in competition compared to training. While training should not be expected to fully replicate competition, the observed differences suggest that monitoring of physical load in both environments is warranted to allow comparisons and evaluate whether training objectives are being met. Key pointsPhysical loads, including intensity, are typically lower in training compared to competition in junior elite Australian football.Monitoring of player loads in team sports should include both internal and external measures.Selected training drills should look to replicate game intensities, however training is unlikely to match the overall physical demands of competition

Formation of cortical plasticity in older adults following tDCS and motor training

Neurodegeneration accompanies the process of natural aging, reducing the ability to perform functional daily activities. Transcranial direct current stimulation (tDCS) alters neuronal excitability and motor performance; however its beneficial effect on the induction of primary motor cortex (M1) plasticity in older adults is unclear. Moreover, little is known as to whether the tDCS electrode arrangement differentially affects M1 plasticity and motor performance in this population. In a double-blinded, cross-over trial, we compared unilateral, bilateral and sham tDCS combined with visuomotor tracking, on M1 plasticity and motor performance of the non-dominant upper limb, immediately post and 30 min following stimulation. We found (a) unilateral and bilateral tDCS decreased tracking error by 12&ndash;22% at both time points; with sham decreasing tracking error by 10% at 30 min only, (b) at both time points, motor evoked potentials (MEPs) were facilitated (38&ndash;54%) and short-interval intracortical inhibition was released (21&ndash;36%) for unilateral and bilateral conditions relative to sham, (c) there were no differences between unilateral and bilateral conditions for any measure. These findings suggest that tDCS modulated elements of M1 plasticity, which improved motor performance irrespective of the electrode arrangement. The results provide preliminary evidence indicating that tDCS is a safe non-invasive tool to preserve or improve neurological function and motor control in older adults

Priming the Motor Cortex With Anodal Transcranial Direct Current Stimulation Affects the Acute Inhibitory Corticospinal Responses to Strength Training

Synaptic plasticity in the motor cortex (M1) is associated with strength training and can be modified by transcranial direct current stimulation (tDCS). The M1 responses to strength training increase when anodal-tDCS is applied during training due to gating. An additional approach to improve the M1 responses to strength training, which has not been explored, is to use anodal-tDCS to prime the M1 before a bout of strength training. We examined the priming effects of anodal-tDCS of M1 on the acute corticospinal responses to strength training. In a randomized double-blinded cross-over design, changes in isometric strength, corticospinal-excitability and inhibition (assessed as area under the recruitment curve [AURC] using transcranial magnetic stimulation [TMS]) were analysed in 13 adults exposed to 20-min of anodal and sham-tDCS followed by a strength training session of the right elbow-flexors. We observed a significant decrease in isometric elbow-flexor strength immediately following training (11-12%; P < 0.05) which was not different between anodal-tDCS and sham-tDCS. TMS revealed a 24% increase in AURC for corticospinal-excitability following anodal-tDCS and strength training; this increase was not different between conditions. However, there was a 14% reduction in AURC for corticospinal inhibition when anodal-tDCS was applied prior to strength training when compared to sham-tDCS and strength training (all P < 0.05). Priming anodal-tDCS had a limited effect in facilitating corticospinal-excitability following an acute bout of strength training. nterestingly, the interaction of anodal-tDCS and strength training appears to affect the excitability of intracortical inhibitory circuits of the M1 via non-homeostatic mechanisms