Corticomotor plasticity following unilateral strength training

Introduction: We used transcranial magnetic stimulation (TMS) to investigate 3 weeks of unilateral leg strength training on ipsilateral motor cortex (iM1) excitability, and short-latency intracortical inhibition (SICI). Methods: Right leg dominant participants (n = 14) were randomly divided into either a strength training (ST) or control group. The ST group completed 9 training sessions (4 sets of 6 to 8 repetitions of single right leg squats). Results: We observed a 41% increase in right leg strength, and a 35% increase in strength of the untrained left leg (P < 0.01). There was a significant increase in motor evoked potential (MEP) amplitude recruitment curve for the untrained left leg (P < 0.01). SICI of the iM1 decreased by 21% for the untrained left leg (P < 0.01). Conclusions: The findings provide evidence for corticomotor adaptation for unilateral leg strength training within the iM1 that is modulated by changes in interhemispheric inhibition. Muscle Nerve 46: 384-393, 2012.     

Neural drive increases following resistance training in patients with multiple sclerosis

The present study tested the hypothesis that lower body progressive resistance training (PRT) increases the neural drive expressed as surface electromyographical (EMG) activity in patients with multiple sclerosis (MS). The study was a randomised controlled trial (RCT) including a 12-week follow up period. Thirty-eight MS patients were randomized to an exercise group (n = 19) or a control group (n = 19). During the intervention period, the exercise group performed a 12-week supervised lower body PRT program, whereas the control group maintained their usual daily activity level. After the 12 week intervention period, the exercise group were encouraged to continue training on their own for a 12-week follow up period, while the control group completed the 12-week supervised PRT program. Surface EMG was recorded from vastus lateralis, rectus femoris and semitendinosus during maximal isometric knee extension and knee flexion, before and after the intervention and at follow up. From the recordings, the area under the rectified, low-pass filtered EMG signal (integrated EMG, iEMG) was calculated. Muscle strength was expressed as the angular impulse (AI) and was measured during the same period as the iEMG. After PRT significant improvements for iEMG of vastus lateralis and rectus femoris during maximal knee extension and for semitendinosus during maximal knee flexion and for AI during both maximal knee extension and flexion were found in the exercise group, when compared to the control group. When compared to the post values, all effects, except for AI during knee flexion, were maintained at follow up in the exercise group. When the control group was exposed to PRT, a similar pattern of improvements were found, albeit not all improvements were significant. In conclusion twelve weeks of intense PRT of the lower extremities improved the neural drive expressed as maximal surface EMG activity in patients with MS, with effects persisting 12 weeks after the intervention. The study was registered at clinicalTrials.gov, Protocol no. NCT00381576.     

Reduction of tremor severity and disability following behavioral relaxation training.

The effects of behavioral relaxation training (BRT) for the treatment of moderate to severe essential tremor (ET) was evaluated with two older adults, ages 73 and 83, using a single-case design and statistical analysis. Measures included within-session clinician and self-rated tremor severity and disability in activities of daily living (ADL), EMG activity, and daily self-ratings of tremor severity and ADL disabilities. Following a brief 2-4 week baseline period BRT was conducted. Clinically significant reductions of 47-66% in within session clinical and self-rated tremor severity and daily self-ratings were obtained. Statistically significant changes in self- and clinician ratings occurred following BRT. In some cases, EMG activity also declined following intervention. Results at a seven week follow up were mixed and related to continued use of relaxation skills. While the cost ratio (medication: BRT) indicates that relaxation training is more expensive relative to standard medical intervention, cost-benefit to patients off sets the financial difference. Relaxation training may be an efficacious first step in a biobehavioral stepped care treatment model.     

Knee extensor strength, activation, and size in very elderly people following strength training.

Muscle strength, activation, and size were studied in 11 very elderly subjects (8 women and 3 men; age range, 85-97 years) who completed 12 weeks of strength training of the knee extensor muscles. Training increased the maximum amount of weight that could be lifted once (134%; P < 0.05) and maximum voluntary isometric strength, measured as both force recorded at the ankle with the knee flexed 90 degrees (17%, ns) and as torque with the knee flexed 60 degrees (37%; P < 0.05). Anatomical lean quadriceps cross-sectional area (LCSA) measured at midthigh using magnetic resonance imaging increased from 27.5 +/- 9.6 cm2 to 30.2 +/- 10.0 cm2 (9.8%; P < 0. 05) after training. Both before and after training, isometric strength was closely related to LCSA, but training resulted in no significant change in muscle force per unit area of quadriceps muscle. Using the twitch interpolation technique, muscle activation during a maximal voluntary isometric contraction was shown to be incomplete in all subjects before training (ranging from 69% to 93%) and was not significantly increased after training. An increase in skeletal muscle mass may have important functional and metabolic benefits for very elderly people.     

Randomized controlled trial of strength training in post-polio patients

Many post-polio patients develop new muscle weakness decades after the initial illness. However, its mechanism and treatment are controversial. The purpose of this study was to test the hypotheses that: (1) after strength training, post-polio patients show strength improvement comparable to that seen in the healthy elderly; (2) such training does not have a deleterious effect on motor unit (MU) survival; and (3) part of the strength improvement is due to an increase in voluntary motor drive. After baseline measures including maximum voluntary contraction force, voluntary activation index, motor unit number estimate, and the tetanic tension of the thumb muscles had been determined, 10 post-polio patients with hand involvement were randomized to either the training or control group. The progressive resistance training program consisted of three sets of eight isometric contractions, three times weekly for 12 weeks. Seven healthy elderly were also randomized and trained in a similar manner. Changes in the baseline parameters were monitored once every 4 weeks throughout the training period. The trained post-polio patients showed a significant improvement in their strength (P < 0.05). The magnitude of gain was greater than that seen in the healthy elderly (mean +/- SE, 41 +/- 16% vs. 29 +/- 8%). The training did not adversely affect MU survival and the improvement was largely attributable to an increase in voluntary motor drive. We therefore conclude that moderate intensity strength training is safe and effective in post-polio patients.     

Lack of muscle stem cell proliferation and myocellular hypertrophy in sIBM patients following blood-flow restricted resistance training

Sporadic inclusion body myositis (sIBM) is characterised by skeletal muscle inflammation, progressive muscle loss and weakness, which is largely refractory to immunosuppressive treatment. Low-load blood-flow restricted (BFR) training has been shown to evoke gains in myofibre cross sectional area (mCSA) in healthy adults. This could partially be due to the activation and integration of muscle satellite cells (SC) resulting in myonuclei addition. Consequently, this study investigated the effect of 12-weeks lower limb low-load BFR resistance training in sIBM patients on SC and myonuclei content, myofibre size and capillarization. Muscle biopsies from sIBM patients randomised to 12-weeks of low-load BFR resistance training (n = 11) or non-exercising controls (CON) (n = 9) were analysed for SC and myonuclei content, myofibre size and capillarization using three-colour immunofluorescence microscopy and computerised quantification procedures. No between-group differences (time-by-group interactions) or within-groups changes were observed for resident SCs (Pax7⁺/Six1⁺), proliferating SCs (Pax7⁺/ Ki67⁺), myonuclei (Six1⁺), type 1 mCSA or capillary number (CD31⁺). However, a time-by-group interaction for type 2 mCSA was observed (p = 0.04). Satellite cell content, myonuclei number, mCSA and capillary density remained unaffected following 12-weeks low-load BFR resistance training, indicating limited myogenic capacity and satellite cell plasticity in long-term sIBM patients.     

Muscle strength enhancement following home-based virtual cycling training in ambulatory children with cerebral palsy

This study is the first well-designed randomized controlled trial to assess the effects of a novel home-based virtual cycling training (hVCT) program for improving muscle strength in children with spastic cerebral palsy (CP). Twenty-eight ambulatory children with spastic CP aged 6-12 years were randomly assigned to an hVCT group (n=13) or a control group (n=15). Outcome measures, including gross motor function of the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) and muscle strength (isokinetic torque of knee extensor and flexor muscle), were administered before and immediately after the 12-week intervention. Analysis of covariance (ANCOVA) at post-treatment showed that, compared to the control group, the hVCT group had significantly higher isokinetic torque in the knee extensor and flexor muscles at 60°/s and 120°/s angular velocities (p<0.05). At post-treatment, the hVCT group also showed greater isokinetic strength improvement in the knee flexor than in the knee extensor at 60°/s (knee flexor: 41%; knee extensor: 19%) and at 120°/s (knee flexor: 36%; knee extensor: 30%). However, the BOTMP scores at post-treatment did not differ between the two groups. Although the proposed 12-week hVCT protocol does not improve gross motor function, it enhances knee muscle strength in children with CP. The protocol obtains larger gains in the knee flexor than in the knee extensor at different angular velocities. The study findings will help clinicians to provide more effective and efficient strategies for muscle strength training in children with CP.     

The effect of a combined strength and proprioceptive training on muscle strength and postural balance in boys with intellectual disability: An exploratory study

The aim of our study was to investigate the effect of a combined strength and proprioception training (CSPT) program on muscle strength and postural balance in children with intellectual disability (ID). The maximum voluntary contraction (MVC) and postural parameters (CoP_Vm, CoP_LX, CoP_LY) of 20 children with ID were recorded before and after 8 weeks of a CSPT program. The participants were divided into two groups: an experimental group who attended a CSPT program and a control group who continued with daily activities. In the trained group, the MVC increased significantly (p < 0.001) after the training period and the postural parameters decreased significantly in Double-Leg Stance (DLS) and One-Leg Stance (OLS) during the firm surface condition as well as in the DLS during the foam surface condition; in both eyes open (EO) and eyes closed (EC) conditions. A CSPT program improves postural balance in children with ID could be due to the enhancement in muscle strength and proprioceptive input integration.     

Penicillin CSF levels following intravenous therapy in syphilitic patients

Serum and CSF levels of penicillin have been determined in 13 syphilitic patients treated with relatively high doses of penicillin G by the intravenous route. Wide individual variability in the CSF/serum concentration ratio was observed. In all patients the concentration of the antibiotic in the CSF was equal to or greater than 0.03 IU/ml., which is considered to be the minimal therapeutic concentration. The potential clinical usefulness of different therapeutic regimens in the treatment of neurosyphilis is discussed.     

Glutathione S-transferase polymorphisms in MS: their relationship to disability

BACKGROUND: Oxidative stress has been implicated in inflammatory demyelination. The glutathione S-transferase (GST) supergene family encodes isoenzymes that appear to be critical in protection against oxidative stress. Certain GST loci are polymorphic, demonstrating alleles that are null (GSTM1/GSTT1), encode low activity variants (GSTP1), or are associated with variable inducibility (GSTM3). OBJECTIVES: To investigate the association between clinical outcome in MS and allelic variants of GSTM1, GSTM3, GSTT1, and GSTP1. METHODS: Four hundred patients with clinically definite MS were studied. Disability was measured using the Kurtzke Expanded Disability Status Scale (EDSS). Disability was graded as mild (EDSS 0-4), moderate (4.5-5.5), or severe (EDSS 6-10). PCR-based genotyping was performed using DNA extracted from lymphocytes. Significant associations between GST genotypes and clinical outcome were corrected for gender, onset age, and disease duration using logistic regression. Results: We found that the GSTM3 AA genotype was associated with severe disability in patients with a disease duration of more than 10 years (p = 0.027, n = 177, OR = 2.4, 95% CI = 1.1-5.0). Homozygosity for both GSTM1*0 and GSTP1*Ile105 containing allele was associated with severe disability in patients with a disease duration greater than 10 years (p = 0.022, n = 179, OR = 5.0, 95% CI = 1.3-19.8). CONCLUSIONS: Our results suggest that long-term prognosis in MS is influenced by a genetically determined ability to remove the toxic products of oxidative stress.     

Optimizing the association between disability and biological markers in MS

OBJECTIVE: Axonal damage is an important feature of MS pathology and the likely substrate of development of progressive disability. Brain volume measurement on MRI can be used as an overall marker of tissue damage and axonal loss. The authors studied the relation of brain volume measurements with the MS Functional Composite (MSFC) in an attempt to improve the clinico-radiologic association. METHODS: In 137 patients with MS (80 relapsing-remitting [RR], 36 secondary progressive [SP], and 21 primary progressive [PP]) and 12 healthy controls, a brain MRI scan was obtained. Patients also underwent MSFC and Expanded Disability Status Scale (EDSS) assessments. MRI analysis included determination of hypointense T1- and hyperintense T2-weighted lesion load, and two brain volume measurements: 1) the parenchymal fraction (PF): whole brain parenchyma/intracranial volume; and 2) the ventricular fraction (VF): ventricular volume/whole brain parenchyma. RESULTS: The median PF was smaller and the median VF larger in the patient group (0.81 for PF and 0.029 for VF) than in the control group (0.87 for PF, p < 0.001; and 0.013 for VF, p < 0.01). For the patient population, moderate correlations were found between brain volume measurements and MSFC (0.36 for PF and -0.40 for VF). Patients with short disease duration showed a correlation of MSFC with both brain and lesion volume measurements on MRI, whereas patients with long disease duration only showed a correlation with brain volume measurements. CONCLUSION: Brain volume measurements are correlated with disability as assessed by the MSFC. Although in the early phase of the disease the amount of focal demyelination is important, the residual brain volume seems to be more relevant in determining disability in later phases of the disease.     

Corticospinal responses following strength training: a systematic review and meta‐analysis

Strength training results in changes in skeletal muscle; however, changes in the central nervous system also occur. Over the last 15 years, non‐invasive brain stimulation techniques, such as transcranial magnetic stimulation, have been used to study the neural adaptations to strength training. This review explored the hypothesis that the neural adaptations to strength training may be due to changes in corticospinal excitability and inhibition and, such changes, contribute to the gain in strength following strength training. A systematic review, according to PRISMA guidelines, identified studies by database searching, hand‐searching and citation tracking between January 1990 and the first week of February 2017. Methodological quality of included studies was determined using the Downs and Black quality index. Data were synthesised and interpreted from meta‐analysis. Nineteen studies investigating the corticospinal responses following strength training were included. Meta‐analysis found that strength training increased strength [standardised mean difference (SMD) 0.84, 95% CI 0.55 to 1.13], decreased short‐interval intracortical inhibition (SMD ?1.00, 95% CI ?1.84 to ?0.17) and decreased the cortical silent period (SMD ?0.66, 95% CI ?1.00 to ?0.32). Strength training had no effect on motor threshold (SMD ?0.12, 95% CI ?0.49 to 0.25), but a borderline effect for increased corticospinal excitability (SMD 0.27, 95% CI 0.00 to 0.54). In untrained healthy participants, the corticospinal response to strength training is characterised by reduced intracortical inhibition and cortical silent period duration, rather than changes in corticospinal excitability. These data demonstrate that strength training targets intracortical inhibitory networks within the primary motor cortex (M1) and corticospinal pathway, characterising an important neural adaptation to strength training.