Effects of Use and Disuse on Non-paralyzed and Paralyzed Skeletal Muscles

Brief High-Velocity Motor Skill Training Increases Step Frequency and Improves Length/Frequency Coordination in Slow Walkers With Chronic Motor-Incomplete Spinal Cord Injury

OBJECTIVE

To quantify spatiotemporal coordination during overground walking among persons with motor-incomplete spinal cord injury (PwMISCI) by calculating the step length (SL)/step frequency (SF) ratio (ie, the Walk Ratio [WR]) and to examine the effects of motor skill training (MST) on the relationship between changes in these parameters and walking speed (WS).

DESIGN

Between-day exploratory analysis.

SETTING

Research laboratory in a rehabilitation hospital PARTICIPANTS: PwMISCI (N=26).

INTERVENTIONS

3-day high-velocity MST.

MAIN OUTCOME MEASURES

Overground WS, SL, SF, and WR measured during the 10-Meter Walk Test.

RESULTS

Among the full sample, MST was associated with increases in WS, SL, SF, and a decrease in the WR. Relative change in WS and SF was higher among slow (ΔWS=↑46%, ΔSF=↑28%) vs fast (ΔWS=↑16%, ΔSF=↑8%) walkers. Change in the WR differed between groups (slow: ΔWR=↓10%; fast: ΔWR=0%). Twenty-six percent of the variability observed in ΔWR among slow walkers could be explained by ΔSF, while ΔSL did not contribute to ΔWR. Among fast walkers, ΔSL accounted for more than twice the observed ΔWR (43%) compared to ΔSF (15%).

CONCLUSIONS

On the whole, WR values among PwMISCI are higher than previous reports in other neurologic populations; however, values among fast walkers were comparable to noninjured adults. Slow walkers demonstrated greater variability in the WR, with higher values associated with slower WS. Following MST, increases in WS coincided with a decrease in the WR among slow walkers, mediated primarily through an effect on SF. This finding may point to a specific mechanism by which MST facilitates improvements in WS among PwMISCI with greater mobility deficits.

Lipid hydroperoxides promote sarcopenia through carbonyl stress

Reactive oxygen species (ROS) accumulation is a cardinal feature of skeletal muscle atrophy. ROS refers to a collection of radical molecules whose cellular signals are vast, and it is unclear which downstream consequences of ROS are responsible for the loss of muscle mass and strength. Here, we show that lipid hydroperoxides (LOOH) are increased with age and disuse, and the accumulation of LOOH by deletion of glutathione peroxidase 4 (GPx4) is sufficient to augment muscle atrophy. LOOH promoted atrophy in a lysosomal-dependent, proteasomal-independent manner. In young and old mice, genetic and pharmacological neutralization of LOOH or their secondary reactive lipid aldehydes robustly prevented muscle atrophy and weakness, indicating that LOOH-derived carbonyl stress mediates age- and disuse-induced muscle dysfunction. Our findings provide novel insights for the role of LOOH in sarcopenia including a therapeutic implication by pharmacological suppression.

Fat to lean mass ratio in spinal cord injury: Possible interplay of components of body composition that may instigate systemic inflammation and metabolic syndrome

OBJECTIVE

To investigate the relationships between percentage fat mass (%FM), percentage lean mass (%LM), and the ratio of %FM to %LM with pro-inflammatory adipokines and metabolic syndrome in individuals with chronic spinal cord injury (SCI).

DESIGN

Observational, cross-sectional. Linear and logistic regression were used to examine the associations between the %FM, %LM, and the %FM to %LM ratio with inflammatory markers and metabolic syndrome, respectively.

PARTICIPANTS

Seventy chronic SCI men and women.

MAIN OUTCOME MEASURES

%FM, %LM, %FM to %LM ratio; fasting lipids, glucose, and tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and high-sensitivity c-reactive protein (hs-CRP); metabolic syndrome as determined by The International Diabetes Federation criteria.

RESULTS

There were significant correlations between %FM, %LM and the %FM to %LM ratio with hs-CRP. The %LM beta coefficient value was negative and greater than the beta coefficient value for %FM. The %FM to %LM ratio had the strongest correlation with hs-CRP and showed the only significant relationship with IL-6. There were strong significant correlations between %FM, %LM and the %FM to %LM ratio with metabolic syndrome. However, the %FM to %LM ratio, again, showed the strongest relationship indicating that it may be the best predictor of metabolic syndrome.

CONCLUSION

Both higher %FM and lower %LM affect cardiometabolic health and can be used as predictors for metabolic syndrome. However, the %FM to %LM ratio was the best predictor of systemic inflammation and cardiometabolic disorders in this group of SCI participants, suggesting that they both contribute to the statistical model.

Novel treatment strategies for acetylcholine receptor antibody-positive myasthenia gravis and related disorders

The presence of autoantibodies directed against the muscle nicotinic acetylcholine receptor (AChR) is the most common cause of myasthenia gravis (MG). These antibodies damage the postsynaptic membrane of the neuromuscular junction and cause muscle weakness by depleting AChRs and thus impairing synaptic transmission. As one of the best-characterized antibody-mediated autoimmune diseases, AChR-MG has often served as a reference model for other autoimmune disorders. Classical pharmacological treatments, including broad-spectrum immunosuppressive drugs, are effective in many patients. However, complete remission cannot be achieved in all patients, and 10% of patients do not respond to currently used therapies. This may be attributed to production of autoantibodies by long-lived plasma cells which are resistant to conventional immunosuppressive drugs. Hence, novel therapies specifically targeting plasma cells might be a suitable therapeutic approach for selected patients. Additionally, in order to reduce side effects of broad-spectrum immunosuppression, targeted immunotherapies and symptomatic treatments will be required. This review presents established therapies as well as novel therapeutic approaches for MG and related conditions, with a focus on AChR-MG.

Effect of the Use of a Cream with Leucine and Lactic Acid Associated with Electrostimulation in Contouring and Facial Tonus: A Randomized Clinical Controlled Trial

Evidence has supported the use of leucine as a promising agent for the maintenance of muscle tone. This study aimed to assess the combined effect of leucine and cream-based lactic acid (novel cosmetic product), associated with the use of surface electrical stimulation to improve contour and facial tonus in women. A total of 23 women were randomly allocated into two groups: Experimental (EG)—use of the leucine-based cream and lactic acid + electrostimulation for facial toning (mean intensity 13 Hz and protocol in progression); and placebo (GP)—use of the placebo cream (without the addition of leucine and lactic acid) + stimulation with the same protocol as the EG. Each group used their cream daily and underwent the intervention protocol three x/week with stimulation for 40 min, for a total of 8 weeks. Three main outcomes were reported: angular variation of facial contour by means of photogrammetry, muscle tone through the electromyographic activity of the masseter and zygomatic muscles during rest and functional tasks of biting and smiling. A significant effect of the intervention and between the groups was obtained for the experimental group against the placebo group for facial contour and muscle tone. An increased muscular activity of the masseter (average 28%) when smiling, and a reduction of zygomatic activity (in average 41%) when biting were found. The use of cream containing leucine and lactic acid combined with electrostimulation contributes to the improvement of facial contour and muscle tone when biting and smiling.

Effects of resistance-guided high intensity interval functional electrical stimulation cycling on an individual with paraplegia: A case report

BACKGROUND AND PURPOSE

Individuals with spinal cord injury (SCI) are more than twice as likely to develop and die from cardio-metabolic diseases as compared to able-bodied. This increased risk is thought to be in part due to accelerated muscle atrophy and reduced blood flow through sublesional arteries. Thus, strategies to recondition paralyzed skeletal muscles may help reduce cardio-metabolic disease risk. The purpose of this case report was to examine the impact of a novel, resistance-guided, high intensity interval training functional electrical stimulation (RG-HIIT-FES) cycling program on cardio-metabolic health in people with chronic SCI.

CASE DESCRIPTION

One adult female with chronic T10 SCI.

INTERVENTION

A novel RG-HIIT-FES cycling program three times per week for 10 weeks. Measures of body composition and cardio-metabolic health (vascular endothelial function of the brachial artery via flow-mediated dilation) and HbA1c blood values were performed at baseline and following completion of the RG-HIIT-FES program.

OUTCOMES

Total body lean mass and legs lean mass increased 2.8% and 5.3% respectively while vastus lateralis thickness increased by 59.5%. Reactive hyperemia and flow mediated dilation change in brachial artery diameter increased by 11.1% and 147.7% following the program, respectively. HbA1c level changed minimally (5 to 4.9%).

DISCUSSION

This case report suggests that RG-HIIT-FES cycling was an effective strategy to improve lean mass, and systemic vascular endothelial health in an individual with chronic SCI.

Stair negotiation made easier using novel interactive energy-recycling assistive stairs

Here we show that novel, energy-recycling stairs reduce the amount of work required for humans to both ascend and descend stairs. Our low-power, interactive, and modular steps can be placed on existing staircases, storing energy during stair descent and returning that energy to the user during stair ascent. Energy is recycled through event-triggered latching and unlatching of passive springs without the use of powered actuators. When ascending the energy-recycling stairs, naive users generated 17.4 ± 6.9% less positive work with their leading legs compared to conventional stairs, with the knee joint positive work reduced by 37.7 ± 10.5%. Users also generated 21.9 ± 17.8% less negative work with their trailing legs during stair descent, with ankle joint negative work reduced by 26.0 ± 15.9%. Our low-power energy-recycling stairs have the potential to assist people with mobility impairments during stair negotiation on existing staircases.