Contralateral Selectivity of Upper-Limb Motor Pools via Targeted Stimulation of the Cervical Spinal Cord.

Transcutaneous spinal cord stimulation (tSCS) at the cervical level may facilitate improved upper-limb function in those with incomplete tetraplegia. While clinical trials are ongoing, there is still much debate regarding the transmission pathway as well as appropriate stimulation parameters. This study aimed to explore the extent to which cervical tSCS can induce mono-synaptic reflexes in discrete upper-limb motor pools and examine the effects of altering stimulus location and intensity. METHODS: Fourteen participants with intact nervous systems completed two laboratory visits, during which posterior root-muscle reflexes (PRMRs) were evoked via a 3 × 3 cathode matrix applied over the cervical spine. An incremental recruitment curve at the C7 vertebral level was initially performed to attain resting motor threshold (RMT) in each muscle. Paired pulses (1 ms square monophasic with inter-pulse interval of 50 ms) were subsequently delivered at a frequency of 0.25 Hz at two intensities (RMT and RMT + 20%) across all nine cathode positions. Evoked responses to the 1st (PRMR1) and 2nd (PRMR2) stimuli were recorded in four upper-limb muscles. RESULTS: A significant effect of the spinal level was observed in all muscles for PRMR1, with greater responses being recorded caudally. Contralateral stimulation significantly increased PRMR1 in Biceps Brachii (p < 0.05, F = 4.9, η2 = 0.29), Flexor Carpi Radialis (p < 0.05, F = 4.9, η2 = 0.28) and Abductor Pollicis Brevis (p < 0.01, F = 8.9, η2 = 0.89). Post-activation depression (PAD) was also significantly increased with contralateral stimulation in Biceps Brachii (p = 0.001, F = 9.3, η2 = 0.44), Triceps Brachii (p < 0.05, F = 5.4, η2 = 0.31) and Flexor Carpi Radialis (p < 0.001, F = 17.4, η2 = 0.59). CONCLUSIONS: A level of unilateral motor pool selectivity may be attained by altering stimulus intensity and location during cervical tSCS. Optimising these parameters may improve the efficacy of this neuromodulation method in clinical cohorts.

Efficacy of resistance training during adjuvant chemotherapy and radiation therapy in cancer care: a systematic review and meta-analysis.

PURPOSE: To determine the effect of resistance training during adjuvant chemotherapy and radiation therapy in cancer patients on measures of lean mass and muscle strength. Secondary aims were to analyse the prescription and tolerability of supervised resistance training in this population. METHODS: EMBASE, Medline, CINAHL, Cochrane Library and Web of Science were searched from inception until 29 March 2021. Eligible randomised controlled trials (RCTs) examining supervised resistance training > 6 weeks duration during adjuvant chemotherapy and/or radiation therapy in cancer patients with objective measurement of muscle strength and/or lean mass were included. The meta-analysis was performed using Revman 5.4. RESULTS: A total of 1910 participants from 20 articles were included (mean age: 54 years, SD = 10) and the majority were female (76.5%). Resistance training was associated with a significant increase in upper body strength (standardised mean difference (SMD) = 0.57, 95% CI 0.36 to 0.79, I2 = 64%, P < 0.0001), lower body strength (SMD = 0.58, 95% CI 0.18 to 0.98, I2 = 91%, P = 0.005), grip strength (mean difference (MD) = 1.32, 95% CI 0.37 to 2.27, I2 = 0%, P < 0.01) and lean mass (SMD = 0.23, 95% CI 0.03 to 0.42, I2 = 0%, P = 0.02). A P value of < 0.05 was considered statistically significant. The quality of the studies included was moderate to high with low risk of bias as per the PEDro scale. CONCLUSION: Resistance training is an effective adjunct therapy to improve muscle strength and lean mass in cancer patients undergoing chemotherapy and/or radiation therapy. PROSPERO REGISTRATION NUMBER: CRD42020180643.

The effect of diurnal variation in exercise-induced bronchoconstriction.

Objective: Exercise-induced bronchoconstriction (EIB) is an acute, transient narrowing of the airway as a result of exercise. Diurnal variation in asthma is well-established, however, few studies have investigated diurnal variability in EIB; no study has used eucapnic voluntary hyperpnea (EVH). The aim of this study was to examine circadian variability in EIB using EVH.Methods: Fourteen recreationally-active males with mild to moderate asthma and nine healthy controls were randomized to first complete either an AM (07:00-08:00) or PM (17:00-18:00) EVH challenge, followed by the alternate test 34 h to 7 days later. The EVH protocol comprised of six-minutes of hyperventilation of a 5% CO2 gas at a minimum ventilation rate of 21 × FEV1 min-1. The primary outcome measure was FEV1 pre- and post-EVH.Results: We observed no diurnal effect on EIB in the asthma group. The minimum observed post-EVH FEV1 in the asthma cohort was 3.58 ± 0.95 L in AM and 3.62 ± 0.87 L in PM tests, corresponding to a 15.0 ± 15.3% vs. 14.9 ± 14.7% reduction from baseline, respectively. The asthma group showed similar baseline FEV1 before AM (4.21 ± 0.79 L) and PM (4.25 ± 0.65 L) tests. No difference was observed in minute ventilation between AM (26.1 ± 3.4 × FEV1 min-1) and PM (25.6 ± 3.8 × FEV1 min-1) tests for the asthma cohort. Controls displayed no significant changes in FEV1 or minute ventilation between tests.Conclusions: When baseline pulmonary function is similar, this study suggests that time-of-day has no effect on EIB in mild to moderate asthma.

A comparison of electromyography and stroke kinematics during ergometer and on-water rowing.

This study assessed muscle recruitment patterns and stroke kinematics during ergometer and on-water rowing to validate the accuracy of rowing ergometry. Male rowers (n = 10; age 21 ± 2 years, height 1.90 ± 0.05 m and body mass 83.3 ± 4.8 kg) performed 3 × 3 min exercise bouts, at heart and stroke rates equivalent to 75, 85 and 95% VO2peak, on both dynamic and stationary rowing ergometers, and on water. During exercise, synchronised data for surface electromyography (EMG) and 2D kinematics were recorded. Overall muscle activity was quantified by the integration of rmsEMG and averaged for each 10% interval of the stroke cycle. Muscle activity significantly increased in rectus femoris (RF) and vastus medialis (VM) (P <0.01), as exercise intensity increased. Comparing EMG data across conditions revealed significantly (P <0.05) greater RF and VM activity during on-water rowing at discrete 10% intervals of stroke cycle. In addition, the drive/recovery ratio was significantly lower during dynamic ergometry compared to on-water (40 ± 1 vs. 44 ± 1% at 95%, P <0.01). Results suggest that significant differences exist while comparing recruitment and kinematic patterns between on-water and ergometer rowing. These differences may be due to altered acceleration and deceleration of moving masses on-ergometer not perfectly simulating the on-water scenario.

Effects of Carbohydrate-Protein Ingestion Post-Resistance Training in Male Rugby Players.

Evidence suggests that carbohydrate-protein (CHO-PRO) drinks post-exercise are an advantageous nutritional recovery intervention. Resistance trained (n = 14, mean ± SD; age 19 ± 1 yr, mass 95 ± 9 kg, % fat 17 ± 4 % and BMI 28.5 ± 1.8 kg.m-2) male rugby players participated in a study investigating effects of carbohydrate (CHO) and CHO-PRO drinks on subsequent resistance exercise performance. Following an initial resistance training (RT) protocol consisting of 8 circuits of 5 discrete exercises at 10 repetition maximum (RM), participants received 10 mL.kg-1 BM of randomised sports drink (LCHO, HCHO and CHO-PRO) on completion of the RT protocol and at 120 min into a 240 min recovery period. Post-recovery, participants completed a test to failure (TTF) protocol performing as many circuits of the same exercises at 10-RM to failure. Individual exercise cumulative load (∑W) lifted and total work capacity (TWC) for each trial was recorded. Both ∑W and TWC were normalised for body mass (kg.kg-1 BM). Data were analysed using repeated measures ANOVA with post-hoc Student-Neuman-Keuls pair-wise comparisons (P<0.05). Despite large intra-subject variability between trials, TWC normalised for body mass was significantly greater following CHO-PRO compared with HCHO and LCHO (188 ± 26 vs. 157 ± 21 and 150 ± 16 kg.kg-1 BM, respectively; P<0.05). The ∑W lifted after ingestion of HCHO and LCHO were not significantly different despite differing CHO and caloric content. The CHO-PRO induced enhancement of recovery was possibly due to higher rates of glycogen restoration after the initial glycogen depleting RT protocol.

The threshold force required for femoral impaction grafting in revision hip surgery.

BACKGROUND AND PURPOSE: Femoral impaction grafting requires vigorous impaction to obtain adequate stability without risk of fracture, but the force of impaction has not been determined. We determined this threshold force in a preliminary study using animal femurs. METHODS: Adult sow femurs were used because of their morphological similarity to human femurs in revision hip arthroplasty. 35 sow femurs were impacted with morselized bone chips and an increasing force was applied until the femur fractured. This allowed a threshold force to be established. 5 other femurs were impacted to this force and an Exeter stem was cemented into the neomedullary canal. A 28-mm Exeter head was attached and loaded by direct contact with a hydraulic testing machine. Axial cyclic loading was performed and the position sensor of the hydraulic testing machine measured the prosthetic head subsidence. RESULTS: 29 tests were completed successfully. The threshold force was found to be 4 kN. There was no statistically significant correlation between the load at fracture and the cortex-to-canal ratio or the bone mineral density. Following impaction with a maximum force of 4 kN, the average axial subsidence was 0.28 mm. INTERPRETATION: We achieved a stable construct without fracture. Further studies using human cadaveric femurs should be done to determine the threshold force required for femoral impaction grafting in revision hip surgery.

Effects of high bone turnover on the biomechanical properties of the L3 vertebra in an ovine model of early stage osteoporosis.

STUDY DESIGN: Investigations of the effects of high bone turnover on the L3 vertebra were carried out, using an ovariectomized (OVX) ovine model of early stage osteoporosis. OBJECTIVE: To assess the contribution of bone turnover to the biomechanics of L3. SUMMARY OF BACKGROUND DATA: Clinically, dual energy x-ray absorptiometry (DEXA) is used to measure bone mineral density (BMD). However, this can only predict 60% to 70% of bone strength; the remainder is due to bone quality. There is currently little information available on how strength is affected by changes in bone quality parameters, particularly bone turnover. Turnover can be assessed clinically using biochemical markers; however, this provides systemic values, whereas localized values are required to predict site-specific fracture risk. METHODS: Thirty-eight sheep were assigned to 2 groups (control, n = 19; OVX, n = 19). Both groups were intravenously administered a fluorochrome dye on the day of surgery and 3, 6, 9, and 12 months thereafter, to label sites of bone turnover. After 12 months, animals were killed and the spinal columns harvested. L3 vertebrae were scanned using DEXA. Bone turnover was quantified using epifluorescence microscopy, and microarchitecture was assessed by microCT scanning. Compressive testing was used to characterize the mechanical properties of the vertebrae. RESULTS: BMD and microarchitecture were unchanged in OVX compared with controls. However, bone turnover, as measured by fluorochrome labeled sites, was significantly increased in the OVX group in cortical and trabecular compartments. As a consequence, the biomechanical properties were significantly reduced in that group. CONCLUSION: These findings show that OVX resulted in changes in bone turnover, which reduced biomechanical properties in a model of early stage osteoporosis. These differences were present despite microarchitecture or BMD remaining unchanged. In the future, the ability to assess site-specific bone turnover would greatly enhance the accuracy with which fracture risk could be predicted.