The Dynamics of Locomotor Neuromuscular Fatigue during Ramp-Incremental Cycling to Intolerance

INTRODUCTION

Traditional neuromuscular fatigue assessments are not task-specific and are unable to characterize neuromuscular performance decline during dynamic whole-body exercise. This study used interleaved maximal isokinetic cycling efforts to characterize the dynamics of the decline in neuromuscular performance during ramp-incremental (RI) cycle ergometry exercise to intolerance.

METHODS

Eleven young healthy participants (10 male/1 female) performed two RI cycle ergometry exercise tests to intolerance: [1] RI-exercise with peak isokinetic power (Piso) at 80 rev·min-1 measured at baseline and immediately at intolerance from a maximal ~6 s effort; [2] RI-exercise where additional Piso measurements were interleaved every 90 s to characterize the decline in neuromuscular performance during the RI-test. Muscle excitation was measured using EMG during all Piso assessments, and pulmonary gas exchange was measured throughout.

RESULTS

Baseline Piso was 832 ± 140 W and RI-exercise reduced Piso to 349 ± 96 W at intolerance (p = 0.001), which was not different from flywheel power at intolerance (303 ± 96 W; p = 0.292). There was no reduction in Piso between baseline cycling and gas exchange threshold (GET; baseline Piso vs. mean Piso below GET: 828 ± 146 vs. 815 ± 149 W; p = 1.00). Piso fell progressively above GET until intolerance (Piso every 90 s above GET: 759 ± 139; 684 ± 141; 535 ± 144; 374 ± 117 W; each p < 0.05 vs. baseline and mean Piso below GET). Peak muscle excitation (EMG) was also reduced only above GET (73 ± 14 % of baseline, at intolerance; p < 0.05). However, the reduction in peak Piso preceded the reduction in peak muscle excitation.

CONCLUSIONS

The dynamics of the decline in neuromuscular performance (reduction in Piso and EMG) during RI-exercise are consistent with known intensity-dependent metabolic and traditional pre-post neuromuscular fatigue responses to discrete bouts of constant-power exercise.

Resistance Training in Post-COVID Recovery: Rationale and Current Evidence

During hospitalisation with COVID-19, individuals may experience prolonged periods of immobilisation. Combined with the inflammatory effects of the virus, this may lead to a significant reduction in both muscle mass and strength. Data from several long-term studies suggest that these symptoms may not fully resolve within one year. Owing to its effectiveness at inducing muscle fibre hypertrophy and improving neuromuscular efficiency, resistance training is of great interest in the rehabilitation of this population. This narrative review aims to identify the rationale and potential efficacy of resistance training for restoring physical function following infection with SARS-CoV-2, as well as evidence of its use in clinical practice. The studies included in this narrative review consisted mostly of multi-component rehabilitation trials. Of these, widespread improvements in muscle strength were reported using intensities of up to 80% of participants' 1-repetition-maximum. Evidence thus far indicates that resistance training may be safe and effective in patients following COVID-19, although its individual contribution is difficult to discern. Future exercise intervention studies investigating the efficacy of resistance training as a sole modality are needed.

Respiratory sequelae of COVID-19: pulmonary and extrapulmonary origins, and approaches to clinical care and rehabilitation

Although the exact prevalence of post-COVID-19 condition (also known as long COVID) is unknown, more than a third of patients with COVID-19 develop symptoms that persist for more than 3 months after SARS-CoV-2 infection. These sequelae are highly heterogeneous in nature and adversely affect multiple biological systems, although breathlessness is a frequently cited symptom. Specific pulmonary sequelae, including pulmonary fibrosis and thromboembolic disease, need careful assessment and might require particular investigations and treatments. COVID-19 outcomes in people with pre-existing respiratory conditions vary according to the nature and severity of the respiratory disease and how well it is controlled. Extrapulmonary complications such as reduced exercise tolerance and frailty might contribute to breathlessness in post-COVID-19 condition. Non-pharmacological therapeutic options, including adapted pulmonary rehabilitation programmes and physiotherapy techniques for breathing management, might help to attenuate breathlessness in people with post-COVID-19 condition. Further research is needed to understand the origins and course of respiratory symptoms and to develop effective therapeutic and rehabilitative strategies.

Early experiences of the Your COVID Recovery® digital programme for individuals with long COVID

Objectives

To describe the early data from the Your COVID Recovery^® digital programme and to explore the data collected from two embedded outcome measures.

Design

Observational.

Setting

Primary and secondary care (England—Online).

Participants

110 individuals completed the programme (68.1% female, 88.1% White British, age: 46.3 (10.8) years, weight: 86.5 (21.1) kg, height: 169.3 (10.0) cm). 47.2% of patients reported comorbidities.

Intervention

Following an assessment by a healthcare professional, individuals with long COVID were offered access to the Your COVID Recovery^® digital programme. The programme comprises of four stages for the participants to progress through. Participants are encouraged to record severity of their symptoms and amount of activity they are doing on a symptom and an activity tracker. Resources and interactive material on managing symptoms of long COVID are available throughout each stage.

Primary outcome measures

Questionnaire (EuroQ0l 5-Dimension 5-Level (EQ-5D-5L) and the chronic obstructive pulmonary disease assessment test (CAT)) data were extracted from the site from 11 March 2021 until 9 November 2021.

Results

Participants were on the programme for 8.6 (4.3) weeks. There was a statistically significant increase in EQ-5D-5L visual analogue scale (VAS) score (pre=48.8 (19.5); post=59.9 (22.1); p<0.01). The EQ-5D-5L Index Value preintervention to postintervention did improve but not significantly (pre=0.5 (0.3); post=0.6 (0.3); p=0.09). CAT total score improved significantly preintervention to postintervention (pre=19.8 (7.2); post=15.6 (7.6); p<0.01). All CAT item scores significantly improved preintervention to postintervention (p<0.005), except the phlegm item score (p=0.168).

Discussion

This early data describes the impact of the Your COVID Recovery^® digital programme on the first cohort of patients to complete the digital recovery programme. The outcome data are promising and should encourage uptake.

Transient correction of genetic defects in cultured animal cells by introduction of functional proteins

Material was introduced into cultures of cells by using the method of scrape loading, in which cells are simply rubbed from the surface of a plastic tissue culture dish by a rubber-tipped rod in the presence of a macromolecule of interest. The volume of solution introduced into cells was comparable to that generally injected in the direct microinjection method with glass capillaries, that is, about 50 to 100 fl per cell. Genetic defects (lack of hypoxanthine-guanine phosphoribosyltransferase and thymidine kinase) in several cell lines were transiently corrected by scraping the cells in the presence of crude cell extracts prepared from wild-type cells.

Elastolytic enzymes and elastin in the aging rat. II. Antielastoproteinase, antitrypsin and antichymotrypsin levels in serum

The age-relationship of antielastoproteinase, antitrypsin, and antichymotrypsin activity of rat serum was studied using alkali-treated elastin as substrate for measuring elasto-proteinase activity and synthetic substrates for measuring trypsin and chymotrypsin activity (trypsin substrate: benzoyl-arginine- <i>p</i>-nitroanalide; chymotrypsin substrate: acetyl-tyrosine-hydrazide). Serum antielastoproteinase levels in both male and female rats increased with age, whereas the levels for ântitrypsin and antichymotrypsin decreased with age. These findings support the hypothesis that the serum contains separate inhibitors for elastoproteinase and trypsin. The effect of age on the antielastoproteinase activity of rat serum was compared with data found in the literature for human serum. Rat serum showed highly significant age-related ‘tryptic and chymotryptic activities’ (both ‘enzyme activities’ increasing with age in both sexes). That these enzymatic activities represent real trypsin and chymotrypsin activities is questioned. Serum amidases and thrombin may be responsible for the measured activities.

Elastolytic enzymes and elastin in the aging rat. I. Pancreatic elastolytic enzymes

Since improved methods make it possible to determine both elastoproteinase and elastomucase activity in crude pancreatic extracts, the effect of age on enzyme titer in the pancreas was studied in virgin Wistar rats of both sexes. In males, the elastoproteinase concentration (in elastoproteinase unit [EU] per gram acetone-dried pancreas) decreased with age over the whole period of 0–24 months; the elastomucase Em-I and Em-S concentrations (in elastomucase unit [Em-U] per gram acetone-dried pancreas) rapidly decreased with age up to 12 months (Em-S) and 18 months (Em-I), remaining nearly constant after that age period. In female rats, the elastoproteinase concentration remained constant during the 1st year of life, increased rapidly between 15 and 18 months, then decreasing to the 15-month level at an age of 27 months. The titer of both elastomucases fell during the growth of the females, remaining constant between 6 and 15 months of age and showed a rapid increase in enzyme level between 15 and 18 months. Although there was a tendency for the enzyme concentration to decrease after 18 months, the fall was not statistically significant. The data obtained with rat pancreas were compared with those for human pancreatic enzymes and for human serum ‘elastoproteinase’ reported previously. Similar age-relationships were found.