Mechanisms of Neuromuscular Fatigability in People with Cancer-Related Fatigue

The 1-min sit-to-stand test induces a significant and reliable level of neuromuscular fatigability: insights from a mobile app analysis

PURPOSE

The performance metric associated with the execution of the 1-min sit-to-stand (1STS) typically relies on the number repetitions completed in 1 min. This parameter presents certain limitations (e.g., ceiling effect, motivational factors) which can impede its interpretation. Introducing additional parameters, such as neuromuscular fatigability level, could enhance the informative value of the 1STS and facilitate its interpretation. This study aimed to assess (i) whether the 1STS induces fatigability and (ii) the reliability of the fatigability level.

METHODS

Forty young, healthy, and active participants underwent the 1STS twice during the same session. Isolated sit-to-stand maneuvers were performed before, immediately, and 1 min after completing the 1STS. A mobile app was utilized to obtain time (STST), velocity (STSV), and muscle power (STSP) from these sit-to-stand maneuvers. The pre-post change in these parameters served as the fatigability marker. Reliability was assessed using the intra-class correlation coefficient (ICC) and the coefficient of variation (CV).

RESULTS

The mean number of repetitions during the 1STS was 63 ± 9. Significant decline in performance was observed for STST (13 ± 8%), STSV (-11.2 ± 6%), and STSP (-5.2 ± 3%), with more than 74% of participants exhibiting a decline beyond the minimal detectable change. Excellent between-session reliability (ICC ≥ 0.9; CV ≤ 5.3) was observed for the mobile app variables.

CONCLUSION

The 1STS induces significant levels of fatigability. The fatigability indicators derived from the mobile app demonstrated remarkable reliability. Utilizing this user-friendly interface for computing fatigability may empower professionals to acquire insightful complementary indicators from the 1STS.

Constructing a picture of fatigue in the context of cancer: assessment of construct overlap in common fatigue scales

PURPOSE

Individuals diagnosed with cancer experience multiple inter-related short- and long-term side effects. Chief among such symptomology is cancer-related fatigue (CRF), which, if left unmanaged, can become chronic and result in increased disability and healthcare utilization. A growing number of self-report scales have been developed to measure CRF symptoms based on various theoretical conceptualizations with the aim of promoting targeted assessment and intervention efforts. It may be, however, unwise to assume that the various measures are conceptually similar (i.e., that they assess for the same constructs). Accordingly, we aimed to characterize item content among nine self-report scales, using a Jaccard index to quantify content overlap among scales.

METHODS

We characterized construct assessment among nine self-report scales recommended to assess CRF by a recent clinical practice guideline, and used a Jaccard index to quantify content overlap among scales.

RESULTS

Analysis of 208 items across nine rating scales resulted in 20 distinct symptoms of CRF assessed. The most common symptoms were energy level (captured in all nine scales), cognitive function, impaired task performance (in eight scales), sleepiness, and physical function (in seven scales). Mean overlap among all scales was low (Jaccard index = 0.455). Only one construct (duration of fatigue; 5.0%) was captured by a single scale, and one symptom (energy level; 5.0%) was common across all scales. The PFS, MFSI, and BFI each captured at least one symptom from each of the NCCN domains of CRF.

CONCLUSION

CRF scales are heterogeneous in the content they measure, critically impairing integration of knowledge across studies using disparate scales. Future work is urgently needed to build more integrated theoretical and/or computational models of CRF based on relevant mechanisms.

Are females getting more fatigable as they age?

PURPOSE

The aim of this study was to compare performance fatigability between young (n = 13; 18-35 yr.; 23.5 ± 3.3 yr.), old (n = 13; 60-79 yr.; 68.2 ± 4.3 yr.), and very old (n = 11; ≥ 80 yr.; 85.6 ± 1.8 yr.) females during single-limb isometric (ISO) vs. isokinetic concentric (CON) vs. cycling (BIKE) fatiguing tasks.

METHODS

Participants randomly performed three incremental fatiguing tasks where increments were set as percentage of body weight to better reflect the daily life: (1) ISO and (2) CON consisted of stages of 75 contractions (120 s, 0.8 s on/0.8 s off) on an isokinetic dynamometer and (3) BIKE consisted of stages of 120 s at 37.5 rpm with similar duty cycle. Knee extensors maximal force, voluntary activation and potentiated twitch amplitude were measured at baseline, after each stage and at exhaustion.

RESULTS

Compared to young, exercise performance was 20% and 53% lower in old and very old females in ISO, 46% and 76% lower in CON and 32% and 62% lower in BIKE (all p < 0.01). For a given workload (i.e. common stages), performance fatigability (i.e. force loss) was greater for very old compared to young females in CON only (p = 0.018). At exhaustion, performance fatigability was similar across groups and conditions (~ 30%; all p > 0.05), with similar impairments in both voluntary activation and twitch amplitude.

CONCLUSION

These results emphasize the importance of the kind of fatiguing task and modalities of evaluation when investigating the effects of aging on performance fatigability.

Comparison of neuromuscular fatigability amplitude and etiologies between fatigued and non-fatigued cancer patients

PURPOSE

Cancer-related fatigue (CRF) is the most reported side effect of cancer and its treatments. Mechanisms of CRF are multidimensional, including neuromuscular alterations leading to decreased muscle strength and endurance (i.e., fatigability). Recently, exercise fatigability and CRF have been related, while fatigability mechanisms remain unclear. Traditionally, fatigability is assessed from maximal voluntary contractions (MVC) decrease, but some authors hypothesized that the rate of force development (RFD) determined during a rapid contraction could also be an interesting indicator of functional alterations. However, to our knowledge, no study investigated RFD in cancer patients. The purpose of this study was to determine whether RFD, fatigability amplitude, and etiology are different between fatigued and non-fatigued cancer patients.

METHODS

Eighteen participants with cancer, divided in fatigued or non-fatigued groups according their CRF level, completed a 5-min all-out exercise in ankle plantar flexor muscles composed of 62 isometric MVC of 4 s with 1 s rest, to assess fatigability amplitude as the force-time relationship asymptote (FA). Before and after exercise, fatigability etiologies (i.e., voluntary activation (VA) and evoked forces by electrical stimulation (Db100)) were assessed as well as RFD in 50 and 100 ms (RFD50 and RFD100, respectively) during rapid contractions.

RESULTS

FA is significantly lower in fatigued group. Significant differences were found between pre- and post-exercise VA, Db100, RFD50, and RFD100 for both groups, with no statistical difference between groups.

CONCLUSION

During treatments, fatigability is higher in fatigued patients; however, the mechanisms of fatigability and RFD alterations are similar in both groups.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04391543, May 2020.

Exacerbated central fatigue and reduced exercise capacity in early-stage breast cancer patients treated with chemotherapy

PURPOSE

The present study aimed to characterize the etiology of exercise-induced neuromuscular fatigue and its consequences on the force-duration relationship to provide mechanistic insights into the reduced exercise capacity characterizing early-stage breast cancer patients.

METHODS

Fifteen early-stage breast cancer patients and fifteen healthy women performed 60 maximal voluntary isometric quadriceps contractions (MVCs, 3 s of contraction, 2 s of relaxation). The critical force was determined as the mean force of the last six contractions, while W' was calculated as the force impulse generated above the critical force. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQTw) evoked by supramaximal electrical stimulation, respectively.

RESULTS

Early-stage breast cancer patients demonstrated lower MVC than controls preexercise (- 15%, P = 0.022), and this reduction persisted throughout the 60-MVC exercise (- 21%, P = 0.002). The absolute critical force was lower in patients than in controls (144 ± 29N vs. 201 ± 47N, respectively, P < 0.001), while W' was similar (P = 0.546), resulting in lower total work done (- 23%, P = 0.001). This was associated with lower muscle activation in the vastus lateralis (P < 0.001), vastus medialis (P = 0.003) and rectus femoris (P = 0.003) in patients. Immediately following exercise, ΔVA showed a greater reduction in patients compared to controls (- 21.6 ± 13.3% vs. - 12.6 ± 7.7%, P = 0.040), while ΔQTw was similar (- 60.2 ± 13.2% vs. - 52.8 ± 19.4%, P = 0.196).

CONCLUSION

These findings support central fatigue as a primary cause of the reduction in exercise capacity characterizing early-stage breast cancer patients treated with chemotherapy.

CLINICAL TRIALS REGISTRATION

No. NCT04639609-November 20, 2020.

Measuring objective fatigability and autonomic dysfunction in clinical populations: How and why?

Fatigue is a major symptom in many diseases, often among the most common and severe ones and may last for an extremely long period. Chronic fatigue impacts quality of life, reduces the capacity to perform activities of daily living, and has socioeconomical consequences such as impairing return to work. Despite the high prevalence and deleterious consequences of fatigue, little is known about its etiology. Numerous causes have been proposed to explain chronic fatigue. They encompass psychosocial and behavioral aspects (e.g., sleep disorders) and biological (e.g., inflammation), hematological (e.g., anemia) as well as physiological origins. Among the potential causes of chronic fatigue is the role of altered acute fatigue resistance, i.e. an increased fatigability for a given exercise, that is related to physical deconditioning. For instance, we and others have recently evidenced that relationships between chronic fatigue and increased objective fatigability, defined as an abnormal deterioration of functional capacity (maximal force or power), provided objective fatigability is appropriately measured. Indeed, in most studies in the field of chronic diseases, objective fatigability is measured during single-joint, isometric exercises. While those studies are valuable from a fundamental science point of view, they do not allow to test the patients in ecological situations when the purpose is to search for a link with chronic fatigue. As a complementary measure to the evaluation of neuromuscular function (i.e., fatigability), studying the dysfunction of the autonomic nervous system (ANS) is also of great interest in the context of fatigue. The challenge of evaluating objective fatigability and ANS dysfunction appropriately (i.e.,. how?) will be discussed in the first part of the present article. New tools recently developed to measure objective fatigability and muscle function will be presented. In the second part of the paper, we will discuss the interest of measuring objective fatigability and ANS (i.e. why?). Despite the beneficial effects of physical activity in attenuating chronic fatigue have been demonstrated, a better evaluation of fatigue etiology will allow to personalize the training intervention. We believe this is key in order to account for the complex, multifactorial nature of chronic fatigue.

How is neuromuscular fatigability affected by perceived fatigue and disability in people with multiple sclerosis?

Whereas fatigue is recognized to be the main complaint of patients with multiple sclerosis (PwMS), its etiology, and particularly the role of resistance to fatigability and its interplay with disability level, remains unclear. The purposes of this review were to (i) clarify the relationship between fatigue/disability and neuromuscular performance in PwMS and (ii) review the corticospinal and muscular mechanisms of voluntary muscle contraction that are altered by multiple sclerosis, and how they may be influenced by disability level or fatigue. Neuromuscular function at rest and during exercise are more susceptible to impairement, due to deficits in voluntary activation, when the disability is greater. Fatigue level is related to resistance to fatigability but not to neuromuscular function at rest. Neurophysiological parameters related to signal transmission such as central motor conduction time, motor evoked potentials amplitude and latency are affected by disability and fatigue levels but their relative role in the impaired production of torque remain unclear. Nonetheless, cortical reorganization represents the most likely explanation for the heightened fatigability during exercise for highly fatigued and/or disabled PwMS. Further research is needed to decipher how the fatigue and disability could influence fatigability for an ecological task, especially at the corticospinal level.

Exercise Counteracts the Deleterious Effects of Cancer Cachexia

Simple Summary

This review provides an overview of the effects of exercise training on the major mechanisms related to cancer cachexia (CC). The review also discusses how cancer comorbidities can influence the ability of patients/animals with cancer to perform exercise training and what precautions should be taken when they exercise. The contribution of other factors, such as exercise modality and biological sex, to exercise effectiveness in ameliorating CC are also elaborated in the final sections. We provide meticulous evidence for how advantageous exercise training can be in patients/animals with CC at molecular and cellular levels. Finally, we emphasise what factors should be considered to optimise and personalise an exercise training program in CC.

Abstract

Cancer cachexia (CC) is a multifactorial syndrome characterised by unintentional loss of body weight and muscle mass in patients with cancer. The major hallmarks associated with CC development and progression include imbalanced protein turnover, inflammatory signalling, mitochondrial dysfunction and satellite cell dysregulation. So far, there is no effective treatment to counteract muscle wasting in patients with CC. Exercise training has been proposed as a potential therapeutic approach for CC. This review provides an overview of the effects of exercise training in CC-related mechanisms as well as how factors such as cancer comorbidities, exercise modality and biological sex can influence exercise effectiveness in CC. Evidence in mice and humans suggests exercise training combats all of the hallmarks of CC. Several exercise modalities induce beneficial adaptations in patients/animals with CC, but concurrent resistance and endurance training is considered the optimal type of exercise. In the case of cancer patients presenting comorbidities, exercise training should be performed only under specific guidelines and precautions to avoid adverse effects. Observational comparison of studies in CC using different biological sex shows exercise-induced adaptations are similar between male and female patients/animals with cancer, but further studies are needed to confirm this.