Limb muscle size and contractile function in adults with cystic fibrosis: A systematic review and meta-analysis

Effects of a remotely supervised resistance training program on muscle strength and body composition in adults with cystic fibrosis: Randomized controlled trial

INTRODUCTION

Among the limited studies on physical exercise interventions in adults with cystic fibrosis (CF), few have specifically addressed the improvement of peripheral muscle strength and body fat-free mass. The aim of this study was to examine the impacts of a remotely supervised, individualized 8-week resistance training program of moderate to high intensity on strength and body composition in these subjects.

METHODS

This was a randomized controlled trial performed in adults with CF. The exercise group (EX) performed three 1-h resistance training sessions per week over 8 weeks. The control group (CON) followed the physical activity recommendations of their physician. The main outcomes were muscle strength and body composition, with secondary measures including pulmonary function and quality of life. Two-way repeated measures analysis was used.

RESULTS

In 23 participants (age 32.13 ± 7.72 years), the intervention showed a significant beneficial effect on leg press strength, with a large effect size, both in absolute (p = 0.011;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.281) and relative (p = 0.007;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.310) terms. Large intervention effects were observed on total fat mass (p < 0.001;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.415), body adiposity index (p < 0.001;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.436), and fat mass index (p < 0.001;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.445), all showing reduction in the EX group. In addition, significant large size effects were detected on total fat-free mass (p = 0.046;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.177), trunk fat-free mass (p = 0.039;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.188), and fat-free mass index (p = 0.048;η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.174), all favoring exercise. No significant effects were observed on pulmonary function and quality of life.

CONCLUSIONS

An 8-week remotely supervised resistance training program, with moderate to high intensity, effectively improved lower limb muscle strength and body composition.

Development of musculoskeletal deficits in children with cystic fibrosis in later childhood

Cystic fibrosis (CF) is a genetic condition primarily affecting the respiratory system, with the associated progressive lung damage and loss of function resulting in reduced lifespan. Bone health is also impaired in individuals with CF, leading to much higher fracture risk even in adolescence. However, the development of these deficits during growth and the relative contributions of puberty, body size and muscular loading remain somewhat unexplored. We therefore recruited 25 children with CF (10 girls, mean age 11.3 ± 2.9y) and 147 children without CF (75 girls, mean age 12.4 ± 2.6y). Bone characteristics were assessed using peripheral quantitative computed tomography (pQCT) at 4 % and 66 % distal-proximal tibia. Muscle cross-sectional area (CSA) and density (an indicator of muscle quality) were also assessed at the latter site. Tibial bone microstructure was assessed using high-resolution pQCT (HR-pQCT) at 8 % distal-proximal tibial length. In addition, peak jump power and hop force were measured using jumping mechanography. Group-by-age interactions and group differences in bone and muscle characteristics were examined using multiple linear regression, adjusted for age, sex and pubertal status and in additional models, height and muscle force. In initial models group-by-age interactions were evident for distal tibial total bone mineral content (BMC) and trabecular volumetric bone mineral density (vBMD), with a lower rate of age-related accrual evident in children with CF. In assessments of distal tibial microstructure, similar patterns were observed for trabecular number and thickness, and cortical CSA. In the tibial shaft, group-by-age interactions indicating slower growth in CF were evident for total BMC and cortical CSA, whilst age-independent deficits in CF were observed for several other variables. Peak jump power and hop force also exhibited similar interactions. Group-by-age interactions for bone were partially attenuated at the distal tibia and fully attenuated at the tibial shaft by adjustment for muscle force. These results suggest that bone and muscle deficits in children with CF develop throughout later childhood, independent of differences in pubertal stage and body size. These diverging growth patterns appear to be mediated by differences in muscle function, particularly for bone characteristics in the tibial shaft. Given the high fracture risk in this population from childhood onwards, development of interventions to improve bone health would be of substantial clinical value.

Body functions and structure, activity, and participation limitations of adult cystic fibrosis patients under the international classification of functioning, disability, and health framework

Objective: There is no study in the literature evaluating impairments and functional limitations in adults with cystic fibrosis (CF) under the framework of the International Classification of Functioning, Disability, and Health (ICF). To evaluate the adults with CF using ICF model. Methods: Twenty-three adults with CF and 23 age-sex matched healthy individuals included in this cross-sectional study. The participants evaluated according to the selected items for domain b, domain s, and domain d from the Obstructive Pulmonary Diseases (OPD) Comprehensive Core Set. The body composition, pulmonary functions, respiratory and peripheral muscle strength/endurance tests and anxiety/depression level were evaluated for domain b and s. For domain d, the Incremental Shuttle Walk Test (ISWT) and Short Form-36 (SF-36) Health Survey were used. Results: The fat-free mass (p = .044), pulmonary functions (p < .05), respiratory muscle endurance (p = .010), absolute and %quadriceps muscle strength (p = .001, p = .025, respectively), number of sit-ups (p = .020), walking speed (p = .035), ISWT and ISWT% distance (p < .001) and peak oxygen consumption (p < .001) were significantly lower in adults with CF compared to healthy individuals (p < .05). There were only significant differences in SF-36 physical functioning and role physical subdimension scores between groups (p = .009, p = .045 respectively). Conclusions: The ICF framework is applicable to comprehensively evaluate limitations of adults with CF among rehabilitation professionals. Especially age, respiratory function, respiratory muscle strength and endurance, dyspnea perception, peripheral muscle endurance were related to activity and participation limitation.

Comparison of quadriceps muscle size and quality in adults with cystic fibrosis with different severities of cystic fibrosis transmembrane conductance regulator protein dysfunction

Background

Cystic fibrosis (CF) is characterized by CF transmembrane conductance regulator (CFTR) dysfunction. CFTR protein is expressed in human skeletal muscle; however, its impact on skeletal muscle is unknown. The objectives of this study were to compare quadriceps muscle size and quality between adults with various severities of CFTR protein dysfunction.

Methods

We conducted a prospective, cross-sectional study comparing 34 adults with severe versus 18 with mild CFTR protein dysfunction, recruited from a specialized CF centre. Ultrasound images of rectus femoris cross-sectional area (RF-CSA) and quadriceps layer thickness for muscle size, and rectus femoris echogenicity (RF-ECHO) (muscle quality) were obtained. Multivariable linear regression models were developed using purposeful selection technique.

Results

People with severe CFTR protein dysfunction had larger RF-CSA by 3.22 cm², 95% CI (1.03, 5.41) cm², p=.0049], after adjusting for oral corticosteroid use and Pseudomonas aeruginosa colonization. However, a sensitivity analysis indicated that the result was influenced by the specific confounders being adjusted for in the model. We did not find any significant differences in quadriceps layer thickness or RF-ECHO between the two groups.

Conclusion

We found no differential impact of the extent of diminished CFTR protein activity on quadriceps muscle size or quality in our study cohort. Based on these findings, CFTR mutation status cannot be used differentiate leg muscle size or quality in people with CF.

Exercise intolerance in cystic fibrosis-the role of CFTR modulator therapies

Exercise intolerance is common in people with CF (pwCF), but not universal among all individuals. While associated with disease prognosis, exercise intolerance is not simply a reflection of the degree of lung disease. In people with severe CF, respiratory limitations may contribute more significantly to impaired exercise capacity than in those with mild-moderate CF. At all levels of disease severity, there are peripheral factors e.g., abnormal macro- and micro-vascular function that impair blood flow and reduce oxygen extraction, and mitochondrial defects that diminish metabolic efficiency. We discuss advances in understanding the central and peripheral mechanisms underlying exercise intolerance in pwCF. Exploring both the central and peripheral factors that contribute to exercise intolerance in CF can help inform the development of new therapeutic targets, as well as help define prognostic criteria.