Functional Tests of Leg Muscle Strength and Power in Adults With Cystic Fibrosis.

BACKGROUND: Muscle weakness is an important systemic consequence in adults with cystic fibrosis, but it can be challenging to evaluate clinically. This study examined the validity of lower-extremity functional tests to assess quadriceps muscle strength and muscle power. METHODS: The subjects underwent 4 functional tests: 30-s sit-to-stand test, stair-climb power test, vertical jump height, and triple hop distance. Quadriceps muscle strength and power were tested by using a dynamometer (the accepted standard). Quadriceps strength was measured from 5 maximum voluntary isometric contractions to obtain peak torque. Quadriceps power was evaluated from the peak power and peak velocity attained during isotonic contractions of the quadriceps at a preset load of 20% of the peak torque. Pearson correlations were used to determine associations between functional tests and accepted measures of quadriceps strength and power. RESULTS: Fifteen adults with cystic fibrosis (9 males; mean ± SD age, 32 ± 13 y; mean ± SD FEV1% predicted, 73 ± 19) completed the study. The stair-climb power test had the strongest correlations with peak torque (r = 0.84, P < .001) and power (r = 0.65, P = .009). Vertical jump height was moderately correlated with quadriceps strength (r = 0.62, P = .014) and quadriceps peak power (r = 0.51, P = .048). Similarly, triple hop distance had moderate correlations with quadriceps strength (r = 0.78, P = .001) and peak power (r = 0.57, P = .026). The sit-to-stand test was only associated with quadriceps strength (r = 0.55, P = .034). CONCLUSIONS: Functional tests can be applied clinically to measure leg muscle strength and power, with the stair-climb power test having the strongest associations with the standard measures. The utility of using functional tests to evaluate longitudinal changes in muscle function and its association with clinical outcomes should be examined in cystic fibrosis.

Relationship between Physical Activity and Fatigue in Adults with Cystic Fibrosis.

Purpose: We examined the relationship between the amount of physical activity and level of fatigue in adults with cystic fibrosis (CF). Method: Participants were recruited from the Toronto Adult Cystic Fibrosis Centre at St. Michael's Hospital. Participants completed the Habitual Activity Estimation Scale, the Multidimensional Fatigue Inventory, and the Depression subscale of the Hospital Anxiety and Depression Scale, in that order. Descriptive statistics and linear and multiple regressions were computed. Results: Over a 6-month period, 51 individuals were approached, and 22 (10 men, 12 women) participated in this study. The participants' median age was 33, and forced expiratory volume in 1 second (FEV1) was 64% predicted. When holding both FEV1 and depression constant, a significant negative correlation was found between total active hours per weekday and general fatigue (ß=-0.735, p=0.03); there was a negative trend between total active hours per weekday and physical fatigue (ß=-0.579, p=0.09). Conclusions: This study is the first to demonstrate that among adults with CF, a higher level of physical activity is associated with a lower level of general and physical fatigue when controlling for lung function and level of depression. Physical activity may be used as a means of mitigating the levels of general and physical fatigue in people with CF.

Objectif : des chercheurs ont examiné la relation entre la quantité d'activité physique et le taux de fatigue chez des adultes atteints de fibrose kystique (FK). Méthodologie : les chercheurs ont recruté les sujets au sein du centre de FK pour adultes du St. Michael's Hôpital de Toronto. Ils leur ont fait remplir, dans l'ordre, l'échelle d'évaluation de l'activité habituelle, l'inventaire de fatigue multidimensionnelle et la sous-échelle de dépression de l'échelle d'anxiété et de dépression en milieu hospitalier. Ils ont calculé les statistiques descriptives et les régressions linéaires et multiples. Résultats : Sur une période de six mois, les chercheurs ont sollicité 51 personnes, dont 22 (10 hommes) ont participé à l'étude. Ceux-ci avaient un âge médian de 33 ans, et leur volume expiratoire maximal par seconde (VEMS) s'établissait à 64 % de celui prévu. Lorsque le VEMS et la dépression des participants étaient maintenus constants, les chercheurs constataient une corrélation négative significative entre le total des heures d'activité par jour et l'état de fatigue général (ß=­0,735, p=0,03). Ils remarquaient également une tendance négative entre le total des heures d'activité par jour et la fatigue physique (ß=­0,579, p=0,09). Conclusion : la présente étude est la première à démontrer que, chez les adultes atteints de FK, un plus fort taux d'activité s'associe à une diminution de la fatigue générale et physique lors des contrôles de la fonction pulmonaire et de la dépression. Ainsi, l'activité physique peut réduire le taux de fatigue générale et physique chez les personnes atteintes de FK.