Characteristics of peripheral muscle strength in patients with interstitial lung disease

Introduction: A common feature of patients with interstitial lung disease (ILD) is the reduced peripheral muscle strength (MS). However, literature is controversial whether this occurs globally or only in lower limbs in these subjects. Aims: To characterise MS and to verify the prevalence of weakness of different muscle groups in patients with ILD. Methods: ILD and control subjects underwent peripheral MS evaluation by maximal voluntary isometric contraction of the muscles: pectoralis major, latissimus dorsi, triceps and biceps brachii, deltoid and quadriceps femoris. MS values of healthy subjects were used to create reference equations. Absolute values of MS of all groups were compared between ILD and controls and lower limits of normality of MS in the control group were used to classify muscle weakness. Results: 121 subjects (56 ILD, 62±10years; and 65 control, 60±9years) were included. Patients with ILD presented lower MS values in all assessed muscles when compared to control subjects (p≤0.002 for all). When described as percentage of the created reference values, MS of patients with ILD were: major pectoralis 69[54-86]%pred; quadriceps femoris 71[55-97]%pred; latissimus dorsi 71[54-103]%pred; deltoid 72[60- 96]%pred; biceps 75[63-90]%pred and triceps brachii 81[64-99]%pred. Prevalence of muscle weakness was of 40% in pectoralis major, 25% in latissimus dorsi, 16% in triceps and 20% in biceps brachii, 27% in deltoid and 46% in quadriceps femoris. Conclusions: Patients with ILD present global reduction of peripheral muscle strength when compared to healthy subjects. Additionally, muscle weakness was more prevalent in lower limb muscles in comparison with other investigated groups.