Is quadriceps endurance reduced in COPD?: A systematic review

BACKGROUND: Although the aerobic profile of the quadriceps muscle is reduced in COPD, there is conflicting evidence regarding whether this leads to reduced quadriceps muscle endurance. We, therefore, performed a systematic review of studies comparing quadriceps endurance in individuals with COPD with that in healthy control subjects. METHODS: Relevant studies were identified by searching six electronic databases (1946-2011). Full-text articles were obtained after two researchers independently reviewed the abstracts. The results were combined in a random effects meta-analysis, and metaregression models were fitted to assess the influence of the type of measurement. RESULTS: Data were extracted from 21 studies involving 728 individuals with COPD and 440 healthy control subjects. Quadriceps endurance was reduced in those with COPD compared with healthy control subjects (standardized mean difference, 1.16 [95% CI, 1.02-1.30]; P < .001) with a 44.5 s (4.5-84.5 s; P = .029) reduction in COPD (large effect size) when measured using a nonvolitional technique. The relationship between quadriceps endurance in those with COPD and control subjects did not differ when comparing nonvolitional and volitional techniques (P = .22) or when high- or low-intensity tasks (P = .44) were undertaken. CONCLUSIONS: Quadriceps endurance is reduced in individuals with COPD compared with healthy control subjects, independent of the type of task performed

T₁ weighted images of lower leg muscles.

<p>Representative T₁ weighted 3-D gradient echo images of A) control, and B) DMD subject. Outline of regions of interest (A) showing different muscles namely TA, tibialis anterior; EDL, extensor digitorum longus; Per, peroneal; MG, medial gastrocnemius; SOL, soleus; TP, tibilais posterior; FDL, flexor digitorum longus. (B) Showing areas of fatty tissue infiltration in leg muscles.</p

Comparison of C-CSA and NC-CSA among different age groups in DMD and control groups.

<p>Red and blue color represents N-CSA and C-CSA respectively. Symbol colors are accordant with the bar colors (red; N-CSA, blue; C-CSA). * Represents significant differences between DMD and age matched Ctrl group (p<0.05); # represents significant differences across the age groups (p<0.05).</p

Comparison of dorsiflexors (DF) and plantarflexors (PF) peak torque (A, B) and specific torque in boys with DMD and healthy Ctrl across different age groups.

<p>* represents significant differences between DMD and Ctrl within age groups (p<0.05), # represents significant differences across the age groups (p<0.05). Data is presented as mean (SD).</p

Relationship between NCC of different leg muscles and 30 feet walk (sec).

<p>There was a significant relationship between increase in NCC of all leg muscles and time taken to cover 30 feet distance (r_s; 0.65–0.80, p<0.0001).</p

Relationship between NCC of different leg muscles and Brooke score.

<p>There was a significant relationship between NCC of all leg muscles and Brooke score (r_s; 0.64–0.84, p<0.0001).</p

Comparison of timed functional tests between control (Ctrl) and subjects with Duchenne muscular dystrophy (DMD).

<p>**p<0.05 versus Ctrl group.</p><p>Values are mean (SD).</p><p>Comparison of timed functional tests between control (Ctrl) and subjects with Duchenne muscular dystrophy (DMD).</p

Contractile cross sectional area (C-CSA), non-contractile cross sectional area (NC-CSA), and non-contractile content (NCC) of all the lower leg muscles of boys with DMD and healthy control subjects.

<p>Significant difference was found in NC-CSA and of peroneal (Per), medial gastrocnemius (MG), and soleus (SOL) (denoted by **, p<0.05). No differences were observed in C-CSA of DMD and Ctrl leg muscles when all age groups were combined. Data is presented as mean (SD).</p

Percent non-contractile content (NCC) in leg muscles of Ctrl and DMD in different age groups.

<p>NCC of leg muscles of DMD at the age of >10 years was significantly different from 5–7.9 and 8–9.9 years age groups (denoted by #, p<0.05). NCC of TA, EDL, Per, MG, and SOL of DMD were significantly different than Ctrl in > 10 year age group (denoted by *, p<0.05). Additionally, only MG showed significant differences between DMD and Ctrl group at the age of 8–9.9 year. Data is presented as mean (SD).</p