title: Reduced exercise capacity in early-stage amyotrophic lateral sclerosis: Role of skeletal muscle.
abstract: Our objective was to correlate skeletal muscle mass (SM) with cardiopulmonary exercise testing (CPET) descriptors of exercise capacity in patients with amyotrophic lateral sclerosis (ALS) and compare ALS CPET data with those of patients with mitochondrial myopathy (MM) and normal subjects (N). Twenty-four early-stage ALS patients (63±11 years) underwent bioelectrical impedance analysis of body composition, resting spirometry, and ramp CPET. Six MM and six N were used as controls (56 ± 7 and 63 ± 4 years, respectively). Results showed that ALS SM index was similar to that of N (9.0±2.1 kg/m(2) vs. 10.4±1.9 kg/m(2), respectively; p = n.s.), whereas peak VO(2)/kg SM was significantly lower (41.5 ± 11.6 ml/kg/min vs. 57.8 ± 7.5 ml/kg/min, respectively; p < 0.01). However, the heart rate/VO(2) slope did not differ between ALS and N, being significantly higher in MM than in both ALS and N (6.1 ± 1.4 beats/ml/kg/min vs. 4.2 ± 1.1 beats/ml/kg/min vs. 3.8 ± 2.0 beats/ml/kg/min, respectively; both p < 0.01), excluding a marked skeletal muscle metabolic impairment in ALS. Neither cardiovascular nor ventilatory dysfunction was detected in ALS. Early-stage ALS patients show a SM similar to N, but with a reduced peak VO(2)/kg SM. Such a reduced peripheral O(2) utilization is consistent with deconditioning as the main cause of impaired exercise capacity in this population.
authors.affiliation: Exercise Pathophysiology Laboratory, Cardiac Rehabilitation Division, Salvatore Maugeri Foundation, IRCCS, Veruno Scientific Institute, Veruno (NO), Italy. alessandro.mezzani@fsm.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mezzani
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Pisano
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cavalli
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Tommasi
authors.forename: Ugo
authors.initials: U
authors.lastname: Corrà
authors.forename: Silvia
authors.initials: S
authors.lastname: Colombo
authors.forename: Bruno
authors.initials: B
authors.lastname: Grassi
authors.forename: Mauro
authors.initials: M
authors.lastname: Marzorati
authors.forename: Simone
authors.initials: S
authors.lastname: Porcelli
authors.forename: Lucia
authors.initials: L
authors.lastname: Morandi
authors.forename: Pantaleo
authors.initials: P
authors.lastname: Giannuzzi
mesh_terms: D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology* / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology / Q000503:physiopathology*; D012129:Respiratory Function Tests