Heterogeneity of muscle activity during sedentary behavior.
Replacing sitting by standing has been hypothesized to reduce the health risks of sitting, based on the assumption that muscles are passive during sitting and active during standing. Interventions have been more effective in overweight (OW) than in normal weight (NW) individuals, but subjects' muscle activities have not been quantified. This study compared quadriceps and hamstring muscle electromyographic (EMG) activity between 57 NW (body mass index (BMI) 22.5 ± 1.5 kg/m2, female n = 36) and 27 OW (BMI 28.4 ± 2.9 kg/m2, female n = 8) subjects during non-fatiguing standing (15 s, EMGstanding) and sitting (30 min). EMG amplitude was normalized to EMG measured during maximal isometric knee extension and flexion (% EMGMVC), and sitting muscle inactivity and bursts were determined using 4 thresholds (60% or 90% EMGstandingand 1% or 2% EMGMVC). Comparisons were adjusted for sex, age, knee extension strength, and the individual threshold. Standing EMG amplitude was 36% higher in OW (1.9% ± 1.5% EMGMVC) than in NW (1.4% ± 1.4% EMGMVC, P < 0.05) subjects. During sitting, muscles were inactive 89.8% ± 12.7% of the measurement time with 12.7 ± 14.2 bursts/min across all thresholds. On average, 6% more activity was recorded in NW than in OW individuals for 3 of the 4 thresholds (P < 0.05 for 60% or 90% EMGstandingand 1% EMGMVC). In conclusion, the OW group had higher muscle activity amplitude during standing but more muscle inactivity during sitting for 3/4 of the thresholds tested. Interventions should test whether the observed heterogeneity in muscle activity affects the potential to gain cardiometabolic benefits from replacing sitting with standing.
a Neuromuscular Research Center, Department of Biology of Physical Activity, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.
Arto J
AJ
Pesola
a Neuromuscular Research Center, Department of Biology of Physical Activity, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.|b Department of Sport Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.
Arto
A
Laukkanen
a Neuromuscular Research Center, Department of Biology of Physical Activity, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.|c Exercise Health and Technology Center, Department of Physical Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Minhang District, Shanghai 200240, China.
Olli
O
Tikkanen
a Neuromuscular Research Center, Department of Biology of Physical Activity, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.
Taija
T
Finni
D000328:Adult; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D015536:Down-Regulation; D004576:Electromyography; D005260:Female; D000070633:Hamstring Muscles / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D009038:Motion; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D050177:Overweight / Q000503:physiopathology*; D011187:Posture; D052097:Quadriceps Muscle / Q000503:physiopathology; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D015854:Up-Regulation
assis; body composition; composition corporelle; debout; electromyography; inactivité musculaire; muscle inactivity; sedentary time; sitting; standing; temps sédentaire; textile electrodes; électrodes textiles; électromyographie