[King Grub]

PURPOSE:

While the lack of muscular activity is a proposed trigger for metabolic alterations, this association has not been directly measured. We examined the associations between electromyography (EMG)-derived muscle inactivity and activity patterns and cardio-metabolic biomarkers in healthy, physically active adults.

METHODS:

Data for this cross-sectional study was pooled from 2 studies (EMG24 and InPact) resulting in a sample of 150 individuals without known chronic diseases and with high quality EMG data (female n=85, male n=65, age=38.8±10.6y, BMI=23.8±3.1kg/m). EMG was measured during 1-3 typical weekdays using shorts measuring quadriceps and hamstring muscle EMG. Muscle inactivity time and muscle moderate-to-vigorous activity were defined as EMG amplitude below that of standing still and above that of walking 5km/h, respectively. Blood pressure index, waist circumference, fasting plasma glucose, HDL cholesterol and triglycerides were measured and long-term exercise behaviors were assessed by questionnaire.

RESULTS:

In a group of physically active participants, muscles were inactive for 65.2±12.9% of the measurement time in an average of 24.1±9.8s periods. As compared to those in the lowest muscle inactivity quartile (<55.5% of measurement time), those in the highest quartile (≥74.8% of measurement time) had 0.32 mmol/l lower HDL cholesterol (P<.05) and 0.30 mmol/l higher triglycerides (P<.05) independent of muscle's moderate-to-vigorous activity.

CONCLUSION:

Clinically significant differences in HDL cholesterol and triglycerides were found favoring participants having low muscle inactivity time, independent of moderate-to-vigorous muscle activity. Even physically active individuals may benefit from light intensity activities which reduce ubiquitous muscle inactivity time.

Med Sci Sports Exerc. 2014 Sep 23. Muscle Inactivity is Adversely associated with Biomarkers in Physically Active Adults.