Enhanced muscle activity during interrupted sitting improves glycemic control in overweight and obese men.

The efficacy of interrupting prolonged sitting may be influenced by muscle activity patterns. This study examined the effects of interrupting prolonged sitting time with different muscle activity patterns on continuously monitored postprandial glycemic response. Eighteen overweight and obese men (21.0 ± 1.2 years; 28.8 ± 2.2 kg/m) participated in this randomized four-arm crossover study, including uninterrupted sitting for 8.5 h (SIT) and interruptions in sitting with matched energy expenditure and duration but varying muscle activity: 30-min walking at 4 km/h (ONE), sitting with 3-min walking at 4 km/h (WALK) or squatting (SQUAT) every 45 min for 10 times. Net incremental area under the curve (iAUC) for glucose was compared between conditions. Quadriceps, hamstring, and gluteal muscles electromyogram (EMG) patterns including averaged muscle EMG amplitude (aEMG) and EMG activity duration were used to predict the effects on glucose iAUC. Compared with SIT (10.2 mmol/L/h [95%CI 6.3 to 11.7]), glucose iAUC was lower during sitting interrupted with any countermeasure (ONE 9.2 mmol/L/h [8.0 to 10.4], WALK 7.9 mmol/L/h [6.4 to 9.3], and SQUAT 7.9 mmol/L/h [6.4 to 9.3], all p < 0.05). Furthermore, WALK and SQUAT resulted in a lower glucose iAUC compared with ONE (both p < 0.05). Only increased aEMG in quadriceps (-0.383 mmol/L/h [-0.581 to -0.184], p < 0.001) and gluteal muscles (-0.322 mmol/L/h [-0.593 to -0.051], p = 0.022) was associated with a reduction in postprandial glycemic response. Collectively, short, frequent walking or squatting breaks effectively enhance glycemic control in overweight and obese men compared to a single bout of walking within prolonged sitting. These superior benefits seem to be associated with increased muscle activity intensity in the targeted muscle groups during frequent transitions from sitting to activity.