Effects of Inter-Set Rest Intervals on Swallowing Pressure and Submental Muscle Activation During Effortful...

This study investigated the effects of rest intervals between sets during effortful swallowing (ES) exercise on swallowing pressure and submental muscle activation in healthy older adults. A within-subject crossover design was employed with 57 healthy older adults (mean age, 76.2 ± 4.9 years). Participants performed ES exercises under two conditions: 0-min rest (50 continuous repetitions) and 3-min rest (five sets of 10 repetitions with 3-min rest intervals). ES pressure was measured using the Iowa Oral Performance Instrument at the posterior oral tongue position and expressed as a percentage of maximum voluntary contraction (%MVC). Submental muscle activation was recorded using surface electromyography during exercise and normalized to the percentage of reference voluntary contraction (%RVC). The 3-min rest condition showed a significantly higher mean swallowing pressure across all 50 trials than the 0-min rest condition (p = 0.024). A set-wise comparison revealed significantly higher swallowing pressure in the fourth set in the 3-min rest condition (p = 0.013). In the 0-min rest condition, submental muscle activation significantly decreased in the fourth and fifth sets compared with the first set (p = 0.018 and 0.004, respectively), whereas the 3-min rest condition maintained consistent activation across all sets. Providing 3-min rest intervals between sets during ES exercise enables healthy older adults to maintain higher and more consistent swallowing pressures and muscle activation. These findings suggest that appropriate rest intervals may optimize exercise intensity and enhance the effectiveness of swallowing muscle-strengthening programs in older adults.