Evaluation of the maximum isometric tongue force of healthy volunteers.

The forces of specific muscle groups have been well described for nearly all parts of the human body. Interestingly, data for the tongue and its forces are rare. In light of ongoing development of systems for managing the tongue (retaining, advancing, suspending or stabilizing), especially in patients with obstructive sleep apnea, knowledge of the maximum tongue force is important for the conceptual design of those systems. The maximum tongue force in a sagittal direction was documented using a custom-built device that included a tongue clamp and a piezoelectric sensor to capture force measurements. Once positioned securely in the device, participants were asked to move the tongue in a posterior sagittal direction, with maximum force, in each of three test positions. Forty-nine healthy volunteers (29 male) were included in the study. Tongue force measurements were collected three times in three different tongue positions. Thirty-three participants had repeated measurements to investigate any potential learning effect. The maximum force of the human tongue in a posterior sagittal direction showed high inter-individual variation and ranged from 3.2 to 52.4 Newton (N; mean 14.1 ± 7.5 N), when measured from a "neutral protrusion or resting" tongue position. The "retracted" and "maximal protrusion" testing positions yielded lower maximum tongue forces. Men (m) showed statistically significantly higher tongue forces than women (w) (m: 16.0 ± 8.4 N, w: 11.0 ± 4.3 N), and there was a positive correlation with BMI and a negative correlation with age. Comparing the first measurement session with the second session (per patient) showed higher mean maximum forces in the second session, but with no statistical significance. The maximum tongue force data showed substantial inter- and intra-individual variability and gender dependency. Some male individuals produced very high forces. These forces should be considered for the future conception and development of tongue management systems and the mechanical stress to which these systems may be exposed.