Abstract
[Purpose] The present study evaluated expiratory muscle strength training (EMST) as a method of strengthening the suprahyoid muscles in 15 healthy volunteers (10 males and 5 females; mean age, 29.3 years).
[Methods] We measured the electromyographic activity of the suprahyoid muscles during EMST, the Mendelsohn maneuver and an isometric head lifting exercise. The EMST load pressure was set at 25% and 75% of maximum expiratory mouth pressure (PEmax) and the participants forcibly exhaled at maximal inspiratory level. We compared the root mean square (RMS) and mean power frequency (MPF) using continuous wavelet frequency analysis for 1 second at high amplitude during training at each level.
[Results] Suprahyoid muscle activity (% RMS) peaked (208.5±106.0%) during EMST at 75% PEmax and significantly differed from that at 25% PEmax (155.4±74.3%), during the Mendelsohn maneuver (88.8± 57.4%) and during isometric head lifting (100%; normalization). In addition, continuous wavelet frequency analysis showed that a high-power component was sustained in the high frequency zone area during EMST. The MPF value was the highest (127.8±20.7 Hz) during EMST at 75% PEmax, which significantly differed from that at 25% PEmax (107.6±20.1 Hz) and isometric head lifting (100.4±19.3 Hz).
[Conclusions] The increased activity of motor unit recruitment and of type II fibers in the suprahyoid muscles indicate that EMST is an effective method of strengthening these muscles.
