Gastrocnemius muscle tone, elasticity, and stiffness in association with postural control characteristics in young men/Kaksik-saaremarjalihase toonuse, elastsuse ja jaikuse seosed asendikontrolli naitajatega noortel meestel

The association between muscle tone and postural sway characteristics during standing was investigated in 27 healthy men aged 17-31 years. Frequency of muscle oscillations as an indicator of the tone, logarithmic decrement of the dampening of muscle oscillations as an indicator of the elasticity, and stiffness of the medial gastrocnemius (MG) muscle were measured bilaterally using a hand-held Myoton-3 device (Estonia). Postural sway of the centre of foot pressure during 30 s quiet bipedal standing was recorded using a Kistler force plate. As compared to the lying position, at standing on stable ground (SG) as well as on unstable ground (USG) (balance pad) the frequency of muscle oscillations was greater (162% and 166%, respectively) and so was stiffness (199% and 203%, respectively) but no significant differences for the logarithmic decrement of the dampening of muscle oscillations were noted. A greater coefficient of variation at standing on SG and USG as compared to the lying position for frequency of muscle oscillations (403% and 471%, respectively), for stiffness (177% and 187%, respectively), and for the logarithmic decrement of the dampening of muscle oscillations (120% and 122%, respectively) was found. Muscle tone and elasticity characteristics correlated positively with sway characteristics (radius and area of the centre of pressure) at USG standing. The change of posture from the supine to the standing position was accompanied by a marked increase in MG muscle tone and stiffness, but elasticity did not change. Coefficients of variation for the measured characteristics are suggested as new criteria for muscle function in relation to postural stability. Key words: kinesiology, biomechanics, passive resting tone, postural muscle tone, postural sway, body balance. Too eesmargiks oli uurida kaksik-saaremarjalihase (MG) toonuse, elastsuse ja jaikuse ning asendikontrolli naitajate seoseid noortel meestel. Uuritavateks olid 27 kehaliselt aktiivset meest vanuses 17-31 aastat (pikkus 172-195 cm ja kehakaal 64-87 kg). MG toonus (lihase vonkesagedus) ja biomehaanilised omadused (lihase elastsus, mida iseloomustatakse lihase vonkumise kustumise logaritmilise dekremendi kaudu, ning lihasjaikus) maarati bilateraalselt, kasutades portatiivset seadet Myoton-3 (Muomeetria OU, Eesti). Asendikontrolli naitajad (survetsentri koikumine) registreeriti 30-sekundilisel seismisel Kistleri jouplatvormi stabiilsel ja ebastabiilsel pinnal (Airexi tasakaalumatil). Lamamisasen