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Fascicle-tendon interaction in v2 skate cross-country skiing : a case study

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Authors
Lemmettylä, Teemu
Date
2015
Discipline
BiomekaniikkaBiomechanics

 
Venymis-lyhenemis –sykli (SSC) on laajalti tutkittu liha-jänne -kompleksin (MTU) toimintamalli ihmisen liikkumisessa. Jotta SSC toiminta voidaan ymmärtää, lihaksen toiminta tulee mitata ultraäänen (US) avulla. Aiemmin yksi tutkimus on käsitellyt MTU:n toimintaa hiihdon aikana perinteisellä hiihtotavalla (Ishikawa, Sano et al. 2010). Tämän tutkimuksen tavoitteena on tarjota ainutlaatuinen kokeellinen tulos MTU:n toiminnasta vapaan hiihdon V2- tekniikan aikana, sekä tarjota suosituksia tulevaa tutkimusta varten. Tutkimuksessa yksi kokenut hiihtäjä suoritti protokolla Vuokatin hiihtotunnelissa. Protokolla koostui kahdesta eri mittauskerrasta, joiden välissä suoritettiin 20 km mittainen hiihtokilpailusimulaatio. Mittauksissa mitattiin lihasaktivaatio (EMG) ja lihaksen pituus (US) vastus lateralis (VL), medial gastrocnemius (MG), triceps brachii (long head) (TRI) ja rectus femoris (RF) lihaksista, normaalissa ja väsyneessä tilassa, useilla eri nopeuksilla. Lihas tiedot yhdistettiin liike- ja voimamittausten tuloksiin lopullista analyysia varten. Suoritusten yhtenäisyys säilyi hyvänä mittauksissa maksimivoimien ja nopeuden valossa. Väsymys ei aiheuttanut muutosta MAX ja MED nopeuksissa (MAX: -0.6%, MED:-1.3%). Lihasten aktivoituminen säilyi samana nopeuden muuttuessa. Kuitenkin, kaikkien lihasten aktivaatiotasot olivat erilaisia suhteessa lihaksepituuden muutoksen suuntaan ja syklin vaiheeseen. Lihas – jänne tasolla TRI ja VL lihakset venyivät enemmän nopeuden lisääntyessä. Kaksi niveltä ylittävät lihakset RF ja MG eivät osoittaneet selvää muutosta toiminnassa nopeuden lisääntyessä. Väsymys ei muuttanut lihas-jänne kompleksin toimintaa selkeästi. Tulosten mukaan SSC on tärkeä toimintamalli TRI ja VL lihaksille nopeuden kasvaessa V2 -tekniikan aikana. Kahden nivelen yli menevät lihakset RF ja MG eivät osoittaneet yhtä selvää muutosta eri nopeuksilla. Väsyminen ei muuttanut lihas-jänne kompleksin toimintaa selkeästi, vaikka aEMG tason lasku ja muutokset käsine ja jalkojen voimantuotto suhteissa viittasivat väsymykseen. Saadut tulokset ovat erittäin kokeellisia ja toimivat esitutkimuksena tuleville mittauksille. Tulevissa tutkimuksissa on kiinnitettävä tarkempaa huomiota ultraäänisensorin valintaan ja kiinnitykseen paremman mittauslaadun varmistamiseksi. Myös mittausalue on suunniteltava tarkemmin, jotta kaikki halutut mittaukset saadaan kerättyä kaikilla halutuilla nopeuksilla. Avainsanat: Maastohiihto, V2 -tekniikka, venymis-lyhenemis -sykli, lihas-jänne kompleksin toiminta, ultraääni ...
 
Stretch-shortening cycle is widely studied movement pattern in locomotion. To understand how it is utilized in muscle-fascicle level ultrasound (US) measurements are needed. One previous study has been carried out which provided the muscle-tendon level information during cross-country (xc) skiing (Ishikawa, Sano et al. 2010). Purpose of this study was to carry out a pilot measurement and provide unique muscle-fascicle level data during V2 skate xc-skiing as well as give further suggestion for the following measurements. One experienced skier carried out measurement in Vuokatti ski tunnel. Measurements consisted of two measurement sets, in between fatiguing 20k race simulation was carried out. In the measurements muscle activity (EMG) and US from vastus lateralis (VL), medial gastrocnemius (MG), triceps brachii (long head) (TRI) and rectus femoris (RF) were recorded in a normal and a fatigued conditions in a different velocities. Muscle based data was combined to the motion and force data for the final analysis. Uniformity of the trails was achieved well in terms of velocity and maximal forces. Fatigue did not change achieved velocities between MAX and MED condition (MAX: -0.6%, MED:-1.3%). Muscle activation pattern did not change within the muscle, however, all measured muscles showed different phase pattern respect to the lengthening direction. In muscle-tendon analysis TRI and VL muscles stretched more with increasing velocity. Biarticular muscles RF and MG did not show clear change in behavior. Fatigue did not change clearly muscle tendon behavior. Results suggest that SSC is main method for TRI and VL muscles to increase the performance during V2 xc-skiing. Biarticular muscles (MG and RF) showed possibly some stretch but behavior did not clearly change with increasing velocity. Fatigue did not change muscle-fascicle behavior clearly, even though lower aEMG levels and shifts in force production in fatigued condition suggest that at least some fatigue was achieved. However, results are highly experimental and serve only as a pilot study. In the following measurements is important to select and attach the US probes more carefully to ensure better quality of US measurements. Measurement setup should be build more carefully to ensure better integrity and quality of the data collection. Keywords: Cross-country skiing, skating, stretch-shortening cycle, muscle-tendon in-teraction, ultrasound ...
 
Keywords
Cross-country skiing skating stretch-shortening cycle muscle-tendon in-teraction ultrasound hiihto luisteluhiihto lihakset ultraäänitutkimus
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http://urn.fi/URN:NBN:fi:jyu-201504271680

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