0000000000135325
AUTHOR
József Tihanyi
The effect of fatigue on store and re-use of elastic energy in slow and fast types of human skeletal muscle
Stretch-shortening exercises are characterized by enhancement of performance when compared to the work output performed in shortening conditions. There is evidence that fast subjects are unable to re-use great amounts of elastic energy during stretch-shortening cycles performed with slow stretching speed and large stretching length. In the present study, 14 subjects possessing different fibre types in m. vastus lateralis performed vertical jumps with and without preliminary countermovement and with large angular displacement and slow stretching speed The jumping tests were executed before and immediately after fatigue induced by short intense exercises (60 s of continuous rebound jumping). …
Store and recoil of elastic energy in slow and fast types of human skeletal muscles.
Stretch-shortening cycle refers to the mechanical condition in which store and recoil of elastic energy occur in the skeletal muscle. This leads to a greater work output when compared to a simple shortening contraction. The subjects performed vertical jumps with and without preliminary counter-movement and with small and large knee angular displacement. The results indicated that those subjects who had more fast twitch (FT) fibers benefited more from the stretching phase performed with high speed and short angular displacement. The amounts of elastic energy stored in this phase were 30 and 26 N X kgBW-1, respectively, for FT and slow twitch (ST) type subjects. The recoil of elastic energy w…
Function of the flexor hallucis longus muscle : what do we know? = A flexor hallucis longus izom működése : mit tudunk róla?
Flexor hallucis longus (FHL) muscle has several functions, including plantarflexion of the ankle, flexion of the big toe and support of the medial longitudinal arch. To date, only a few studies have used non-invasive methods to examine FHL behavior during real-life movements, although the proper functioning of this muscle may be important to increase sport performance, the altered FHL function may contribute to the susceptibility to Achilles tendinopathy and the function of FHL is altered in other clinical conditions such as flatfoot. FHL seems to be multifunctional but other active and passive structures also contribute to the same functions. Because of the multifunctionality of the foot s…
Superimposing hip extension on knee flexion evokes higher activation in biceps femoris than knee flexion alone.
Hamstring muscle function during knee flexion has been linked to hamstring injury and performance. However, it is unclear whether knee flexion alone (KF) requires similar hamstring electromyography (EMG) activity pattern to simultaneous hip extension and knee flexion (HE-KF), a combination that occurs in the late swing phase of sprinting. This study examined whether HE-KF maximal voluntary isometric contraction (MVIC) evokes higher (EMG) activity in biceps femoris long head (BFlh) and semitendinosus (ST) than KF alone. Effects of shank rotation angles were also tested. Twenty-one males performed the above-mentioned MVICs while EMG activity was measured along ST and BFlh. Conditions were com…
Mechanical power test and fiber composition of human leg extensor muscles.
The present study was undertaken to assess the relationship between the mechanical power developed during new anaerobic power test and muscular fiber distribution. Ten track and field male athletes were used as subjects, whose muscle fiber composition (m. vastus lateralis) varied from 25 to 58 fast twitch (FT) fibers. The test consisted of measuring the flight time with a special timer during 60 s continuous jumping. A formula was derived to allow the calculation of mechanical power during a certain period of time (e.g., in the present study every 15 s during 60 s of jumping performance). The relationship between the mechanical power for the first 15 s period correlated best with fast twitc…