The Affects Of Aging On Skeletal Muscle — страница 2

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margins of brachioradialis and the flexor carpi radialis. This muscle pronates the forearm and is a weak flexor of the elbow. The Flexor carpi radialis runs diagonally across the forearm; midway its fleshy belly is replaced by a flat tendon that becomes cordlike at the wrist; it is a powerful flexor of the wrist, it abducts the hand and is a synergist of elbow flexion. The ankle dorsi flexor muscles consist of the tibialis anterior, extensor digitorum longus, peroneus tertius, and the extensor hallucis longus the nerve supply is the deep peroneal nerve. The Tibialis anterior muscle is superficial of the anterior leg, laterally it parallels the sharp anterior margin of the tibia. The tibialis anterior is the prime mover of dorsi flexion; it also inverts the foot and assists in

supporting the medial longitudinal arch of the foot. The Extensor digitorum longus (EDL) is on the anterolateral surface of the leg, lateral to the tibialis anterior muscle. The EDL dorsi flexes the foot and is the prime mover of toe extension. The Peroneus tertius is a small muscle that is usually continuous and fused with the distal part of the extensor digitorum longus. It dorsi flexes and everts the foot. The Extensor hallucis is deep to the extensor digitorum longus and tibialis anterior it extends the great toe and dorsi flexes the foot. The study done by Lexell, et al. (1997) focused on the fatigue rate, endurance level and the relative reduction in muscle force during maximal voluntary contraction (MVC) while performing dynamic knee extensions. The knee extensors measured

were the rectus femoris, vastus lateralis, vastus medialis, vastus intermedius (quadriceps), and the triceps surae. The rectus femoris is a superficial muscle of the anterior thigh it runs straight down the thigh and is the only one of the quadriceps to cross the hip joint. It extends the knee and flexes the thigh at the hip. The nerve supply is the femoral nerve. The vastus lateralis forms the lateral aspect of the thigh and extends the knee. The vastus medialis forms the inferomedial aspect of the thigh, it extends the knee and its inferior fibers stabilize the patella. The vastus intermedius is obscured by the rectus femoris, and lies between the vastus lateralis and vastus medialis on the anterior of the thigh. Like the above muscles it extends the knee and its nerve supply

is the femoral nerve. This group, along with the rectus femoris, forms the quadriceps. The Triceps surae refers to the muscle pair that shapes the posterior calf and inserts by a common tendon into the calcaneus of the heel (Gastrocnemius and soleus). Research Review Skeletal Muscle Fatigue and Endurance in Young and Old Men and Women Britta Lindstrom, Jan Lexell, Bjorn Gerdle, and David Downham Lindstrom et al (1997) used 38 physically healthy individuals, 22 young and 16 old to test the fatigue rate, the endurance level, and the relative reduction in muscle force. There were 14 men and 8 women 28 years old that made up the young group. The older group consisted of 8 men and women 73 years old. None of the 38 volunteers were elite athletes, but all of them participated regularly

I low intensity aerobic exercise (walking, cycling, etc.). (Lindstrom et al.1997) The term fatigue is defined as failure to maintain force or power output, in contrast to weakness, which is failure to generate force. The method used to assess muscle fatigue has been used for over 10 years and measured the reduction in muscle force during 100 ? 200 repeated contractions. It also allows the researchers to estimate indirectly the maximal voluntary contraction and to determine muscle endurance. (Lindstrom et al.1997) In this study, muscle fatigue and endurance were assessed in the knee extensors, previous studies assessed muscles in the thigh, these muscles have different actions and different muscle fiber type compositions, and the results are not always comparable. A common well

known problem studying human muscles is the difficulty controlling factors such as the individual?s nutritional status, level of physical activity, etc. (Lindstrom et al.1997) It was found that the rate at which muscle force was lost during the fatigue test was unaffected by increasing age. The only noticeable difference between younger and older individuals was the larger variability in fatigue rate among both older men and older women compared to younger men and younger women. This increased variability in fatigue rate in older individuals could be due to age-related alterations in fiber-type composition. (Lindstrom et al.1997) The results in this study imply that increasing age does not markedly alter the ability of the quadriceps muscle to maintain force throughout repeated