발육기 초기 신체훈련이 백서의 골격근섬유형 조성비에 미치는 영향

Abstract

[한글]

성숙한 포유동물의 골격근섬유는 수축속도, 효소의 활성도, myosin ATPase와 같은 효소활성도의 조직화학적 염색 및 면역화학적 방법에 의하여 type Ⅰ섬유(slow twitch fiber-ST fiber)와 type Ⅱ섬유(fast twitch fiber-FT fiber)로 대별된다(Padykula 및 Herman, 1955; Stein 및 Padykula, 1962; Guth 및 Samaha, 1969, 1970; Burke 및 Edgerton, 1975; Gauthier, 1979).

이런 골격근섬유의 조성은 골격근의 종류에 따라 다르며 이같은 근섬유는 태아말기나 출생초기에 분화하기 시작하여 연령이 증가됨에 따라 지속적으로 변화된다(Kuge1berg, 1976; Rubinstein 및 Kelly, 1978). 물론 이같은 근섬유조성이 신경 impulse의 발생빈도에 의하여 조절된다함은 이미 잘 알려져 있으나(Salmons 및 Vrbova, 1967: Barany 및 Close, 1971; Streter등,1973) 신체지구력훈련이 근섬유조성에 미치는 영향에 대하여서는 학자들간에 논란의 대상이 되고 있다. 즉 대부분의 학자들은 신체지구력 훈련이 성숙한 포유동물의 근섬유조성을 변화시키지 않는 것으로 믿고 있으나(Gollnick등, 1972, 1973; Saltin등, 1977; Buchtal 및 Schma1bruch,1980) 장기간 신체지구력훈련을 부하할 경우 type Ⅱ섬유가 type Ⅰ섬유로 혹은 type Ⅱ^^B섬유가 type Ⅱ^^A섬유로 전환될 수 있다는 보고가 있다(Andersen 및 Henriksaon, 1977; Guy 및 Snow,1977: Jansson 및 Kaijser, 1977; Jansson등, 1978).

그러나 Baldwin등(1975)은 신체지구력훈련에 의한 근섬유조성의 변화에 대하여 학자들간에 상이한 결과를 보이는 것은 신체지구력훈련을 부하한 시기가 다르기 때문이라고 하였다. 따라서 저자는 발육초기 신체지구력훈련이 근섬유분화에 미치는 영향을 관찰하기 위하여 본 실험을 시행하였다.

출생후 5일된 흰쥐 (Wiatar strain)를 실험군과 대조군으로 분류하여 실험군에는 신체지구력훈련으로 수영훈련을 10일, 20일 그리고 30일간 부하시켰다. 훈련전 및 훈련후 근섬유조성을 myosin ATPase의 조직화학적 염색방법 (Brooke 및 Kaiser, 1969, 1970a,b)으로 분석하였으며 아울러 최대수영시간 및 체중을 측정하여 다음과 같은 성적을 얻었다

1. 흰쥐의 체중은 성장함에 따라 증가하였는데 출생후 20일까지는 수영훈련군의 체중은 대조군에 비하여 유의한 변화가 없었으나 20일 이후부터는 체중이 대조군보다 의의있게 증가되었다.

2. 흰쥐의 최대수영시간 역시 성장함에 따라 증가하였는데 발육초기 10일 및 20일간 수영훈련을 시킨 군의 최대수영시간은 대조군에 비하여 유의한 차이가 없었으나 30일간 수영훈련을 부하한 군에서는 최대수영시간이 대조군보다 의의있게 증가되었다.

3. 발육초기에 부하한 수영훈련은 가자미근과 전경골근의 근섬유조성에 영향을 미치지 않았으나 나머지 장지신근, 비복근, 족척근 및 외측광근의 경우 10일간 수영훈련을 시킨 군에서 type Ⅱ섬유는 증가하였고 type Ⅰ섬유는 감소하였다. 그러나 27일, 30일간 수영훈련을 부하한 군에서는 대조군에 비하여 근섬유조성의 유의한 변화가 없었다.

이상의 성적으로 미루어 보아 발육초기 흰쥐에 부하한 수영훈련은 근섬유분화를 억제하고 신체운동수행능력을 증가시키나 이같은 신체운동수행능력의 증가는 근섬유조성 이외의 다른 요인즉 훈련효과에 의한 것으로 생각된다.

[영문]

Skeletal muscle fibers in various adult mammals are generally classified into type Ⅰ and type Ⅱ fibers depending on 1) their contraction time, 2) their enzyme activities, 3) their histochemical staining characteristics of the specific enzyme

activities, such as myosin ATPase, and 4)their immunochemical criteria(Padykula and Herman, 1955: Guth and Samaha, 1969; Burke and Edgerton, 1975; Gauthier, 1979). However, the muscle fiber differentiation begins at the late fetal or early postnatal life and differentiation rate of individual muscle fiber types are

changed progressively with ageing(Kugelberg, 1976; Rubinstein and Kelly, 1978). It is a1so well established that transformation of the muscle fiber types is determined by the frequencies of nerve impulses reaching the muscle fibers(Salmons and Vrbova, 1969; Barany and Close, 1971; Streter et at., 1973). But recently the

possibility of interconversion of muscle fiber tapes induced by physical endurance training has been widely investigated. Most investigators believe that physical endurance training does not alter the muscle fiber composition(Saltin et al., 1977; Buchtal and Schmalbruch, 1980). However, it has been reported that transformation of type Ⅱ into type Ⅰ fiber or type Ⅱ^^B into type Ⅱ^^A fiber is possible with more strenuous and prolonged endurance training(Guy and Snow, 1977; Jansson et al., 1978). Ba1dwin et al.(1975) suggested that transformation of muscle fiber types by physical training may also be dependent on developmental stage of the animals when a training program is started.

Therefore, the present study was undertaken to evaluate the effect of the physical endurance training at early developmental stage of rat on the transformation of musc1e fiber types.

Rats(Wistar strain) of 5 days old after birth were divided into an experimental group and a control group. The experimental groups were trained by swimming for 10 days, 20 days and 30 days. During training period, maximal swimming time and changes in body weight in both groups were measured. At the end of training

program, rats were killed and the six different muscles (m. soleus, m. tibialis anterior, m. extensor digitorum longus, m. gastrocnemius, m, vastus lateralis) were dissected out and the proportions of type Ⅰ and type Ⅱ fiber were determined

according to their histochemical staining of myosin ATPase activity.

The reaults obtained are summerized as fellows;

1. Body weight of rats increased with age. Both groups showed no significant difference changes in body weight from 5 day to 20 days after birth. But after 20 days of training, the experimental group gained significantly larger body weight compared to controls.

2. Maximal swimming time also increased with age in both groups. The experimental groups trained for 10 days and 20 days from 5 days after birth showed no significant difference in maximal swimming time compared to the controls. However, in the case of 30 days training group, maximal swimming time of the experimental group was significantly higher compared to that of controls.

3. The muscle fiber composition of m. soleus and m. tibialis anterior have not changed by the swimming training at the early developmental stage. But in case of the other muscles(m. extensor digitorum longus, m. vastus lateralis), at the age of 15 day i.e., 10 days of physical training after birth, the proportion of type Ⅱ fibers was bigher significantly, whereas type Ⅰ fibers was lower in the experimental group compared to the controls. On the other hand, in the trained groups for 20 days and 30 days have not shown any significant changes in muscle fiber composition.

From the above results, it is suggested that the normal pattern of differentiation of muscle fibers could be delayed temporarily by the physical endurance training at the early developmental stage, but the increase in physical performance induced by physical endurance training was resulted from the another factor rather than the muscle fiber composition i.e., from training effect.