Tensile Force in Total Striated Muscle, Isolated Fibre and Sarcolemma

115

SUMMARY1. Relations between sarcomere length, tension and time course of isometric twitches at 200 C were determined for thirty-two sartorius muscles from Rana temporaria.2. The maximum isometric twitch tension per unit cross-sectional area of muscle ranged from 0-56 to 2-2 kg/cm2 at 200 C and initial sarcomere length about 2* 1 u. This variation was not correlated with the corresponding measure of tetanic tension.3. The maximum isometric twitch tension per unit cross-sectional area of muscle at 2 1 ,z sarcomere length was directly correlated with twitch contraction time and inversely correlated with the cross-sectional area of the muscle.4. The isometric twitch contraction was potentiated with increase in initial sarcomere length from about 2d1 to about 2-8 ,t at 200 C, and the degree of potentiation was inversely correlated with the maximum isometric twitch tension per unit cross-sectional area of muscle at 2 1 a sarcomere length. 5. The sarcomere length:twitch tension relation is labile and may be altered by changes in temperature and the after-effects of repetitive stimulation.6. Variation in twitch contractions at different sarcomere lengths are discussed in connexion with excitation-contraction coupling and the degree of activation of muscle fibres during twitch contractions at 20°C.

Section: Resultsmentioning

confidence: 60%

The relations between sarcomere length and characteristics of isometric twitch contractions of frog sartorius muscle

Close¹

1972

115

“…More recent attempts to measure the contribution of connective tissue to stiffness have suggested that it contributes only at long sarcomere lengths, > 30 0,m according to Casella (1951) and Rapoport (1973) and > 26,um according to Tidball (1986). It now appears that structures within muscle fibres contribute to resting stiffness (Magid & Law, 1985).…”

Section: Interpretation Of Stiffness Measurements In Intact Limbsmentioning

confidence: 99%

Muscle stiffness, strength loss, swelling and soreness following exercise‐induced injury in humans.

Howell

Chleboun

Conatser

1993

293

216

SUMMARY1. In order to study injury-related changes in muscle stiffness, injury to the elbow flexors of thirteen human subjects was induced by a regimen of eccentric exercise.2. Passive stiffness over an intermediate range of elbow angles was measured with a device which held the relaxed arm of the subject in the horizontal plane and stepped it through the range of elbow angles from 90 deg to near full extension at 180 deg. The relation between static torque and elbow angle was quite linear over the first 50 deg and was taken as stiffness.3. Stiffness over this range of angles more than doubled immediately after exercise and remained elevated for about 4 days, and may result from low level myofibrillar activation induced by muscle stretch.4. Arm swelling was biphasic; arm circumference increased by about 3 % immediately after exercise, fell back toward normal, then increased by as much as 9 % and remained elevated for as long as 9 days.5. Ultrasound imaging showed most of the swelling immediately following the exercise to be localized to the flexor muscle compartment; subsequent swelling involved other tissue compartments as well,.6. Muscle strength declined by almost 40 % after the exercise and recovery was only slight 10 days later; the half-time of recovery appeared to be as long as 5-6 weeks.

“…There is evidence to suggest that most of the energy lost during a stretch-shortening cycle is absorbed in the sarcolemma (Tidball, 1986;Tidball & Daniel, 1986) and that most of the passive tension at longer muscle fibre lengths (> 140-150 % of resting muscle length, Lo) is borne by the sarcolemma (Casella, 1951;Higuchi & Umazume, 1986;Rapoport, 1972).…”

Section: Role Of Mechanical Factors In Muscle Injtjrymentioning

confidence: 99%

Mechanical factors in the initiation of eccentric contraction‐induced injury in rat soleus muscle.

Warren

Hayes

Lowe

et al. 1993

203

191

SUMMARY1. Alechanical factor(s) associated with the initiation of eccentric contractioninduced muscle injury were investigated in isolated rat soleus muscles (n = 180; 42 protoc ols with 4-6 muscles per protocol). Five eccentric contractions were performed with 4 min between contractions. Three levels of peak eccentric contraction force (100, 125 and 150% of pre-injury maximal isometric tetanic tension. P0), length change (041. 0 2 and 0 3 muscle length, Lo) and lengthening velocity (0(5, 1P0 and 1P5 Lo/s) were utilized. Force was varied with stimulation frequency (10-150 Hz). The eccentric contractions were initiated at muscle lengths of 0(85 or 0(90 Lo.Following the fifth eccentric contraction, the muscle was incubated in Krebs-Ringer buffer for 60 min. Peak isometric twitch tension (PT), PO, maximal rate of tension development (+dPI/dt), maximal rate of relaxation (-dP/dt), and creatine kinase (CK) release were measured prior to the five eccentric contractions and at 15 min intervals during the incubation period. Total muscle [Ca2+] was measured after 60 min incubation.2. The mean (+S.E.M.) initial decline in P0 for the muscles performing the most injurious protocol was 13-6 + 4-8 % (n = 6); P0 in control muscles immediately following performance of five isometric contractions was elevated 1P2 + 1 0 % (n = 8). These means were different at probability. p = 0(005. Mean [ATP] G. L. WARREN AND OTHERS control muscles but the elevation was unrelated to any of the four mechanical factors. 4. These data support the hypothesis that eccentric contraction-induced injury is initiated by mechanical factors, with muscle tension playing the dominant role. They also demonstrate that specific mechanical factors differentially affect the various injury criteria, i.e. reductions in contractile performance were most related to produced forces, and CK release was most related to lengthening velocity.