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Laboratory 8 Muscle Soreness Lab Manual

Lab 8: Muscle Soreness & Exercise Injury – Study on delayed onset muscle soreness (DOMS), eccentric exercise effects, fatigue, and recovery using soreness ratings and performance data.

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    LABORATORY 8 MUSCLE SORENESS AND EXERCISE-INDUCED MUSCLE INJURY Piirpngp Learn - Methods for measuring the time course of muscle injury Understand - Mechanisms underlying muscle injury following eccentric exercise - Basic relationships between perceived exertion, fatigue, and delayed onset muscle soreness. Background Most of us have experienced sore muscles following exercise or strenuous activity. Soreness that persists long after the exercise stops is called delayed onset muscle soreness (DOMS). This soreness is usually relatively mild, and goes away in several days. Alternatively, soreness can be severe enough to limit physical activity in normal subjects and reduce exercise performance in athletes—this soreness has been associated with muscle damage. Evidence for muscle damage includes ultrastructural disruption of myofibers seen with a microscope in biopsy samples, reduced muscle strength lasting long after muscle fatigue is thought to have ended, and the presence of muscle specific proteins in the blood. Previous studies have shown that muscle injury is most often associated with unaccustomed exercise and with a particular kind of muscle action called an eccentric action. Muscle adapts rapidly to muscle damage such that repeating an exercise that had previously caused muscle soreness no longer does (called the protective effect or repeated bout effect). The protective effect is specific to the exercised muscle, can occur after a single bout of exercise, and can last 3-4 weeks. The mechanisms associated with muscle resistance to injury on repeated exposure to exercise stress are not fully understood and remains a fertile area for future research. Because DOMS is so common, and because it can disrupt exercise and function, it is important to develop a better understanding of what it is and what activities are associated with the greatest muscle soreness. In this way we can find ways to avoid or minimize the negative effects of muscle soreness/injury. Procedures **Barring injury or sickness all students will perform the *exercise** The class should pair-up; groups of 3 are permissible if necessary. During each round of the exercise protocol the non-exercising student will supervise the exercise and record data. The non-exercising student is responsible for correcting their partner's stepping form. 1. Prior to exercise, please record subjects' height, weight, age, and dominant leg. Muscle soreness will be recorded using a continuous scale (see data sheet below). 2. Soreness in the calf muscle will be assessed using two methods beginning in lab

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    and continuing over the following 72 hours. a. First, the observer presses on the calf firmly for 2 seconds and subjects provide a pain rating. This is repeated in a number of spots and the highest reading is recorded. b. Second, the subject fully flexes and extends the muscle and rates the pain. Any alteration in the normal range of motion should be noted. 3. Exercise consists of calf raising , using one leg to go up and one leg to go down (see illustration below). The timing is one second up and 2 seconds down This will be continued for 50 contractions. 4. During exercise, the student should note the overall rating of perceived exertion (RPE) of the exercise bout at 0 (baseline), 25, and 50 contractions. The student should also note the ratings of fatigue sensations (difficulty in doing the exercise) within each leg, using the same scale as that used for the RPE, at 0, 25, and 50 contractions. EXERCISE PROTOCOL Calf Raise References McCully, K. Exercise-induced muscle injury to skeletal muscle. Federation Proceedings 45: 2933-2936, 1986. Warren GL, Lowe DA, Armstrong RB. Measurement tools used in the study of eccentric contraction-induced injury. Sports Med Jan; 27(l):43-59, 1999.

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