Lab 5 - Muscle Physiology

During Electromyography contraction “biceps brachii contraction,” which muscle showed a higher level of EMG activity? What is that muscle’s role?

• biceps brachii show higher level of EMG activity because it is the agonist muscle

• role is elbow flexion and forearm supination during contraction

During Electromyography contraction “biceps brachii contraction,” did the triceps muscle show any level of EMG activity? What is the triceps brachii role?

• tricep brachii showed low-level EMG activity

• tricep acts as antagonist to biceps - provides joint stabilization and controlled resistance

During Electromyography increasing resistance, what was the pattern of EMG activity observed in the biceps as the number of books increased?

• EMG activity in biceps increased progressively

• there is higher resistance → requiring more motor unit recruitment and firing frequency

During the Muscle Fatigue Activity, which percentage of maximal grip force showed the least decline in force output between the 5 second point and the 20 second point?

• the 25% of max grip force showed the least decline in force output

• due to lower intensity required less motor unit recruitment and produced less fatigue

During the Muscle Fatigue Activity, why did the participants grip force decline so dramatically during the 100% of maximal grip force trial? What are some factors that lead to fatigue?

• grip force declined dramatically because maximal muscle contraction was occurring, causing faster muscle fatigue

• due to high motor unit recruitment and depletion of ATP

Agonist Muscle

muscle performing the activity

Antagonist Muscle

muscle resisting the activity

Types of Contractions

isotonic and isometric

Isotonic Contractions

muscle is allowed to change length, force can stay constant

Isometric Contractions

held at constant length (dependent on length while contracting)

Fatigue

a decline in a muscles ability to maintain a constant force of contraction in the face of long term, repetitive stimulation

Fatigue Can Be

induced by high intensity or low intensity activity

Body Has Various Methods of Combating Fatigue

recruitment of more motor units

recruitment of larger motor units

switching to synchronous firing of motor units