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Q11 - Temperature, Lactic Acid and Salbutamol Effects on Muscle Fatigue

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Muscle Physiology

Muscle fatigue during work results in increasing extracellular concentration of K+. This may be modified by changes in physiological temperature and lactic acid level, and can be treated medically with the drug salbutamol. This was studied experimentally with rat muscles stimulated electrically once every 20 minutes (Fig.). Effect of warm-up at 20°C, 30°C and 35°C before work or addition of lactic acid or a combination of lactic acid and salbutamol at 35°C on the change in muscle force (as percent of force at 4 mM [K+]).

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. During work, contracting muscles lose K+, leading to increased extracellular [K+]
B. Temperature increase, and addition of lactic acid and drug operate mainly additively
C. The study design is incomplete
D. At physiological temperature (here 35°C), lactic acid protects completely against muscle fatigue
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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)