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I Hate Running!

And Lactate Is to Blame, Right?


Ashley E. Rhodes
Division of Biology
Kansas State University
Timothy G. Rozell
Animal Sciences and Industry
Kansas State University
Abigail R. Wilson
Division of Biology
Kansas State University


This interrupted worksheet case study, developed for introductory or intermediate undergraduate physiology courses, aims to eliminate misconceptions that many students have about lactate, lactic acid, and changes in the body during exercise. The case begins with two fictional undergraduate students discussing the causes of muscle soreness; both of these characters have obvious misunderstandings about this issue that are likely to be shared by many students. As the case develops, students are presented with information in a variety of forms including flow charts and work through some of the chemical reactions that take place in actively contracting skeletal muscle cells to better understand the real cause of muscle soreness. By the end of the case, students will have explored this complex issue from multiple angles.


  • Distinguish between lactic acid and lactate including production in skeletal muscle.
  • Explain why lactate is a useful compound for skeletal muscle cells.
  • Describe why skeletal muscle cells produce different LDH isoforms and that LDH is a protein thus created via transcription and translation.
  • Describe lactate elimination from the muscle cell producing it and the value of symporters for facilitated diffusion.
  • Clarify H+ production and elimination in muscle cells, and why lactate is not a cause of proton production (acidification) and muscle soreness.
  • Relate how misuse of correlations has allowed faulty information to be propagated for decades.


Exercise; lactate; lactic acid; muscle physiology; metabolism; aerobic respiration; anaerobic respiration

Topical Areas

History of science

Educational Level

Undergraduate lower division, Undergraduate upper division



Type / Methods




Subject Headings

Biology (General)  |   Cell Biology  |   Physiology  |   Sports Science  |  

Date Posted


Teaching Notes

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Supplemental Materials

For instructor convenience, several of the figures that appear in the case study handout are also included in the PowerPoint presentation below.

  lactate.pptx (~1.2MB)

Answer Key

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