Physiology of endurance

The Physiology of Muscle Endurance

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The Physiology of Muscle Endurance

Exercise has many benefits, all of which can be manipulated based on your goals and a consistent and progressive exercise program. On a cellular level you can achieve major adaptations in skeletal muscle. These include increases in the mitochondrial content (the lungs) of your muscle fibers. An increase in mitochondrial density means that you will be able to perform exercise of the same intensity with less effort required (and less pain!). Your muscles will also become more efficient, requiring less blood glucose, achieve a slower utilisation of muscle glycogen (stored energy), an increased ability to use fat as a fuel source (fat oxidation), and result in less lactate (waste product) produced at a given intensity.  These adaptations play an important role in the large increase in the ability to perform prolonged strenuous exercise that occurs in response to endurance exercise training.


  • Increased mitochondrial density
  • Reduced reliance on blood glucose as a fuel source
  • Slower utilisation of muscle glycogen
  • Increase fat oxidation
  • Reduced lactate production

Great! Right? So, how do you apply this to your  training? By having a play with the below variables, you are able to apply the right amount of stress to the system at the right tempo for the right duration with the most appropriate load with just a little rest period and viola! you are away.

Essentially, we always want fatigue. I would encourage you to start with 2 sets of 15-18 reps, and as long as you fatigue within this rep window, then you have the most appropriate weight. Fatigue is paramount. Low load does not mean light intensity. You should be working hard, just working for longer. Have a look at the guidelines below and get in touch with your local exercise physiologist if you have any questions about how to apply these principles to your chosen activity.


Sets: 1-2 sets per exercise / movement pattern

Reps: >15 (typically 15-25)

Load: Less than 60% 1RM

Tempo: 3 seconds eccentric, 2 seconds concentric (5 seconds per movement)

Time under tension: >75 seconds

Rest: 30-60 seconds

Duration: 6 weeks +



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Hoppeler H, Fluck M. Plasticity of skeletal muscle mitochondria: structure and function. Med Sci Sports Exerc. 2003 Jan; 35(1):95-104.

Favier RJ, Constable SH, Chen M, Holloszy JO. Endurance exercise training reduces lactate production. J Appl Physiol (1985). 1986 Sep; 61(3):885-9.

Holloszy JO. Muscle metabolism during exercise. Arch Phys Med Rehabil. 1982 May; 63(5):231-4.

Crenshaw AG, Fridén J, Thornell LE, Hargens AR. Extreme endurance training: evidence of capillary and mitochondria compartmentalization in human skeletal muscle. Eur J Appl Physiol Occup Physiol. 1991; 63(3-4):173-8.

Holloszy JO, Coyle EF. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. J Appl Physiol Respir Environ Exerc Physiol. 1984 Apr;56(4):831-8.

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