QuestionSBA
QuestionChoice
These fibres provide intermediate contraction speed. They display moderate fatigue resistance due to the reliance on both aerobic and anaerobic metabolism. They are recruited in activities requiring both endurance and strength, such as middle-distance running and swimming.
10026626
b
Type IIa (intermediate muscle fibres)
QuestionChoice
There is no type IV motor unit.
10026629
e
Type IV (fast twitch muscle fibres)
QuestionChoice
There is no type III motor unit.
10026628
d
Type III (slow twitch muscle fibres)
QuestionChoice
These fibres provide slow and sustained contractions and hence are well suited to maintain an upright posture. They display high fatigue resistance due to a rich blood supply and numerous mitochondria. They primarily rely on aerobic respiration (oxidative phosphorylation) for energy production.
10026625
a
Type I (Slow twitch muscle fibres)
QuestionChoice
These fibres provide fast and powerful contractions. They display low fatigue resistance due to reliance on anaerobic metabolism. They are suited for high-intensity, short-duration activities, such as weightlifting and sprinting.
10026627
c
Type IIb (fast twitch muscle fibres)
Concept
Chapter
2693
5905
Types of muscle fibres
Topic
154
Musculoskeletal physiology and disease
17723
A 26-year-old female athlete who runs long-distance marathons presents to the clinic with back pain. You ask the patient to stand up to examine her.

Which muscle unit is recruited to maintain an upright posture?
a