Question

Which could result in fatigue by hindering the binding of Ca⁺⁺ to troponin?

Select one:

a. calcium

b. lactate

c. AMP

d. low pH

e. potassium

A 90 kg person is pedaling a Monark leg ergometer (distance = 6m) at a VO2 of 40 ml/kg/min. If their rpms are 70, what resistance are they pedaling against?

Select one:

a. 1.8 kg

b. 3.9 kg

c. 3.2 kg

d. 2.6 kg

e. 4.2 kg

Answer 1

## Binding of calcium to contractile protein calcium results in muscle contraction.
With repeated contraction, fatigue sets in resulting in decreased neuronal firing and decreased strength of muscle contraction.
Accumulation of metabolites such as potassium, chloride, lactic acid are the main cause of fatigue development.
The lactic acid produced decreases the sensitivity of troponin to calcium resulting in reduced binding of calcium to troponin which causes decreased rate and strength of contraction.
Answer : b. Lactate
## To find the resistance first we need to find work rate
step 1. VO2 (mL/kg/min) = [(1.8 x WR) / BW] + 7
Step 2. VO2 = 40ml/kg/min

----> body weight(BW) = 90kg

---->WR is work rate.
Step 3. 40 = [(1.8 x WR)/90] + 7

-----> WR = 1650 kg.m/min
Step 4. WR = R (kg) x D (m) x Rev/min

----> Distance (D) = 6

----> Rev/min= 70

----> R is resistance

Step 5. 1650 = R x 6 x 70

Step 6. R = 1650/420

-----> R = 3.92 kg or 3.9 kg

Answer : b. 3.9kg