As the concentration of glucose in tear fluid increases, the resistance of the sensor decreases and this reduction in turn decreases the resistance of the parallel circuit of the LED and the sensor. (nanotechweb.org)
On the other hand, if the exercise is too hard for you, then you can decrease the resistance by placing your feet on the floor instead of the other bench. (fitnessandpower.com)
If you're using an exercise band, try to get a few bands of varying tension so you can decrease the resistance as you get stronger. (womenshealthandfitness.com.au)