I have a different routine now and working mostly on the lower body but great job to those who started early and followed through this challenge. They probably do 50 to 100 push ups in a row but it's just a mere warm up before lifting hehe. Can you confirm this JJG?
I have been doing some lunges, and I am thinking that the lunges might be good since they can be done anywhere, just like pushups.
Lunges exercises are also good exercise, outside that this exercise can be done anywhere it's also a powerful exercise that help to strengthen and shape almost every muscle in the lower body like the glutes, hips, quads etc.
Sometimes I use lunges exercise to end my push-up exercise in any of my session I usually start with the minimum of 3 set 10 reps in the first set, 12 reps in the second set and 15 reps in the third set, then when I want to increase my intensity I do a walking lunges exercise. This exercise has really helped me a lot combined with my push-up exercise.