Stand in a side lunge position with one leg bent parallel to the floor and the other leg straight to the side. Jump up explosively as you switch legs. Now the previously straight leg will be bent and the previously bent leg will be straight to the other side. Try and keep your core tight and stay as low as possible as you switch sides as fast as you can.
You’ll find planks among Ceasar Barajas‘, Jessica Muenster’s, and Amanda Murdock’s favorites exercises to do with no equipment. Murkdock (who recommends “planks all day long”— ouch) says that they work the entire body, can be done anywhere, and have a lot of variations. Muenster specifically favors plank jacks with palm-to-elbow movement because they also raise your heart rate.
Back to the tricep pushups and really activating those tricep muscles for toned arms. If you need a rest, that's totally cool. Just take a break in the up position and maintain that plank form. This way you are still working your arm muscles just by holding your body weight up. So that's totally fine for some of our beginners out there. For those who are more advanced, we want you going as hard as you can and trying to hit that 15 to 20 reps. You're doing great.