Worried that their parents are hurting their health from not being active, the children encourage them to exercise.
Lincoln and Clyde are playing Muscle Fish in Lincoln's room. After beating a boss, Clyde says that he has to leave because his fathers are competing in the Royal Woods Ultra Extreme Ninja Competition. He explains that it's the ultimate obstacle course that tests a person's strength and athletics. Clyde says that Howard and Harold are doing this because they want to have a healthy life, so they can live long enough to see him grow up. After Clyde leaves by riding in a car being hauled by Howard and Harold, Lincoln discovers his mother and father sitting lazily on the couch. Lincoln tries to encourage them to go out for a walk, but they tell Lincoln that they're fine, and Charles comes by, wanting to go for a walk. The parents play "Nose Goes", and both of them win, forcing Lincoln to take Charles out.
Later at night, the siblings hold a house meeting, and Lincoln shows his sisters how inactive their parents are, which is further explained when Lisa shows them their urine samples, and fecal study (the latter of which is quickly rejected). Lincoln says that he has a plan to get them into shape so they can be healthy enough to see their kids grow up, to which all the sisters agree.
The next day, Rita and Lynn Sr. deny the fact that they need exercise. However, they're proven wrong when Lynn Sr. can't put on his socks, Rita is unable to bend over to pick up the van keys, and say they can't walk up the stairs. At a park, Lynn suggests that they try rock climbing, but are unable to get a good grip. Lana suggests mud wrestling, and single-handedly takes down Rita, causing Lynn Sr. to hide in the van. Lincoln suggests that they tone down their methods. Lisa suggests tai chi, Leni suggests t-shirt folding (as a way to work on triceps), Lana and Lola suggest jump rope, Luna suggests guitar playing, and Lori suggests jogging, all of which Rita and Lynn Sr. can easily do (although, during Lori's jog, Lynn Sr. tries to chase an ice cream truck, but is tackled by Lana). Later on that day, the parents thank their kids for introducing them to the joys of exercising and decide to go a run around the block. Because of them being active now, the siblings declare that their job is done.
In the middle of the night, Rita and Lynn Sr. wake all of their children up, because they were so excited with all the exercising, that they want to do more. They also said that because the kids cared about their health, they thought they'd also cared about their health in return. The parents make their kids go through exhausting exercises such as jumping jacks, push-ups, weightlifting, and jogs around the block (just like Lynn Sr. yesterday, they chase after an ice cream truck, but the parents stop them). After the exercising, Rita and Lynn Sr. present the kids with onion-infused water and (actual) grubs, all of which (except Lana) find disgusting.
A week later, the siblings are exhausted from all the exercising, and Lola initially blames Lincoln for making the parents' health crazy, with Luna agreeing. Luckily, Lincoln says he has a plan to make them stop. He has the sisters fake that the parents are making excellent progress such as tampering with the scale, discretely swapping their clothes with bigger sizes, adding big numbers to their weights, and turning the clock back. When the parents fall for these tricks, they surprise the kids with a spaghetti dinner. They say that because they've made such great progress, that they get an exercise-free day tomorrow, much to their joy.
The next morning, the siblings wake up, completely relaxed. However, their moment of relaxation is cut short when Lincoln discovers a note their parents left behind. Lincoln reads the letter and discovers that they're competing in the Royal Woods Ultra Extreme Ninja Competition. Fearing that they'll fail the competition, they quickly rush off to the arena.
The siblings arrive at the arena and discover their parents hanging precariously on a beam. After scaling the rock climbing wall, the siblings jump onto the beam their parents are on and ask why they're competing in the competition. The parents say that they believed that they were fit enough to join the competition, but the siblings tell them that they were staged. They only wanted to make them look like they lost weight so that they won't have to exercise with them. Despite this, the parents won't punish the kids, but the tender moment is cut short when the beam they're hanging from breaks due to all of their combined weight.
Later on, the Louds are power walking with Lynn Sr. blowing his whistle and telling them to speed up. When Rita tells her husband that they need to tone down their activeness, they witness an ice cream truck passing by and begin to chase it down.