At least from what I've seen. Can never stop advocating for the Step Up Exercise. It truly is one of the most essential yet underrated leg exercises there is. Shit if the legendary Bob Backlund can do them and the strength & conditioning they gave him, why not others? Sure it's important to make sure you're not working with potentially harmful injuries especially in the knees and ankles but for the most part, these can highly be a godsend for building incredible leg strength, health and for your cardio.
I've been doing this exercise for many years now and it doesn't seem to slow me down, matter of fact, has kept me in pretty damn good shape. I hate jogging and Sprinting in below ten weather in the wintertime here is not always an option. If you want an alternative to sprints, do the Bear Crawls bro (read about my micro workout on this exercise). Step Ups especially done in high numbers bring incredible benefits which one of the perks is that you won't get as sore as you would with squats. Now that doesn't mean squats aren't good, they're awesome, I'll do them as part of my deck of cards workout with the Step Ups. Squats have their place and are as essential as any basic movement, I just prefer Step Ups as my go to Leg Exercise.
Although it doesn't look like much (quite frankly its the exercise equivalent to a leg exercise from Wish to some people) but for others, it brings out all the benefits of cardio training without needing a treadmill or getting burned out from hundreds of squats. You ever hear the story about Backlund and the Marathon runner? I've written about it before but it's for a repeat: So this marathon runner thought Step Ups were pretty easy since after all, he withstands 26.2 miles for a lot of years so he wanted to see if he could give a Backlund a run for his money (no pun intended). So for the most part, this guy thinks this is a no brainer but roughly 20 minutes in, Bob is still killing it and this distance runner walks out the door and is never heard from again. He couldn't take it and it goes to show that you never underestimate the power of a simple yet effective exercise.
I've done my fair share of them over the years in a variety of ways from doing them straight through for 30 min to an hour at a time to doing supersets with other exercises such as Farmer's Walks, shoulder carrying my 50 lb sandbell or bear hug carry to slamming my slam ball. The deck of cards workout where it's Step Ups & Squats ranks right up there with that Rugged Conditioning type of training. The objective is to get to 500 Step Ups & 250 Squats by the end of the deck and if you can finish it in under 30 minutes, kudos for you man; I'm just a notch above the 30 min mark when I finish it. One time, I doubled the reps that came out to 1000 & 500 respectively going back and forth between two decks of cards with barely a break. Until you've done it, it's not something easily to describe.
Despite it's overwhelming simplicity, Step Ups gives you not incredible leg strength and conditioning, it's a pretty damn good muscle builder too since you're working your legs unilaterally. It's had me keeping my California Redwood legs in tact so far. My dad doesn't call me a tree trunk for nothing. With natural muscle, strength & cardio, you're looking at some solid boosting of testosterone and HGH. Our legs provide the means to develop our sex organs, energy and power. When you consistently train your legs (safely of course and not getting injured frequently), you're bringing more vitality and desire into play. Don't be surprised if you start to feel like a wild teenager again, it is possible. It's important that we can increase our testosterone as we age ( with the right tools and not always go to drugs) but we also don't want to overload it because too much testosterone isn't always a good thing. Work it until you reach a certain level and maintain that. Mine's in the normal range for men in my age group and normal to elite level of testosterone is around 300 and 1,000 nanograms per deciliter (ng/dL); I'm in around the 350's so for 35-45, that's pretty good. It could be better with diet and intense training but take things one at a time.
Training and eating good gives off incredible boosts but the type of training you do should be intense and rugged like Sprints, Isometrics, Strength Training whether with weights or bodyweight and doing enough to recover efficiently. The diet is not always easy especially if you're on a budget but if you keep the junk to a bare minimum if at all, stick with a good source of meats, eggs, certain fruits and veggies along with drinking plenty of water. We all have our vices but I do love a good steak and eggs or rice with some liquid IV for hydration or make bunless cheese burgers with eggs. I usually scramble my eggs or do them fried with butter. I' am getting a bit better to not eat a ton of bread or minimize a bit more than what I'm doing now. Heavily on the Carnivore type plan but I like my sandwiches and some good Tempura Shrimp & Fries from time to time. You don't want to completely deprive yourself, enjoy things every now and then.
Overall, add Step Ups into your routine or do them by themselves it's up to you. Start with a few minutes doing 5-10 reps per leg continuously and start adding time. You can add reps especially if you want to test yourself (like with the deck of cards) but if you work 10-25 reps each leg and keeping doing that for up to 30 minutes straight, that's some awesome cardio. I've done 1000 total reps in 41 minutes so I think my cardio is right where it needs to be. Doing Supersets with them is just another addition to boosting your body's natural levels of hormones.
Train with intent but also make it as enjoyable as possible. Be amazingly awesome.