Jason said cardio can improve your strength if it's a cardio activity you aren't very strong in and the movements are new to your muscles. "Let's say, for example, rowing," he told POPSUGAR. "For some people, maybe they don't train their upper body very much, so rowing ends up being a pretty significant load on their upper-body muscles because they're just not used to it."
If your body hasn't adapted to cardio that targets your arms, like rowing, or cardio that targets your legs, like when you do an assault bike workout, cardio can improve your strength. But if you row four times a week, you shouldn't expect your strength levels to improve, especially if you aren't constantly progressing the workouts and challenging your cardiorespiratory endurance and muscles.
According to Jason, you'll notice gains in your strength when you're doing a style of cardio your body has yet to adapt to or if you are deconditioned and have been sedentary for a long period of time. This is because "the act of getting back into doing any sort of cardio is a strain for the muscles," Jason explained.
For "most people who are generally active, you're not really getting as much as a strength gain from cardio versus doing resistance training," he explained. If you're trying to lose weight, Jason emphasized doing resistance training a couple of days a week as part of your weight-loss effort "to make sure that you try to retain your muscle as best as you can as you're losing weight."
He also recommends strength training so your body will ideally decrease the fat stores instead of lean muscle. According to Jason, it's pretty hard to only lose fat if your goal is weight loss, but incorporating strength training into your routine can help. Here's a four-week workout program you can follow to get started.