For decades, resistance training and cardiovascular exercise have been pinned against one another as polar opposites. Cardio bunnies are afraid they will get too bulky if they start lifting weights. Lifters are likewise afraid of going on a twenty minute jog and losing all of their gains. Ironically, a member of one camp will quite readily recognize the absurdity of the other’s fear, but fail to see how baseless their own reservations really are. A lifter knows that no one accidentally becomes a professional body builder. A runner knows that no one accidentally becomes an elite marathon runner. To claim that strength and conditioning are two incompatible modalities that cannot be joined in a balanced manner is not only false but harmful to the populace as a whole who would benefit from both.
The interference effect is often cited as the reason that strength and conditioning training should not be done together. This is the phenomenon by which results derived from resistance training can inhibit the results derived from endurance training, and vice versa. This effect is real and does play a role in competitive sports and the unique demands they place on the athlete. For example, a competitive powerlifter should not incorporate much conditioning into their program, if at all. Likewise, a competitive marathon runner does not need to incorporate much strength training into their program, if at all, to improve in their sport. Thankfully, the vast majority of the population are not highly competitive athletes and can enjoy the benefits of both strength and endurance training. Lifting weights builds strength, which increases independence and reduces the risk of physical injury in later years. Conditioning keeps the circulatory and respiratory systems healthy and reduces the risk of diabetes, heart disease, and stroke.
If you do not want to lift weights, that is okay. If you do not want to do cardio, that is okay, too. But do not be afraid that doing one will reverse the progress you have made in the other. The result will be a healthier you!