Strength training is certainly of great importance, particularly as we age (to slow the long slide to muscle loss). Helps with stability, power, agility, bone density, among other things.

Cardio training is certainly also important. For that other "muscle" (the lungs) and all the associated areas of the body impacted by strong bloodflow and availability of nutrients. (Including muscle growth from strength exercises.)

Dumbbells. Floor exercises. Ruck marches (with weight in a smaller backpack). Trail climbs. Plus cardio exercise. With sufficient nutrition and sleep to help support all that activity. Can all help.