The muscles around your shoulders work hard when you are holding heavy weights. Your deltoid, or shoulder muscles, and your trapezius, or upper back muscles, contract to keep your shoulders stable. A heavy set of farmer’s walks can leave your upper back fatigued.
Walking while holding heavy weights will overload your leg muscles. The muscles doing the hard work are your gastrocnemius and soleus muscles — better known as your calves, quadriceps and hamstrings, respectively.
The weak link in farmer’s walks is your gripping muscles. A set of farmer’s walks usually ends when you can no longer hold the weight so farmer’s walks are often considered a forearm strengthening exercise. Your main gripping muscles are your flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, flexor carpi ulnaris, palmaris longus and flexor pollicis longus.