If you’re not bending, you’re not strengthening
In order to get stronger, you have to bend to use those joints the way they were intended. This is why walking doesn’t make you stronger, your whole body is fairly upright the whole time. Our joints were meant to be used. For instance, to get stronger biceps, you have to bend your elbow to get your forearm towards your shoulder. You can squeeze your biceps with that motion, or even better, use resistance such as weights (full grocery bags are great), bands or cables.
If you want the front of your legs stronger, which are the quads, you have to bend your knees. Lunges (pick up something off the floor with one foot in front and the other leg behind, with the back leg bent, with the knee close to the floor), squats (sit on a chair and get up without grabbing onto something, or using momentum to get up), and step-ups (climbing stairs, two at a time are effective, just use your legs, and don’t cheat by pulling up with the railing). If you’re not doing any of the above exercises on a daily basis, your muscles will atrophy and you’ll be more susceptible to falls, knee pain, imbalances, and injury.
If you want your lower back and back of your legs strong, you need to bend at your knees and ankles, and hinge forward with a flat back. That’s why deadlifts are strengthening; the problem is that people go too heavy and use improper form by rounding their back.
We don’t get weaker as we get older because of our age, people get weaker because they stop doing the exercises and sports they did when they were younger. Walking is great for the heart and to get outside, but you want to bend and use every single muscle to be fit and healthy, and to reduce pain, stiffness, instability and fractures.
Photo: me, doing biceps curls