150 minutes/week. Physical activity guidelines for americans recommend that adults get 150 min/wk of moderate-intensity or 75 min/wk of high-intensity physical activity. Moderate intensity allows you to talk while you're exercising. High intensity means that you can't carry on a conversation. It's also recommended that adults do strength training, like lifting weights, twice a week to keep bones and muscles strong.
Fitness exercise. I serve mainly elders with mental health, from above 60 till the late 80s = i demand a strictly 1h walk twice daily or 1h walk then every hours 60-100 times alternated leg lifting = from standing position (holding onto a chair in front for stability) then lift each leg to horizontal and knee bent 90 degrees or/and arms from dropping along body to lift frontally or laterally to straight up.
Some. Based on physiologic responses, aerobic exercise has been far overrated. Simple walking, climbing stairs when you can and parking out in the store lots to walk helps a great deal. Some resistance or weight bearing exercise in conjunction with calcium is also good. Ankle and wrist weights while walking could be a part of this.