I am 75 and have similar situation as you. Have had idiopathic peripheral polyneuropathy of feet and legs for 8-10 years. Fortunately, no pain. At first didn't affect my daily jogging, (45+ min) or swimming, energy or balance. . But gradually over years have had increasing problems and had to gradually decrease jogging to walking and then to walking less minutes/less often. Now down to 15 minutes usually and real problem going up or down hills. Seem to now have significant loss of muscle mass, energy, balance/coordination, feeling. At point now where even minimal physical activity brings temporary fatigue with shortness of breath. Balance, outside hot/cold temps, fatigue are now gradually decreasing some physical activities and enjoyment used to have.. Neurologist has done many tests initially to conclude is idiopathic and thus no treatment options. Blood tests and B12 tests are within acceptable ranges. So, guess increasing problems of late are just result of age----which is what many doctors often conclude with whatever maladies arise for seniors. Hope your challenges don't progress and can still be manageable.