My Friend Is 82. Can Walk Short Distances But Cannot

my friend is 82. can walk short distances but cannot stand for 5 minutes or gets light headed. he has bad veins in his legs from heavy lifting during his career. his blood pressure is usually right on. he is now a diabetic and has had two minor strokes in past 8 years and a Stent inserted. but problem standing is more than 20 years his spine is slightly bent from heavy lifting also. any clues?