Hello thank you for trusting HCM Dear resting heart rate may be low in adults who are physically active(athletes).but doesn t cause any problem to them.elderly people more prone for slow heart rate faces problems. causes are sinus bradycardia ,nodal blocks, conduction blocks,metabolic problems (hypothyroidism). if your feeling tired,weak and dizziness you may need to consult your doctor. if your severe symptomatic avoid beta blockers,check for electrolytes,check for hypothyroidism. patient severe bradycardia may need peacemaker implant. I think I answered to your question if you have more questions feel free to ask. take care