Hi, am 38 old woman who never played any kind of sports b4 except walking,,,,a did lots of diets to stay in shape,i don t smoke neither drink alcohol,,i felt this year that my muscles are getting weak so i decided finally to exercise,(i have lack of vit D and i take supplements) i started to go to gym 7 months ago and everything was ok,,,getting stronger muscles and feeling more healthier. 3 months ago i wanted to take it to another level cos i was happy so i started to take more advanced courses like insanity courses,bootcamps exercises,zumba and more,,,(with good nutrition and protein shakes after exercising),,,everything was fine with exercising except jogging,,,when they ask to run like 1 to 3 mins i do it but i feel like hell,,,but i always said to myself it will pass,,,,4 weeks ago they added more cardio exercises into our class,like jumping jacks or jumping rope,,,,,so i had severe heart palpitations,shortening of breath and dizziness, throat pain that lasts for 15 mins... My instructor said it s normal and that i ll get used to it after a while....the second and third class i had the same symptoms,,,,so i stopped the classes for a 2 weeks,,,,now i m back again,went 3 days ago to exercise,,,,,everything was ok except when we start the cardio exercises,,,the symptoms start again,,,,,,do you think i need to be concerned? Or just i ll go to my rhythm till i ll be capable to do the exercises the right way?,,,i don t want to stop u know,,,,,thank you.