Hello Doctors, My name is Arthur I am a Male 21 years old 128lbs. First I want to say that I never had any medical conditions I tried to live with a healthy lifestyle . I went to gym the parts of the year when I wasn t busy. My question is I want to know why my body reacts this way here is my story. One month ago I signed up for boxing classes and I trained with a personal trainer who pushed me too punch in fast paced without enough rest , and I could feel my heart was pumping very fast like it couldn t keep up with my body and I still kept doing it. After the training my heart rate slowed down but I felt very weak and on my left side (my chest and left hand ) was weak and and felt little numb . I did not sleep well that night and the second day the problem was still there I felt more numbness on my left hand and my heart was beating heavy, and that night I woke up i don t remember why I was scared because I felt weird and my left hand was little numbed I took Valeriana and went to sleep . Next week I was feeling much better and as time passed I returned to normal and forgot about the problem. After having rest for a month I went back to gym myself (which was 5days ago) I tied not to push hard and started doing in slower paced , I usually leave one day space before my next workout for my muscle recovery. After workouts my hearth started doing the same thing like a month ago I tried doing pull-ups and that s when I felt my heart is again giving me problems, (I usually do many pull-ups and push-ups I am light weight 128lbs) It has been 4 days that I haven t done anything physical but I steel feel weak. I never check my heart rate before but I checked yesterday evening before it was 62-65 I couldn t sleep until 4:30pm at that time it was 58-62. I checked again when I was in the bed when I woke up it was 75-80 and it was changing after few minutes it was 80-85. its 7:30 now I steel feel weak but slightly better . I would appreciate a lot if you can give your thoughts about my problem. Thank you