I resting heart beat goes to as low as 52 sometimes, and 168 after 25 mins of hiit. do i need to worry? i am male, 45 years old, i do 3 time hiit per week and 45 mins walking 5 times a week?

Check the accuracy of your pulseometer first. But should be OK. There are charts that show acceptable heart rates but you want one from Kuwait in men like you. Keep up the exercise but beware of heat stroke risk.

I see no worries for you. At age 45 your target heart rate during vigorous exercise computes to 220-45=175. A resting heart rate in the 50's is not unusual for you& your regular exercise schedule unless you're experiencing lightheadedness, fatigue,shortness of breath on exertion. If you have any risk factors for cardiovascular disease,I recommend having a maximal treadmill stress test as a checkup