Averaging data at 30-sec intervals.

Hi, I'm new to this forum and a bit of a rookie when it comes to excel.
I have conducted an exercise physiology experiment which contains a lot of measured variables and have exported the data into excel. The problem is that each variable was sampled every 3 secs, giving me way too many data points. I need to work out 30-second averages for each one of the variables. I know i could go through cell by cell and average every 10 cells individually, however i would love to find a quicker way to do this. For example, the values in the column "VO2"are measured every breath using gas analysis during the experiment. I need to find the values for average VO2 over 30 second increments for the duration of the test. Is there any way i could average all of the data to 30s increments simultaneously, saving me a heap of time? Thanks in advance VO2 max test data.xlsx

Cheers, really appreciate it!