Start working at nine. Plan to have a rest every 20 miniutes.
9:00 9:20 trapezius ache at about 15th minute
9:40 10:00 trapezius ache at about 18th minute. waist ache at 15th minute.
10:06 10:25 waist ache at 15th minute.
10:58 11:24 waist trapeezius ache slightly all the time