Alison, heres a description of strides from;
http://www.timeoutdoors.com/run/training/4RUNMRS01032901E.htm
STRIDES
Warm up: 5 mins gently building heart rate, incorporated in run time.
Training focus: Race pace preparation
Effort: Same as Recovery run but after 20 mins, inject 2/20x1 min relaxed efforts (or 'strides') at 10 km pace concentrating on stride length, arm swing and breathing. Recover with 2 mins easy jogging between each stride. The object is to prepare your body for race pace in the days before race day.
Key words: Race pace strides
Heart rate: 50-65%
Aerobic/Anaerobic: Aerobic
RPE: (6-20) 6-9
Cool down: Incorporated in running pace