People living with type 1 diabetes (PwT1D) are recommended to administer insulin 10-15 minutes before meal consumption (pre-bolus), to account for the delay in the glucose lowering action associated with subcutaneously administered insulin. Due to the demands of day-to-day life, pre-bolusing is not always possible or may be forgotten. With continuous glucose monitors (CGMs), PwT1D may be alerted to this missed insulin dose by a CGM alert, including rapidly rising glucose (change \>2.5mmol/L/15min) or hyperglycemia (\>10.0 mmol/L), and deliver a mistimed (post-prandial) dose in response to CGM alert. This study was designed to determine the effect of combining a post-prandial/mistimed insulin dose with 15 minutes of brisk walking. It is expected that walking will help to minimize or prevent hyperglycemia after a mistimed bolus insulin dose, as well as blunt the rise in glucose following a mistimed insulin dose.