Ladder intervals are a great workout for mental toughness. Because the intervals get shorter and shorter you are aiming for the pace of each one to be quicker than the one before, which is where the mental toughness comes in! Ideally you would jog the recoveries but you can absolutely walk the recoveries if you need to.
This run totals 6km so if you are newer to running – halve the intervals and do:
600m fast, 200m recovery
500m fast, 200m recovery
400m fast, 200m recovery
300m fast, 200m recovery
200m fast, 200m recovery
And that will give you a 3km workout.
Happy running!