MEDIC! Jason Koop Shares the Contents of His Ultrarunning Blister Kit

Jason Koop's blister kit and ultramarathon first aid kit KOOP

This excerpt comes from Training Essentials for Ultrarunning by Jason Koop. In his book, Koop reveals the highly effective ultramarathon training methods he uses with elite ultrarunners and shows how you can use them, too.

Training is the first level of prevention in blister formation. Your skin adapts to stress just like any other organ in your body. Many studies, primarily involving the military, have demonstrated that gradual exposure to frictional forces on the foot (through hikes and marches) decreases the skin’s susceptibility to blisters (Allan 1964; Hodges, DuClos, and Schnitzer 1975; Knapik et al. 1995). As you train, your epidermal skin cells become thicker and in theory more cohesive, making them more resistant to blistering. How does this happen? As you run, you slough off skin cells faster than normal. These are rapidly replaced by new skin cells, but these young cells don’t get the chance to differentiate into layer-specific cells (epidermis, dermis) before they are stressed by another run (S. H. Kim et al. 2010). When this happens frequently over a relatively short time, it results in overthickened skin (i.e., the callus).

Still, you’ve got a great chance of getting blisters during an ultramarathon. Whenever you stress an organ or a structure in your body beyond its capabilities, you cause damage. Ultramarathons normally represent a longer, more difficult run than your day-to-day training, complicated by the fact most ultramarathon events occur in areas away from your home training grounds. The trail surface, camber, dirt, dust, and debris your feet encounter are undoubtedly different during the race than at home. Furthermore, your biomechanics are different depending on the properties of the trails, placing stresses on different areas of the skin of the foot. Therefore, the shoe/sock/powder/tape/lubricant/insole combination that worked in training may not always work during the race. Just as training on flat ground will not completely prepare you for a mountainous ultra, training on your home trails might not fully prepare your feet for the rigors of race day. Therefore, a combination of education, preventive measures, and wound care skills offers the most comprehensive way to ensure that your hard-earned training does not come undone by the unraveling of your feet on race day.

Jason Koop's blister kit and ultramarathon first aid kit KOOP


This small assortment of products will be enough to fix minor and moderate blisters out in the field and keep you moving. It is manageable for your crew to carry or to pack in a drop bag. It is neither a substitute for a full medical kit nor what you would use to treat skin injuries after a race.

  • Adhesive felt sheet or moleskin
  • Needles or small scalpel (size 11)
  • Alcohol pads or Betadine swabs
  • Gloves
  • Kinesio Tex Gold tape, Elastikon tape, or Leukotape (to patch or prevent)
  • Scissors
  • Adhesive such as tincture of benzoin
  • Lubricant such as Body Glide or BlisterShield
  • Gauze pads

See Jason Koop’s 9-Step Blister Fix for Ultrarunners here.

Adapted from Training Essentials for Ultrarunning: How to Train Smarter, Race Faster, and Maximize Your Ultramarathon Performance by Jason Koop, coach to elite ultramarathoners. In his book, Koop reveals his highly effective ultramarathon training methods for ultrarunners of all abilities. Jason Koop is the Director of Coaching for CTS, coach to elite ultrarunners, and an accomplished ultramarathoner.