If you have worked with a coach you may have seen the workout on your training plan that states “Recovery Run, Bike or Swim.” Many athletes seem to be very diligent about keeping their legs spinning and their watts or speed low when doing a recovery bike session or subsequently, with the swim, keeping the focus on drills and really easy swimming but when it comes to the Recovery Run, that can be a whole different story.Often, we see athletes doing their recovery run only marginally slower than their Z1 or Endurance run efforts. If I am looking at pace alone, this tells me that they have either been doing their Endurance Runs way to slow (dogging it) or their Recovery Runs – way too fast. This is where using a heart rate monitor can help to paint the real picture. For Recovery runs – heart rate should be ideally, anything less than 76% of Threshold Heart Rate while Z1 Endurance Runs should be between 80-86% of threshold heart rate.Let’s take a step back and define what Threshold Heart Rate is. This is the average heart rate based off approximately one hour of maximal intensity effort that can be maintained (also known as Functional Threshold). To help determine this, and if we stick with running as our example, there are a few different methods that can be used. A field test such as race might be a good starting place since in most cases you will be putting forward your best effort.If using a 5km Fun Run to determine your threshold, determine your average HR (generally based off your watch) and then subtract 15 beats to extrapolate the result to be based off a one hour based effort. Alternatively, if you have completed a recent 10km race, then subtract 10 beats off the average HR and for a Half Marathon subtract 5 beats. Another method that works well is a 4 x 1 mile test (with 1.5 min recovery) and then subtract 2 beats off the average HR.The Karvonean method which takes into account the maximal and resting heart rate is also a nice way to approximate threshold HR. Since most athletes will know what the highest heart rate is that they have seen and are also familiar with their resting heart rate, this is an easy method to try. Using these numbers they can be applied using the following formula: .81*(Max HR – Resting HR) + Resting HR = TH HR.You may decide to use one of the above methods or try each of them to approximate your Threshold HR for running. Keep in mind that due to differences in the nature of running and cycling and athletic experience, threshold values are generally different for each discipline and therefore should be tested independently.Once you have determined your Threshold value then HR training zones can be established. Using our HR training zone system and also that adopted by USAT, heart rate training zones are as follows:ZR: (Recovery/Pliability) Everything below 76% of TH HRZ1: (Aerobic) 80-86% of TH HRZ2: (Tempo – Sub Aerobic Threshold) 86-83%Z3: (Tempo – Sub Lactate Threshold) 93-100%Z4: Best Sustainable EffortNow that you have a basic understanding of Threshold HR, let’s return our attention to ZR Recovery Runs. I am sure you are asking so what is the purpose of doing a Recovery Run. The recovery runs purpose is not necessarily to derive direct “fitness” gains; instead, a recovery run is Active Recovery. It provides an opportunity to actively engage the soft tissue: muscles, tendons, and ligaments by promoting blood flow without the catabolic effect of over stressing muscle fibers. The low-intensity active effort helps to flush the muscles of accumulated by products of lactic acid. Mentally, the recovery run also gives an athlete the opportunity to recharge, a mass volume and subsequently, add to the durability needed for long course racing.Athletes that struggle with injuries such as chronic Achilles Tendonosis and Plantar Fasciitis tend to respond well to inserting regular short recovery runs into their training as opposed to simply having long periods of rest between runs. Since tendons receive very little blood flow it makes sense that keeping the tendons actively engaged but not overly stressed helps promote blood flow to the area and help with the recovery process.So, what should a recovery run look like? A good rule of thumb is to keep the run under 35 minutes and while HR should be in the ZR range this would generally equate to a pace of at least 1.5 to 2 minutes slower than current Z1 pace. Interestingly enough some of the fastest runners have the biggest differentiation between Endurance and Recovery paces. Just look up some of the Kenyan runners and you will see just how easy their recovery runs are. Keeping the cadence high will also help ensure that you are keeping the feet under you as you run and not overstriding and placing additional stress on the extremities.Next time you see a Recovery Run on your schedule remember the many other benefits associated with it and embrace the challenge of going slow.Karen Allen Turner is a coach for QT2 Systems for both the QT2 and OutRival Racing brands and has been involved in the sport of triathlon as both a participant and a coach since 1986. As a regular national presenter for the USAT coaching certification program, Karen's ability to draw on her many years of coaching experience and ongoing quest to expand her understanding of the sport provides a valuable resource to new and experienced coaches alike. For her athletes, the combination of her analytical approach, teaching methods and her ability to look at each athlete as an individual with unique needs has lead to her success as a coach.