HR Training Zones

Now that we have our training zones figured out, we need to know what to use them for and how to structure our training to take advantage of this information.  You’ll likely find a variety of different definitions and numbers of training zones if you do a little searching online.  I base my zones off of Friel and the Triathlete’s Training Bible.

Zone 1 – Recovery (under 75% of LTHR) – This is a very easy effort used primarily for warm-up, cool-down, and recovery.

Zone 2 – Basic Endurance (75-85% of LTHR) – The low end of Z2 is your “all day pace” and is used for aerobic base building. this is the classic long slow distance (LSD) effort and begins to build slow-twitch fiber fatigue resistance.

Zone 3 – Intensive Endurance (85-95% of LTHR) – In this training zone you are not optimally training LT or aerobic base. It is often considered a grey area and depending on your goal race distance it might be appropriate to avoid this zone completely.  Benefits include increased glycogen storage capacity, increased oxidative enzymes, and some improvements in LT.  Most often it is better to train either above or below this range to target the specific adaptations you are looking for.  The exception would be those training for longer events such as marathon, 1/2 Ironman and Ironman where Z3 is the primary zone that you will be racing in so it makes sense to do a good portion of your specific training in Z3.

Zone 4–5a Tempo/LT (95-105% of LTHR) – This is your lactate threshold training zone and ranges from just below to just above your LTHR.  These our ‘hard’ sessions during the week.  The Master’s swim workout, the tempo run, or the spin class are all LT types of workouts. Studies have shown that training at, or just below, LT creates the greatest overall benefit as it allows the body to recover quicker then if we train above LT.  Benefits of tempo and threshold training include maximizing aerobic fitness, maximal improvement in LT, maximal improvement in oxidative enzymes, increased glycogen storage, increased VO2max, and increased blood plasma volume.

Zone 5b – VO2max (>105% of LTHR) – Training at this intensity should be limited due to the risk of over-training.  VO2max training generally consists of short intense (2-8min) intervals with longer recoveries and hurts like heck.master swims and spin classes can put you into this zone but be careful, the recovery cost is significant and often requires multiple days of easier training before resuming high quality sessions.  HR becomes an unreliable metric at this level since the efforts tend to be so short and HR lags effort.  You’ll most often see Zone 5b and above during the final push to the finish line in races.  When appropriately incorporated into your training benefits include maximizing cardiac fitness, maximal improvement in VO2max, maximal increase in blood plasma volume, and moderate increases in muscle capillarization.

Zone 5c – Anaerobic Capacity/Power – This is explosive max-effort training including sprints, stomps, and track starts.  Endurance athletes typically don’t need to be concerned with training at this intensity and HR is not a useful guide.