Understanding Lactate Threshold And Heart Rate Training Zones

There is a lot of talk about training at your lactate threshold - what does this mean? What would a session look like?


We spoke to Dr Alan Ruddock PHD, Lecturer - Physiology of Sport and Exercise Science at Sheffield Hallam University about lactate thresholds and heart rate training zones. Here's what he had to say:

Lactate threshold can mean either the 1st or 2nd threshold so it’s important to define that. What people are usually referring to here is the 2nd threshold or lactate turn point. So when people say they’re training at threshold what they’re doing is running at a speed, heart rate or RPE that is equivalent to that blood lactate concentration. It represents an intensity that could be held for around 45 min and for most runners that’s equivalent to 10 km. Clearly it’s hard to train at this intensity all the time so what some coaches do is schedule intervals at this intensity. These can range from 2 x 10 min, to 3 x 20 min with 5 min easy running between depending on the training status of the athlete.


Is there a possibility that someone's lactate threshold might not allow them to get into the top training zones (zone 5). How would you know and how would you correct this?


Yes, this can occur, if endurance athletes haven’t been exposed to high-intensity training then there’s a possibility that if they pushed past their 2nd threshold they wouldn’t be able to sustain this intensity for too long. You’d know this from interval training, the athlete wouldn’t be able to run as fast as others and they might fatigue quickly when pushed or not have a kick when the pace is pushed high, or respond to surges in pace. The obvious way to correct for this would be to schedule in high-intensity interval training, and depending on the athlete some under-and-overs whereby the pace of an interval is pushed slightly over the threshold for a few minutes before bringing it back down.


Should I rely on heart rate as my main source of feedback for my intensity?


It depends on the type of training. For long runs it’s better to use RPE and heart rate together – in long runs heart rate can drift upwards due to increased heat production, fluid loss and decreases in muscle glycogen so it can artificially elevate intensity – especially on hot days. For tempo training, I’d use RPE and speed. For HIIT it depends on the physiological target. If the goal is to spend 10 min above 90% HRmax then absolutely use heart rate and take speed as a secondary measure. If the goal is to induce significant metabolic acidosis (10 – 12 mmol/L blood lactate) then speed and RPE (in absence of lactate) are key metrics rather than HR. When prescribing a training session it’s key to understand the physiological targets and choose metrics that best reflect a valid attempt to quantify training intensity that will elicit that adaptation.


Between 80-87% max heart rate is sometimes described as "no man's land". Are there any benefits to training in this area? Or are there more favourable training zones?


No man’s land is required for specific preparation, especially to improve running economy at race-specific speed but it’s not the best option when we’re looking to improve physiology that underpins endurance performance. The reason is that athletes aren’t training easy enough on easy days, or hard enough on hard days. Zone 2 training or no man’s land is actually the most enjoyable but if you’re serious about performance it’s a sub-optimal training zone the majority of the time. This might be because you’re providing your body with mixed adaptative signals, or training is too monotonous with little time for recovery or quality training. The amount of training you spend in zone 2 will depend on what type of event you’re preparing for, if you’re training for a half-marathon then you’ll need to spend some time in this zone preparing for the specifics of half-marathon running, and the same is true for a 10 km race as you transition towards extensive 10 km race pace training.


If you'd like to know more about the training zones encountered by athletes, check out Alan's post "What Are Training Zones? And How Can We Work Them Out?


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