Polarized training, threshold training...how should you train?
Polarized, threshold, and how you should train for triathlon performance
Triathlon is unique when compared to other endurance sports as athletes must train in three distinct modalities. This often leads to higher training volumes and a greater workload for triathletes when compared to runners or cyclists, for example, as training frequency (number of sessions per week) is very high. As an example, a recent study (Mujika, 2014) has shown that an elite female triathlete performed an astounding 796 sessions in the 50 weeks leading up to the 2012 London Olympics.
While most (if not all) of us cannot be considered elite, training volumes are very high at lower levels of the sport as well. Olympic distance triathletes (sub-elite) have been reported to perform an average of 12 sessions per week, while Ironman athletes might have an even higher training frequency (Vleck, Millet, & Alves, 2014). Such training volumes are justified as athletes must develop high levels of aerobic fitness, in addition to muscular endurance, strength, and power to optimize performance. However, while overall training volume plays a key role in the training program, how those sessions are performed is also a critical factor in ensuring positive adaptations from training will occur.
Training intensity distribution (TID) is related to how much time is spent at each training zone on a weekly basis. Endurance training is often performed utilizing 5 different zones. These range from 50% to 100% of maximal oxygen consumption (VO2max) or 60% to 100% of maximum heart rate (HRmax). This approach is widely used by different sports organizations and you can see an example below from the Norwegian Olympic Federation.
Still, despite the popularity of this model, in recent years training intensity distribution has focused on a three-zone model. Similar to the 5-zone model, the three zones are demarcated based on individual thresholds. Zone 1 consists of low intensity exercise, below the first lactate or ventilatory threshold (LT1 / VT1), zone 2 encompasses training at moderate intensities, commonly referred to as threshold training, while zone 3 includes high intensity training that occurs above the second lactate or ventilatory threshold (LT2 / VT2). If you are curious, since both models are anchored around the same physiological thresholds, the 5 zones can be “transformed” into 3 by collapsing zones 1 and 2 and zones 4 and 5 from the 5-zone model into zones 1 and 3 in the 3-zone model, respectively. If you are interested, the gold standard to determine these zones is to connect with an exercise physiologist or sport scientist and perform a maximal exertion test in the laboratory, so that you can determine the where each zone lies based on your heart rate, running speed, cycling power, or perceived effort, for example. A recent study showed that in recreational runners the heart rate values for the first and second thresholds were respectively 77 ± 3% and 91 ± 3% of the athletes’ HRmax. Based on this approach research has showed that elite endurance athletes organize their training around a polarized approach, where athletes perform a high volume of training at lower intensities combined with a few sessions at higher intensities. Specifically, this polarized approach requires athletes to spend about 70 to 80% of their total training time at zone 1, and 10 to 20% at zone 3, while minimizing the amount of zone 2 or threshold training that is performed (5 to 10% of total training time).
But why is this important?
Well, this approach to training is supported by retrospective studies of training logs from successful endurance athletes (the female triathlete previously mentioned and the most successful female cross country skier ever are just two of the many examples) and by research that has demonstrated that improvements in endurance performance are related to the time spent at zone 1, as long as the contribution of high-intensity training (zone 3) remains significant. In addition, studies that compared different TIDs have demonstrated the superiority of a polarized approach. For example, one study (Stoggl & Sperlich, 2014) demonstrated that while a polarized approach led to positive results in maximal oxygen consumption (VO2peak), time to exhaustion, and peak velocity and power, no improvements were seen in the group that performed a training program focused on threshold training over a period of 9 weeks. Similar results were found in recreational Ironman athletes over a period of 6 months, where the lack of adaptation in swimming and cycling was likely related to a small amount of time spent at zone 1 and too much training time spent at zone 2 (threshold training) (Neal, Angus, & Galloway, 2011). These are just a couple of examples from research that are corroborated by other studies performed in recreational-level athletes and emphasize that a polarized TID seems to be the optimal approach for performance improvements for elite or recreational athletes.
Thus, it seems that minimizing training at threshold intensities is key for performance improvements. There is only one problem: this is usually the intensity at which we perform most of our training sessions. Research has shown that a polarized approach is not what is commonly employed by recreational athletes as they often perform their easy sessions at a higher intensity while not pushing as hard as needed on intense training sessions, leading to a constant pattern of zone 2 or threshold training. When combined with a high training frequency, this constant pattern of training at intensities that are sub-optimal for performance improvements and health is the perfect recipe for an overly tired, cranky, and under performing triathlete.
The lack of improvement due to too much threshold training lie in the fact that the first threshold is a key turning point where the stress that is experienced by the body is significantly higher and thus, recovery is delayed. This stress also doesn’t seem to increase as the intensity of the session goes up, meaning that training at zone 2 or zone 3 produces a very similar stress response. However, training at zone 3 leads to greater improvements in fitness, meaning that, compared to threshold training you can get a bigger “bang for your buck”. Considering recovery is delayed after training at higher intensities, it is no surprise that too much training at these intensities is also possibly detrimental to athletes’ health as well, with research linking it to overuse injuries and a greater potential to lead to overreaching and overtraining.
So, what should you do?
Well, the first step is to ensure your training follows a polarized approach. And there’s a very simple and practical way to do it. Using the rate of perceived exertion (RPE), a self-assessed measure of how intense the training was, provides a reliable indication. While there are 2 commonly used RPE scales, if you use the original one (that ranges from 6 to 20), zone 2 would be indicated by intensities between 14 and 16, meaning that below this intensity, training would be performed at zone 1, and above it, zone 3. If using a 10-point scale (ranging from 1 to 10), zone 1 would occur below 4, and zone 3 above 7, which means 5 and 6 are your threshold intensities. The same approach can be done for each session, using what is called session-based RPE to indicate how intense the session was. This is simple: 30 minutes after your training session is over, go through the scale again and self-select how intense you perceived the session was. If the value is equal to 5 or 6, then the session was at zone 2. Below that would be zone 1, and zone 3 would be 7 and above.
Now that you know where each session falls in the 3-zone model, it is time to calculate your overall training intensity distribution. Aim for 70 to 80% of your total time performed at zone 1, with 10 to 20% spent in zone 3, leaving little room for training at zone 2. And if you are not there yet, don’t worry. Training at zone 2 won’t immediately ruin your gains. Remember, you actually want to perform some sessions at this intensity as this is your race pace. Just make sure you are not overdoing it. Considering how often you are likely training, ensuring that your training is performed at optimal intensities is key. After all, with better training comes not only better performance, but better health as well.
Now that you know where each session falls in the 3-zone model, it is time to calculate your overall training intensity distribution. Aim for 70 to 80% of your total time performed at zone 1, with 10 to 20% spent in zone 3, leaving little room for training at zone 2. And if you are not there yet, don’t worry. Training at zone 2 won’t immediately ruin your gains. Just make sure you are not overdoing it. Just remember that with better training comes not only better performance, but better health as well.
Have a question you would like to ask our sport scientist? Feel like you need help with your training or your athletes? Send it to J.Falk@edmontontriathlon.org
And if you are interested in any of the papers that were mentioned, here’s the list.
Esteve-Lanao, J.; San Juan, A.F.; Earnest, C.P.; Foster, C.; Lucia, A. How do endurance runners actually train? Relationship with competition performance. Med Sci Sport Exer 2005, 37, 496-504, doi:10.1249/01.Mss.0000155393.78744.86
Hydren, J.R.; Cohen, B.S. Current Scientific Evidence for a Polarized Cardiovascular Endurance Training Model. J Strength Cond Res 2015, 29, 3523-3530, doi:10.1519/JSC.0000000000001197
Mujika, I. Olympic Preparation of a World-Class Female Triathlete. Int J Sport Physiol 2014, 9, 727-731, doi:10.1123/Ijspp.2013-0245.
Muñoz, I.; Cejuela, R.; Seiler, S.; Larumbe, E.; Esteve-Lanao, J. Training-Intensity Distribution During an Ironman Season: Relationship With Competition Performance. International Journal of Sports Physiology & Performance 2014, 9, 332-339
Munoz, I.; Seiler, S.; Bautista, J.; Espana, J.; Larumbe, E.; Esteve-Lanao, J. Does Polarized Training Improve Performance in Recreational Runners? Int J Sport Physiol 2014, 9, 265-272, doi:10.1123/Ijspp.2012-0350
Seiler, S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform 2010, 5, 276-291
Solli, G.S.; Tonnessen, E.; Sandbakk, O. The Training Characteristics of the World's Most Successful Female Cross-Country Skier. Front Physiol 2017, 8, 1069, doi:10.3389/fphys.2017.01069
Stöggl, T.; Sperlich, B. Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Frontiers in Physiology 2014, 5, doi: 10.3389/fphys.2014.00033
Stöggl, T.L.; Sperlich, B. The training intensity distribution among well-trained and elite endurance athletes. Front Physiol 2015, 6, 295, doi:10.3389/fphys.2015.00295