From the elite athlete to the deconditioned patient, selecting the appropriate intensity, frequency and duration of aerobic activity is pivotal for performance and recovery. In fact, aerobic conditioning is essential for everyone, and like all exercise programs it needs to be individualized.
Zone training is the standard in cardiovascular training and can be monitored with biochemical markers such as blood lactate (BLa) or VO2max, or with biometric data such as heart rate (HR) and relative perceived exertion (RPE).
Management of the elite-level athlete requires the use of BLa and VO2max as biomarkers of their aerobic load. While this technology is currently available for the individual practitioner, a majority of our patients from the injured patient to the chronically fit can be easily monitored with HR and RPE with great success.
Regardless of the biomarker used, the percentage of training at various intensities, or zones, is directly related to the desired outcome. In discussing zone training, there are two different models: a three-zone formula and a six-zone formula. In this article, let’s discuss the six-zone model. (Please refer to Table 1 for details of each zone.)
The importance of aerobic conditioning cannot be underscored. First and foremost, cardiovascular disease is the number-one killer in America and consistent cardiovascular activity will reduce that risk up to eightfold. The current recommendation is at least 120 minutes/week of aerobic activity.
Second, cardiovascular exercise improves blood flow and oxygenation of tissues. Whether an athlete is trying to recover from a workout or improve performance, or a patient is recovering from an injury – they all benefit from increased oxygenation of their tissues. Therefore, a general recommendation is at least 120 min/ week of light to moderate aerobic activity for everyone.
| TABLE 1 |
|
| 6-Zone |
3-Zone |
BLa (mmol/L) |
%Max HR |
%VO2max |
RPE/20 |
|
| 6 (Sprints) |
3 |
N/A |
N/A |
N/A |
N/A |
|
| 5 (HIIT) |
3 |
8-18 |
>97 |
94-140 |
18-20 |
|
| 4 (HIIT) |
3 |
4.5-8 |
92-97 |
88-94 |
16-18 |
|
| 3 (Moderate Intervals) |
2 |
3.5-4.5 |
87-92 |
84-88 |
14-16 |
|
| 2 (Light) Intervals) |
2 |
2-3.5 |
82-87 |
80-84 |
12-14 |
|
| 1 (LSD) |
1 |
.7-2 |
82-82 |
55-80 |
9-12 |
|
| |
Zone 1 Training
Light training is considered zone 1. This is easy cardiovascular activity designed to improve circulation, oxygenation and overall cardiovascular health. It will also help to maintain blood sugar levels and is beneficial in the recovery from zone 3+ workouts, as well as from an acute injury. An effective method to enhance tissue oxygenation, without out a hyperbaric chamber! Classically, zone 1 workouts are LSD: long, slow distance.
Clinical Tip: Regardless of your workout intensity, all workouts will require a warm-up. Using a foam roller, massage stick, or a few minutes of dynamic stretching is sufficient for a zone 1 workout.
Zone 2 Training
Zone 2 training is a current buzzword in the fitness space. Zone 2 training has been shown to increase mitochondrial function, assist in the recovery from long COVID, and is consistent with endurance training. In fact, elite-level athletes do a majority of training in Zone 2.
Zone 2 training can be considered a moderate level of cardiovascular activity – the patient can still have a conversation; hence it is frequently called a “conversational pace.” This pace can be maintained for hours. Zone 2 is also referred to as aerobic base training.
Zone 3 Training
In zone 3 training it is difficult to maintain a conversation and is consistent with a workload that can be sustained for 30-45 minutes. The effects are cardiorespiratory, and assist in increasing oxygen utilization and respiratory efficiency. This includes short intervals, as in hill climbing with a return to zone 3 intensity. Progressive increase in intensity (measured by BLa, VO2max, HR, or RPE) is not allowed. This is easily monitored with HR and RPE.
Clinical Tip: When discussing zone training with patients/athletes, be sure you are using the same model. For example, in the three-zone model, zone 2 incorporates zones two and three of the six-zone model; one includes intervals and one does not.
Zone 4 Training
As training levels increase into zone three and four, the intensity will increase and the duration will decrease. High-intensity, short-duration workouts, HIIT, is considered a zone 4 workout. It has been shown to be beneficial for burning visceral fat, reducing insulin resistance, and for cardiorespiratory fitness. Avila-Ganda found HIIT training programs also reduced blood pressure, but had lower compliance compared to low-intensity training.
Zone 5 / Zone 6 Training
Zones 5-6 are short-duration, maximal-effort events, as in sprints. Essential for patients involved with high-intensity and short-duration activities; it must be incorporated into their training plan. For the general population, proceed with caution, as speed kills. An excellent substitute for speed training for the general population is agility – it incorporates speed with a lower aerobic load. Speed and agility are not synonymous with zone 5+ training.
Clinical Tip: Agility training is important for our general population, as they may need to catch a falling object or take 3-10 steps to get out of the way while crossing the street. It is still speed work, but the intensity and duration is less than zone 5+ training.
Exercise Intensity
Different zones can be related to percentages of maximum heart rate, as listed in Table 1. In fact, HR training has been in use for decades. However, 15% of the general population does not follow the standard HR percentage equation for intensity. One subset that does not generally follow the HR% is the chronically fit patient. These patients often can exercise at a higher percentage of their maximum allowable heart rate, yet still be in the target zone.
Relative perceived exertion (RPE) is a documented biomarker to assess exercise intensity. Often used is the Borg Scale, with the exertion level as the numerator with a base of either 10 or 20 as the denominator. Although accurate to the patient, it is not necessarily accurate to the biological load.
To ensure the patient is exercising at the desired intensity, they need to cross-reference their exertion level with their RPE. Once the patient “knows” what a specific HR% training zone feels like, then they can accurately replicate it with using RPE. This can be done with any biomarker: HR, BLa or VO2max.
Once cross-referenced to actual exertion, RPE is a highly accurate indicator for the individual patient. However, if this cross-referencing is not performed, HR% cannot be considered accurate.
Elite-level endurance athletes train mostly in zones 1-3, with two primary patterns. In the pyramidal model, approximately 70%-80% of the training is zone 1, with the remainder in zones 2-3. A subtle contrast is the polarized model: approximately 80% in zone 1 with 20% in zone 3, bypassing zone 2 completely.
Notice the commonality of the two models is mostly zone 1 training, with no more than 20% of training at high intensity. Again, these are endurance athletes.
General Recommendations
To advise patients on training for recovery and performance enhancement, start with zone 1, 70-80%. As conditioning improves the patient will remain in zone 1 (based on the chosen biomarker) and be able to exercise longer or cover more distance. Note that since only 20%-30% of training is over zone 2-3, high-intensity workouts will be once or maybe twice a week in a six-day training cycle.
Clinical Tip: Zone 1 workouts are often more important than the level 4+ workouts in a training cycle.
While it is important to train for speed, the patient needs adequate recovery to prepare for the next workout. Relative, active rest and recovery are essential to performance enhancement and healing.
Remember, as the patient’s fitness level improves, the biomarkers may not change, but the patient’s performance does improve. Faster times, longer distances and greater metabolic efficiency are achieved. These are the objectives of aerobic training. Simply going faster and training harder because you can may in fact lead to injury and reduced performance. Teach your patients to train smart to recover, improve performance and avoid injuries.
Resources
- Ávila-Gandía V, et al. High versus low-moderate intensity exercise training program as an adjunct to antihypertensive medication: a pilot clinical study. J Pers Med, 2021 Apr 10;11(4):291.
- Casado A, et al. Does lactate-guided threshold interval training within a high-volume low-intensity approach represent the “next step” in the evolution of distance running training? Int J Environ Res Public Health, 2023;20:3782.
- Magalhaes PM, et al. Effects of a 16-week training program with a pyramidal intensity distribution on recreational male cyclists. Sports, 2024;12:17.
