Zone 5 Training: Improve VO2max, Fitness, and Metabolic Health
Zone 5 cardio training maximizes cardiovascular adaptations by pushing the body to 90-100% of maximum heart rate, significantly enhancing VO2max, and anaerobic performance. This high-intensity interval training triggers profound metabolic improvements, including increased insulin sensitivity and glucose utilization, while strengthening heart capacity for improved longevity and fitness outcomes.
Zone 5 Cardio Training
Zone 5 cardio is a targeted, high-intensity training done at a near-maximal or maximal intensity of 90-100% HRmax. (1) (2) It’s specifically geared towards increasing VO2max, heart capacity, and anaerobic performance. Such intensity can also profoundly impact longevity due to the various metabolic and cardiac adaptations that occur.
In terms of VO2max, zone 5 cardio is done at 95-120% of VO2max. The starting intensity slowly increases VO2max % as time progresses. There’s a significant elevation in lactate levels, as such training heavily relies on anaerobic metabolism to sustain energy.
Such high intensity is done at 9-10/10 maximal effort that can be typically sustained for 30 seconds – 4 minutes, depending on the specific intensity the work is done at, within the range of Z5. This makes Z5 training unique, requiring a combination with Z2 lower intensity as an active recovery, which we call interval training.
5 Training Zones
There are 5 training zones in total, based on level of effort, fuel use, and % of HRmax. From zone 1 which is light intensity like walking, all up to zone 5 which is sprinting, there are 5 bands of intensity. The lower the intensity, the more aerobic the activity, the lower the % HRmax. The higher the intensity, the more anaerobic the activity, the higher the % HRmax.
| Zone | Use / Benefit | Intensity |
|---|---|---|
| Zone 1 | Stimulates Recovery, Warm up | 50-60% HRmax |
| Zone 2 | Improves Endurance, Fat Burning | 60-75% HRmax |
| Zone 3 | Improves Aerobic Fitness | 70-85% HRmax |
| Zone 4 | Trains Lactate Threshold, Improves Speed Endurance | 80-95% HRmax |
| Zone 5 | Increases VO2max and Anaerobic Capacity | 90-100% HRmax |
How long can you stay in Zone 5?
Depending on the absolute intensity, zone 5 can last from 10-30 seconds (<95% HRmax, maximal efforts) or 1-3 minutes (90-95% HRmax, submaximal efforts).
At what heart rate is zone 5 training?
Zone 5 corresponds to 90–100% of your maximum heart rate.
Adaptations to Zone 5 Training
There are various physiological adaptations that occur in the body as a result of training at high intensity (Z5). These can profoundly impact one’s longevity and performance. It trains the ability to complete high-effort, anaerobic tasks which improves the way the heart, lungs, and muscles work.
Cardiovascular Adaptations
High intensity training stimulates the heart and lungs to work harder, to pump out more blood quickly. Although the demands for oxygen aren’t met in zone 5, the heart adapts to contract stronger and increase blood output. The increase in stroke volume increases cardiac output (Q), which is mainly challenged at high intensities.
Increased capitalization is another potential mechanism by which the body adapts to bring more oxygen and clear more lactate. Research shows high-intensity cardio to stimulate endothelial cell proliferation and induce capillary growth, to improve blood flow. (3) (4) (5) (6)
Metabolic Adaptations
The most profound effects of high-intensity cardio are improvements in metabolic function. Essentially, glycogen stores are quickly depleted, increasing muscle’s ability to absorb more glucose. This stabilizes blood sugar levels and improves glucose utilization further.
The data shows HIIT to be an effective way to increase insulin sensitivity, improve glucose transport, and increase muscle’s oxidative capacity. (7) Many studies have found improvements in fat-loss, amongst markers like HbA1C, HOMA-IR, and fasting insulin. (8) (9) (10)
While lower-intensity targets the mitochondria more by stimulating their function, high-intensity cardio has also been shown to increase PGC-1α expression which stimulates mitochondrial biogenesis. (11) (7)
Anaerobic Capacity
At high intensities, the body is forced to increase glycolytic enzyme function to break glucose down for energy, rapidly. Such stressors improve the body’s ability to perform in anaerobic activities during short and intense efforts. The muscles become better at dealing with increased acidity, as buffering capacity is enhanced to clear out accumulated lactate.
Neuromuscular Adaptations
Fast-twitch muscle fibers are predominantly activated during high-intensity, explosive efforts. This stimulates recruitment of larger motor units which trains both central nervous system activation (CNS) important for strength, and increases reaction speed and power.
Psychologically, things like cold showers and intense-cardio train the ability to endure discomfort, increasing mental resilience and the ability to sustain challenging tasks.
Increase VO2 max levels
Higher VO₂max levels are strongly linked to improved longevity and cardiovascular health. (12) (13) (14) (15)
Zone 5 training occurring in intervals is the most effective way to raise VO2max levels. (16) Different training modalities like short sprints or interval training can be incorporated to optimize for VO2max. The goal is to endure zone 5 intensity (>90% HRmax) for 30 sec. to 4 minutes, alternating it with low-intensity recovery periods at zone 2. Work to rest ratio can range from 1:1 to 1:4, depending on the strategy. *Exercise examples are shown below.
VO₂max, or maximal oxygen uptake, is the highest amount of oxygen the body can take in, transport, and utilize to produce energy during exercise. It’s a reliable indicator of aerobic capacity, cardiorespiratory fitness, and physical performance, particularly in endurance sports. (17) (13)
Measured during an incremental exercise test, VO₂max represents the point where oxygen uptake plateaus despite increasing exercise intensity, signaling the body’s peak aerobic capacity.
An elite endurance athlete will likely exhibit greater VO2max values ~ 60-85 mg/kg/min, while their sedentary peers would likely hover ~ 30-45 mg/kg/min. The increase in VO2max is strongly dictated by enhanced cardiac output, which is a key determinant of oxygen delivery to working muscles. (18)
Benefits of Zone 5 Training
The strenuous nature of high-intensity cardio is the primary driver of the various adaptations that lead to the potential benefits of zone 5 training. These are highly variable and dependent on multiple factors like training status, genetics, age, VO2max levels, etc.
It’s important to emphasize that most of the data looks at HIIT training, comprising of intervals of low-intensity (zone 2) recovery and high-intensity (zone 4 or 5) work. This is because of the nature of zone 5 training which is heavy, intense, maximal effort workload that can’t be sustained for more than 4-6 minutes.
The majority of the metabolic, cardiovascular, and performance benefits depend on higher work-volume than 5 minutes. The most practical and doable exercise for humans to elevate VO2max and get the zone 5 benefits is, therefore, HIIT.
Anaerobic Performance
Training at 90-100% is predominantly anaerobic, using fuels like glycogen and creatine. Such intensity pushes the body to the limits, which is key for enhancing anaerobic capacity, vital for increasing speed, explosiveness, and stamina.
Zone 5 training helps improve the body’s ability to perform at a near-maximal intensity, promoting a competitive edge in sports that require speed, agility, and endurance. (19) (20) (21) (22)
Some of the underlying mechanisms include:
- increasing power output
- enhancing lactate clearance
- recruiting more fast-twitch muscle fibers
The short active recovery in-between helps glycogen resynthesis and lactate clearance, allowing for longer duration at zone 5. (6)
The muscles are conditioned to use quick-energy sources, particularly the phosphagen (CrP) and the glycolytic system (glycogen). Additionally, lactate buffering ability is improved, leading to faster recovery between bouts of high-intensity work.
Heart Health
As the heart works at near maximal capacity during zone 5 cardio, two profound adaptations happen. The myocardium (heart muscle) strengthens and stroke volume increases. These two elements increase the amount of blood that can be pumped out and flow to the muscles, enhancing performance. (18) (23)
Long-term, trained people have lower resting heart rate (RHR) which is associated with better cardiovascular fitness and longevity.
Additionally, intense training can aid in improving endothelial function, the cells that comprise the lining of blood vessels. This can improve blood flow and reduce the risk of atherosclerosis and plaque build-up. (24) (25) (26) (27)
HIIT has been consistently shown to improve lipid profiles, a key factor for determining CVD. In most studies, HIIT reduced LDL and total cholesterol, triglycerides, and increased the good HDL cholesterol. (28) (29) (30)
Metabolic Function
Exercise strongly impacts metabolic function, primarily due to its effect on the muscle’s ability to absorb glucose. Both strength training, zone 2, and zone 5 cardio play a major role. High-intensity training seems to be one of the most time-effective strategies to cause significant shifts in metabolic function.
When glycogen stores deplete, glucose transporters like GLUT-4 are activated, helping the muscle absorb more glucose. This is particularly important for individuals with poor glycemic control, common for diabetic or overweight people.
Data on REHIT cycling shows a strong effect on improving insulin sensitivity by 28%, the key determinant of metabolic function. (31)
Additionally, studies have shown the potential of HIIT to elicit:
- reduction in total abdominal and visceral fat (8)
- reduction in the risk of insulin resistance and improve HbA1C levels (9) (10)
- improvement of blood lipid profile, decreasing LDL and TC, increasing HDL (29)
Overall, high-intensity cardio is a significant stressor that stimulates the heart, lungs, and muscles to adapt for higher efforts. This results in various adaptations that can enhance the body’s ability to control glucose and stabilize energy levels.
Is zone 5 good for weight loss?
Zone 5 burns more calories per minute but relies on glycogen, not fat. However, the metabolic adaptations and improvement in cardiorespiratory function lead to improvements that support weight management.
Additionally, HIIT training has a non-significant EPOC effect (afterburn) that slightly contributes to weight loss. However, it is not the most sustainable long-term way to weight loss, due to an increase in appetite, hunger and higher recovery cost.
Does zone 5 increase VO2max?
Yes, HIIT (zone 5) is the most effective method for boosting VO2max. Compared to LISS (low intensity steady-state cardio) or MICT (moderate intensity cardio) it is more effective in increasing VO2max levels.
What are the benefits of Zone 5 cycling?
Zone 5 cardio predominantly works the anaerobic system, improving anaerobic capacity or the ability to perform at very high intensities. Additionally it improves metabolic function (insulin sensitivity) and cardiorespiratory function.
What exercises improve VO2 max?
Intense HIIT cardio, particularly interval cardio that contains 1:1 or 3:1 ratio of low-intensity (40-60% HRmax) and high-intensity (90-100% HRmax).
Do you burn fat in zone 5?
No, minimal fat burning occurs at high intensities, as the body preferes quick energy sources like ATP, Creatine phosphate, and Glycogen.
What cardio is best for insulin resistance?
While a healthy balance of both zone 2 (low-intensity) an zone 5 (high intensity) cardio is required to support metabolic function, higher intensities are more effective at improving insulin sensitivity.
What cardio zone is best for longevity?
A healthy balance of both high intensity (1 weekly) and low-intensity stedy state (2x weekly) cardio is close-to-optimal for longevity, developing both the aerobic and anaerobic system.
Low intensity is building the aerobic foundation, improving mitochondria function, fat oxidation and circulation. High intensity works the anaerobic system, improving lung capacity, increasing VO2max levels and metabolic function.
Zone 5 Training Examples
Zone 5 training involves structured high-intensity intervals that push the cardiovascular system to its limits. The key is to achieve 90-100% of your maximum heart rate for short durations, followed by active recovery periods. Here are effective Zone 5 training protocols that can be incorporated into your regimen:
30-30 Intervals
Alternating between 30 seconds at 90-95% intensity and 30 seconds of active recovery (40-50% intensity) for 10-20 rounds. This 1:1 work-to-rest ratio allows for substantial time at VO2max while providing just enough recovery to maintain quality. Running, cycling, or swimming are ideal modalities.
4×4 Method
Four minutes at 90-95% HRmax followed by three minutes of active recovery at 60-70% HRmax, repeated 4 times. This approach, popularized in research, has shown remarkable improvements in VO2max and endurance capacity. (16)
Sprint Interval Training (SIT)
All-out 15-30 second sprints followed by 2-4 minutes of complete or active recovery. This highly anaerobic approach recruits maximum muscle fibers and has shown exceptional efficacy for fat loss and metabolic conditioning. SIT can be performed running, cycling, or on specialized equipment like air bikes or ski ergometers.
