Who should not do high intensity interval training?

September 24, 2025 •

4 min read

While High Intensity Interval Training (HIIT) is lauded for its time-efficient benefits, approximately one-third of American adults do not get enough physical activity, and diving into HIIT without caution can be dangerous for some. The demanding nature of HIIT makes it an unsuitable or even risky option for many individuals, depending on their health status.

Quick Summary

Individuals with serious heart conditions, pre-existing injuries, osteoporosis, or those new to exercise should typically avoid or significantly modify HIIT, seeking medical advice before starting.

Key Points

Heart Conditions: Individuals with existing heart disease, uncontrolled high blood pressure, or irregular heart rhythms should avoid HIIT unless cleared and supervised by a doctor.
Joint and Injury Issues: Those with arthritis, osteoporosis, or current injuries are at high risk for worsening their condition with high-impact HIIT movements.
Beginners and Low Fitness: Beginners should first build a solid fitness foundation with moderate exercise to prevent injury and burnout before attempting HIIT.
Pregnancy and Postpartum: Pregnant women and new mothers in the early postpartum period should avoid or modify HIIT and consult a healthcare provider for safe exercise options.
Overtraining Risk: The intense nature of HIIT increases the risk of overtraining, which can lead to chronic fatigue and other negative health effects.
Safe Modifications Exist: For many, low-impact HIIT modifications or other forms of exercise can provide similar benefits without the high risk.

Critical considerations before starting HIIT

High Intensity Interval Training (HIIT) is a form of exercise characterized by short, intense bursts of anaerobic exercise followed by brief recovery periods. While beneficial for many, its rigorous nature can exacerbate certain health conditions or lead to injury if not approached correctly. It is critical to understand your own health profile and fitness level before beginning a HIIT regimen.

Heart conditions and risk factors

For individuals with pre-existing heart conditions, the rapid fluctuations in heart rate and blood pressure inherent in HIIT can be dangerous. The stress placed on the cardiovascular system can be too great for those with conditions such as:

Coronary artery disease: The increased demand on the heart can be risky for patients with narrowed arteries.
High blood pressure (uncontrolled hypertension): Intense bursts of exercise can cause significant spikes in blood pressure, which is a particular risk for those with uncontrolled hypertension.
Heart failure: While monitored HIIT can be tolerated in cardiac rehabilitation settings, unmonitored sessions are risky.
Arrhythmias: The rapid changes in heart rate during intervals can exacerbate irregular heart rhythms.
History of heart attack or surgery: Clearance from a cardiologist is mandatory before attempting strenuous activity.

For those with existing or at-risk cardiovascular disease, always consult a doctor first. The American Heart Association recommends a minimum of 150 minutes of moderate-intensity activity per week for most adults, a safer starting point than high-intensity efforts.

Joint and musculoskeletal injuries

The high-impact and explosive movements often found in HIIT, such as burpees, jump squats, and box jumps, place significant stress on joints and connective tissues. Individuals with the following issues should be cautious or avoid traditional HIIT:

Osteoarthritis: High-impact exercises can worsen joint pain and stiffness in conditions like knee osteoarthritis.
Osteoporosis: The intense, jarring impact can be unsafe for individuals with decreased bone density.
Pre-existing injuries: People recovering from ankle, knee, shoulder, or back injuries should avoid stressing the affected area, as HIIT can worsen the condition or delay recovery.
Poor exercise form: Performing complex movements rapidly without proper technique can lead to misalignment and overuse injuries.

Low-impact modifications exist and can be an effective way to get the benefits of HIIT without the joint stress.

Pregnancy and postpartum

While exercise is generally encouraged during pregnancy, high-impact activities like HIIT should be approached with extreme caution, especially for those who were not previously active. The American College of Obstetricians and Gynecologists (ACOG) suggests 150 minutes of moderate-intensity activity per week, but medical clearance is essential for any higher intensity exercise. Similarly, new mothers in the first 3-6 months postpartum should avoid intense workouts like HIIT to allow their bodies to heal.

Beginners and individuals with low fitness levels

Jumping into HIIT with a low fitness base is a recipe for injury and burnout. For beginners or those who have been sedentary for a long time:

Build a foundation: Start with consistent moderate-intensity cardio and strength training for several weeks to build a foundation of fitness.
Learn proper form: Mastering the basic movements of squats, lunges, and planks is essential before adding speed and intensity.
Start with low-impact modifications: Opt for safer alternatives like cycling or speed walking intervals until your fitness improves.

The risk of overtraining

Performing HIIT too frequently or intensely can lead to overtraining syndrome, characterized by persistent fatigue, decreased performance, and increased risk of injury. The physiological stress can also raise cortisol levels, potentially harming health for those with high stress or adrenal fatigue.

Signs of overtraining: Persistent fatigue, sleep disturbances, increased muscle soreness, and mood changes.
Limit HIIT frequency: Most experts recommend limiting HIIT to 2–3 sessions per week and incorporating other types of exercise, like steady-state cardio and resistance training, to allow for adequate recovery.

When to seek medical advice

Beyond specific conditions, anyone with symptoms such as chest pain, extreme shortness of breath, dizziness, or irregular heartbeats during exercise should stop immediately and consult a doctor. Always listen to your body and prioritize safety over pushing your limits unnecessarily.

Comparison: HIIT vs. MICT for different populations


Feature	High-Intensity Interval Training (HIIT)	Moderate-Intensity Continuous Training (MICT)
Heart Stress	High; involves rapid heart rate fluctuations. Risky for those with certain conditions.	Moderate; steady heart rate. Generally safer for cardiac patients.
Joint Impact	Often high-impact with movements like burpees and jumps. Can strain joints, increasing injury risk.	Lower impact, easier on joints. Examples include walking, swimming, or cycling.
Time Efficiency	Very time-efficient; shorter workouts for high results.	Requires longer durations to achieve similar cardiovascular benefits.
Beginners	Not recommended initially; requires a foundational fitness level to avoid injury.	Ideal for beginners to build endurance and form safely.
Injury Recovery	Generally not recommended due to high stress on muscles and joints.	Can be suitable with a doctor's approval for low-impact recovery.
Overtraining Risk	Higher risk if done too frequently without proper recovery.	Lower risk of overtraining due to reduced intensity.

Conclusion: Prioritizing safety over intensity

For all its benefits, HIIT is not a one-size-fits-all exercise solution. Prioritizing your health by understanding the contraindications is paramount to a safe and sustainable fitness journey. For those who should not do high intensity interval training, safer, lower-impact alternatives can still yield excellent results. Always seek medical advice before embarking on a new exercise program, especially if you have pre-existing health conditions. Exercise should build your body up, not break it down.

For more detailed information on high-intensity exercise and your heart health, consult trusted medical resources like the American Heart Association.

Frequently Asked Questions

If you have a known heart condition, you should not do high intensity interval training without first getting clearance from your doctor or a cardiologist. The rapid changes in heart rate and blood pressure can be risky. Supervised, low-intensity interval training may be a safer option.

HIIT can be bad for your knees and other joints, especially if you have pre-existing issues like arthritis or osteoporosis. The high-impact, explosive movements common in many HIIT routines put significant strain on joints. However, low-impact HIIT modifications are available and safer for joints.

No, beginners should not start with HIIT. It is important to first build a base level of fitness with consistent, moderate-intensity exercise to improve form and endurance. Rushing into high-intensity workouts can increase the risk of injury and burnout.

Signs of overtraining can include persistent fatigue, increased muscle soreness that doesn't go away, sleep disturbances, mood changes, and decreased performance. If you experience these symptoms, it is important to reduce your intensity and allow for proper recovery.

HIIT is generally not recommended for pregnant women, especially those who were not previously active. The high intensity can increase risks, and medical consultation is essential for any high-intensity exercise during pregnancy.

For those with health concerns, safe alternatives include moderate-intensity continuous training (MICT) like brisk walking, swimming, or cycling. Low-impact HIIT modifications can also be a viable option, such as using a stationary bike for interval training.

Individuals at a higher risk of injury from HIIT include beginners with poor form, those with pre-existing joint or muscle injuries, and those who perform high-impact movements without a proper warm-up.

Yes, overdoing HIIT can increase cortisol levels, the body's primary stress hormone. For individuals already dealing with high stress or adrenal fatigue, this can be detrimental to overall health.