Is a Warm-Up Really Necessary Before Exercise?

woman doing a light jog

Getty/Design by Cristina Cianci

It can be tempting to skip a warm-up prior to exercising for a variety of reasons. Whether you're on a time crunch, aren’t a fan of stretching, or simply want to get your workout over with, it can be easy to gloss over your warm-up and jump right into whatever movement you love most. But is this the safest practice? To get to the bottom of whether or not warm-ups can actually prevent injury (and improve workout performance), we've tapped sports medicine doctor Elizabeth Gardner, MD and celebrity trainer Jillian Michaels.

Meet the Expert

  • Elizabeth Gardner, MD is a Yale Medicine sports medicine doctor in the department of Orthopaedics & Rehabilitation.
  • Jillian Michaels is a celebrity trainer, health and fitness expert, and the creator of The Fitness App.

What Is a Warm-Up?

A warm-up is basically a wakeup call for your body, preparing your muscles for exercise, explains Gardner. “When we are seated or sedentary, many of our muscles shorten, or contract, due to our position in the chair. However when you start moving, those muscles will elongate in the new position,” she says. “If this change happens too quickly, there is risk for injury.”

“A warm-up is a period of activity done before a workout that helps prepare the body for the demands of their chosen exercise or fitness regimen,” adds Jillian Michaels, health and fitness expert and creator of The Fitness App, explaining that it should be essential prior to any exercise. “A warm-up quite literally warms the body up and raises your core temperature slightly in order to make the muscles, ligaments, tendons, joints etc. more mobile and flexible in order to improve performance and prevent injury. It also increases blood flow, which supports the body during exercise by better facilitating the delivery of oxygen and nutrients to working muscles.”

Contrary to misconceptions, a warm-up isn’t the same thing as the form of stretching you were taught about as a kid, Dr. Gardner reveals. “Static stretching is what you likely remember from gym class—it is reaching down to touch your toes, or stretching your arm across your body to stretch your shoulder.” Typically these stretches are held at the point of mild discomfort for at least 30 seconds.  “However, we’ve learned that static stretch, when done before any activity, does not have the desired effect,” she continues. “It doesn’t replicate the motions and activity that you will be doing, and doesn’t start to get the muscles working ahead of your exercise.  This means that you aren’t preventing injuries, and in fact, there is some suggestion that it can actually negatively affect workouts.”

Instead, your warm-up stretch session should involve dynamic stretching—performing gentle repetitive motions in a way that gradually increases motion, circulation, and muscle length. “For example, arm swings that start small and gradually increase to become bigger, but always remain within the normal range of motion,” says Dr. Gardner. “You should also include motions that replicate your planned exercise, such as bounding high-knee jumps or butt-kicks if you are planning to run. Even at a low-intensity, these dynamic movements will slowly increase your heart rate and raise your body temperature. This is believed to improve the muscle elasticity and allows for more efficient cooling and oxygen exchange, thus preparing the body for the exercise that you are about to perform.”

How to Warm-Up Correctly

According to Michaels, a warm-up can last anywhere from five to 10 minutes, and often involves cardiovascular exercise and/or the dynamic stretching Dr. Gardner discussed above. “The goal is to perform relaxed easy activity,” she explains. This can be in the forms of a brisk walk around the block, a quick five minute ride on a stationary bike, or a 1000 meter row of light resistance at a moderate pace. “I also like to include dynamic stretches and or joint mobilizers like: Cat and cow, knee circles, hip circles, arm circles, bodyweight lunges with torso rotation etc.,” she says. 

Benefits of a Warm-Up

Warmups help in a multitude of ways, but the most important are:

  • Increases Body Temperature: “A good warm up should increase your body temperature, which improves the elasticity of muscles, and allows improved oxygen delivery to the muscles,” Dr. Gardner points out. “This allows the body to perform more intense and strenuous activity.”
  • Improves Workout Performance: Michaels points out that one of the key benefits of a warmup is that it will improve your overall performance during your workout, “via the facilitation of greater range of motion, improved oxygen delivery to the muscles for better power and endurance, and enhanced neuromuscular function.” It quite literally “allows your muscles to start to contract also improves nerve transition and the delivery of oxygen and nutrients to muscles,” adds Dr. Gardner. “This allows the muscles to contract and relax faster.”
  • Can Help Improve Flexibility: Dynamic stretching before exercise improves the elasticity and flexibility of your muscles, Dr. Gardner explains. “This has benefits not only for that work-out, but when done consistently, can aid in long-term flexibility improvement.”  
  • May Prevent Injury: Because of all the reasons above, warmups are an effective tool against preventing injury, Michaels points out. 
  • Help You Mentally Prepare for a Workout: In addition to all the physical benefits of a warm up, there is a huge mental component as well. “A warm-up is a good time for you to collect your thoughts as well, and mentally prepare to take on a strenuous workout,” Dr. Gardner reveals. “This ensures that your body, and your mind, are ready for the exercise.”

The Takeaway

Warming-up sends important signals to your body that you're about to work hard. Doing a quick warm-up before you dive into your official workout not only prepares your body mentally and physically for the exercise to come, but can also prevent injury and improve flexibility. Even just a few minutes

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