Warming up

In Chicago, researchers from Northwestern University had 1,492 female school students who played sports (mainly soccer and basketball) do a specific warm-up taught by 90 coaches who had been trained for this [12]. In this case, the warm-up was neuromuscular and consisted of strength exercises, plyometric exercises and agility exercises. They saw fewer cases of knee, ankle and cruciate ligament injuries in the group that had done the warm-up [12].

Australian researchers compared multiple studies on this point and found five high-quality studies [13]. Of these five studies, three indicated that a warm-up reduces the chance of injuries. The other two showed no significant difference.

The members of the "Joint Services Physical Training Injury Prevention Work Group" (try saying that quickly three times in a row) reached the same conclusion after comparing 13 studies [26]. This task force of the US Department of Defense compared the studies to optimize training methods in the military. They saw that a specific warm-up, aimed at the sport that follows, especially reduces the chance of injuries.

As mentioned, there can be many causes of an injury. It seems plausible that these can be limited insofar as they are caused by limited elasticity in the muscle, limited blood flow, limited oxygen uptake, etc. In other words, insofar as they are due to the body processes that are improved by a warm-up (which seems very logical). A good warm-up will not enable you to head a 50 kg dumbbell without suffering from it. That seems like a sentence with a very high "Duhhh factor", but it serves to illustrate that despite all your preparation, shit can still happen.

Less muscle soreness through warming up?

First of all: most people involved in bodybuilding have no problem at all with "good" muscle soreness, also known as delayed onset muscle soreness. It is actually seen as a sign of a workout that has led to hypertrophy, the growth of muscles through repair of damage ("No pain, no gain"), although there is not always a one-to-one relationship.

The Australian researchers Law and Herbert divided 52 volunteers into four groups [14]. One group did a warm-up and cool-down, the second group did only a warm-up, the third only a cool-down and the fourth group did nothing (control group). The warm-up and cool-down consisted of 10 minutes of walking on a treadmill at about 5 km/hour and a 3-degree incline. The training itself was performed eccentrically because this is known to lead to muscle soreness the fastest. They concluded that a warm-up can cause a small reduction in muscle soreness (13%).

When researchers from the University of Tennessee did a similar type of study, they reached a different conclusion in 1986 [15]. They looked at the combination of warm-up and stretching or stretching alone. Their research showed that neither led to less muscle soreness in the three days after a workout.

In Utrecht, Rodenburg and colleagues also investigated influences that reduce muscle soreness, but combined a 15-minute warm-up with stretching and massage [16]. They saw a reduction in muscle soreness of 1 point on a six-point scale. The question, however, is to what extent the warm-up, stretching or massage contributed to this result. Moreover, the researchers themselves indicated that the results in the group that had warmed up and stretched varied too much to state that this had an effect.

So if you can already say that a warm-up can reduce possible muscle soreness, the effect seems limited. Since reducing muscle soreness is in itself not a goal for many serious athletes, this will not be a reason for them to do a warm-up.

Psychological effect of warming up

A major advantage of a warm-up is that you are mentally prepared for the workout. Sitting on the bike or walking on the treadmill, for example, you look over the part of the gym where strength training is done and cannot wait to start "the real workout". Just like when you have to sit on the bench during a sport and you are eating yourself up while your team messes things up. You are then itching to get started.

Especially if you are someone who would prefer to skip the warm-up, it is like eating your vegetables before you are allowed dessert. Not only do you start wanting the strength training, but after the warm-up you also feel ready for it. Instead of starting your exercise stiffly, you have already set your system to "action mode!".

According to researchers from the University of Illinois, this psychological effect was even the most important effect of a warm-up contributing to better athletic performance [17]. They hypnotized their subjects so that they would forget they had done a warm-up. It then turned out that their performance was no better than that of the group that had actually done no warm-up. That the reverse also applies was shown seven years earlier (1954) by researchers who used hypnosis to make people think they had done a warm-up and saw that they performed better as a result [18].

Warming up increases testosterone, but not cortisol

A warm-up raises your testosterone level, but not that of the catabolic stress hormone cortisol. This was shown in a study at Emory University in Atlanta, where researchers examined the saliva of volleyball and tennis players [19]. They were curious about the effect of a warm-up on the muscle-building and strengthening hormone testosterone and on the muscle-breaking stress hormone cortisol. It is known that intensive training raises the levels of both. In this study, however, the researchers saw that testosterone did rise, but cortisol did not. Exactly what you want, of course. The researchers also saw that during the match that followed the warm-up, testosterone levels remained higher and were therefore already being benefited from at the start of the match. Cortisol levels only began to rise during the match.

You can therefore say that testosterone rises during the warm-up and that you benefit from this during the rest of the training. With cortisol, it is less clear whether it does or does not rise during a warm-up because studies on this show conflicting results. This may be caused by the type of warm-up.

In the case of the study among the volleyball and tennis players, only a one-hour warm-up before the match is mentioned. If this is a warm-up like in many game sports, a large part of the training is aimed at skill and improving the connection between the brain and the muscles. A tennis player, for example, will serve some balls, hit from the baseline and stand at the net. This does not necessarily have to cost a lot of energy, causing cortisol to be produced (to provide that energy by breaking down, among other things, proteins in muscles).

In Brazil, researchers also looked at hormonal effects, but they compared the effects of cardio followed by neuromuscular training/strength training and the reverse order [20]. In both groups (recreationally trained young men with an average age of 23), they saw that testosterone rose, although this was more the case when aerobic training was done first and strength training afterward (the order you use when doing a warm-up), rather than the other way around. In contrast to the Atlanta study, cortisol increased in both cases after the first part of the training and then fell again after the second part ended, regardless of the order.

In the Brazilian study, training was done at 75% of maximum heart rate. In terms of energy systems, that can happen in two different energy systems (aerobic and anaerobic), depending on the training status of the subjects. In any case, there is a good chance that the intensity was higher than during preparation for a tennis or volleyball match. This could explain why cortisol increased. If that is the case, you could prevent this by training at no higher than 70% of your maximum heart rate (or even 60% if you are untrained). However, more research would need to be done in which the warm-up is performed at different intensities and the effects are compared.

Cortisol is always a personal concern for me when it comes to combining any form of cardio with strength training, because it extends your strength training while no extra food is coming in. The chance is then high that your body remains in a catabolic state longer until you take in food again after training. This also became clear from the two-part article I wrote about combining strength training with cardio. It showed that this almost always comes at the expense of optimal results from strength training because glycogen, the fuel for your muscles, is depleted sooner. This then leads sooner to an energy deficit, causing your body to increase cortisol faster. That in turn causes more fat to be burned for energy, but also causes proteins in the muscles to be broken down into amino acids, which can then be converted into fuel again.

Better athletic performance through warming up?

You have now read enough to reasonably assume that a warm-up leads to better athletic performance. However, you first have to ask yourself what "better performance" means. When it comes to muscle growth, a good performance is when you have loaded your muscles "beyond the point of failure". For muscle growth, it is about exhausting the muscles in the right way to stimulate them to grow, as described in the article: hypertrophy and muscle growth. How much weight or how many repetitions you need for that is of secondary importance. Good bodybuilders actually find ways to make a weight feel heavier through technical execution (large range of motion, keeping muscles under tension, forced repetitions, etc.).

That is a completely different principle from powerlifters, for example, who like to see that they can move more and more weight with as little effort as possible. In addition, many bodybuilders use the principle of "pre-exhaustion". You do this by doing a few sets with a relatively light weight and relatively many repetitions, so that the muscle is already fatigued before the workout begins and you have a greater chance of exhausting it. They know that during the real workout they are less strong than without pre-exhaustion, but again, what matters to them is how much the muscle is loaded, not what number is written on the dumbbell.

The athletic performance, as it will be described further here in the studies on the effectiveness of a warm-up, is therefore less applicable to anyone who is focused on muscle mass as the result than it is to other sports.

Research results on warm-up effectiveness

Researchers from New Zealand compared cycling performance after a warm-up and without a warm-up [21]. They saw no significant difference in both average power and peak power, but did see that the men who had done the warm-up felt more fatigued because of it. They also saw that power declined faster in the group that had done a warm-up. This may suggest that the warm-up had already fatigued them. This was probably due to the type of warm-up. The warm-up consisted of 8 minutes of cycling, five minutes before the test. The first five minutes had to be at "very light intensity", then two minutes at "moderate intensity" and finally one minute at "moderate/heavy intensity". What "light", "moderate" and "heavy" meant was left for the participants to decide. I therefore think there is a high chance that the final minute in particular was cycled at too high an intensity for a warm-up.

When a similar study was carried out by Canadian researchers, the results were different [22]. They actually saw a 7% increase in average power during the Wingate test. Two differences from the New Zealand study: first, this time a general warm-up was done instead of a specific one. In addition, the subjects were boys aged 7 to 9 who were "not yet familiar with the principle of a warm-up". The latter could mean that they did not have the psychological advantage of a warm-up because they did not know it would contribute to better performance (just as it no longer made a difference in people who had forgotten that they had done a warm-up).

The fact that they did a general warm-up (so not cycling in this case) may have caused the legs to be less fatigued. There are studies that used the Wingate Anaerobic Test to measure performance. In this test, you have to perform maximal effort for 30 seconds on a bike with relatively high resistance. You therefore use the anaerobic energy system (with ATP and lactic acid instead of oxygen as the main source), which bodybuilders and weightlifters also use.

Researchers from Bloomsburg University in Pennsylvania wanted to provide clarity in the studies with different results [23]. They conducted a comparative study in which the results of all relevant studies were compared in order to reach a conclusion.

They compared 32 studies, set criteria for "better performance" and concluded that in 79% of the criteria, a warm-up led to better performance.

The vast majority of the 32 studies therefore showed better performance after doing a warm-up.

Warm-up in practice: which exercises?

First, you have the choice between a general warm-up and a specific warm-up.

Personal advice: always do a specific warm-up or a combination of general and specific warm-up. After all, we have seen that both offer different benefits.

To do this, adapt your warm-up to the training that follows.
For example, if you are going to train chest and biceps, you can do a specific warm-up such as the cross-trainer, where you make both the pushing movement that you will later also make during chest exercises and the pulling/arm-bending movement that prepares you for biceps exercises. You can also start with a general warm-up and perform the first exercise(s) of your "real" workout as a specific warm-up.

As a general warm-up, you could for example cycle. If you then go bench pressing, you could do the first two sets with a relatively light weight with which you can perform at least 25 repetitions. Or you could do your usual number of repetitions, but with very slow reps using a light weight.

Even if, in this case, you have used the cross-trainer as a specific exercise and you train chest first and then biceps, it is better to start your first biceps exercise with a relatively light weight again because the effect of the warm-up has already (almost) disappeared due to the time that has passed. You also do not have to limit yourself to the machines in the gym. A warm-up can be any activity in which you exert yourself in a way that leads to increased body temperature and heart rate. Whether that is walking, cycling, swimming, rowing, jumping rope, bouncing on a space hopper or an athletic sex session does not matter. As long as the right intensity and duration are maintained.

Warm-up in practice: intensity and duration

What "the right duration and intensity" is depends on the athlete's training status, but also on environmental factors such as ambient temperature [3].

Heart rate

Fitness instructors are therefore taught as standard to have their clients do cardio as a warm-up at an intensity of 60%-70% of maximum heart rate for 8-10 minutes. The fitness instructor takes the client's training status into account and will advise untrained people to do 8 minutes at 60%, while experienced athletes will more often move toward 10 minutes at 70% of maximum heart rate. If you do not have a heart rate monitor: in practice, this is an effort level at which you are still able to hold a conversation. The better trained the athlete is, the better the body handles regulating body temperature. A greater effort will then be needed to achieve the desired rise in body temperature [24].

"Sweating means knowing"

As mentioned, the goal is to raise body temperature by 1 to 2 degrees Celsius. You probably will not quickly do your warm-up with a thermometer in your mouth (let alone elsewhere). You do not need to. In practice, this is an intensity that leads most people to light/moderate sweating [27]. One person sweats sooner and/or more than another, but especially in combination with your heart rate, whether or not you can talk and the duration of the warm-up, this should indicate the right intensity.

Duration depends on the activity

If you do a warm-up before strength training in the gym, ten minutes should be enough. Any time you spend on your warm-up beyond that costs energy that comes at the expense of the rest of your training.

A completely different principle applies when you train for a sport that involves fine motor skills. Then, in addition to raising your body temperature, you mainly want to improve control from the brain. Think of the tennis players and volleyball players mentioned earlier, football players passing a ball back and forth, baseball players throwing to each other, basketball players doing layup lines, etc. This can be done at a lower intensity, allowing a longer warm-up to improve motor skills. In many cases, more than an hour is used for this before, for example, a match. For these fine motor skills, more time is also needed to calibrate the system, as it were [24].

Cooling down

Briefly, the cool-down. With a cool-down, you gradually bring your body back to its resting state. For example, heart rate is gradually brought back down to a normal resting heart rate. That reduces the chance of rhythm disturbances. In addition, resting heart rate after a cool-down is lower than if you did nothing for the same period [25].

Blood circulation also returns to a normal resting situation. During exercise, relatively much blood goes to the muscles. At rest, other body parts receive more blood. If you suddenly stop after intense exertion, you run the risk of becoming dizzy, among other things, because blood circulation cannot recover gradually. You can prevent that with a cool-down.

Finally, a cool-down promotes the removal of waste products such as lactic acid. This lactic acid, which can temporarily give a heavy feeling in your legs, for example, accumulates in the muscles during exertion and disappears faster with a cool-down than without one. This could be an indication that less muscle soreness follows. However, the study by Australian researchers that showed a warm-up could reduce muscle soreness did not show that this also applied to a cool-down [14]. There is relatively little research on cooling down, making it difficult to say anything about it with much certainty.

I have only one major problem with this study. The training itself consisted of 5 minutes of cycling at an intensity of 70% VO2max. You may think: "that is the intensity of a warm-up", but converted for me that would be 82% of my maximum heart rate. So, short cycling at a fairly high intensity. You then get off the bike with a high heart rate and researchers look at what influence a cool-down has.

This is not comparable at all with a cool-down after strength training. During a typical strength workout with six to eight exercises divided over two muscle groups, for example with 3 sets per exercise, you have a total of 18 to 24 sets with the same number of rest periods in between. You have already let your heart rate drop many times. Will a cool-down after that last set with which your heart rate is elevated still make much difference? That has not been studied.

For me personally, it is not yet convincing enough to spend some of my scarce time on a cool-down as well. I am already happy when I obediently do my warm-up!

Summary

• A warm-up serves as physical and mental preparation for the exertion that follows.
• Through a warm-up, muscles receive oxygen better, use energy more efficiently, blood supply improves, friction in joints is reduced, muscles are controlled better by the brain and the heart responds better to exertion.
• By increasing heart rate, a warm-up causes greater activity of the orthosympathetic nervous system. This part of the nervous system brings the body into a state of readiness.
• A passive warm-up means heating by an external source such as a bath or sauna. With an active warm-up, body temperature rises through muscle activity.
• A general warm-up mainly focuses on a temperature increase and activation of the nervous system in general. A specific warm-up also prepares for the activities that follow. It is better to do a specific warm-up or both.
• A warm-up can limit injuries insofar as they are caused by muscle elasticity, limited blood flow, limited oxygen uptake and other things improved by a warm-up.
• Muscle soreness is reduced only to a very small extent by a warm-up.
• Through a warm-up, you are mentally better prepared for the activities that follow. According to some, this mental aspect is the main cause of better performance after a warm-up.
• A warm-up of limited duration and intensity (aerobic) raises your testosterone level, but not that of the catabolic stress hormone cortisol.
• Whether a warm-up contributes to better athletic performance depends on the nature, duration and intensity of the warm-up. For a bodybuilder, however, athletic performance is the extent to which the muscles have been loaded and stimulated to grow, not so much the weight moved or the number of repetitions.
• Depending on the athlete's training status, the warm-up for strength training can last 8 to 10 minutes at an intensity of 60%-70% of maximum heart rate. A warm-up for game sports lasts longer to prepare fine motor skills.
• A cool-down gradually returns the body to a resting state, reducing the chance of heart rhythm disturbances and accumulation of lactic acid.

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