Sometimes a little bit of a bad thing can be a good thing. This phenomenon, known as hormesis, is what happens when a chemical agent or environmental factor that is damaging at high doses yields a positive effect when used in smaller quantities. Perhaps the most common example is vaccinations. Inject a tiny bit or weakened form of a toxin, and your body will build up resistance to that thing. Expose yourself to too much, and you’ll probably get sick. Athletes have been using this strategy for years, but only recently have scientists started exploring how hormesis can be best used in the context of fitness.

This past May, researchers published a paper in the Journal of Applied Physiology titled “Modulating Exercise-Induced Hormesis: Does Less Equal More?” They evaluated hormesis training strategies and found that some can be quite beneficial, but the fine line between too much and too little is still being explored, and similar to other hormesis strategies, if done improperly, it can cause injury and illness.

Here’s what we know so far:

Low-Carb Workouts

What It Is: Exercising without carbohydrates stored in the body or ingested during training, sometimes referred to as “starvation workouts,” can improve the body’s ability to store glycogen (the stuff that powers intense activity, which, ironically, is made from carbohydrates) and use fat for fuel. Starvation workouts have also been shown to increase activity in mitochondria, the part of the muscle cell that generates energy. “Collectively, these findings suggest that manipulating carbohydrate availability before and/or during exercise stimulates several of the metabolic and molecular responses that promote adaptations to training,” wrote the study’s authors.

The easiest way to prepare for a low-carb training session is either to eat a low-carb dinner and train before breakfast or to perform two workouts in the same day (e.g., morning and afternoon) without ingesting carbohydrates in between.

How to Do It: Matt Dixon, a physiologist, founder of Purplepatch Fitness, and coach of world-champion triathletes, says athletes should keep low-carb sessions at lower intensity and refuel immediately following the workout. Moreover, these workouts should be executed infrequently (such as once or twice a month) and when the athlete has limited stress beyond his or her training—rest must be prioritized after these sessions. It’s also important to note that a low-carb workout does not mean a low-carb diet, something sports nutritionist Matt Fitzgerald told us in an article published in February.

Dixon believes that “before an athlete should even begin playing with this type of thing, they need to establish great baseline habits and a nonemotional relationship with eating and fueling.” He warns that this sort of approach is often a slippery slope to ongoing caloric restriction, something that “certainly yields negative results.”

Inflammation

What It Is: Quick word association test—when I say “inflammation,” what comes to mind? Go.

Perhaps you came up with “bad,” or “pain,” or “ibuprofen.” You probably did not think “stronger” or “repair.”

It turns out that a little inflammation is both completely normal after a hard workout and helps the body adapt to exercise. Additionally, the Applied Physiology paper found evidence that taking nonsteroidal anti-inflammatory drugs (like ibuprofen) diminishes exercise adaptation and recovery by inhibiting pathways that increase blood flow to the muscles. Other research suggests NSAIDs may slow bone remodeling and healing.

Which makes us ask: Should we lay off the vitamin I?

Yes and no, according to Todd Weitzenberg, a sports medicine physician in Santa Rosa, California. While some inflammation is beneficial, chronic inflammation can cause pain and mobility loss that prevents athletes from training. It may also directly contribute to muscle wasting. “The key is to use NSAIDs appropriately,” says Weitzenberg.

How to Do It: A good rule of thumb is to never take them prophylactically (that is, before a workout to make it hurt less) or for typical post-training soreness. Not only does this lessen fitness adaptations, but it also poses a risk of GI bleeding and kidney damage. “I’m amazed by how many people take NSAIDs as a ‘preventative’ measure,” says Weitzenberg. “Adults even do this with their kids. It’s so bad—and shocking, really.”

Dixon’s rule with the athletes he coaches is simple: “We tend not to mess with inflammation, especially post-workout.”

In other words, only in very specific cases should you turn to NSAIDs. For instance, if you suffered an acute injury with severe pain and swelling or have an overuse injury that isn’t resolving on its own, then taking NSAIDs as recommended by your physician is not a bad idea, according to Weitzenberg. “There is a time and place for NSAIDs,” he says. Just be sure to rule out bone injuries like stress fractures, since NSAIDs can delay the healing process.

Preloading

​

What It Is: Training hard when you are already fatigued is no fun. However, when done at the right time and dose, the effects are powerful. According to Samuele Marcora, a physiologist at the University of Kent, training on tired muscles doesn’t just improve physical fitness, it also improves mental fitness. Preloaded workouts overload the body and mind, forcing both to work harder and get stronger. As discomfort and deep fatigue set in, the mind wants to quit, but in essence you are making it “choose” to tell the muscles to fire, says Marcora, building up the mental muscle. And much like a stronger body, a stronger brain allows an athlete to tolerate more effort and push harder.

Jesse Kropelnicki, coach of world-class triathletes and runners and founder of QT2Systems, says the ability to perform with fatigued muscles, or what he calls “durability,” is vital to success in most endurance sports. “Training under fatigue will likely improve the ability to perform under fatigue,” he says.

How to Do It: There are many ways to go about preloading. Examples include two-a-day workouts, back-to-back hard days, or an endless variety of “brick” workouts where you run after biking, bike after lifting, row after running, and so on. Yet while these sessions can generate a nice fitness boost, they are, as we mentioned, stressful on both the body and mind, which is useful only to a point. Both Kropelnicki and Dixon agree that preloaded training sessions should be used only by athletes who have already built up a solid fitness base, and these workouts should always be followed with adequate rest and recovery. In other words, be sure you can execute a long run on its own before trying to do one after biking or lifting weights. And be sure to follow preloaded training with an easy day or two.

Another creative and less risky way to preload without causing much additional fatigue is by doing resistance exercises with the muscles you are about to train prior to the main workout. Kropelnicki uses this technique with distance runners to build durability, which comes in handy during the home stretch of a marathon. The Applied Physiology paper also found that eccentric muscle contractions prior to exercise “induce positive adaptations” and help prevent post-workout muscle pain, commonly known as delayed-onset muscle soreness (DOMS). Eccentric sets need not be heroic to reap benefits: For example, three sets of 12 eccentric calf raises (performed on a step with the heel finishing below the toes) does the trick.

Heat Training

What It Is: According to the Korey Stringer Institute at the University of Connecticut, heat acclimation is a “complex series of changes or adaptations that occur in response to heat stress.” These changes enhance performance and safety in hot conditions and include a decrease in heart rate, body and skin temperature, and perceived exertions and an increase in sweat onset, sweat rate, and blood plasma volume.

According to coaches and scientists, heat acclimation is especially beneficial for those competing in unfamiliar hot conditions. Without acclimatizing prior to a hot-weather race, performance will suffer, and the chance of experiencing serious health problems, like heat stroke, increase significantly.

Purplepatch’s Dixon occasionally uses this strategy for altitude racing and before key competitions since the physiological changes brought about by heat training can improve performance at altitude as well as in normal conditions. (Heat training increases blood plasma volume, lessening the effects of elevation, and the combination of adaptations can boost general fitness.) That said, Dixon emphasizes that “heat training is extremely stressful, with risks that can outweigh rewards,” and thus he doesn’t advise rushing into it unless you have a hot-weather event coming up.

How to Do It: Historical research suggests a protocol of seven to 14 days of 90-minute workouts in 100-degree-plus conditions. In practice, however, Dixon observes an effect after 30-minute low-intensity workouts in extreme heat/humidity without hydration during (but with rehydration after). Another strategy Dixon uses to reap the benefits of heat training is a sauna protocol, whereby the athlete trains in normal conditions, quickly refuels, and then spends 15 to 30 minutes in a sauna without drinking—which Dixon notes is not easy to do. In both strategies, Dixon sees benefits after seven to ten days. He makes sure the heat training regimen ends two to three days before departure to the hot-weather event.