There’s tons of evidence, from hundreds of studies with hundreds of thousands of participants, showing that exercise is an effective tool to combat depression and other mental health issues like anxiety. These studies find that it’s at least as good as drugs or therapy, and perhaps . It’s now recommended in official guidelines around the world as a or treatment. Still, there’s an important caveat to consider: is all this evidence of a connection between exercise and mental health any good?

That’s the question debated in in Medicine & Science in Sports & Exercise, based on a symposium held at the annual meeting of the American College of Sports Medicine. Four researchers, led by Patrick O’Connor of the University of Georgia, sift and weigh the various lines of evidence. Their conclusion is mixed: yes, there’s a relationship between exercise and mental health, but its real-world applicability isn’t as clear as you might think.

The Observational Evidence on Exercise and Mental Health

O’Connor and his colleagues assess three main types of evidence. The first is observational studies, which measure levels of physical activity and mental health in large groups of people to see if they’re connected, and in some cases follow up over many years to see how those relationships evolve. The headline result here is pretty clear: people who are more physically active are less likely to suffer from depression and anxiety now and in the future.

Observational studies also suggest, albeit more weakly, that there’s a dose-response relationship between exercise and mental health: more is better. is enough to produce an effect, but higher amounts produce a bigger effect. It’s an open question, though, whether doing too much can actually hurt your mental health. Some studies, for example, have found links between overtraining in endurance athletes and symptoms of depression.

The big problem with observational studies is the question of causation. Are active people less likely to become depressed, or is it that people who are depressed are less likely to be active? To answer that, we need a different type of study.

The Evidence from Randomized Trials

The second line of evidence is from randomized control trials, or RCTs: tell one group of people to exercise, tell another group not to, and see if they fare differently. Overall, the evidence from RCTs lines up with the observational evidence: prescribing exercise improves or prevents the occurrence of depression and anxiety.

For example, here’s a graph from a 2024 meta-analysis of 218 RCTs with a total of over 14,000 participants, :

Dots that are farther to the left indicate how much a treatment aided depression compared to a control group. Notice that walking or jogging ranks slightly above cognitive behavioral therapy and far above SSRI drugs. That’s an encouraging picture.

The evidence still isn’t bulletproof, though. One problem is that it’s very difficult to avoid placebo effects. Participants who are randomized to exercise know that they’re exercising, and likely also know that it’s supposed to make them feel better. Conversely, those who sign up for an exercise-and-depression study and are assigned to not exercise will expect to get nothing from it. These expectations matter, especially when you’re looking at a difficult-to-measure outcome like mental health.

Another challenge is the timeframe. Exercise studies are time-consuming and expensive to run, so they seldom last more than six months. But a third of major depressive episodes spontaneously resolve within six months with no treatment, which is in part why FDA guidelines suggest that such trials should last two years, to ensure that results are real and durable.

Why Context Matters When Studying Exercise and Mental Health

The third and final body of evidence that O’Connor and his colleagues dig into is the contextual details. Exercise itself seems to matter, they write, but “who we play with, whether we have fun, whether we are cheered or booed, and whether we leave the experience feeling proud and accepted, or shamed and rejected also matters.”

For example, most of the research focuses on “leisure time physical activity,” meaning sports and fitness. But there are other types of physical activity: occupational (at work), transportation (active commuting), and domestic (chores around the house). Is there a difference between lifting weights in the gym and lifting lumber on a construction site? Between a walk in the park and a walk down the aisle of a warehouse?

One view of exercise’s brain benefits is that it’s all about neurotransmitters: getting the heart pumping produces endorphins and oxytocin and various other mood-altering chemicals. If that’s the case, then manual labor should be as powerful as sports, and working out alone in a dark basement should be just as good as meeting friends for a run on a sunny day. Both intuition and research suggest that this isn’t the case.

Instead, some of exercise’s apparent mental-health benefits are clearly contextual. Doing something that creates social connection and provides a feeling of accomplishment is probably helpful even if your heart rate doesn’t budge above its resting level. And conversely, an exercise program that leaves you feeling worse about yourself—think of the cliché of old-school phys ed classes—might not help your mental health regardless of how much it boosts your VO2 max.

This is where the big research gaps are, according to O’Connor and his colleagues. It’s pretty clear at this point that exercise isn’t just correlated with mental health; it can change it. But the best ways to deploy it in the real world remains understudied. For now, the best advice is probably to follow your instincts. Don’t stress about what type of exercise you’re doing, how hard to push, or how long to go. For improving mental health, these variables seem to have surprisingly weak effects. Instead, focus on the big levers: whether you’re enjoying it, and whether you’ll do it again tomorrow.

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Earlier this month, the Journal of Applied Physiology published a paper with the title “Evidence on Sex Differences in Sports Performance.” Seems pretty straightforward, but of course it’s not. The gap between male and female athletes has become a major flashpoint in debates on whether transgender women and athletes with differences of sexual development, like the South African runner Caster Semenya, should be able to compete in women’s sports.

Three scientists—Michael Joyner of the Mayo Clinic, Sandra Hunter of the University of Michigan, and Jonathon Senefeld of the University of Illinois Urbana-Champaign—present a series of seven statements on the topic of sex differences in sport, along with the evidence to support them. Some of them seem obvious, others less so. Whatever your opinion on the debate, I think it’s worth considering each of these statements (which I’ll paraphrase) in turn, in order to understand what the current evidence says and where the gaps are. The full paper, including references, is free to read .

A note on terminology: the article deals with differences in sex rather than gender. Although it’s an oversimplification, I’ll use the terms male and female to refer to people with XY and XX chromosomes, respectively.

1. Males outperform females in events that depend on strength, speed, power, and endurance.

The evidence cited here is primarily performance data from sports like running, jumping, and weightlifting, where outcomes are easily measured. Among elite adults, the male-female gap is typically above 10 percent. The largest gaps are seen in sports that depend on explosive power, like high jump and long jump, where the gap approaches 20 percent. Field sports are harder to measure, but to the extent that they involve running and jumping and lifting, similar conclusions should apply.

Are these gaps biologically determined, or, , the result of social factors like the limited opportunities for women in sport? Elite performance data, on its own, can’t answer this question. But there’s no question that the gap exists, and is nearly universal. There may be some exceptions in activities like , where the determinants of performance are more complex. Overall, though, this statement should be uncontroversial.

2. This male-female gap shows up before puberty.

This seems like a significant claim, because it suggests that males may have a performance advantage that isn’t erased even if a transgender woman has undergone hormone therapy to lower testosterone levels. The evidence, once again, is primarily from performance data. Take a look at this graph of age-group track and field results for boys and girls between 7 and 18 years old:

Between the ages of 7 and 9, boys seem to be ahead, on average, by 4 to 5 percent. The gap narrows between the ages of 10 and 12, presumably as girls start puberty earlier than boys. After the age of 13, male puberty gets going and the gap widens rapidly.

So what gives 8-year-old boys an edge? As Joyner and his colleagues acknowledge, it’s once again hard to distinguish between biological and social factors. There is a possible hormonal explanation. We undergo a “minipuberty” during the first few months of life, with a temporary increase in sex hormones that is associated with a subsequent increase in muscle and decrease in fat accumulation in boys. But it’s also true that boys tend to spend more time running and jumping in unstructured play, and this may reflect gendered social expectations rather than sex differences.

Overall, the small gap in pre-puberty performance doesn’t seem like strong evidence of ineradicable differences between males and females. Instead, it’s the subsequent shape of that curve that, as we’ll see, turns out to be more significant.

3. The gap widens with puberty, along with changes in body structure and function.

In the graph above, male-female differences accelerate dramatically after the age of 13 and continue all the way to adulthood. Now it gets harder to attribute the changes to social factors, because there are a host of other changes that accompany puberty and are associated with sports performance: males see a greater increase in muscle, airway and lung size, heart size, oxygen-carrying capacity of the blood, and so on.

Perhaps the most obvious difference is height: by the age of 20, the average male is taller than 97 percent of women. Differences in lung size or hemoglobin levels are invisible to us; differences in muscle mass could conceivably be because boys are encouraged to work out more. But height? We see it all around us, and accept that it’s driven by biological sex differences.

4. The main driver of the male-female performance gap in adults is the surge in testosterone during male puberty.

Here’s when things get more contested. Where, you might ask, is the randomized controlled trial proving that males who go through puberty without testosterone are worse athletes, or that females who go through puberty with male levels of testosterone are better athletes? Such studies haven’t been done, for obvious practical and ethical reasons.

Joyner and his colleagues argue that we can instead piece together the evidence from studies showing links between testosterone levels and increased physical performance during puberty; the various studies in humans and animals showing testosterone’s effects on muscle, bone, and blood parameters; doping studies where volunteers took testosterone; and strong circumstantial hints like the graph above showing the widening performance gap during puberty. The evidence here isn’t perfect, but as a whole it’s convincing.

5. Body changes during female puberty can have negative effects on sports performance.

This is an angle I hadn’t thought much about. The discussion usually focuses on the advantages conferred on males by testosterone, but there are a distinct set of changes that females experience during puberty. For example, they accumulate more body fat; their growth plates fuse so they stop growing taller; they develop breasts, which can alter balance and movement patterns; their hips widen, which may increase injury risk; they experience hormonal fluctuations associated with the menstrual cycle that may (or may not!) affect performance; they may eventually miss training time during pregnancy and face increased injury risk when returning to training after childbirth.

There’s no doubt that all these changes occur, and that they have the potential to influence performance. Whether they collectively make a significant contribution to the gap between male and female athletic performance is less clear. It’s worth considering, but I’d classify it as an open question for now.

6. Suppressing male testosterone levels after puberty only partly eliminates the male-female performance gap.

There’s a smattering of case studies and comparison studies to support this statement. A 2023 U.S. Air Force in Military Medicine, for example, tracked fitness test scores for nearly 400 transgender servicemembers for up to four years after they began hormone therapy. For transgender women, performance on some tests, like the 1.5-mile run, ended up corresponding to average female times by the fourth year of hormone therapy. But for other tests like push-ups, there were still differences.

Here’s how push-up scores evolved in transgender women over the course of four years of hormone therapy. The red band shows the range of male scores within one standard deviation of average; the blue band shows the corresponding women’s range. Scores are still higher than average even after four years.

One reason for the retained advantage is that some of the changes that occur during puberty are irreversible. Those who go through male puberty will, on average, be taller and have bigger lungs. They’ll lose muscle mass during hormone therapy, but still retain more than the female average. There’s also evidence for “muscle memory,” a phenomenon that makes it easier to build muscle if you’ve previously had it.

It’s worth noting that the significance of retained advantages will vary from sport to sport. Greater height and muscle mass matter a lot in sports like basketball and rugby; they may matter less in, say, marathon swimming.

7. Adding testosterone improves female performance, but doesn’t eliminate the male-female gap.

This claim is the mirror image of the previous one: transgender men improve various facets of sports performance after beginning hormone therapy, but they don’t gain the full ten percent. This supports the idea that testosterone matters for performance, but that timing also matters: it plays its most significant role during puberty.

These are the seven claims that Joyner and his co-authors make. Some are stronger than others. But even if you take them all at face value, they don’t tell you what the rules for transgender or intersex athletes should be. That involves a difficult balance between fairness and inclusion. Maybe the male-female differences discussed here are the most important consideration; maybe they’re outweighed by other factors. I don’t think there are any easy answers here, but any compromises we reach need to acknowledge that these differences exist and are persistent.

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Researchers in Germany recently published one of those studies that, now and then, make me question my core beliefs. I’m a supplement skeptic, but I try not to let that identity prevent me from assimilating new data. And if there’s one supplement whose possible benefits I’ve been on the fence about in recent years, it’s vitamin D.

The new study, , is part of a major initiative to improve the performance of German elite athletes. A research team led by Sebastian Hacker of Justus Liebig University in Giessen studied 474 athletes on German national teams in a range of sports including hockey, table tennis, and three-on-three basketball. They tested vitamin D levels and measured (among other outcomes) handgrip strength.

Here’s the money shot:

This graph shows handgrip strength as a function of 25(OH)D levels, which is how vitamin D status is assessed in the blood.  The two dashed lines indicate the thresholds between vitamin D deficiency (below 20 ng/mL), insufficiency (between 20 and 30 ng/mL), and sufficiency (above 30 ng/mL). There have been long debates on where these thresholds should be set, but that’s the current thinking. Note that you’ll sometimes see 25(OH)D levels expressed in nmol/L; to get to those units, multiply the values above by 2.5.

The key point: there’s a clear slope to the line. Higher levels of vitamin D are associated with stronger grip strength, which in turn has been associated with health, longevity, and (less clearly) athletic performance. For every 1 ng/mL increase in 25(OH)D, handgrip strength increases by 0.01 N/kg, which means that going from 20 to 30 ng/mL should boost your strength by about three percent.

The Case for Vitamin D Supplements as a Performance Aid

Vitamin D plays roles in a whole bunch of body systems, including bone health, immune function, and—perhaps most notably for athletes—muscle performance. If you’re truly deficient in vitamin D, there’s no doubt you should get your levels up. But the evidence in the “merely insufficient” range is less clear, even in this data. If you took all the values below 20 mg/mL out of the analysis, would there still be a relationship between vitamin and handgrip strength? It’s not clear.

This isn’t the first time researchers have shown a relationship between vitamin D and strength. In fact, pooled data from 28 studies with 5,700 participants and concluded that there’s a positive relationship between vitamin D levels and quadriceps strength. At least, that’s the headline result—but when you look closer, it’s less convincing. The positive relationship was for quad strength when contracting the muscle at a specific speed of 180 degrees per second. But there was no relationship at a slower speed of 60 degrees per second. Worse still, there was a negative correlation for maximal contractions against an immoveable force: higher vitamin D levels were associated with smaller max force.

In other words, we shouldn’t be too quick to assume the new German data is definitive. Instead, it’s another data point in an ongoing debate. Another review, , finds “mixed results” in studies on the relationship between vitamin D levels and muscle mass and strength.

Causation or Correlation?

Even if we eventually conclude that there is a positive relationship between vitamin D levels and strength, it doesn’t necessarily follow that we should all start popping vitamin D pills. First of all, there’s the possibility of reverse causation. People who are strong and healthy may choose to spend more time exercising outdoors, which in turn may produce higher vitamin D levels. That’s actually one of the strengths of the new German study: since all the subjects were elite athletes, we can assume that they have similar levels of general fitness and physical activity.

There may also be confounding factors. Back in 2019, şÚÁĎłÔąĎÍř contributing editor Rowan Jacobsen wrote a surprising article in which he argued that the benefits of sunlight extend beyond merely raising vitamin D levels, most notably in triggering the release of nitric oxide from your skin into your bloodstream. If that’s the case, then taking vitamin D supplements won’t necessarily fix whatever problems are associated with lack of sunshine.

What we really want are intervention studies, where we give extra vitamin D to people and see if they get stronger. And we don’t want subjects who already have sufficient levels of vitamin D, because they stand to benefit less; instead we want people with insufficient levels. That’s what , this one from Estonia, did.

The Estonian researchers took 28 volunteers with “insufficient” 25(OH)D levels in the low 20s mg/mL. Half of them got a placebo, and the other half took 8,000 IU per day of vitamin D, which eventually got their 25(OH)D levels up to a healthy 57 ng/mL. Both groups did 12 weeks of resistance training, but there were no discernible differences in their results, which were published in the journal Nutrients. Here are the gains in one-rep maximum for various exercises for the two groups:

In fact, the further you dig into the literature, the less convincing the data looks for vitamin D as an athletic supplement. For example, there was that found no significant benefit of vitamin D supplementation on muscle strength but a trend in the right direction. But even that weak finding was tainted by “key errors in the analytical approach,” according to : the true effect is close to zero.

Of course, vitamin D’s merits as an athletic supplement are distinct from its potential for more general health purposes. Might it be that taking vitamin D supplements helps prevent cancer, heart disease, or type 2 diabetes; increases bone density; or reduces your risk of falls? No, no, no, no, and no, according to . More than 60 Mendelian randomization studies, which use genetic data to divide people into pseudo-randomized groups with high or low vitamin D levels, have generally found no difference in health outcomes.

Put it all together and the overall case for taking vitamin D supplements doesn’t look very compelling to me—assuming, that is, that you don’t have a genuine deficiency. Defining that threshold is the tricky part. Is it below 20 ng/mL, which health authorities consider deficient? Is it below 30 ng/mL which they label insufficient? Is it somewhere higher or lower or in between? I’m not sure, so for now I’ll hedge my bets: despite all my skepticism, I’m going to arrange to get my levels tested at my next doctor’s appointment.

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One of the big debates in endurance sports these days is about “training intensity distribution,” which is a fancy term for how much of your training time you spend going easy, medium, or hard. The dominant paradigm is the polarized distribution, which calls for a lot of easy running, a little bit of hard running, and not much in the middle. But there are various other viewpoints, including the currently fashionable Norwegian training, which puts a heavy emphasis on medium efforts.

One way of exploring which training distribution is best is to look at the training diaries of the best endurance athletes in the world. That’s how the concept of polarized training was born, and it’s why Norwegian training is rising in popularity. Of course, this isn’t as reliable as a randomized trial. Maybe most elite athletes train in a certain way because it’s popular, not because it’s objectively better than the alternatives. And even if we figure out the best way for elites to train, it’s not clear that those insights will apply to the rest of us.

Another option to assess training intensity is to look at how the unwashed masses train: to sift through reams of data looking for the patterns and variables that predict the best race performances. That’s the approach taken in , from a group of researchers led by Daniel Muniz-Pumares of the University of Hertfordshire and Barry Smyth of University College Dublin. They analyzed 16 weeks of training data leading up to a marathon for 120,000 runners who recorded their training in Strava.

To Run Faster, Run More

Before delving into the nitty-gritty of training intensity distributions, we should start with the elephant in the training room. By far the best predictor of marathon time was how many miles a runner racked up. The researchers divided their sample into half-hour finishing groups: the fastest group was the sub-2:30 marathoners, the slowest group was those between 6:00 and 6:30.

On average, the runners accumulated 28 miles per week over the 16 weeks prior to their goal race. But there were big differences. Sub-2:30 runners ran 67 miles per week, about three times as much as those running slower than 4:30 and 60 percent more than even the sub-3:00 runners. Here’s the weekly mileage (in kilometers, on the vertical axis) as a function of marathon finishing time (in minutes, on the horizontal axis):

This is the men’s data; the women’s data show essentially the same pattern. The four different lines show the average mileage during four different four-week blocks before the race. There are some slight differences—mileage is highest five to eight weeks before the race, for example—but the overall pattern is the same throughout: faster runners run more.

What the Training Intensity Distribution Reveals

You could be forgiven for thinking that this is painfully obvious. But what’s interesting is how the faster runners ran more. They didn’t just scale up their training proportionally compared to the slower runners. Instead, the difference was almost exclusively in how much easy running they did.

You can divide the accumulated training into three zones loosely corresponding to easy, threshold, and interval or race pace. (I won’t belabor the details of how they crunched the training data or defined the zone boundaries, but it’s based on calculating each runner’s critical speed using the approach I described in this article.)

When you break out the different training zones, you find that runners of all levels, from sub-2:30 all the way through 6:30 marathoners, did virtually identical amounts of hard zone 3 training. They also did very similar amounts of zone 2 threshold training. There’s a slight trend toward the faster runners doing a bit more, but it’s barely noticeable. All the variation—remember, there’s a threefold difference in total training volume—is packed into easy zone 1 running.

The graph below is a little busy (it once again breaks out the results into four-week blocks, even though the trends in each block are similar). The key point is that the red lines (zone 3) are flat, meaning that all the different pace groups accumulated similar amounts of hard running time. The orange lines (zone 2) are nearly flat. But the green lines curve sharply upward on the left side of the graph, showing that the faster runners do more easy running.

So It’s Polarized Training for the Win?

That depends on what you mean by “polarized.” There’s a fairly convoluted debate (which I summed up here) on the meaning of the term, but there are two key elements. One is the idea that most of your running should be easy. That’s often summed up (as in the title of ) as 80-20 running: around 80 percent of your running should be easy, with the other 20 percent medium or hard. Muniz-Pumares’s new results support this view.

The second element is the idea that you should avoid medium intensities, since they’re too slow to give you the benefits of interval training but too hard to recover from if you’re trying to run big miles. That is where the name “polarized” originally comes from, since most of your training is supposed to cluster at the extremes of easy or hard. But the new data doesn’t back this claim up: very few of the runners, whether fast or slow, were doing truly polarized training.

What the runners were doing instead is called pyramidal training. Classic polarized training might involve an 80:5:15 breakdown of easy, medium, and hard. Pyramidal training, instead, might be 80:15:5. Instead of avoiding the middle zone, you do a moderate amount. In practice, though, the distinction between polarized and pyramidal is hazier than it seems. Previous research has found that the exact same training plan might look either polarized or pyramidal depending on whether you calculate the intensity distribution using running speed, heart rate, or even the intended effort.

The bottom line, from my perspective, is that it’s not worth getting too wound up about the specific nomenclature. This data supports the idea of doing lots of easy running and modest amounts of medium or hard running. It doesn’t support the idea of avoiding the medium zone. Whether you call that polarized or pyramidal is up to you.

What’s Lost in Translation

As I noted at the top, this isn’t a randomized trial. We know that faster runners did more easy running than slower runners. We don’t know if doing more easy running would have turned the slower runners into faster runners. But even if it did, that assumes that the slower runners have the time or desire to run more—and that’s by no means a safe bet.

The fundamental assumption for elites is that their training is primarily limited by what their bodies can handle. Polarized (or pyramidal) training is supposed to be effective because it’s an optimal way of racking up the greatest possible combination of training volume and intensity. To max out what your body can handle in a given week, aim for that 80-20 split.

Meanwhile, out in the real world, the key question isn’t how much my body can handle. It’s how much training I can squeeze in before work or between picking up the kids and making dinner or whatever. The 3:30 marathoners are putting in about four hours of training per week. It’s not hard to believe that adding an extra hour or two of easy running on top of what they’re already doing would make them faster.

The trickier—but also more relevant—question is how to make them faster on four hours of training per week. Switching to an 80-20 split would actually mean doing less total mileage, because they would be replacing a big chunk of their medium or hard running with easy running. Sure, they would recover more quickly from each training session. But would they really end up going faster?

This is an open question, and I don’t think there’s any firm answer at this point. But my takeaway from all this is that we should think carefully about what constraints we’re imposing or accepting on our training. If time is really the issue, then spending more of that precious time running hard might make sense for you. But if “I don’t have time” is just another way of saying “I don’t want to,” or if you’ve been held back by the fatigue and injuries that often accompany hard training, then it’s worth considering doing more easy running. It’s the easiest and least risky type of training—and in this analysis, at least, it’s the one weird trick that distinguishes faster marathoners from slower ones.

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The more time you spend pursuing a skill, the better you get. So you can bet that an elite skier like 2023 Men’s Freeride World Tour Rider of the Year has spent a lot of time touring backcountry terrain. That experience has helped the athlete become both a champion skier and an expert at layering and packing for long days with variable conditions. He knows that if you’re not worried about being too cold, too warm, or too underprepared for remote exploring, you can focus on the things that really matter: technique, scenery, friends, and fun. From fuel and layers for the expedition to cozy slip-on shoes for post-tour comfort, here are some of the essentials Hitzig takes whenever he heads into the backcountry.

Safety and Navigation

Returning safely should always be priority number one. In addition to the critical avalanche safety equipment that every skier should carry when venturing beyond resort boundaries, Hitzig always packs a headlamp and carries his phone, which he uses to plan routes the night before a tour. The tools and tech are great, but, he emphasizes, “it’s important to behave according to the conditions.” Since many of his backcountry pursuits start at dawn and end at dusk, Hitzig is always sure to double-check his headlamp battery before setting out on his route: “Unexpected things happen in the backcountry—you don’t want to be left in the dark.” And no matter the intensity of your objective, you should always inform someone about your plans.

Skin and Eye Protection

Even on bluebird days, expect exposure to the cold and wind—there’s not much shelter from the elements above tree line. That’s why you need to go prepared with UV protection, goggles, and a neck gaiter to pull over your nose and mouth. Hitzig always protects exposed skin with sunscreen and uses a face covering. “It takes time to find the right gaiter, but this is the safest and easiest way to protect your skin,” he says. “I also protect my eyes with good ski goggles and rarely take them off.”

Hydration and Fuel

Your body needs fuel and hydration to perform in the backcountry. Skinning up steep terrain and being out in the cold is physically demanding, plus it requires a lot of calories and carbohydrates. That’s why Hitzig always packs a bottle of water and an energy drink. For food, he keeps it simple with something he enjoys like a sandwich and a sweet treat. And it’s not enough to pack water—make sure you’re storing it in an insulated bottle. You don’t want to get caught in the mountains with a solid ice block and no water to drink.

Essential Layers

Base Layer: Xperior Merino 200

Comfort in the backcountry starts with your base layer. That’s why Hitzig puts his trust in the Xperior Merino 200, made with high-quality 100 percent merino wool. Merino is nature’s magic fabric, providing insulation while naturally wicking away moisture. This helps regulate your core body temperature during transitions and strenuous activity. Plus, merino naturally resists odor buildup and is soft on skin. “The Xperior Merino 200 is very light, it keeps me super warm, and it’s comfortable,” Hitzig says. “If it gets too hot in the sun, you don’t start sweating immediately, which is what I really like about this long-sleeve.” If you thought this base layer couldn’t get any better, it’s also made with renewable materials in an effort to help end plastic waste.

Midlayer: Xperior PrimaLoft Loose Fill Jacket 

When the temperatures drop and the wind picks up, a lightweight insulated jacket becomes an essential for warmth (and safety). “The is the perfect second layer for everyday adventures and backcountry tours,” Hitzig says. “If you need to shed a layer, this jacket packs up nice and small into its own pocket for easy storage.” Even if a light rain or wintry mix picks up, the jacket has a water-repellent outer layer for uncompromised warmth in damp conditions, making it perfect for pursuits deep in the backcountry. A midlayer like this is a workhorse, getting pulled on and off countless times, so it’s made with durable 100 percent recycled nylon fabric designed to hold up in extreme elements.

Shell: Techrock C-Knit Jacket

Whether bombing a descent or skinning in a storm, Hitzig stays dry and warm in the . This reliable three-layer Gore-Tex shell does what it should, promising protection and comfort in the white room—where the jacket’s removable inner powder skirt becomes essential. Working hard in wet conditions? Pit vents and waterproof-breathable Gore-Tex C-Knit fabric help keep you moisture-free inside and out. “This jacket is tough,” Hitzig says. “After a long season with long days on the mountain, it shows hardly any signs of wear and tear, and the Gore-Tex ePE still keeps the water out.” And like all the layers in Hitzig’s backcountry kit, his outer layer, made from 100 percent recycled nylon, makes no sacrifices in durability. This shell will work with you on every turn as you make your way back to civilization.

Après-Ski Comfort

Beacon off, car defrosting, warm drink in hand: It’s time for a footwear swap and an expedition recap with the crew. The Winter Slip-On Cold.Rdy is a sweet reward for the day’s efforts. Trading ski boots for comfy après shoes is something every backcountry skier looks forward to, including Hitzig. This shoe goes a couple levels better than most. It features ultragrippy tread for traveling wintry parking lots or walkways. And the cherry on top is the integrated heel step-down, so you can go from shoe to mule for max comfort and convenience at the end of every ski day.

is a global leader in the outdoor sporting goods industry. With the mission to enable all humans to live a more connected, conscious, and adventurous life, adidas Terrex combines high-performance technologies with fashion-forward designs to weather the forces of nature and inspire every human being to find their own summits.

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For the past decade or so, sports scientists have been obsessed with the benefits of heat training. The extra stress of heat triggers various adaptations that help you handle hot conditions, like more sweating. Some of these adaptations, like increased blood volume, may even give you a boost when competing in cooler conditions. As a result, many top athletes now incorporate elaborate heat protocols into their training.

What if the opposite is also true? At in Montreal last month, a physiologist named Dominique Gagnon presented new data suggesting that cold training might offer some unique metabolic benefits that translate into enhanced health and endurance performance. It’s just a hypothesis at this point, based on a decade’s worth of incremental research. But as we head into the darkest, coldest months of the year, it’s kind of nice to think that our winter training might pack an extra punch.

Gagnon is a Canadian who recently moved from Laurentian University, in northern Ontario, to Finland’s University of Jyväskylä, three hours north of Helsinki. He knows cold, in other words. At the annual Canadian Society for Exercise Physiology conference, he presented comparing the training effects of working out in either warm (77 degrees Fahrenheit) or cool (32 degrees) conditions. The goal was to figure out whether training in the cold would boost levels, which is one of the key adaptations that underlies aerobic fitness.

What’s So Great About Cold?

Gagnon’s research on exercise in the cold goes back over a decade. Back in 2013, for example, he published showing that cold-weather exercise relies on a different fuel mix than warmer conditions, burning more fat and less carbohydrate. He suspects that this is because when you’re exercising in comfortable temperatures, there’s actually some local overheating in the muscles themselves.

Human metabolism is only about 25 percent efficient—comparable to the internal combustion engine in your car—so three-quarters of the energy in your food is released as heat in the muscles. That means that the temperature inside your muscles can be high even when the rest of you is cool. The advantage of exercising in the cold, then, is that it prevents your muscle cells from overheating and enables them to keep burning more fat for aerobic energy, which relies on the mitochondria in your muscles. In the long run, that should boost mitochondria levels and train your body to become more efficient aerobically.

There are various other hints supporting this view. Researchers at the University of Nebraska at Omaha, for example, that exercise in the cold produced a bigger spike in the cellular signals that tell the body to produce more mitochondria, though the difference wasn’t statistically significant. And have shown that they get a bigger fitness boost from exercise when the air is mildly cold.

The New Findings on Cold Training

In Gagnon’s new study, 34 volunteers trained three times a week for seven weeks, doing interval workouts on an exercise bike. Before and after the training period, they had muscle biopsies, which involve removing a small chunk of muscle from the leg, in order to analyse how much mitochondria was present. Sure enough, the group that trained in 32-degree air had a significantly greater increase in several different markers of mitochondrial content. Gagnon is still analyzing the VO2 max data, but initial signs are that those training in the cold were more likely to see a significant increase.

Those are encouraging findings. But even if the results (which have not yet been peer-reviewed) hold up, the next big question is whether this approach is practical. How cold do you have to be? Gagnon’s subjects performed their cold training in the equivalent of shorts and a T-shirt, which is less than I would typically wear at that temperature, but not totally unreasonable. Would the effects be nullified if you wore a long-sleeve shirt and tights? Gagnon’s not sure yet—but he emphasized that the goal isn’t to be cold, with measurably lower muscle and body temperature. Instead, it’s to avoid letting your muscles get too hot.

At this point, it’s worth flashing back to some findings I wrote about earlier this year. Stephen Cheung and his colleagues at Brock University in Canada showed that getting superficially cold, with no drop in core temperature, reduced time to exhaustion in a cycling test by about 30 percent. That involved sitting in a 32-degree room with a light breeze for half an hour before the subjects even started cycling. Staying in the room for longer, so that their core temperature actually dropped by a degree, reduced endurance by another 30 to 40 percent. This is not what Gagnon is aiming for.

Instead, the goal of cold training seems to be to let yourself get just cool enough that your muscles don’t overheat. Where that threshold is remains to be determined, and the results will need to be replicated before anyone takes them seriously. Gagnon is in discussions with the Finnish military, which has lots of personnel engaging in physical activity in perennially cold conditions, about further studies. Maybe it will turn out to be the next big thing in endurance training. Or maybe not. To be totally honest, I normally wouldn’t write about such preliminary results—but the idea that it might be true will help get me through some cold training runs this winter.

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If you could patent and sell the idea of holding your breath before exercise to boost performance, it would be a bestseller. Not because it works, necessarily—the jury is still out on that. But because the logic is so good, the physiology is so fascinating, and the technique is so simple.

Instead, without a commercial imperative behind it, the idea has been floating around for years with no clear answers about whether it really works or not. Now , from a team led by Yiannis Christoulas of Aristotle University of Thessaloniki in Greece, offers the most encouraging sign yet that breath-holding might function as a legal form of do-it-yourself blood doping to temporarily enhance your endurance.

The idea is based on the mammalian diving reflex, which is the suite of physiological responses that automatically takes over when you dunk your head underwater. In a whole bunch of different ways, your body switches into oxygen-conserving mode to make sure you don’t run out while you’re submerged. For example, your heart rate slows down, and blood-flow to your extremities ramps down.

How Divers Get a Boost in Red Blood Cells

Most relevant here is that your spleen stores an extra reserve of oxygen-carrying red blood cells. When you dive, your spleen contracts, squeezing these extra red blood cells out into general circulation. This is the bit that is “similar to blood doping interventions,” Christoulas and his colleagues explain: instead of giving yourself an IV with fresh red blood cells, you get them from your spleen. Previous experiments suggest that spleen contraction could boost hemoglobin levels and VO2 max by as much as 5 percent.

Nobody is suggesting that you should go freediving a few minutes before your next marathon. But you can elicit some aspects of the diving response simply by holding your breath; and you can ramp up the response by doing it with your face submerged in cold water. This is the idea that prompted by researchers in France suggesting apnea—that is, breath-holding—as “a new training method in sport.”

Since then, there have been several attempts to harness the benefits of breath-holding for athletic gain, with different activities (swimming, cycling) and protocols (single breath-holds, repeated breath-holds, various recovery durations). Earlier this year, Jan Bourgois and his colleagues at Ghent University in Belgium an overview of these attempts in Experimental Physiology. The overall picture is that the physiology is real, but the practical effects seem to be too small to measure. Hard exercise makes your spleen contract anyway, so it may be that pre-contracting it with breath-holds doesn’t offer any additional benefit.

Dunking Your Face in Water May Be the Key to Breath Hold Success

Christoulas’s new study takes a different view, which is that previous studies haven’t gotten the protocol quite right. In particular, the failed studies have asked athletes to hold their breath, but haven’t dunked their faces in water, so they didn’t fully contract their spleens. The new study had 17 volunteers complete an incremental cycling test to exhaustion, lasting roughly ten minutes, with and without a series of five maximal breath-holds with face submerged in water at 50 degrees Fahrenheit. They took two minutes recovery between each breath-hold and then started the cycling test two minutes after the final hold.

The subjects were recreational athletes with no training in freediving or breath-holding. Their average breath-hold time was 71 seconds—though it’s interesting to note that the duration of each successive hold got longer. The first hold averaged just over 40 seconds; the second one was over 60 seconds; the last couple averaged close to 80 seconds. Here are the average breath-hold times (BHT), plus and minus standard deviations, for the five holds:

This progression is partly a result of the spleen’s extra red blood cells in action. Sure enough, blood tests showed that hemoglobin and red blood cell count were both up by 4 percent by the end of the last breath-hold.

The key performance result was that the subjects lasted, on average, 0.75 percent longer in the cycling test after the breath-holds, which was a small but statistically significant difference. It also took longer before they hit the second ventilatory threshold, which is the point when your breathing gets really labored.

It’s More than Just Red Blood Cells Increasing Subjects’ Endurance

It’s worth noting that there are several other mechanisms that might play a role in addition to spleen contraction. Breath-holding raises levels of carbon dioxide in the blood, which in turn (through a mechanism called ) makes it easier for your muscles to unload oxygen from circulating red blood cells. This boosts your aerobic metabolism, and helps explain why the blood tests also showed that resting lactate levels dropped by 15 percent after the breath-holds. The full physiological picture gets quite complicated, but the bottom line is that the subjects in the new study had better—slightly ˛ú±đłŮłŮ±đ°ů—e˛Ô»ĺłÜ°ů˛ą˛Ôł¦±đ.

What does this mean in practice? Personally, I can’t imagine completing a set of five maximal breath-holds two minutes before a race. But some researchers have suggested that a single hold should be enough to get most of the benefits. If you look back at that graph of breath-hold times, it does appear that the biggest change occurs after the first bout, and there are fewer changes after the second one. Maybe two breath-holds a few minutes before competition is feasible.

The other big question is whether a good, hard warm-up accomplishes the same thing. In the new study, all subjects did a ten-minute warm-up that included jogging and “dynamic whole-body stretches.” But it’s possible that a longer and harder warm-up might trigger spleen contraction on its own. These are questions that future studies will have to answer—and I hope they do, one way or the other, because it’s refreshing to consider a weird and wonderful source of potential “marginal gains” that, for a change, is free for everyone.

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Shaun White has been the face of snowboarding for two decades. So what is he doing in retirement? A lot. He’s launching his own snowboard brand. He’s raising money to protect public lands. He’s even starting his own half-pipe competition. In this live interview from The şÚÁĎłÔąĎÍř Festival in Denver, former NFL linebacker Dhani Jones talks with White about life after pro sports and how the keys to his past success play a role in his future.

Tickets to the 2025 şÚÁĎłÔąĎÍř Festival and Summit are on sale now at early bird prices at

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Learning to ride a bike can be your first taste of freedom. Suddenly, the world beyond your front door opens up, ready to be explored on two wheels.

But for Marley Blonsky it wasn’t that simple. Back when she was eight years old, trying to ride with her older sister and her friends, she was told she was too slow. “I always wanted to be part of the club,” she says. “It felt like something I was constantly striving for and not really accomplishing.”

As an adult, Blonsky, 38, faced similar barriers—and some new ones she hadn’t anticipated. She found that the weight limits on most road bikes were too low for her; her rides were hampered by broken spokes and cracked saddle rails. Most cycling-apparel brands had limited sizing, so she struggled to find comfortable jerseys and bibs. On group rides, she felt that familiar sensation of being left behind.

So she did something about it. In 2021, along with Kailey Kornhauser, Blonsky founded , a club that welcomes riders regardless of their size, gender, race, or ability. Over the past three years, the group has expanded to ten chapters, with plans to add nearly 30 more by 2027. Each chapter is encouraged to organize rides, collaborate with other bike-advocacy organizations in its area, and host events like gear swaps and fix-a-flat clinics. “We don’t care why you’re riding a bike,” she says. “We just want to empower you to do it joyfully.”

In 2024, All Bodies on Bikes led several bike-camping trips (the one hosted by the Kansas City chapter had 50 riders) and cohosted the biggest finish-line party in gravel cycling: the DFL party (for Dead Fucking Last) at MidSouth Gravel. Looking forward, the organization’s strategic plan includes establishing industry standards for weight limits on bikes and components, pushing brands to represent a greater range of sizes in their advertising, and creating a retail certification for bike shops to let would-be clients know that “this shop is knowledgeable in working with customers of size and will treat you with dignity and respect,” Blonsky says.

By creating a cycling community that embraces people of all shapes and sizes, Blonsky has made what can be an intimidating sport more approachable for new riders. She regularly receives messages from people about how meaningful it is to see a diversity of bodies represented in cycling. After years of feeling excluded, the self-identified fat cyclist has found power in throwing open the gates.

“It doesn’t feel like what we’re doing is that radical,” she says. “To slow down a little bit, to see folks and meet them where they’re at, it shouldn’t be that incredible of a thing. But it is.”

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