Includes a Few Easy Pointers on How to Read a Health Book Critically
Originally posted in Science for Life on Medium on June 26, 2024
As someone who has really embraced exercise as a daily routine late in life, in my mid-forties, I have been looking for the best ways to exercise and reap the benefits of my workouts. And one day at a used bookstore, I found the perfect book: Gretchen Reynolds’s The First 20 Minutes. The Surprising Science of How We Can Exercise Better, Train Smarter, and Live Longer (Icon Books UK, 2013).
The author used to be a Phys Ed columnist for the New York Times and now writes the “Your Move” column at The Washington Post.
Reynolds’s book can convince anyone to start exercising regularly, even if only twenty minutes a day — but she has more compelling words of wisdom in her book than that. Many of them are well-known today, as the book was first published in 2012 (in the US), but even so, this collection of fitness science stories has many surprises in store. They are intriguing bits of data that make exercise appealing from a science perspective in many ways that someone not familiar with fitness science would be unfamiliar with. The book offers a rewarding journey to anyone who enjoys reading about scientific experiments in biology and physiology and has been wondering about the science behind exercise benefits. It will also help those who are already into physical exercise adapt their routines according to scientific data — even if the science in the book opens up a few questions, as I’ll discuss.
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Let’s delve into the book, starting with one important concern I had about exercise: flexibility. I’m not a flexible person physically, and that, compounded with a lower-back hernia, has kept me away from regular exercise, as I was advised not to do certain routines when I felt lumbar pain, and I was struggling with the latter for a good portion of each year. To my surprise, I read in Reynolds’s book that flexibility is mostly genetic, and there’s little I can do about it. I’ve now embraced that, and while I have made some progress, I am not pushing stretching as much as I did in the past. I have done a chiropractic and acupuncture treatment that eventually worked for my hernia, and I don’t want to lose the gains.
And now to the book. Did you know that stretching a muscle actually makes it weaker during subsequent exercise? Reynolds quotes Dr. Malachy McHugh, an expert on flexibility, who says that the brain’s response to stretching a muscle is to inhibit its contractions, so, according to the author, you may be better off warming up without stretching, as stretching gives only an increased mental tolerance for the sensation of the stretched muscles — rather than flexibility. And while it’s true that the muscles react too — how could they not — , they return to their initial state in about an hour.
Dr. Hugh doesn’t seem to acknowledge an hour of temporary changes is a good thing for people who exercise because he seems focused in his discussion with the author on the permanent effects of flexibility. To achieve structural changes needed for flexibility, he says, you’d need to stretch for at least an hour every day for months.
In contrast to stretching, warmups do achieve immediate physical results, allowing athletes to perform better, though not when the warmup lasts two hours and the race 35 seconds, as was the case with the Canadian skating team at the 2010 Winter Olympics. Sometimes only 10–15 minutes of warmup are enough, the author says. As a side note, Reynolds also mentions that dynamic stretching — also known as dynamic movement, as in skipping or bottom kicks — in warmups is improperly called stretching. At the same time, there are many health benefits to static stretching, and there’s a place for it, even if many people these days agree it’s one post-workout — and regularly, but not during warmup (there are exceptions).
Another surprising piece of fitness wisdom derived from science is that ice baths don’t actually help much. In one study, people who hopped on one leg and then took an ice bath were more sore than the control group — people who didn’t do the ice bath — when trying to get up from a chair using the leg they’d hopped on. So I take it many tennis players of the 1970s did things better when they didn’t soak in ice baths after a match. Now some athletes have moved from ice baths to cryotherapy chambers, which, according to this book, have temperatures as low as –110 Celsius/–166 Fahrenheit. Athletes spend two to three minutes there, moving their body to increase blood circulation — even though, as shown by creatine kinase, muscle damage stays the same as in people in control groups. The author attributes athletes’ belief in these routines to magical thinking and the fact that an ice bath — or a post-workout massage — may be perceived as soothing.
As for the workout itself, in terms of nutrition, according to Reynolds, scientists seem to agree that carbs, preferably two parts glucose to one part fructose, during moderate exercise lasting longer than an hour are needed and improve performance. Not so the carb loading many athletes are doing days before their sports event. She mentions a study where cyclists who used carb drinks during their race performed the same whether or not they had loaded on sugary foods the preceding days.
As for the rest of the day after exercising, including competitively, a study on Kenyan runners who subsequently gained medals at World Championships showed that their habit of drinking large quantities of rooibos tea with milk is, indeed, a great way to recuperate and regain one’s weight by the next morning, and to perform well at the next workout. If you’re not familiar with rooibos tea, this is a red-bush tea from South Africa that apparently works wonders on the body, including killing cancer cells in vitro. The Kenyan athletes drank that after their workouts in which they’d lost pounds and it helped them recover their strength and body weight.
Not drinking much water or other fluids during long workouts, including marathons, seems to have been the norm in the past, up to the 1970s — before Gatorade came onto the scene. Gatorade pushed for studies about the importance of ingesting fluids during workouts, to relieve higher body temperatures and for other reasons, and for a while the American College of Sports Medicine advised athletes to drink as much as possible, as much as they could tolerate.
Then the 1998 Chicago Marathon happened, where a woman died because she drank too much water. Water intoxication, or hyponatremia, became a scarecrow and things changed again. The word hyponatremia comes from hypo (“low”) and natrium (“sodium”). It describes a condition of dangerously low levels of sodium in the blood, which causes the body to try to balance the rest of the body to that more diluted state, leading to swollen hands and feet and even swelling in the brain, causing confusion, fatigue, nausea, vomiting, and, in extreme cases, death.
The author argues that in the 1990s marathoners started pacing themselves differently than in the past, slowing their rhythm. As a result, marathoners now need less water than other runners because theirs has become a leisurely jog-and-walk. Reynolds quotes Dr. Timothy Noakes, PhD saying that people should pay attention to their thirst rather than try to drink those eight glasses of water a day or follow whatever other guidelines about hydration. According to a 2010 metastudy mentioned by Reynolds, people have a rather precise sense of their hydration needs — and so they should listen to those rather than hydrate at every aid station in a marathon, for instance. Not sure how much of that is true, though. I do see older women who drink very little water even when it’s really hot, claiming that they don’t want to need to pee when they don’t have easy access to a hygienic toilet — but then they get used to less water and it’s not healthy for them.
The book is full of surprising facts, some of them more creditable than others, as the author seems to have relied on the advice of experts she had interviewed and her own prior knowledge as a columnist without delving much into expertise elsewhere. For the most part, however, her journalistic reporting is commendable — but there are some glitches. One of them is her saying that proper hydration doesn’t prevent heatstroke. You can develop heatstroke even when you’re properly hydrated, the author says, as was the case with several athletes at a triathlon in Australia a few years before the book was published. The author then takes that idea in a different direction, saying that you could drink less than you sweat and not be in danger of heatstroke, which is less helpful as an argument, as your body needs to sweat to lower its core temperature (something she does expressly acknowledge), so it stands to reason and many other studies and scientific opinions that you need to be well hydrated to minimize the risk of heatstroke. And then water also stimulates cells to release the famous ATP (adenosine triphosphate, the energy-providing nucleotide in all living cells).
Another surprising fact in the book, one which again may be wobbly, is that you don’t actually lose much potassium at all when you sweat, so if you’re healthy, you’re most likely not to need electrolytes with sodium and potassium (we tend to have more sodium than we need anyway). That milky rooibos tea Kenyans drink, the author says, may be just the thing for you as well, as it has small amounts of sodium and potassium, enough for the amounts you lose in a marathon — so most of the time there’s no need to overdo it with electrolytes and huge quantities of water. On the other hand, conditions vary and you may sweat a lot during a marathon, after all, and then sweat varies from person to person. You could lose 200 mg of sodium per liter, or 1,500 mg or more. Also, not all electrolytes are just sodium and potassium. There’s also magnesium, which tends to be a great idea when exercising. I have a glass with an effervescent magnesium tablet almost every day now that I started working out regularly.
The book answers some good questions someone might ask about the practical details of taking up exercise. To give an example, we all debate what to eat for breakfast — some say shakes while others are firmly against eating sugars and recommend protein and healthy fats instead, since sugars after fasting may contribute to higher levels of insulin resistance — , but then when we adopt a workout regimen we may be even more at a loss, since moderate regular exercise of one to two hours a day is different on the body than taking a nice walk now and then. So then one question could be, what do we eat post-workout? Some top physiologists suggest a combination of good carbs and protein, such as a lasagna on the evening of a bike race. Others argue that you need a certain combination of protein and sugars such as it’s found in low-fat chocolate milk.
Then there are nutrition fads, both for pre- and post-workouts and during workouts. The author dismisses them because, she says, whether you load on carbs or fats during a bike ride, for instance, doesn’t make much difference in your performance. And for people who struggle with blood sugar, a banana before an exercise session, she says, may be just enough.
She also cites scientific studies in support of the theory that vitamins and antioxidant supplements undermine the body’s own responses and sometimes fail to make up for disrupting these mechanisms. Antioxidants, for instance, are shown to blunt the body’s healthy response to free radicals when it comes to stimulating growth factors and activating enzymes that help muscles repair and reap exercise benefits.
But what about one’s nutrition throughout the day? From what I gathered reading this book, you should eat a meal of protein and carbs right after the exercise if you’re concerned about helping your cells be more sensitive to insulin and your muscles recover better. But then she makes some conflicting claims when it comes to the overall makeup of calories throughout the day. First, she suggests 60 percent or more carbs, and then she comes back and says that for weight loss and fitness purposes, a high-fat diet may be better — even as it comes with health risks in the long term, she says, though, again, one can have a diet rich in healthy fats like omega-3 and omega-9 fatty acids.
Again, some of the findings the author shares are surprising, but the question is, are they borne out by more general evidence? For instance, the author quotes one professor, Edward Melanson, and his research on EPOC (Excess Post-Exercise Oxygen Consumption) a.k.a. afterburn, with Melanson ostensibly arguing that exercise doesn’t cause an afterburn effect. She qualifies that by adding moderate to exercise, and she’s right to do so, since high-intensity workouts, such as HIIT, spring interval training, and steady-state cardio, do cause the body to spend energy for a short while post-workout in order to cool down and slow down. In fact, the author comes back to this notion of afterburn later in the book, where she refers to a study where a group of healthy men of 22 to 33 benefited from this EPOC effect for fourteen hours after their strenuous exercise on stationary bikes. The question then remains, how would a group of women respond to high-intensity exercise, and, building on that, what would such effects be on women of various ages? Of course, this could be varied even further to include men or women with different health conditions.
Another contestable claim is that exercise alone doesn’t lead to weight loss. I have different experiences with exercise and weight loss, and so have countless others. True, the author then launches into a story where light walking did lead to some minor weight loss and into another one about how some of the women in a group who started biking indoors for 150 minutes a week did not lose weight because they actually ate more during the eight-week study and moved less outside of their workouts (which is why, the author says, it helps to keep a food diary and use a pedometer). So explanations exist for why some may not lose weight, and one of them involves ghrelin, which increases our appetite after a light workout, particularly in women. In contrast, leptin helps us lose weight after a more strenuous workout, increasing our feeling of satiety throughout the day. The latter may suggest that HI exercise may be able to push homeostasis to a different place with more prodding, just as it does when combined with a calorie-restricted diet.
An exciting finding shared in the book is that 90 minutes of HI exercise before breakfast over six weeks can help maintain one’s weight even if one takes up a diet with 50 percent more fats — though, again, what kind of fats exactly? — and 30 percent more calories. Again, this study was done on men: young, fit, and healthy. I would be interested to see results for women—and women of different ages as well. And then an interesting variation on this study would take into account the afterburn effects, performing the study once with a high-fat breakfast of eggs and healthy fats, and then a second time with a breakfast high in carbs, to see what kind of an advantage the egg-based breakfast maintains in this pre-breakfast workout scenario. I say this because the author notes that eating eggs in the morning brings down the number of calories in the day — and also because strenuous exercise increases levels of leptin — so combining the two, and having eggs right after the morning workout may add up synergistically to some nice results.
What’s important to know is that, at the very least, regular moderate exercise of about an hour almost every day can help us maintain our weight, as shown by a longitudinal study on 34,000 women done at Harvard University over thirteen years. The author mentions this in a section about weight loss, but I wish she’d included findings about the health of these women, since regular workouts improve our health in numerous ways. I’d also be interested to know how age, perimenopause, and menopause impacted the data.
Exercise appears to help set a new weight point, contradicting the set point theory — about weight — which maintains that each body has a certain set point it keeps wanting to return to. In contrast to the latter, Reynolds points to a study on rats where exercise, combined with a calorie-restrictive diet for a period of time after weight loss, can help set a lower baseline weight because exercise helps induce satiety.
I’m drawing to the close of this review, which dealt only with the first half of the book. The remaining pages in the book deal with strength training and the physiology of muscles; injuries; and the effects of exercise on the brain and on aging. I may write another piece about the impact exercise has on brain and aging, with data from this book and others.
For now, I’ll reference one longitudinal study on 11,300-plus women — mentioned briefly in the book — which showed that fitness and the risk of premature death correlate negatively. Unfortunately, looking up this research by the year of its published study yielded no success online — not even on the website of The Cooper Institute, mentioned in Reynolds’s book. The Cooper Institute has been sponsoring The Cooper Center Longitudinal Study of more than 116,000 healthy individuals for decades.
I did find, however, other studies, such as one paper from 2014 mentioning a study done on 16,533 participants, women and men, over a period of time of 28 years, which supports the conclusions presented by Reynolds. (But I wish the author had included references.)
There’s a nice bar graph in the abstract of this 2014 study which relates 30-year CVD mortality risk of 50-year-old men and women both to low and high fitness and to the absence or presence of five cardiovascular risk factors: hypertension (greater than 160 mmHg), diabetes (present), total cholesterol (greater than 140 mg/dl), smoking (present), and BMI (greater than 25 kg/m2). The good news for those worried about being overweight (BMI greater than 25) is that if you’re fit, your 30-year mortality risk is much lower. That said, if you’re fit and have no CVD conditions, your 30-year mortality is only about 5% if you’re a man and 3% if you’re a woman, compared to 26% and 22%, respectively, if you have all the cardiovascular risks.
One thing is for sure: exercise is worth it — and for many more reasons than the author lists in her book. Walking, cardio workouts — including moderate-intensity gardening — , and strength training give us more cardiovascular fitness, help us do more with our bodies, more and better, improve our mood and mental health, keep our brain fit as far as boosting memory and other cognitive skills, and, not lastly, ameliorate a good number of health metrics, including blood pressure, HDL cholesterol — and, in some cases, especially if combined with weight loss, LDL cholesterol as well — , and triglycerides.
Exercise also improves our metabolism, helps with diabetes, and reduces inflammation — among other health benefits. But it does more than just change these big biomarkers. Blood pressure comes down because arteries widen and become more flexible as more nitric oxide is produced by endothelial cells, and less prone to accumulating plaque as more blood is pumped through them. And even when blood pressure is not relieved by these improvements, as shown by a 16-week-long study — which I came across online — involving physically inactive young adults with hypertension, the internal carotid artery and the M1 segment of the middle cerebral artery — some of the blood vessels that supply blood to the brain — grow in diameter.
Capillaries also increase with exercise, including in the muscles, which makes them more efficient, and so do the number of mitochondria in the cells, giving cells, and us, more energy. Exercise also makes our bones stronger — and I’m sure I forgot many other important things, stress reduction and a boost to the immune system among them. And then, of course, there’s something many people are aware of: regular workouts can significantly help reduce the risk of Alzheimer’s and other dementias.
Thank you for reading! I hope I’ve convinced you to talk to your doctor and see what kinds of exercise are right for you. Here’s to hoping you’ll find something you’ll enjoy!
To a happier, healthier life,
Mira
HappierHealthier.Blog 