Chaos, tennis racquet technology change, and the horrifying ancestors of whales
And other things I read about last week
A new collection of interesting links and articles …
Active versus inactive sitting
I think that concerns about the negative health effects of sitting are generally over blown. There is no good reason to believe that “sitting is killing us” or is “the new smoking.” (or that it will shorten your hip flexors.) On the other hand, there is some evidence that long periods of sitting might cause minor negative metabolic health effects that can’t be completely offset by getting adequate exercise when you’re out of the chair. On yet another hand, it seems strange that lots of sitting around would cause metabolic problems in humans, because it's common for many animals in natural settings to do a lot of sitting around, including humans.
With all those different hands in mind, here's a recent paper that may be relevant. The authors looked at the sedentary behavior of the Hadza tribe in Tanzania. They found that the Hadza actually spent about the same amount of time sitting as modern humans – 9 to 10 hours a day. But they sat in postures that require low levels of muscle activity, like kneeling. Time spent in a chair sitting position was uncommon, but there was up to two hours of squatting.
EMG data showed that assisted or unassisted squatting postures elicited muscle activity that was 20-40% as much as walking, and similar to standing. The authors concluded:
We suggest human physiology is adapted to more consistent muscle activity throughout the day associated with a combination of both physical activity and nonambulatory time spent in active rest postures. Recent work suggests that it is prolonged muscular inactivity that drives the negative health effects of sitting. Sitting in postures that do not require much muscle activity (i.e., chair sitting) leads to reduced local muscle metabolism, with detrimental effects on lipid and glucose metabolism, blood flow and endothelial health, and regulation of inflammation.
My tennis racquet hypothesis validated
(Caution: this topic for tennis geeks only)
I started playing tennis in the late seventies. One of my first racquets was the iconic Donnay Borg Pro.
I remember it as a thing of absolute beauty, and I wish I still had it. But as a tool for performance, it absolutely sucked compared to the oversize and graphite racquets that came soon after. The bigger sweet spots made it far easier to hit the heavy topspin-style ground strokes that took over the game in the early 80s.
At that time, all the pros started switching to the bigger composite racquets, and hitting the ball more aggressively. The era of Borg/McEnroe gave way to Lendl/Becker and then Sampras/Aggassi, and each generation of players were hitting with more power and spin. And at some point things just got ridiculous. By the early 2000s, the speed of the game was so high that it looked almost unrecognizable to me. Part of the explanation was that the athletes were bigger and stronger. But I also guessed that it had something to do with the equipment. Even though it had been 20 years since the shift to better rackets, this was the first time we were seeing adults who had used those racquets since they were kids. So the full effect of the technological change was delayed.
Anyway, this recent paper provide some evidence in favor of my hypothesis! Plus it may explain help why Boris Becker managed to win Wimbledon at age 17, how Jim Courier ever became number one, and why Federer and Nadal have so much longevity:
We find that the introduction of composite rackets temporarily helped younger players at the expense of older players, reduced the rank correlation in player quality overtime, and increased exit rates of older players relatively younger ones.
The transition from wood to composite rackets temporary early disadvantaged older players because the skills they had spent their career investing and we're no longer as valuable.
Over time, these temporary shifts largely reversed, so the transition took 2 to 4 generations.
Depending on the figure it took until 2005 to 2010 for outcomes to return to the levels they were at before composite rackets were introduced.
Amputee football
I had no idea they were this good. Fun to watch, and inspiring.
Running and cartilage
How does running affect cartilage? This systematic review and meta-analysis provides yet another reason to discard the myth that running causes “wear and tear” on your joints:
Changes to lower limb cartilage following running are transient. Immediate changes to cartilage morphology and composition, which likely reflect natural fluid dynamics, do not persist and were generally not significant when pooled statistically. Results suggest that cartilage recovers well from a single running bout and adapts to repeated exposure. Given that moderate evidence indicates that running does not lead to new lesions, future trials should focus on clinical populations, such as those with osteoarthritis.
The horrifying ancestors of whales
In a previous post I pointed out that whales and other sea-based mammals swim by flexing and extending the spine, which is interesting because other fish swim by moving the spine side to side. Whales use flexion/extension because they descend from land-based mammals, and they inherited their basic movement patterns. Which makes me wonder what whales’ ancestors looked like when they were making the transition from land to water. Click this link to see the frightening answer.
Wisdom from Jeremy Frisch
I like this quote: “Children don't need a progressive change of direction agility program … They need chaos and lots of it.” Follow Jeremy on Twitter for plenty of videos like this:
Chaos in the brain and the lack thereof
An an article in Wired discusses some new discoveries about why we lose conscious awareness during anesthesia. It may have something to do with the fact that neural firing patterns become very coordinated and repetitive, like white noise, lacking any interesting patterns:
the less frequent spikes of neural activity during anesthesia are actually more coordinated than in any other mental state. Whether you’re alert, reading, sleeping, or meditating, your brain waves are chaotic and tough to parse. But no signal is as clear and rhythmic on an EEG as anesthesia. And, critically, he believes, it’s this uniformity that undermines consciousness. That lunchroom chatter from an alert brain seems like noisy chaos, but it’s actually a coherent language of memories, feelings, and sensations. The hum of anesthesia is clear, but it’s an information desert.
How to exercise while doing nothing
This paper from Rhonda Patrick and Theresa Johnson summarizes the evidence showing health benefits from sitting in a hot sauna, which may include reduced mortality, protection against numerous diseases, and even better cardiovascular fitness. Why? Heat stress puts the cardiovascular system to work in cooling the body and this mimics the physiological response to exercise.
My highly scientific Twitter poll on back pain
Here’s the result, which I found optimistic. (Includes my vote, which is yes.)
Have a good week.