Is there an optimal time of day to exercise?

Two new studies say yes. Unfortunately, each claims a different time.

woman working out in gym
Bronx, N.Y.: NYPD officer Julissa Camacho works out at the 44th precinct gym in the Bronx, New York on April 3, 2019. (Photo by Alejandra Villa Loarca/Newsday via Getty Images)
  • Research at the Weizmann Institute of Sciences declares evening to be the best time for an exercise session.
  • Not so fast, says a new study at UC Irvine, which replies that late morning is the optimal workout time.
  • Both studies involved mice on treadmills and measured different markers to produce their results.

We know timing is everything, but does everything rely on timing? When it comes to when you exercise, the answer might be yes.

Two complementary studies were recently published in the journal Cell Metabolism, detailing the relevance of circadian rhythm on exercise. Both studies relied on mice huffing it on treadmills (along with a dozen human counterparts in one of the studies). Both presented an optimal time of day to exercise. The problem is, each study claims a different time.

In the first, mice were put on varying cardio protocols at different times of day. "Mouse evening" is different than "human evening" since rodents are nocturnal. According to this research, evening appears to be the best time of day for exercise efficiency.

The team, led by Dr. Gad Asher in the Department of Biomolecular Sciences at the Weizmann Institute of Sciences, focused on skeletal muscle. They discovered higher levels of post-workout ZMP during mouse evening, affording the rodents an increased exercise ability. When 12 humans were tested in a similar manner the result was the same. As the team writes,

"The distinct daytime and exercise-type transcriptomic and metabolic signature in skeletal muscle point toward a difference in nutrient utilization and metabolic pathway activation, in particular, fatty acid oxidation and glycolysis."

Asher believes this offers a leg-up on those that hit the treadmill in the evening, noting that ZMP is "an endogenous analog of AICAR [aminoimidazole carboxamide riboside], a compound that some athletes use for doping." Apparently, our internal alarm clock offers access to our inner pharmacy at different times.

Morning vs Evening | Best Time of Day to Workout

Not so fast, says Dr. Paolo Sassone-Corsi at the Center for Egpigenetics and Metabolism at UC Irvine. His team also investigated the effects of circadian regulation on metabolism. He says that by the end of the study his team looked out a much different time window.

"Using mice, we compared the impact of exercise on the skeletal muscle metabolism at different times of day. We discovered that exercising at the correct time of day — around mid-morning — results in more oxygen in the cells and a more rejuvenating effect on the body."

Sassone-Corsi measured changes in muscle tissue as they related to glycolysis and lipid oxidation. The key component was a transcription factor, HIF-1α, and its role in exercise efficiency. Homing in on this particular process offered another perspective.

Specifically, Sassone-Corsi says that our bodies utilize carbohydrates and ketone bodies better during a late morning workout; we also break down fats and amino acids more efficiently during this phase.

While both studies involve circadian rhythms, Sassone-Corsi admits that mice living in a laboratory experience reality differently than humans. Physiological differences between an early rising human and a night owl signify varying optimal times of day for pretty much everything, workouts included. If you're not accustomed to hitting the gym at the break of dawn, it is unlikely that a 6 a.m. session will be better when compared to your normal evening regimen.

Nathaniel Clyne attends the gym session during the AFC Bournemouth warm weather training session at NAS Sports Complex on March 21, 2019 in Dubai, United Arab Emirates. Photo credit: AFC Bournemouth / AFC Bournemouth via Getty Images

In my experiences, there are advantages to both. In the morning (my personal preference, being an early riser), exercise wakes you up and prepares you for the day ahead. I notice a qualitative difference between getting on my laptop on days when I work out first compared to when I do not.

Other benefits of a morning routing include:

  • More efficient weight loss
  • REM sleep aids in motor control
  • Early birds are more consistent (likely because willpower is a limited resource)

Yet evening exercise also has advantages. For example, your body is more limber, having moved around all day; hitting the yoga mat first thing in the morning can be torturous. The wash of chemicals after an evening session sets you up for a restful sleep. Other research suggests that evening workouts allow you to blow off steam from your day while also increasing the intensity of your session. Strength and flexibility are highest in evening.

The answer to the optimal workout time appears to be: it depends. Like diet, exercise programs are individual. Experience and habitual patterns must be factored in. The most important takeaway from these studies is the fact that exercising at any time of the day is better than not exercising at all. Whatever your movement protocol, that you have one is the most important factor.

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A landslide is imminent and so is its tsunami

An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.

Image source: Christian Zimmerman/USGS/Big Think
Surprising Science
  • A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
  • A wall of rock exposed by a receding glacier is about crash into the waters below.
  • Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.

The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.

Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .

"It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

The Barry Arm Fjord

Camping on the fjord's Black Sand Beach

Image source: Matt Zimmerman

The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.

Not Alaska’s first watery rodeo, but likely the biggest

Image source: whrc.org

There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.

The Barry Arm event will be larger than either of these by far.

"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."

Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.

What the letter predicts for Barry Arm Fjord

Moving slowly at first...

Image source: whrc.org

"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."

The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.

Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.

Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.

While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.

Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."

How do you prepare for something like this?

Image source: whrc.org

The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:

"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."

In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.

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