Seabirds called common murres appear to use preening as a way to negotiate whose turn it is to watch their chick and who must find food. And when one parent is feeling foul, irregularities in this grooming ritual may send the other a signal that all is not well, researchers report in the July issue of The Auk: Ornithological Advances.

“The fascinating part of this study is the inference that communication between mates allows murres to negotiate the level of effort that each member of the pair puts into the breeding effort,” says John Piatt, a wildlife biologist with the U.S. Geological Survey in Anchorage, Alaska. “Reproductive success of this species requires a high degree of cooperation by each mate as they switch duties.”
Common murres (Uria aalge) lay only one egg each breeding season. Parental roles aren’t determined by gender for the birds; mothers and fathers take turns watching over their chick and foraging for fish. When one parent returns with a fish for the chick, the couple preen each other and switch roles. This swapping ceremony typically happens three to four times a day.

But study coauthor Carolyn Walsh noticed that switches don’t always go smoothly. Video of 16 pairs of murres, documenting a total of 198 role swaps, showed that sometimes both birds appeared indecisive. Each parent would hop on and off the chick several times before the birds preened each other and one left to fish. “It’s as if they’re resisting leaving the colony; neither bird actually wants to go,” says Walsh, an animal behavior researcher at Memorial University of Newfoundland in Canada.
For about a fifth of all switching ceremonies, the brooding parent was slow to preen its mate and then refused to switch, forcing the parent that had just returned with a fish to go back out and fish some more.
Irregular behavior also occurred when the parent on fishing duty returned without food, which happened about 10 percent of the time. The empty-beaked bird would quickly start preening its mate, but the mate would be slow to preen back, or might not preen at all. “The brooder is basically communicating, ‘The chick still needs a fish, you better go get one,’” Walsh says.
The ceremony could be a way for the seabirds to communicate their well-being, Walsh says. By withholding preening and delaying the switching ceremony, a murre in poor condition may be trying to negotiate with its partner to have the easier job of brooding. Staying in the nest may allow the bird to rest and recover its strength.

Flying out to sea to fish is energetically costly for murres because they aren’t very aerodynamic. The seabirds are “absolutely ridiculous looking” when they fly, Walsh says. “Their wings are really meant for swimming in the water.”

In physical tests, Walsh and colleagues found a correlation between body condition and ceremony irregularities. Her team captured birds, weighed them and sampled their blood for beta-hydroxybutyrate, a metabolite associated with continual weight loss.

Switching ceremonies lasted about two minutes longer for the lightest birds, around 900 grams, compared with the heaviest birds weighing in at about 1,000 grams. Birds with lower mass and higher metabolite levels also were more likely to preen irregularly, Walsh says.

The longer ceremonies may also be a sign that there’s unrest in the nest. Murres usually mate for life, but pairs can “divorce.” A previous study by Walsh found that mates heading for a split take more time to switch roles.

The benefits of statins for people older than 75 remain unclear, a new analysis finds. Statins did not reduce heart attacks or coronary heart disease deaths, nor did they reduce deaths from any cause, compared with people not taking statins, researchers report online May 22 in JAMA Internal Medicine.

Recently published guidelines cited insufficient data to recommend statins for people older than age 75 who don’t have a history of cardiovascular disease. The new analysis considered a subset of older adults enrolled in a study of heart attack prevention and mortality conducted from 1994 to 2002. The sample included 2,867 adults ages 65 and older who had hypertension, 1,467 of whom took a statin.

There was no meaningful difference in the frequency of heart attacks or coronary heart disease deaths between those who took statins and those who did not. There was also no significant difference in deaths from any cause, both overall and among participants ages 65 to 74 or those 75 and older.

Statin use may be associated with muscle damage and fatigue, which could especially impact older adults and put them at higher risk for physical decline, the authors say.

Ancient rock artists were drawn to echo chambers. Members of early farming communities in Europe painted images in rock-shelters where sounds bounced off walls and into the surrounding countryside, researchers say.

Rock-shelters lacking such sound effects were passed up, at least in the central Mediterranean, report archaeologist Margarita Díaz-Andreu of the University of Barcelona and colleagues in the July Journal of Archaeological Science. In landscapes with many potential rock art sites, “the few shelters chosen to be painted were those that have special acoustic properties,” Díaz-Andreu says.
Some hunter-gatherer and farming groups studied over the past couple centuries believed in spirits that dwell in rock and reveal their presence via echoes. But acoustic evidence of special echoing properties at rock art sites is rare.

Díaz-Andreu’s team studied two rock art sites in 2015 and 2016. Baume Brune is a kilometer-long cliff in southeastern France. Of 43 naturally formed cavities in the cliff, only eight contain paintings, which include treelike figures and horned animals. Rock art in the Valle d’Ividoro, on Italy’s east coast, appears in an 800-meter-long section of a gorge. Only three of its 11 natural shelters contain painted images. Researchers generally date these French and Italian paintings to between roughly 6,500 and 5,000 years ago, several thousand years after the Stone Age had ended, Díaz-Andreu says.

To investigate the acoustics of the decorated and unadorned shelters, the researchers developed a new technique for determining the direction, intensity and timing of sound waves arriving at a particular point from every direction. A special microphone connected to a digital recorder measured the acoustic properties of any echoes set off by balloons popped just outside each rock-shelter. This setup was moved to various spots outside the caves to record the acoustic reach of reflected popping sounds. Echo measurements in France were taken at distances ranging from 22 to 36 meters from cliff shelters. Due to rougher terrain in Italy, measurements there were taken at distances ranging from 77 to 300 meters.
Then, the acoustic data were transformed into 3-D, slow-motion depictions of echoes, represented by moving circles, indicating where sound reflections originated. At both sites, shelters with rock paintings displayed better echoing properties than undecorated shelters, Díaz-Andreu says. And in each location, the shelter that best reflected echoes had the highest number of paintings.
“This novel technique shows a clear correlation between audible echoes and decorated shelters,” says music archaeologist Riitta Rainio of the University of Helsinki in Finland, who did not participate in the new study.

Echoes that bounce off steep rock cliffs bordering three lakes in northern Finland also attracted ancient artists, Rainio says. She and her colleagues took acoustic measurements at Finland’s painted cliffs from 2013 to 2016. Microphones placed on boats positioned at different spots on nearby lakes measured sound waves generated, in most trials, by a starter’s pistol. These Finnish paintings date to between around 7,200 and 3,000 years ago, Rainio says.

In some cases, echoes reflect directly from cliff paintings. “That, and possible drumming figures painted on the cliffs, suggest that sound played some role in rituals at these sites,” Rainio says. Her team will report its findings in an upcoming Journal of Archaeological Method and Theory.

Creators of older Stone Age cave art also appear to have focused on sites where echoes abounded, says archaeologist Paul Pettitt of Durham University in England. For instance, many roughly 14,000- to 12,000-year-old animal drawings and engravings at France’s Niaux Cave cluster in a cathedral-like chamber where sounds echo loudly.

“The new study provides convincing evidence that echoes, which were scientifically inexplicable to prehistoric people, played a determining role in how art was created,” Pettitt says.

Big, rogue planets — ones without parent stars — are rare.

A new census of free-floating Jupiter-mass planets determined that these worlds are a tenth as common as previous estimates suggested. The results appear online July 24 in Nature.

Planets can go rogue in two ways: They can get kicked out of their parent planetary systems or form when a ball of gas and dust collapses (SN: 4/4/15, p. 22).

In the new study, Przemek Mróz of the Astronomical Observatory of the University of Warsaw and colleagues estimated the number of large, rogue planets in our galaxy using a technique called microlensing. When an object with a mass of a planet passes in front of a distant, background star, the gravity of the planet acts as a gravitational magnifying glass. It distorts and focuses the light, giving up the planet’s existence.
Mróz and colleagues looked at 2,617 microlensing events recorded between 2010 and 2015 and determined which were caused by a rogue planet. For every typical star, called main sequence stars, there are 0.25 free-floating Jupiter-mass planets, the analysis suggests.

The new result sharply contrasts an estimate published in 2011, which suggested that rogue Jupiters are almost twice as common as main sequence stars. About 90 percent of stars in the universe are main sequence stars, so if that estimate were accurate, there should be a lot of free-floating Jupiters.

“That result changed our conceptual framework of the universe just a little bit,” says astronomer Michael Liu of the University of Hawaii in Honolulu. It challenged long-held ideas about how planets go rogue because the known methods wouldn’t generate enough planets to account for all the wanderers.

The 2011 result was based on a relatively small sample of microlensing events, only 474. Since then, infrared telescope images haven’t detected as many free-floating planets as expected. “Over the years, serious doubts were cast over the claims of a large population of Jupiter-mass free-floaters,” Mróz says.

David Bennett, coauthor of the 2011 study, agrees that the new census failed to find evidence for a large population of Jupiter-mass rogue planets. He notes, however, that the new data do reveal four times as many Jupiter-mass failed stars called brown dwarfs than predicted in the original census. So some of the rogues that were originally classified as planets may, in fact, be failed stars. Bennett, of NASA’s Goddard Space Flight Center in Greenbelt, Md., and colleagues are working on a new analysis of potential rogues with nearly 3,000 microlensing events and plan to compare their results with those from the new census.
Liu says the latest census is much more in line with theories of how planets form. Most rogues should be Earth-mass or a little heavier. Those lighter planets get tossed out of their planetary systems much easier than behemoths like Jupiter. Still, the smaller planets are harder to detect.

The new microlensing analysis did identify several events in which stars brightened and dimmed in less than half a day. Such short events hint at the existence of Earth-mass free-floaters because smaller planets with less gravity should brighten a distant star more briefly than more massive stars. Determining whether those small planets are really rogue and counting how many there are will take better telescopes, the team notes.

When Hurricane Maria’s 250-kilometer-per-hour winds slammed into Puerto Rico on September 20, they spurred floods, destroyed roads and flattened homes across the island. A week-and-a-half later, parts of the island remain without power, and its people are facing a humanitarian crisis.

The storm also temporarily knocked out one of the best and biggest eyes on the sky: the Arecibo Observatory, some 95 kilometers west of San Juan. The observatory’s 305-meter-wide main dish was until recently the largest radio telescope in the world (a bigger one, the FAST radio telescope, opened in China in 2016).

As news trickled out over the past week, it appeared that the damage may not be as bad as initially reported. The observatory is conserving fuel, but plans to resume limited astronomy observations September 29, deputy director Joan Schmelz tweeted earlier that day. “#AreciboScience is coming back after #MariaPR.”

But the direct whack still raises the issue of when – and even whether – to repair the observatory: Funding for it has repeatedly been on the chopping block despite its historic contributions to astronomy.

Arecibo’s recent work includes searching for gravitational waves by the effect they have on the clocklike regularity of dead stars called pulsars; watching for mysterious blasts of energy called fast radio bursts (SN Online: 12/21/16); and keeping tabs on near-Earth asteroids.

It played a key role in the history of the search for extraterrestrial intelligence: In 1974, astronomers Frank Drake, Jill Tarter and Carl Sagan used it to send messages to any extraterrestrial civilizations that might be listening (SN Online: 2/13/15). It was also the telescope that, in 1992, discovered the first planets outside the solar system.

Arecibo also holds a special place in my personal history: Watching actress Jodie Foster use the giant dish to listen for aliens in the movie Contact when I was 13 cemented my desire to study astronomy. I chose to go to Cornell University for undergrad in part because the university managed Arecibo at the time, and I hoped I might get to go there. (I never did, but my undergrad adviser, Martha Haynes, uses Arecibo to study the distribution of galaxies in the local universe.) And one of the first science stories I ever had published was about Cornell professors testifying to the National Science Foundation, which owns Arecibo, to defend the observatory’s funding.
Ten years after that story ran in the Cornell Daily Sun, Arecibo’s funding situation is still in doubt. It’s not clear how the recent damage will affect its future.

Telescope operator Ángel Vázquez sent the first damage reports via short-wave radio on September 21. A line feed antenna, used to receive and transmit radio waves to study the Earth’s ionosphere, broke off and fell onto the observatory’s main dish, damaging some of its panels. A second, 12-meter dish was thought to have been destroyed entirely.

But the smaller dish survived with only minor damage. “Initial reports said it had just been blown away, but it turned out that was not correct,” says Nicholas White of the Universities Space Research Association, which co-operates the observatory with SRI International, a nonprofit headquartered in Menlo Park, Calif., and Metropolitan University in San Juan, Puerto Rico. “That looks like it’s fine, although obviously we have to get up there and check it out.”

On September 23, observatory director Francisco Córdova posted a picture to the observatory’s Facebook page of two staff members standing in front of the big telescope dish with an outstretched Puerto Rican flag. “Still standing after #HurricaneMaria!” the post declares. “We suffered some damages, but nothing that can’t be repaired or replaced!”
The line feed antenna is a big loss, but it should be replaceable eventually, White says. And the damage to the main dish is fixable. Among the tasks was to get inside the Gregorian dome — the golf ball‒like structure suspended over the giant dish — and make sure the reflectors within it were aligned correctly. (Those reflectors were knocked askew by Hurricane George in 1998, says Cornell radio astronomer Donald Campbell.)

Meantime, Arecibo staff, who managed to safely shelter in place during the storm, “have been showing up for work, funnily enough,” White says. “People just want to get back to normal.”

But normal is also a state of uncertainty. The NSF, which foots $8.3 million of the observatory’s nearly $12 million a year operating costs, has been trying to offload their responsibility for it for several years. (NASA covers the balance.) And NSF’s agreement with the three groups that jointly maintain and operate the observatory runs out in March 2018. In 2016, the NSF called for proposals for other organizations to take over after that.

The NSF can’t estimate yet how expensive the repairs will be or how long they will take to complete, so it’s reserving comment on how the damage will affect decisions about the observatory’s future. “We need to make a complete assessment,” says NSF program director Joseph Pesce.

Personally, I hope the observatory remains open, both for science and for inspiration. I’m still waiting for a reply to that 1974 Arecibo message.

"It's the worst possible news on the eve of the tournament," said England midfielder Izzy Christiansen to BBC Sport. Spanish football journalist David Menayo called it "a jug of cold water" thrown over his nation.

They were referring to the loss of Alexia Putellas, who suffered a torn ACL on the eve of this the women's Euro 2022 tournament, leaving Spain without their reigning Ballon d'Or winner. The loss of such a superstar was evident, as Spain, a pre-tournament favorite, looked tame in bowing out to England in the quarterfinals.

Just a week later, young France star Marie-Antoinette Katoto suffered a similar fate in the Euro group stage, and a toothless Les Bleus attack fell short in the semifinals to Germany.

Bright young USWNT star Cat Macario, who lit up the Champions League for Lyon en route to winning the title over Putellas's Barcelona, tore her ACL in the early stages of a meaningless Ligue 1 match in early June. Two weeks later, legendary American striker Christen Press tore her ACL during NWSL play with expansion club Angel City FC. Just a month prior, Macario's Lyon teammate Dzsenifer Marozsan suffered the same fate, ruling the German star out of the Champions League final and leaving her sidelined for the Euros.

It doesn't stop there. USWNT defender Tierna Davidson went down in March of 2022 with an ACL injury during a shortened NWSL preseason. The Australian national team lost three players to ACL tears in a year's span, including young superstar Ellie Carpenter, who has already collected a massive 57 caps at just 22 years old, but went down in late May. A similar rising star for the German national team, Giulia Gwinn, suffered the injury in early October of 2021, her second ACL tear at just 23 years old.

As time progresses, the list just continues to grow — NWSL finalists Kansas City Current saw midfield fixture Claire Lavogez fall victim in the 2022 playoff quarterfinals. In the run-up to the 2023 Women's World Cup, stars Beth Mead and Vivianne Miedema both suffered ACL tears that ruled them out of the game's biggest event.

"The amount of ACL injuries in professional women's soccer in the last two years has just been shocking," Christen Press told ESPN in May of 2023. "If this happened on the men's side, we would have immediately seen a reaction of 'how are we going to solve this and figure this out, and make sure that these players are going to be available at the biggest moments of their career?'"

This is not just limited to the top of the game; clubs and college programs across the United States are noticing an increase in serious knee injuries. The Wake Forest women's team, a top ACC Division I program, has suffered six ACL tears in the past year, an increasingly common struggle for NCAA women's soccer coaches to navigate.

ACL tears have always been a danger in both men's and women's football, but as top players across the women's global game began dropping like flies, The Sporting News began asking questions. It turns out, there are scientific reasons to explain the wave of ACL tears that strike women's soccer.

Women soccer players more prone to ACL tears than men?
Over recent years it has become mainstream knowledge that women are, quite simply, more prone to serious knee injuries than men.

Slight anatomical differences between men's and women's bodies, largely concerning variations in hip structures, leave women at a higher risk of ACL tears or other serious knee damage. "These are trends that we've seen in the sports medicine world for years now," said Dr. Howard Luks, Chief of Sports Medicine and Arthroscopy at New York Medical College and a 20-year orthopedic sports surgeon with over a thousand ACL surgeries under his belt.

"Women in general are at higher risk. They have various differences compared to male athletic counterparts."

Research published by the Yale School of Medicine shows that women are two to eight times more likely to suffer ACL tears than men. Due to a wider hip structure, the knees of females are angled slightly differently, putting more pressure on the ACL. The differences are incredibly slight, but the effects can be witnessed over long periods of time.

"The ACL sits within a narrow notch on the inside of the knee joint," Dr. Luks noted. "That notch has more narrow confines in females, which can increase the risk of injuries."

While anatomical differences between sexes are a large contributing factor, there's another significant difference from males to females. There's medical evidence to support that women are significantly more prone to injury during their menstrual cycle. Given the private and personal nature of this information, research has not permeated the athletic community.

"Our ligament tissue changes based on the influence of hormones," Dr. Luks explains. "The best example of this is a woman's pelvis expands significantly due to the influence of hormones, but pelvis ligaments are not the only ones to change during the various cycles that occur."

Even with all the above, an individual's sex is not the only contributing factor in the ACL tears that occur with greater frequency in women's sports. Playing multiple sports, especially at a young age, can help.

"We've seen an increase in ACL tears due to single-sports participation," says Dr. Luks, explaining that repeated pressure in the exact same manner without variation over time can increase the risk of injury.

"The same stress on the same limbs in the same joints on the same ligaments month after month without any rest has an impact."

ACL injury prevention in women's sports
In recent years, women's soccer and other women's sports have sought to acknowledge the differences in injury risk, and to take steps to try and develop methods of prevention to counter the potential causes.

FIFA 11+ program

While there's no silver bullet when it comes to injury prevention, there's one program that stands out from the rest. The FIFA 11+ program was cited by multiple interview subjects for this report, and often without any prompting.

The FIFA 11+ program focuses on forcing athletes to build muscle memory for one key part of athletics, particularly soccer, that athletes often overlook: landing. The program is designed to be implemented as a short 10-minute warm-up performed before training and/or matches to positively reinforce proper landing techniques.

"They look at the way women jump and land on a surface, and what happens in their knees and ankles," says Brian Maddox, head athletic trainer for NWSL club North Carolina Courage. "They find that [women] move with more motion in their knees and hips when they land."

Dr. Luks, a proponent of the FIFA 11+ program, pointed to a superstar of the men's game for inspiration. "Watch Ronaldo when he lands on a header in the box. He lands on a flexed knee, the leg is as straight as possible, and when he lands he cushions the blow by going into a single-legged or a double-legged squat. These are all techniques that are taught [in the program] to diminish ACL ruptures.

"It's drilled into their heads," Dr. Luks explains. The idea being that such a simple action becomes healthy muscle memory. "Let's say you break your ankle, I put you in a cast, I take the cast off — your muscles are all atrophied. Half of that weakness is loss of muscle strength, but the other half of it is the lack of neuromuscular connections — your brain is no longer connected to those muscle fibers."

Dr. Luks' hypothetical metaphor is meant to show that building neuromuscular connections can create what we know as "muscle memory."

Wake Forest women's soccer senior defender Lyndon Wood, who serves as president of the school's Student Athlete Advisory Committee and is conducting her own research on ACL injuries in women's sports, said she brought the FIFA 11+ program to the Demon Deacons. It was quickly given approval by longtime head coach Tony da Luz.

"I felt like something needed to be done; anything we can do to keep one more girl on the field longer we should do," she said. "I brought it to [Wake Forest Sports Medicine program director] Dr. [John] Hubbard and Tony, and they were like 'Yeah, let's do it.'"

U.S. Soccer medical staff confirmed to The Sporting News that FIFA 11+ and other similar models are employed in training programs at all national team levels, although they would not dive into specifics of the programs at the different levels.

The FIFA 11+ program, however, still has yet to catch on everywhere. When Dr. Luks, whose three kids all play youth soccer, brought the FIFA 11+ program to the directors of their youth soccer programs and volunteered his time, they didn't jump at the opportunity.

"We went out to the schools assuming they would love it…no. Nobody wanted it. I can't explain it, and I was never given a good reason."

Special training regimens
The topic of a woman's menstrual cycle and how it affects injury risk in athletics is a sensitive one, and as a result, action has been slow in taking shape.

An assistant coach at a NCAA Division I women's lacrosse program in a Power 5 conference confirmed to the Sporting News that their program has just this season begun to track their athletes' cycles with the backing and participation from the players themselves.

With this information, women experiencing their menstrual cycle conduct separate, lower intensity training to minimize the risk of injury. It's not yet a practice that's widely adopted, and the same coach indicated that the women's soccer team at his school has yet to implement this same practice.

That's not surprising, says Maddox, the head trainer with the NWSL's Courage. "To my knowledge, it is not widely done in the U.S. because it can be a sensitive subject for some." Maddox says that he is aware of one top European club that does track their athletes' cycles, although he's not sure if they have yet to offer separate training based on the information.

It was widely covered following their 2019 Women's World Cup victory that U.S. women's national team players tracked their menstrual cycle throughout the four years leading into the tournament, and national team players publicly stated that there were several off-field programs implemented to complement this with regards to sleep and mental health. However, U.S. Soccer did not confirm whether these methods currently impact training intensity and injury prevention practices.

This may be the next step in the evolution of injury prevention in women's soccer if the USWNT's experience and that of other college programs yields positive results.

An assistant coach at another NCAA Division 1 women's lacrosse program confirmed to the Sporting News that their program suffered five ACL tears in the past year, and all five women were on their period at the time they were injured.

Mental health and injuries
In recent years mental health has gained increased attention throughout the athletics community, and its importance in injury prevention and recovery is being recognized as part of that push.

"Taking care of the athlete holistically…mentally and nutritionally, those resources are available to athletes these days when maybe they weren't as dialed in 15 or 20 years ago," says Maddox, who has prior athletic training experience in the NHL and minor league baseball.

"You can't disregard the mental aspect of it, this day and age every professional team across sports has those resources available to the athletes because it's useful."

When asked what she's learned through the recovery process, USWNT defender Tierna Davidson told The Sporting News, "Just to be patient with myself. It feels cheesy and simple, but I think as athletes we are impatient because we want results and we want to be 100 percent as quick as possible.

"But I think that through this process I have learned how to celebrate where I'm at in each stage, and not getting down on the fact that I suck at heading at the moment or I'm not as fast at the moment, or whatever it is."

A long way still to go
While more information is being gathered, some programs across the globe have been slow to implement change due to social and societal boundaries that are still difficult to breach.

"[ACL injury research] became a really hot topic in the late '90s and early 2000s," says Maddox. "That's when a lot of the research was conducted, specifically with regards to why women tear their ACLs more than men."

Maddox explains that strength training is a key part of injury prevention, but that the culture around women's sports doesn't lend itself to nearly the amount of strength training that is prevalent in men's sports.

"The way women are training from the youth on up…the emphasis in men's sports and boys sports is that you're not an athlete unless you lift weights. That culture is slowly hitting women's athletics, but it's behind the men."

When asked what they've learned in recent years regarding ACL tear prevention, the U.S. Soccer Federation didn't share any specific details or data points, except to confirm that it's top of mind with their programs.

"U.S. Soccer continuously builds loading programs for players. We work diligently with their clubs and/or universities in monitoring the players and develop individualized plans based on multiple factors in building out ACL prevention, but also soft tissue injuries as well. This has been a long-standing pillar for U.S. Soccer’s care of its players."

Why have so many women's soccer stars torn their ACLs?
The ability to pinpoint specific causes of injuries is ultimately an inexact science. When it comes to the human body, there are so many factors and variables that can affect an athlete's propensity or resistance to injury.

U.S. women's national team star Alex Morgan, who tore her ACL way back in high school, told The Sporting News during a USWNT press conference in the fall of 2022 that she thinks it's possible a shortened preseason and extended competition at the domestic level in the United States could be to blame for injuries in her part of the world.

"We look at the [NWSL] Challenge Cup, it was a great preseason tournament to have," Morgan said in early September in reference to the kickoff tournament of the U.S. women's professional season. "But having that bonus set for players to win, having it be a little more competitive than I think players were really ready for, having players playing 90 minutes week-in and week-out…is that the best for players in the first five weeks of the preseason? Probably not."

Dr. Luks says a quick ramp-up to competitive matches early in the season potentially increases the risk for injury. He explained how a proper and full preseason is critically important to avoiding injury during the year. Essentially, nerves that direct muscle movements connect to those muscles via "motor end plates" which degrade over time. Preseason, which features a slow increase in repetitive activity, is required to rebuild those connections.

"If you don't have connections to all the muscle fibers, I don't care how many weights you put on the rack, it's irrelevant, you're only exercising a third of the muscle fibers, because the other two-thirds don't have a connection to your brain, so they're not firing," Dr. Luks explains. "So that's such a critical component of a preseason program."

The Chicago Red Stars' Davidson, who suffered her ACL tear in preseason training in March 2022 before the Challenge Cup, was less convinced there was a common link in the rash of injuries that afflicted the stars of the women's game in 2022, but she acknowledged that an accumulation of minutes could potentially be responsible for her injury.

"I definitely think you can point to the volume and load that a lot of international players take through their club and country, so I'm sure that a bit of fatigue has to do with it. Sometimes it could just be coincidence, I don't know everybody else's schedule, but I do think there could have been some overuse of players."

A look at the numbers does support Davidson's suspicions. From January to November of 2021, the 24-year-old played 3,224 minutes across both club and international duty, including 1,780 minutes after the start of August. Add in three February 2022 national team appearances in the SheBelieves Cup, and with the short preseason ramp-up, she suffered her tear in March.

Many of the top international players injured this spring had similarly heavy loads. The chart below illustrate the range of matches and minutes played by some of the stars who suffered the ACL injuries (statistics via FBref.com).

Work load for soccer stars prior to ACL injury
(Note: Players listed below in alphabetical order.)

Player Date Range Games Minutes
Tierna Davidson Jan 22, 2021 — Nov 30, 2021 41 3,224
Giulia Gwynn Aug 29, 2021 — Oct 2, 2022 43 3,305
Marie-Antoinette Katoto Aug 5, 2020 — Jun 25, 2022 66 5,145
Catarina Macario Jul 1, 2021 — Jun 1, 2022 45 3,021
Dzsenifer Marozsan Jan 15, 2021 — Apr 12, 2022 70 4,893
Christen Press Oct 4, 2020 — Jun 11, 2022 36 2,686
Alexia Putellas Sep 19, 2020 — Jun 25, 2022 36 2,846
The table above shows 30-year-old Marozsan played close to 5,000 minutes across a 15-month period. So did 24-year-old Katoto, who logged 5,145 minutes over two years. Christen Press's numbers don't quite jump off the page, but what stands out is that she had little activity between mid-July 2021 before the Challenge Cup in March 2022.

The schedule congestion is not unique to these players specifically, but many top players across the globe are juggling busy club and international schedules that are increasing in load as the women's game explodes in popularity.

Alex Morgan, who's been a professional since 2011, ultimately labeled the rash of star knee injuries in 2022 an "unlucky run." But what is clear is that there are more variables that impact a women's soccer player's injury chances than in the case of a male player. And there's more research and information sharing that still can be done to investigate each of those factors.

Was it an unlucky run? We'll find out soon enough in the lead-up to the expanded Women's World Cup with 32 teams in July 2023. Given the names forced to sit out due to injury in the summer of 2022, a similar rash of injuries would not go unnoticed ahead of the biggest tournament in the sport.

California’s crops are creating some noxious air.

The Golden State is at the vanguard in the United States in reducing auto emissions of nitrogen oxide gases, which help produce toxic smog and acid rain. But the NOx pollution problem isn’t limited to auto exhaust. California’s vast agricultural lands — particularly soils heavily treated with nitrogen fertilizers — are now responsible for as much as 51 percent of total NOx emissions across the state, researchers report January 31 in Science Advances.
The catchall term “NOx gases” generally refers to two pollution-promoting gases: nitric oxide, or NO, and nitrogen dioxide, or NO2. Those gases react with incoming sunlight to produce ozone in the troposphere, the lowest layer of the atmosphere. At high levels, tropospheric ozone can cause respiratory problems from asthma to emphysema.

Between 2005 and 2008, regulations issued by the California Air Resources Board on transportation exhaust reduced NOx levels in cities such as Los Angeles, San Francisco and Sacramento by 9 percent per year. However, the U.S. Environmental Protection Agency has increasingly recognized nitrogen fertilizer use as a significant source of NOx gases to the atmosphere.

NOx gases are produced in oxygen-poor soils when microbes break apart nitrogen compounds in the fertilizer, a process called denitrification. The release of those gases from fertilized soils increases at high temperatures due to increased microbial activity, says Darrel Jenerette, an ecologist at the University of California, Riverside, who was not involved in the new study.

Jenerette and others have studied local NOx emissions from soils in California, but no statewide assessment existed. So Maya Almaraz, an ecologist at the University of California, Davis, and her colleagues designed a study to examine the question — both from above and below.
Using a plane equipped with scientific instruments including a chemiluminescence analyzer to detect NOx gases in the atmosphere, the researchers measured the concentrations of the gases above the San Joaquin Valley, an area of California’s fertile Central Valley, over six days at the end of July and beginning of August. The team also simulated NOx emissions from soils across the state, using the San Joaquin Valley data to ensure that the simulations gave accurate results. Finally, the researchers compared those data with nitrogen fertilizer inputs, as estimated by crop type and U.S. Department of Agriculture fertilizer consumption data.

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Croplands are contributing 20 to 51 percent of the total NOx in California’s air, Almaraz’s team reports. In the simulations, those soil emissions were particularly sensitive to two factors: climate, especially temperature, and rates of nitrogen input. That findings suggests that regions with greater inputs of nitrogen fertilizer will also see greater soil emissions — and that the emission of NOx gases from the soils will also increase as temperatures rise in the region due to climate change.

Although food demands — and the need for fertilizer for crops — are likely to increase in the future, there are numerous possible ways to limit unwanted nitrogen fertilizer spillover, the researchers note. For example, farmers can use more efficient fertilization strategies such as adjusting how much fertilizer is used depending on specific growing stages, or planting what are called cover crops along with the target crops that enrich soils and consume the excess nitrogen.

Almaraz’s team has produced an important finding, Jenerette says. “The combination of bottom-up soil emission measurements and top-down airborne measurements provide strong evidence for their emission assessments,” he says. The finding that NOx emission rates will increase with warming temperatures also highlights the urgency of taking steps to better manage nitrogen fertilizer use in a warming world, he says.

Female polar bears prowling springtime sea ice have extreme weight swings, some losing more than 10 percent of their body mass in just over a week. And the beginnings of bear video blogging help explain why.

An ambitious study of polar bears (Ursus maritimus) in Alaska has found that their overall metabolic rate is 1.6 times greater than thought, says wildlife biologist Anthony Pagano of the U.S. Geological Survey in Anchorage. With bodies that burn energy fast, polar bears need to eat a blubbery adult ringed seal (or 19 newborn seals) every 10 to 12 days just to maintain weight, Pagano and his colleagues report in the Feb. 2 Science. Camera-collar vlogs, a bear’s-eye view of the carnivores’ diet and lifestyle secrets, show just how well individual bears are doing.
The study puts the firmest numbers yet on basic needs of polar bears, whose lives are tied to the annual spread and shrinkage of Arctic sea ice, Pagano says. As the climate has warmed, the annual ice minimum has grown skimpier by some 14 percent per decade (SN Online: 9/19/16), raising worries about polar bear populations. These bears hunt the fat-rich seals that feed and breed around ice, and as seal habitat shrinks, so do the bears’ prospects.
Pagano and colleagues used helicopters to search for polar bears on ice about off the Alaska coast in the Beaufort Sea. It’s “a lot of grueling hours looking out the window watching tracks and looking at whiteness,” he says.
After tracking down female bears without cubs, the researchers fitted the animals with a camera collar. A full day’s doings of bears on the sea ice have been mostly a matter of speculation, Pagano says. Collar videos showed that 90 percent of seal hunts are ambushes, often by a bear lurking near a hole in the ice until a seal bursts up for a gulp of air. Videos also caught early glimpses of the breeding season and what passes for courtship among polar bears. Males, Pagano says, “pretty much harass the female until she’ll submit.”

The researchers also injected each bear with a dose of water with extra neutrons in both the hydrogen and oxygen atoms. Eight to 11 days later, the team caught the same bear to check what was left of the altered atoms. Lower traces of the special form of oxygen indicated that the bear’s body chemistry had been very active, and that the bear had exhaled lots of carbon dioxide. (The unusual form of hydrogen let scientists correct results for oxygen atoms lost in H2O, for instance when the bear urinated.)

Using CO₂ data from nine females, Pagano and his colleagues calculated the field metabolic rates for polar bears going about their springtime lives. The team found that female bears need to eat a bit more than 12,000 kilocalories (or what human dieters call calories) a day just to stay even. That estimate adds some 4,600 kilocalories a day to the old estimate. But merely maintaining weight isn’t enough for a polar lifestyle. To survive lean times, polar bears typically pack on extra weight in spring.

To get a broader view of the bears’ energy needs, similar metabolic measurements for other seasons would be useful, says physiological ecologist John Whiteman of the University of New Mexico in Albuquerque. That could help resolve whether and how much bear metabolism drops when there’s little food, a response that might protect bears during hard times. Using temperature loggers to estimate metabolic rates, he has seen only a gradual decline in metabolic rates in summer as food gets tougher to find. Winter metabolic rates remain a mystery.

Hunting success and bear activity are only part of the picture of polar bear health, says ecotoxicologist Sabrina Tartu, of the Norwegian Polar Institute, which is based in Tromsø. Tartu coauthored a 2017 paper showing that toxic pollutants such as polychlorinated biphenyls, or PCBs, can build up in bear fat. Such “pollutants could, by direct or indirect pathways, disrupt metabolic rates,” she says. So changing the climate is far from the only way humankind could affect polar bear energy and hunting dynamics.

Zeptonewton
ZEP-toe-new-ton n.
A unit of force equal to one billionth of a trillionth of a newton.

An itty-bitty object can be used to suss out teeny-weeny forces.

Scientists used an atom of the element ytterbium to sense an electromagnetic force smaller than 100 zeptonewtons, researchers report online March 23 in Science Advances. That’s less than 0.0000000000000000001 newtons — with, count ‘em, 18 zeroes after the decimal. At about the same strength as the gravitational pull between a person in Dallas and another in Washington, D.C., that’s downright feeble.
After removing one of the atom’s electrons, researchers trapped the atom using electric fields and cooled it to less than a thousandth of a degree above absolute zero (–273.15° Celsius) by hitting it with laser light. That light, counterintuitively, can cause an atom to chill out. The laser also makes the atom glow, and scientists focused that light into an image with a miniature Fresnel lens, a segmented lens like those used to focus lighthouse beams.

Monitoring the motion of the atom’s image allowed the researchers to study how the atom responded to electric fields, and to measure the minuscule force caused by particles of light scattering off the atom, a measly 95 zeptonewtons.

“Pop” goes the knuckle — but why?

Scientists disagree over why cracking your knuckles makes noise. Now, a new mathematical explanation suggests the sound results from the partial collapse of tiny gas bubbles in the joints’ fluid.

Most explanations of knuckle noise involve bubbles, which form under the low pressures induced by finger manipulations that separate the joint. While some studies pinpoint a bubble’s implosion as the sound’s source, a paper in 2015 showed that the bubbles don’t fully implode. Instead, they persist in the joints up to 20 minutes after cracking, suggesting it’s not the bubble’s collapse that creates noise, but its formation (SN: 5/16/15, p. 16).
But it wasn’t clear how a bubble’s debut could make sounds that are audible across a room. So two engineers from Stanford University and École Polytechnique in Palaiseau, France, took another crack at solving the mystery.

The sound may come from bubbles that collapse only partway, the two researchers report March 29 in Scientific Reports. A mathematical simulation of a partial bubble collapse explained both the dominant frequency of the sound and its volume. That finding would also explain why bubbles have been observed sticking around in the fluid.