"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.

Though they be but little, they are fierce.

Airborne particles smaller than 50 nanometers across can intensify storms, particularly over relatively pristine regions such as the Amazon rainforest or the oceans, new research suggests. In a simulation, a plume of these tiny particles increased a storm’s intensity by as much as 50 percent.

Called ultrafine aerosols, the particles are found in everything from auto emissions to wildfire smoke to printer toner. These aerosols were thought to be too small to affect cloud formation. But the new work suggests they can play a role in the water cycle of the Amazon Basin — which, in turn, has a profound effect on the planet’s hydrologic cycle, researchers report in the Jan. 26 Science.
“I have studied aerosol interactions with storms for a decade,” says Jiwen Fan, an atmospheric scientist at the Pacific Northwest National Laboratory in Richland, Wash., who led the new study. “This is the first time I’ve seen such a huge impact” from these minute aerosols.

Larger aerosol particles greater than 100 nanometers, such as soot or black carbon, are known to help seed clouds. Water vapor in the atmosphere condenses onto these particles, called cloud condensation nuclei, and forms tiny droplets. But water vapor doesn’t condense easily around the tinier particles. For that to be possible, the air must contain even more water vapor than is usually required to form clouds, reaching a very high state of supersaturation.

Such a state is rare — larger aerosols are usually also present to form water droplets, removing that extra water from the atmosphere, Fan says. But in humid places with relatively low background air pollution levels, such as over the Amazon, supersaturation is common, she says.
From 2014 to 2015, Brazilian and U.S. research agencies collaborated on a field experiment to collect data on weather and pollution conditions in the Amazon Basin. As part of the experiment, several observation sites tracked plumes of air pollution traveling from the city of Manaus out across the rainforest. During the warm, wet season, there is little difference day to day in most meteorological conditions over the rainforest, such as temperature, humidity and wind direction, Fan says. So a passing pollution plume represents a distinct, detectable perturbation to the system.

Story continues after image
The international team examined vertical wind motion, or updrafts, and aerosol concentration data from one of these stations from March to May 2014. When a large plume of aerosols with an abundance of ultrafine particles passed by an observation station, the researchers observed a corresponding, more powerful vertical wind motion and heavier rain. Such updrafts intensify storms, helping to drive stronger circulation.

Next, the researchers conducted simulations of an actual storm that occurred on March 17, 2014, matching its temperature, wind and water vapor conditions, as well as a low level of background aerosols in the atmosphere. Then, the team introduced several pollution scenarios to interact with the storm, including no plume and a typical plume from the Manaus metropolis. The results suggested that the ultrafine aerosol particles, in particular, were not only acting as cloud condensation nuclei over the Amazon Basin, but also that the water droplets the aerosols created significantly strengthened the gathering storm.

If the conditions are right, the sheer abundance of the ultrafine particles in such a plume would rapidly create a very large number of cloud droplets. The formation of those droplets would also suddenly release a lot of latent heat — released from a substance as it changes from a vapor to a liquid — into the atmosphere. The heat would rise, creating updrafts and quickly strengthening the storm.

Aside from the Amazon, Fan notes that such pristine, humid conditions can also exist over large swaths of the oceans. One recent study in Geophysical Research Letters that she points to found a link between well-traveled shipping lanes, which would contain abundant exhaust including ultrafine aerosols, and an increase in lightning strikes. “This mechanism may have been at play there,” she says.

Atmospheric scientist Joel Thornton of the University of Washington in Seattle, who led the study on the shipping exhaust, says it’s possible that ultrafine particles play a role in that scenario. “What this paper does is raise the stakes in needing to develop a deeper, more accurate understanding of the sources and fates of atmospheric ultrafine particles,” Thornton says.

Meteorologist Johannes Quaas of the University of Leipzig in Germany, who was not involved in either study, agrees. “It’s a very interesting hypothesis.”

But the observations described in the new study don’t definitively demonstrate that ultrafine aerosols alone drive updrafts, Quaas adds. The weather conditions may appear highly consistent from day to day, but such systems are still highly chaotic. Everything from wind to temperature to how the land surface interacts with incoming solar radiation may be variable, he notes. “In reality, it’s not just the aerosols that change.”

Ultrasounds during pregnancy can be lots of fun, offering peeks at the baby-to-be. But ultrasounds aren’t just a way to get Facebook fodder. They are medical procedures that involve sound waves, technology that could, in theory, affect a growing fetus.

With that concern in mind, some researchers have wondered if the rising rates of autism diagnoses could have anything to do with the increasing number of ultrasound scans that women receive during pregnancy.

The answer is no, suggests a study published online February 12 in JAMA Pediatrics. On average, children with autism were exposed to fewer ultrasounds during pregnancy, scientists found. The results should be “very reassuring” to parents, says study coauthor Jodi Abbott, a maternal fetal medicine specialist at Boston Medical Center and Boston University School of Medicine.
To back up: Autism rates have risen sharply over the last several decades (though are possibly plateauing). Against this backdrop, researchers are searching for the causes of autism — and there are probably many. Autism is known to run in families, and scientists have found some of the particular genetic hot spots that may contribute. Other factors, such as older parents and maternal obesity, can also increase the risk of autism.

Scientists suspect that in many cases, autism is caused by many factors, all working together. Could prenatal ultrasounds, which have become more routine and more powerful, be one of those factors? These scans use sound waves that penetrate mothers’ bodies, and then collect the waves that bounce back, forming a picture of fetal tissues. During this process, the waves may be able to heat up the tissue they travel through.

Work on animals has suggested that ultrasounds can in fact interfere with fetal brain development, derailing the normal movements of cells that populate the brain. Mice exposed to 30 or more minutes of ultrasound in utero had abnormal brain development, for instance. But it’s not at all clear whether a similar thing might happen in humans, and if so, whether such effects might contribute to autism.
The new study compared ultrasound exposure among three groups: 107 children diagnosed with autism spectrum disorder, 104 children diagnosed with a developmental delay, and 209 typically developing children. On average, the children with autism were exposed to 5.9 ultrasound scans over the course of pregnancy. Children with developmental delays were exposed to 6.1 scans, and typically developing children were exposed to 6.3 scans, the researchers found. (For all groups, these numbers are way above the one to two scans per low-risk pregnancy recommended by the American College of Obstetricians and Gynecologists.)

For all three groups, the duration of the scans was similar. So was the thermal index, an indication of how much warming might have happened. “In almost every parameter we looked at, ultrasound seemed perfectly safe,” says study coauthor N. Paul Rosman, a pediatric neurologist at Boston Medical Center and Boston University School of Medicine.

One measure was different, the researchers found: During the first trimester, mothers who had children with autism had slightly deeper ultrasounds than women who had typically developing children and children with developmental delays. Ultrasound depth measures the distance from the transducer paddle that emits the waves to the spot that’s being imaged. The measure “has a lot to do with the size of the mother and the distance between her skin, where the ultrasound transducer is, and where the baby is,” Abbott says.

Lots of questions remain about whether — and how — ultrasound depth, or other aspects of the technology, might affect fetuses. “The study certainly wasn’t perfect,” Rosman says. It combed back through medical records of women instead of following women from the beginning. And it didn’t control for certain traits that may influence autism, such as smoking.

The results suggest that on their own, ultrasounds don’t cause autism spectrum disorder, says Sara Jane Webb of Seattle Children’s Research Institute and the University of Washington, who cowrote a JAMA Pediatrics companion piece. “At this time, there is no evidence that ultrasound is a primary contributor to poor developmental outcomes when delivered within medical guidelines,” she says.

While there’s more science to sort out here, the news is reassuring for women who might be worried about getting scanned. Women should follow their doctors’ guidance on ultrasounds, Rosman says. “We don’t think there’s anything in this study to recommend otherwise.”