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Discussion: Masks and exercise

in: Orienteering; General

Nov 19, 2020 6:22 PM # 
Hammer:
Good article in the NYT on masks and exercise

https://www.nytimes.com/2020/11/18/well/move/mask-...
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Nov 19, 2020 7:47 PM # 
Vector:
Correction: Bad, hysterical, screwed up article. Pass along
Nov 19, 2020 8:34 PM # 
BorisGr:
What's hysterical about it? It summarizes the results of some research studies and does not advocate anything.
Nov 19, 2020 10:28 PM # 
barb:
The photo shows a fleece mask, which has been shown in an unreproduced study to be worse than no mask. Other than that, it's nice to hear wearing a mask does not significantly affect athletic performance.

The reference that I've been most interested in lately is this article about aerosols from Time magazine. I also like this related article that Cristina brought to my attention.

Given the data - combination of how quickly aerosols are dispersed and how unlikely it is to become infected by highly diluted airborne virus - I'm feeling pretty safe interacting with other masked people outdoors.

I realize I'm digressing a bit.
Nov 20, 2020 1:46 AM # 
Mr Wonderful:
article: "invited 16 healthy, active adult men to come into the lab"

Abstract: "Sixteen male volunteers (mean age and BMI of 34 ± 4 years and 28.72 ± 3.78 kg/m2, respectively)"

Point to Vector
Nov 20, 2020 3:18 AM # 
tRicky:
That's a big focus group.
Nov 20, 2020 5:44 PM # 
commonsense:
LARGEST RANDOMIZED CONTROL TRIAL ON MASKS: MEDICAL MASKS NOT EFFECTIVE AGAINST INFECTION

After this Danish study on masks, conducted during Covid-19, was conspicuously refused by multiple medical journals, it was finally published today by the Annals of Internal Medicine*.
Why are randomized control trial (RCT) studies on the efficacy of masks considered the gold standard of mask studies?
Because unlike other studies, like simulation models of droplets and aerosols being projected through different types of masks to analyze the efficacy of masks, RCTs compare different groups of human participants, e.g., unmasked vs. masked or medical masks vs cloth masks, by using verified outcomes, that is, did participants become infected or not.
This study confirms decades' worth of other RCTs that came to the same conclusion on masks, like a 2015 BMJ study: A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.
*Annals of Internal Medicine is an academic medical journal published by the American College of Physicians. It is one of the most widely cited and influential specialty medical journals in the world.

Study: https://www.acpjournals.org/doi/10.7326/M20-6817

Tweet: https://twitter.com/JamesTodaroMD/status/132908499...

BMJ Study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC44209...

Article summarizing: https://dnyuz.com/2020/10/22/horowitz-danish-newsp...
Nov 20, 2020 5:52 PM # 
Gswede:
So, it looks like someone just created this anonymous account today to post this about how masks are not effective, despite all the research cited by the CDC.

Thanks but no thanks.

Edit: not to mention these limitations listed in the study itself.

Limitation:
Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others.
Nov 20, 2020 5:56 PM # 
Gswede:
https://www.cdc.gov/coronavirus/2019-ncov/more/mas...
Nov 20, 2020 6:30 PM # 
BorisGr:
@commonsense: I get irritated by one-off and anonymous accounts on AP, but since your post was coherent and cited actual evidence, I followed the links and read the article.

I think the study is convincing. I am willing to believe that in Denmark, under the circumstances described, adding mask wearing to the existing precautions did not greatly reduce the risk of Covid spread.

However, applying those conclusions to the U.S., especially the communities that believe that Covid is a hoax and do not practice any precautions, is a huge stretch. The article discusses how the Danish population was already compliant with social distancing precautions at the time of the experiment, thus limiting their exposure. Additionally, according to the article, "46% of participants wore the mask as recommended" which casts the entire outcome of the study in doubt.

In other words, I think we can use this study to say that, given societal compliance with other precautionary measures, such as strict lockdowns and social distancing, it is possible that mask wearing does not add a whole lot. However, those are not the conditions we see in many places here in the U.S., at the very least. Applying the results of this study as general policy guidance to a population that does not currently observe a whole lot of precautions would be foolish, to say the least.
Nov 20, 2020 6:39 PM # 
jjcote:
To put it in perspective along the lines of what Boris is saying, I rarely wear a mask. Very rarely. I'd be surprised if it were an hour a week. And increasing that would not have any significant effect on my chance of acquiring or transmitting disease. Because I rarely leave my house, and when I do, there's almost never anybody within view (running in the woods at night, etc.). With the lone exception of my frequent proximity to Nancy, but all of the above applies to her as well. (I do venture out to the supermarket, but I do it just before they close, when the place is practically deserted. That's when I wear the mask.)

Does my situation apply to people in general? Definitely not.
Nov 20, 2020 7:04 PM # 
Mr Wonderful:
From your link, assuming we are still on the topic of during exercise

Data regarding the “real-world” effectiveness of community masking are limited to observational and epidemiological studies.

#1 - prolonged exposure (15 minutes)
#2 - prolonged exposure (most of the day)
#3 - exposure time not as easily inferable here, locations were nightclub, 23%, work, 34%, home, 23%, other 20%, which sounds like over half at a minimum = prolonged exposure
#4 - prolonged exposure
#5 - prolonged exposure (10 hrs)

Is there anything CDC related to what would be more typical outdoor exercise and the highly transitory encounters that would entail? Trail running, sidewalk walking, cycling, etc.
Nov 20, 2020 7:06 PM # 
BorisGr:
I think we are having multiple conversations here and they are intersecting... My comment was not specific to exercise at all. At orienteering events here in Montana, we require folks to wear a mask at registration and beginner instruction, but once they are on the course, they can do whatever they want. Some still wear masks, most don't.
Nov 21, 2020 1:22 AM # 
gordhun:
"At orienteering events here in Montana," Man, I like the sound of that!. Great stuff, Boris.
Nov 21, 2020 12:00 PM # 
Bash:
Toronto infectious diseases physician Dr. Andrew Morris had this to say about the Danish study:

Take-home messages from me on this one:

- Ignore studies that aren't designed to answer your question (masking is pretty low on the hierarchy of controls for infection, and so effect sizes are usually small, and require many people and time to show benefit.)

- Ignore studies that don't have ethics approval where they actively affect the risk of disease in one group—it is usually a red flag for a poorly designed trial. [He’s referring to the fact that a group of subjects in the experiment were told not to wear masks when they went out, contrary to public health recommendations. You can guess why most studies are simulations!]

- The study is too small to say if that 0.3% difference means anything. But if we were talking 10 million people wearing a mask and 10 million not, with these numbers, we are talking about an extra 30K infections after 30 days. So do masks make a difference? I still really don't know for sure. I think so. But this paper doesn't really help me out.
Nov 21, 2020 5:04 PM # 
graeme:
Did anyone bother to read that Danish study, people just seem to copy the headline.

It shows that a smaller percentage of mask wearers contracted COVID than non-maskwearers.

So its either weak evidence in favour of mask wearing or (probably) statistically insignificant. What it isn't (and doesn't claim to be) is evidence that masks are not effective.

The weirdest thing is the way the pro-mask people are bashing the study for what it doesn't even say!
Nov 21, 2020 5:30 PM # 
Gswede:
My problem with this stuff since the beginning is that wearing masks was never intended as personal protection, but rather to keep others from catching your viruses Although the CDC is indicating now there may be evidence of some level of personal protection from mask wearing.

But some people, Commonsense included, present a misleading interpretation of these studies or parts of these studies to say that masks in general are ineffective.

The study itself even said that it had "no assessment of whether masks could decrease disease transmission from mask wearers to others." Again, keeping others from catching your germs has been the primary rationale for wearing masks since they were first recommended.

Btw, personally, I have no problem at all with others with different points of view or approaches based on substantiated facts or properly done studies. Different thoughts and open discussion are some of the things I value most about democratic societies. But I have no tolerance for people who use debunked or misleading facts and studies to make calls for action or non-action.

If Commonsense wanted to debate the merits of wearing a mask for personal protection, we could discuss that since it appears to be somewhat less clear still. But their post was far from that, in that they made misleading sweeping statements about the inefficacy of masks against infection and used language hinting at a cover-up because most medical journals rejected a faulty study.
Nov 21, 2020 7:43 PM # 
Cristina:
I think it's good that the Danish study was published, because there really aren't (any?) other controlled, randomized trials involving masking. The authors are clear both about the purpose of the study and about the limitations and, as Gswede points out, they even very clearly state that their study has nothing to say about the effectiveness of community-level mask-wearing on slowing the spread of the disease.

Bringing this back to the OP, the reason people are asked to wear masks while exercising is not so that they won't get sick but so that they don't infect others. I think most people on this site realize that wearing a mask while out orienteering serves little purpose, but certainly wearing one while on a treadmill in a gym makes a lot of sense. And maybe some people actually care about what was in the study with respect to gauging their training efforts. I don't really care, but that doesn't mean it is a 'hysterical' or 'bad'.
Nov 21, 2020 11:00 PM # 
gordhun:
The news report out of Kansas concerning counties that ordered mask wearing and those that didn't is very interesting and if real news it is very telling.
Nov 21, 2020 11:34 PM # 
MCrone:
It was interesting seeing an American colleague react to people here working in offices and labs without masks (with COVID safe measures in place). There is little evidence to suggest that wearing a mask in an office or lab area makes much sense because over time there will be aerosols everywhere anyway. According to a virologist at my university who is part of SAGE (Scientific Advisory Group for Emergencies) wearing masks outside makes no sense at all. There was also the following advice given, notice the wording, essentially we don't know whether masks are actually effective. I still wear a mask because it can't hurt, but it is not so straightforward. And visors do nothing...

"The asymptomatic and airborne transmission from an infected person might be reduced by wearing a face covering to reduce airborne droplets emitted during breathing and speaking. A typical surgical paper or cloth mask won’t block every respiratory droplet – some virus emitted in breath are already in droplets of less than 5 microns that are small enough to escape the masks and remain suspended in air until someone else breathes them in. However, a proportion of large droplets that contain virus will be caught in the mask, and since some of those would also have gone on to become aerosols after evaporation, the overall viral burden in the air will be reduced. Masks achieve around a 25 fold reduction in the medium-sized droplets emitted from the individual wearing the mask, and a 4 fold reduction in smaller droplets. Whether that is enough to make a difference to transmission is not clear because we still don’t know the infectious dose of this virus.

Normal masks won’t protect you from aerosols that have been released from other people. Visors won’t protect against aerosols either, nor will they stop virus released from the wearer entering the air and forming aerosols.

Wearing face coverings in places where distancing is not possible, such as small shared offices and lifts, might help reduce transmission and face covering in communal spaces around the College is now expected where practical."
Nov 22, 2020 1:31 AM # 
Cristina:
It's amazing that "I still wear a mask because it can't hurt" is not a more widely shared sentiment.
Nov 22, 2020 2:35 AM # 
Cristina:
Regarding, “eventually there will be aerosols everywhere anyway”, wouldn’t that depend on the ventilation of the room? (Ono, back to totally off-topic stuff)
Nov 22, 2020 5:02 AM # 
Bash:
Yup. Ventilation was hugely important in the requirements for dentists to reopen because many of their procedures generate aerosols. In addition, HEPA filters and UV air sterilization improved safety.
Nov 22, 2020 1:31 PM # 
Hammer:
A twitter thread linking to 70 studies about masks.

https://threader.app/thread/1279144399897866248
Nov 22, 2020 1:49 PM # 
Mr Wonderful:
How long did it take to read all of those studies?
Nov 22, 2020 2:51 PM # 
MCrone:
@Hammer - Most of those papers are theoretical or based on past studies. There is very little current information on exactly what is effective for SARS-CoV-2. And the Danish study was probably the first study in a real world context, rather than laboratory context.
Nov 22, 2020 10:02 PM # 
commonsense:
https://covidinfos.net/wp-content/uploads/2020/05/...

An extensive literature review by a Canadian researcher Denis Rancourt found that face masks do not provide measurable protection against colds and influenza.
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https://pubmed.ncbi.nlm.nih.gov/25903751/

Conclusions: This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.
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https://www.technocracy.news/blaylock-face-masks-p...

As for the scientific support for the use of face mask, a recent careful examination of the literature, in which 17 of the best studies were analyzed, concluded that, “ None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.” Keep in mind, no studies have been done to demonstrate that either a cloth mask or the N95 mask has any effect on transmission of the COVID-19 virus. Any recommendations, therefore, have to be based on studies of influenza virus transmission. Russell Blaylock, MD Several studies have indeed found significant problems with wearing such a mask. This can vary from headaches, to increased airway resistance, carbon dioxide accumulation, to hypoxia, all the way to serious life-threatening complications.
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https://www.nejm.org/doi/full/10.1056/NEJMp2006372...

"We know that wearing a mask outside health care facilities offers little, if any, protection from infection." "In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic."
"A mask will not protect providers caring for a patient with active Covid-19 if it’s not accompanied by meticulous hand hygiene, eye protection, gloves, and a gown. " "It is also clear that masks serve symbolic roles. Masks are not only tools, they are also talismans that may help increase health care workers’ perceived sense of safety, well-being, and trust in their hospitals. " "Although such reactions may not be strictly logical, we are all subject to fear and anxiety, especially during times of crisis. One might argue that fear and anxiety are better countered with data and education than with a marginally beneficial mask"
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https://www.cadth.ca/use-surgical-masks-operating-...

Key Messages ● No evidence was found to support the use of surgical face masks to reduce the frequency of surgical site infections. ● No evidence was found on the effectiveness of wearing surgical face masks to protect staff from infectious material in the operating room. ● Guidelines recommend the use of surgical face masks by staff in the operating room to protect both operating room staff and patients (despite the lack of evidence).
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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC44805...

However, overall there is a lack of substantial evidence to support claims that facemasks protect either patient or surgeon from infectious contamination. More rigorous contemporary research is needed to make a definitive comment on the effectiveness of surgical facemasks.
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https://onlinelibrary.wiley.com/doi/epdf/10.1111/j...

Discussion: None of the studies we reviewed established a conclusive relationship between mask ⁄ respirator use and protection against influenza infection.
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https://pubmed.ncbi.nlm.nih.gov/19216002/

Results: Thirty-two health care workers completed the study, resulting in 2464 subject days. There were 2 colds during this time period, 1 in each group. Of the 8 symptoms recorded daily, subjects in the mask group were significantly more likely to experience headache during the study period (P < .05). Subjects living with children were more likely to have high cold severity scores over the course of the study. Conclusion: Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds. A larger study is needed to definitively establish noninferiority of no mask use.
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https://onlinelibrary.wiley.com/doi/epdf/10.1111/j...

Conclusion: The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza. It suggests that N95 respirators should not be recommended for general public and non high-risk medical staff those are not in close contact with influenza patients or suspected patients.
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https://jamanetwork.com/journals/jama/fullarticle/...

Face masks should not be worn by healthy individuals to protect themselves from acquiring respiratory infection because there is no evidence to suggest that face masks worn by healthy individuals are effective in preventing people from becoming ill. Face masks should be reserved for those who need them because masks can be in short supply during periods of widespread respiratory infection. Because N95 respirators require special fit testing, they are not recommended for use by the general public.
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https://www.nejm.org/doi/10.1056/NEJMp2006372

We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic. It is also clear that masks serve symbolic roles. Masks are not only tools, they are also talismans that may help increase health care workers’ perceived sense of safety, well-being, and trust in their hospitals. Although such reactions may not be strictly logical, we are all subject to fear and anxiety, especially during times of crisis. One might argue that fear and anxiety are better countered with data and education than with a marginally beneficial mask, particularly in light of the worldwide mask shortage, but it is difficult to get clinicians to hear this message in the heat of the current crisis.
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https://www.cmaj.ca/content/188/8/567

In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection
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https://www.acpjournals.org/doi/10.7326/m20-1342

We do not know whether masks shorten the travel distance of droplets during coughing. Further study is needed to recommend whether face masks decrease transmission of virus from asymptomatic individuals or those with suspected COVID-19 who are not coughing. In conclusion, both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs of patients with COVID-19 to the environment and external mask surface.
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https://pubmed.ncbi.nlm.nih.gov/25336079/

A total of 22 tents were randomised to 'mask' (n=12) or 'control' (n=10). There were 164 pilgrims recruited; 75 in 'mask' and 89 in 'control' group. Mask use compliance was 76% in the 'mask' group and 12% in the 'control' group. Based on developing syndromic ILI, less contacts became symptomatic in the 'mask' tents compared to the 'control' tents (31% versus 53%, p= 0.04). However, laboratory results did not show any difference between the two groups.
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https://pubmed.ncbi.nlm.nih.gov/312/

This study showed that the filtering efficiency of cloth face masks were relatively lower, and washing and drying practices deteriorated the efficiency. We believe that the findings of this study will be very helpful for increasing public awareness and help governmental agencies to make proper guidelines and policies for use of face mask.
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https://www.cdc.gov/niosh/nioshtic-2/20033859.html...

CONCLUSION: None of these surgical masks exhibited adequate filter performance and facial fit characteristics to be considered respiratory protection devices.
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https://pubmed.ncbi.nlm.nih.gov/20088690/

Results: We observed significant reductions in ILI during weeks 4-6 in the mask and hand hygiene group, compared with the control group, ranging from 35% (confidence interval [CI], 9%-53%) to 51% (CI, 13%-73%), after adjusting for vaccination and other covariates. Face mask use alone showed a similar reduction in ILI compared with the control group, but adjusted estimates were not statistically significant. Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively.
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https://www.sciencedaily.com/releases/2015/04/1504...

Respiratory infection is much higher among healthcare workers wearing cloth masks compared to medical masks, research shows. Cloth masks should not be used by workers in any healthcare setting. The penetration of cloth masks by particles was almost 97% compared to medical masks with 44%.
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https://pubmed.ncbi.nlm.nih.gov/21103330/

Households were randomized either to the mask or control group for 7 days “Influenza-like illness was reported in 24/148 (16.2%) of the contacts in the intervention arm and in 25/158 (15.8%) of the contacts in the control arm.”
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https://wwwnc.cdc.gov/eid/article/26/5/19-0994_art...

Here, we review the evidence base on the effectiveness of nonpharmaceutical personal protective measures and environmental hygiene measures in nonhealthcare settings and discuss their potential inclusion in pandemic plans. Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza.
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https://pubmed.ncbi.nlm.nih.gov/22188875/

Eight of nine retrospective observational studies found that mask and/or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS). Findings, however, may not be applicable to influenza and many studies were suboptimal. None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection. Some evidence suggests that mask use is best undertaken as part of a package of personal protection especially hand hygiene.
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https://pubmed.ncbi.nlm.nih.gov/27531371/

Standard N95 mask performance was used as a control to compare the results with cloth masks, and our results suggest that cloth masks are only marginally beneficial in protecting individuals from particles <2.5 μm. Compared with cloth masks, disposable surgical masks are more effective in reducing particulate exposure.
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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC48686...

In the 1919 influenza pandemic, masks were available and were dispensed to populations, but they had no impact on the epidemic curve. A number of studies have shown the inefficacy of the surgical mask in household settings to prevent transmission of the influenza virus.
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https://pubmed.ncbi.nlm.nih.gov/19193267/

We concluded that household use of face masks is associated with low adherence and is ineffective for controlling seasonal respiratory disease.
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https://pubmed.ncbi.nlm.nih.gov/19652172/

Results: Sixty (8%) contacts in the 259 households had RT-PCR-confirmed influenza virus infection in the 7 days after intervention. Hand hygiene with or without facemasks seemed to reduce influenza transmission, but the differences compared with the control group were not significant.
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https://pubmed.ncbi.nlm.nih.gov/26952529/

Results: We identified 6 clinical studies (3 RCTs, 1 cohort study and 2 case-control studies) and 23 surrogate exposure studies. In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection.
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https://pubmed.ncbi.nlm.nih.gov/31479137/

Conclusions: Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.
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https://bmjopen.bmj.com/content/5/4/e006577#T1

The rates of CRI, ILI and laboratory-confirmed virus infections were lowest in the medical mask arm, followed by the control arm, and highest in the cloth mask arm. The control arm was ‘standard practice’, which comprised mask use in a high proportion of participants. As such (without a no-mask control), the finding of a much higher rate of infection in the cloth mask arm could be interpreted as harm caused by cloth masks, efficacy of medical masks, or most likely a combination of both.
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https://pubmed.ncbi.nlm.nih.gov/28039289/

Results: In an intention-to-treat analysis, rates of clinical respiratory illness, influenza-like illness and laboratory-confirmed viral infections were consistently lower in the mask arm compared with control, although not statistically significant. A post hoc comparison between the mask versus no-mask groups showed a protective effect against clinical respiratory illness, but not against influenza-like illness and laboratory-confirmed viral respiratory infections.
Nov 22, 2020 10:36 PM # 
EricW:
So cs, how did you get started in orienteering?
Nov 23, 2020 2:02 AM # 
tRicky:
Probably asked if there were any sports out there where social distancing wasn't an issue and you didn't have to wear a mask (so ruled out ice hockey).
Nov 23, 2020 3:52 AM # 
JanetT:
Disregarding exercise, there's this circumstantial evidence supporting use of masks indoors. I'll continue to do so. I only wear one outdoors when in close proximity to others.
Nov 23, 2020 4:17 AM # 
Mr Wonderful:
Circumstantial evidence

Greg posted it two days ago
Nov 23, 2020 6:03 AM # 
tRicky:
SARS-CoV-2 infection is transmitted predominately by respiratory droplets generated when people cough, sneeze, sing, talk, or breathe.

I guess The Masked Singer isn't going anywhere soon then.
Nov 23, 2020 6:57 AM # 
TheInvisibleLog:
Amusing that a quick PubMed search for systematic reviews on the effectiveness of masks comes up with two recent publications that offer different and more nuanced conclusions. Obviously the authors lack "common sense". Or maybe it helps that one of the authors is an Australian, a country where these issues have not been deeply politicised.
Nov 23, 2020 1:34 PM # 
Mr Wonderful:
Pubmed from July, it says wattage is lower when wearing a mask, and the tested folks (n=12, BMI avg <25) experienced "marked discomfort" when wearing masks.

https://pubmed.ncbi.nlm.nih.gov/32632523/

Why wasn't it included in the NYT article?
Nov 23, 2020 4:08 PM # 
jjcote:
If nothing else, masks serve as a reminder to stay away from people.
Nov 23, 2020 6:27 PM # 
igoup:
I looked at the first of the long list of articles that commonsense provided (MacIntyre CR, Seale H, Dung TC, et al A cluster randomised trial of cloth masks compared with medical masks in healthcare workers BMJ Open 2015;5:e006577. doi: 10.1136/bmjopen-2014-006577 ).

I can see how if one looked only at the Conclusion, didn't actually read the article, and was perhaps looking to reinforce an already established opinion, one might come away with a skewed version of the message. It certainly DOES NOT say that "... face masks do not provide measurable protection..." What it says is that if you use a poor mask, you get poor protection. While that seems rather obvious, the message was directed to those in resource poor parts of the world, where inexpensive yet poor masks are abundant.

A better message for most of us would to be more circumspect about the mask we might grab while waiting in the grocery or pharmacy checkout line. Back in the spring, quality masks were hard to come by. These days, high quality masks are obtainable. I have a bunch.
Nov 23, 2020 6:38 PM # 
div:
https://pubmed.ncbi.nlm.nih.gov/32632523/

In addition - there is inconsistency in ventilation data - it doesn't follow established pattern of previous metrics:
"... The maximum power was 269 ± 45, 263 ± 42 and 277 ± 46 W with sm, ffpm and nm, respectively; p = 0.002; the ventilation was significantly reduced with both face masks (131 ± 28 vs 114 ± 23 vs 99 ± 19 l/m; p < 0.001). ..."
Nov 24, 2020 9:55 AM # 
Kitch:
I'd love to know commonsense's views on vaccination
Nov 24, 2020 6:24 PM # 
div:
Most likely bots don't have independent views

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