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Resistance training has been examined as a possible way to relieve covid-19 symptoms<\/p>\n
Bailey-Cooper Photography\/Alamy<\/p>\n<\/p>\n
In the hunt for ways to alleviate long covid<\/a> \u2013 a relatively new condition with no cure, experienced by millions of people worldwide<\/a> after contracting covid-19 \u2013 exercise<\/a> has been a bright spot. It\u2019s drug-free, it costs nothing and a handful of studies have suggested it boosts long covid recovery. But concern is growing that these studies aren\u2019t robust enough to support exercise as a treatment approach, reigniting a decade-long controversy over the use of exercise in addressing other conditions, such as chronic fatigue syndrome.<\/p>\n \u201cI think there can be no excuse for doing further trials on exercise that don\u2019t make it explicitly clear that if it works, it only works for a subgroup of people and they need to be really carefully defined, and that any results that are presented should not generalise across the entire long covid population,\u201d says Caroline Dalton<\/a> at Sheffield Hallam University, UK.<\/p>\n One of the highest-profile studies of exercise in long covid was conducted by Colin Berry<\/a> at the University of Glasgow, UK, and his colleagues. When long covid began to emerge as a post-covid condition in 2020, Berry knew that developing a drug-based treatment for it would take a long time, so he wanted to see if a lifestyle intervention like exercise could help. \u201cIt was an open hypothesis,\u201d he says.<\/p>\n So, from 2021 to 2024, Berry and his team asked people with long covid to take part in a three-month resistance training programme, adjusted to their abilities. They found that those who completed the programme could then walk an additional 83 metres on a timed beep test<\/a>, compared to what they managed at the beginning of the study, versus an extra 47 metres in the control group. The researchers wondered if resistance training rebuilds muscle strength that may have been damaged by covid-19, and concluded in their paper that the intervention may be a \u201cgeneralizable therapy\u201d for long covid\u2019s physical symptoms, such as fatigue, weakness and impaired mobility.<\/p>\n The study quickly garnered press coverage and was widely discussed on social media. But many scientists have pointed out issues with this trial. Firstly, the difference between the distances walked by the control and exercising groups fell 10 metres short of the minimum threshold for clinical significance chosen by the team at the start of the experiment<\/a>. \u201cIf you don\u2019t achieve the level that\u2019s minimally clinically important, you don\u2019t go around claiming success,\u201d says David Tuller<\/a> at the University of California, Berkley. In response, Berry says it\u2019s not for us to say whether an individual would benefit from this improved mobility. \u201cI think that\u2019s open to interpretation.\u201d<\/p>\n Secondly, the trial was made up of a diverse group of participants<\/a>: some had been hospitalised with covid-19 and were still recovering from their hospital stints, while others had had much milder infections. \u201cWhat you end up with is a mean of the group, and the mean may indicate some equivocal effect,\u201d says Todd Davenport<\/a> at the University of the Pacific in Stockton, California.<\/p>\n Post-exertional malaise<\/p>\n Perhaps most importantly, the study was patchy in its assessment of one of the most debilitating aspects of long covid: post-exertional malaise. This is a worsening of symptoms, such as extreme fatigue, after exertion that isn\u2019t proportional to the amount of activity that was done. \u201cPost-exertional malaise is the most unifying and profound and debilitating aspect [of long covid],\u201d says Danny Altmann<\/a> at Imperial College London. \u201cIt\u2019s incredibly non-trivial.\u201d<\/p>\n However, post-exertional malaise was only assessed at the end of Berry\u2019s study, when it was seen at similar levels in both the control and exercise groups. Because it wasn\u2019t assessed at the start, it is unclear what effect, if any, the programme had on post-exertional malaise, but there are concerning signs.<\/p>\n The team found that 67 per cent of those who did the exercise programme said they wouldn\u2019t recover within an hour or two of seeing friends or doing activities at the three-month follow-up, compared with 49 per cent in the control group. \u201cSo, in a sense, the intervention group is actually doing kind of worse,\u201d says Leonard Jason<\/a> at DePaul University in Chicago, Illinois, who developed the tool the team used to assess post-exertional malaise.<\/p>\n There have been other hints that exercise might be actively harmful. One 2024 study<\/a> found that exercise can cause severe muscle damage in people with long-covid-related post-exertional malaise and may negatively affect their mitochondria, which provide cells with energy.<\/p>\n But the study by Berry and his colleagues is far from alone in suggesting that exercise is beneficial for long covid. It was shortly followed by a review of 33 randomised-controlled trials<\/a>, which concluded that exercise can \u201csignificantly improve quality of life\u201d for people with long covid. Yet the review made no mention of post-exertional malaise, which is thought to affect more than 80 per cent of people with the condition<\/a>.<\/p>\n \u201cThe thing that has messed up my life is the post-exertional malaise,\u201d says Margaret O\u2019Hara<\/a> at the charity Long Covid Support, who has long covid. \u201cSo any study which isn\u2019t addressing that is just tinkering around the edges.\u201d<\/p>\n Similarities with chronic fatigue syndrome<\/p>\n This situation is reminiscent of chronic fatigue syndrome<\/a>, also called myalgic encephalomyelitis (ME\/CFS), which may be caused by an infection and commonly involves post-exertional malaise. In 2011, The Lancet published the PACE trial<\/a>, which concluded that graded exercise therapy \u2013 incrementally increasing the duration and intensity of activity from an achievable baseline \u2013 moderately improved fatigue and the ability to perform daily tasks in people with ME\/CFS.<\/p>\n But that trial has been plagued by criticism ever since. In a letter to The Lancet in 2011, Bart Stouten<\/a>, an independent statistician, writing with health psychologist Ellen Goudsmit and the then-chairman of the ME Association Neil Riley, pointed out that the researchers behind the trial changed their definition of improvement from its starting protocol to the final paper<\/a>. Five years later, Tom Kindlon<\/a> at the Irish ME\/CFS Association and his colleagues reanalysed the data according to thresholds specified in the starting protocol and concluded that this change to the definition increased the rate of recovery<\/a> among those doing the exercise intervention four-fold. \u201cWe highlighted that there was minimal or no changes in objective measures, and there was no change in long-term improvement,\u201d says Kindlon.<\/p>\n What\u2019s more, Kindlon, Tuller and their colleagues reported in 2018 that serious adverse events, such as hospitalisation, were twice as high in the graded exercise therapy group<\/a> as the control one, based on the procedures set out in the PACE trial protocol and data obtained via a freedom of information request. \u201cWhat we learned from trials of exercise studies in ME is that it\u2019s not a benign intervention,\u201d says Dalton.<\/p>\n When contacted for this article, Peter White \u2013 formerly at Queen Mary University of London and one of the lead researchers of the PACE trial, told New Scientist: \u201cAll these criticisms are old news, having been made repeatedly over the 15 years since the trial results were published. This is in spite of the fact that we have addressed these criticisms many times.\u201d<\/p>\n However, there is now evidence that exercise causes sustained immune, metabolic and neuromuscular degeneration<\/a> in people with ME\/CFS-related post-exertional malaise. The UK\u2019s National Institute for Health and Care Excellence no longer recommends graded exercise therapy for ME\/CFS and says people should manage their energy based on their limits<\/a>, known as pacing.<\/p>\n A similar approach might now be needed for people with long covid. Davenport and his colleagues have found that people with ME\/CFS and long covid experience a similar failure to recover after exertion<\/a>. \u201cThese data suggest we should be as cautious with exercise in long covid as we have come to be in ME\/CFS,\u201d says Davenport. \u201cI don\u2019t know how often we need to continue to put our finger on that light socket.\u201d<\/p>\n Untangling the risks and benefits for individual cases<\/p>\n NICE doesn\u2019t recommend graded exercise therapy for long covid<\/a>, but says other exercise interventions<\/a> should be investigated. \u201c\u2018Long covid\u2019 is an umbrella term,\u201d says Dalton. \u201cThe question is: who does exercise work for, or does it work for anybody?\u201d<\/p>\n For example, the safety and effectiveness of exercise may depend on the cause of someone\u2019s long covid<\/a> \u2013 for some, it may be brought on by the underlying SARS-CoV-2 virus persisting in their body; for others, it could be the result of their immune system misfiring, their mitochondria becoming dysfunctional or adverse changes to their microbiome. \u201cIn order to have any effective studies, they really have to be subtyped by symptoms or subtype the population,\u201d says Tuller.<\/p>\n