Lactic acid is made in the body. It is made mostly by muscle tissue and red blood cells. When the oxygen level in the body is normal, carbohydrate (energy source from food) breaks down into water and carbon dioxide. When the oxygen level is low, carbohydrate breaks down for energy and makes lactic acid.
During aerobic exercise, the heart and lungs supply adequate amounts of oxygen to the body for energy. Anaerobic exercise uses more oxygen than the lungs and heart can supply to the body so the energy supply is less, thus causing high lactic acid levels in the blood. Lactic acid is made by the liver and kidneys and the body is constantly trying to remove it.
Usually anaerobic exercise forces a person to slow down or stop exercising because lactic acid buildup causes moderate to severe muscle aches, stiffness and soreness.
Lactic acid levels get higher with strenuous exercise, and also other conditions such as heart impairment, liver damage, a severe infection, or shock.
Very high levels of lactic acid cause a serious, sometimes life-threatening condition called lactic acidosis. The symptoms of include rapid breathing, excessive sweating, cool and clammy skin, sweet-smelling breath, abdominal pain, nausea or vomiting, confusion, and in extreme cases coma.
Lactic acid is used regularly as serum markers of inflammation. High levels of lactic acid have been identified as strong predictors of COVID-19 disease severity. A study in Wuhan China showed severe hospitalised Covid-19 patients had high levels of Lactic acid. The study also showed that those with elevated blood lactic acid levels also had low lymphocyte levels. Lymphocytes are the white blood cells which help fight off viruses. Lactic acidosis suppresses the proliferation of lymphocytes.
Many patients with Long Covid have persisting shortness of breath - dyspnoea . It is usually investigated by resting tests such as pulmonary function tests (aka lung function tests), an echocardiogram and a CXR which for many can be non-diagnostic (within normal limits). Some will then have a Cardiopulmonary Exercise Test (CPET) organised. A CPET measures physiological parameters during exercise which can enable accurate identification of the cause of dyspnoea. What happens during a CPET is discussed in more detail in this paper "Cardiopulmonary exercise testing in the assessment of exertional dyspnoea" Datta et al
Some LC patients have had this paired with lactic acid monitoring and were found to have increased lactic acid levels during the exercise.
At the University of Bergen Dr Petterson presented research that confirmed that patients with Myalgic Encephalitis (ME) were unable to convert carbohydrate into a form which mitochondria ( the cell's power houses) can use for energy production. This results in less use of carbohydrate for energy production and an increase in use of proteins. When a ME patient is under strain (physical/mental exertion) they produce less energy and more lactate.
And you have to remember that those with ME and Long Covid that even the simplest thing like getting out of bed, cleaning your teeth, reading a book, brushing your hair and climbing the stairs put our bodies under strain. It is this exertion that leads to Post Exertional Malaise (PEM) - see previous blog.
I am sure with due course more research into Long Covid will link the ongoing breathlessness, increased lactic acid levels and PEM.
So back to the matter at hand - Exercising with Long Covid.
It is now widely accepted that exercise is very beneficial. Those with joint, musculoskeletal and mental health issues are actively encouraged to exercise and there are known benefits.
Long Covid is one of the conditions where exercise can make you worse. We only have to think of the many years poor ME sufferers have been forced to do Graduated Exercise at great detriment to themselves.
There have been so many new stories of young keen athletes who after their initial Covid-19 infection tried to heal themselves by restarting a vigorous exercise regime only to find themselves severely relapsing with a reoccurrence of all there Covid-19 symptoms and confined to bed, unable to walk. I am also very concerned to hear of new trials emerging trying to get those with Long Covid to engage in graduated exercise. Its as if the lessons of ME have not been learnt!! Example https://runningthrough.org/?fbclid=IwAR3xh4-u7qUp6TW_fjFZn-9Qxn_Nd0YfyJx2G_uaH_L_qJE0V2KWxzQuq5Q
The lead physiotherapist at CoverScan recommends the following advice:
Return to normal daily activity FIRST - getting out of bed, getting dressed, cleaning your teeth, helping cook a meal. If you are unable to do these then you are not ready to exercise.
Have a cautious, slow return to activity - exercise needs to be at a low level with an effort level of 3 to 4 out of 10. A gentle walk on the flat is good at around 50 % of what you think you can manage - "I think I can walk 10 minutes" = a 5 minute walk. If this invokes PEM reduce to 70 %. These can over time be built up to a gentle swim or cycle but ALWAYS cautious to not push too hard and invoke PEM.
Monitor your resting heart rate - your baseline heart rate may have increased after a Covid-19, others have lowered. Get to know your resting heart rate by lying down flat, comfortably for 10 minutes. If whilst doing an activity it raises exponentially then reduce that activity as above. (Difficult for going up the stairs I know! Can't really stop doing that?)
When I was able to do the above tasks without a relapse I calculated my Anaerobic Threshold (AT) and only exerted myself within this parameter. The AT is 50 -60% of your maximum heart rate.
For a women its 206 - 88% of your age - for men use 90%
So for me its [ 206 - (48 x 0.88) ] x 50%. = 82
and [ 206 - (48 x 0.88) ] x 60 % = 98
So I know if I push myself too hard on my recumbent bike and my heart rate goes above 98 bpm I am pushing the limits of my energy envelope and my body and mind will pay later so I slow down and stop.
Of course for those with POTS it is hard to keep an erratic heart rate under control - it's not a perfect science more a guide but you might find switching your walk to recumbent cycling or a gentle swim a bit more forgiving.
The take home points are CAREFULLY, PATIENTLY and INDIVIDUALLY plan your increase in activity.
Further information will be available from physiotherapists at Long Covid Clinics in the UK and also the British Association of Sport and Exercise Sciences https://www.bases.org.uk and the ME Association https://meassociation.org.uk/about-what-is-mecfs/management/ .