By Dr Dan Plews
The act of grounding has undoubtedly become popular recently, at least in the circles I move in. But what is it? Grounding, also called earthing, involves doing activities that “ground” or electrically reconnect you to the Earth. This depends on earthing science and grounding physics to explain how electrical charges from the Earth can positively affect your body.
The Earth’s surface has free electrons (and speculatively); contact with the Earth’s surface may allow electron migration into the body. The electrons can act as antioxidants and neutralise reactive oxygen species (ROS). As I have discussed in the past, ROS accumulates in muscle during high-intensity exercise. ROS appears to have a fatiguing effect on muscle, possibly through effects on calcium handling processes that are critical in muscle contraction (3). Antioxidants help ‘mop up ROS in muscle; so, if we have more antioxidants, we are more able to manage the ROS that accumulates during high-intensity exercise. Having a significant antioxidant capacity may therefore help accelerate recovery. However, the implications of neutralising ROS in recovery for training adaptations is still debated (1). My interest has undoubtedly been spiked as my athlete Jan Van Berkel (Pro Ironman Triathlete) purchased a grounding mat to sleep on and has had very positive things to say about it. Specifically, he mentioned less muscle soreness after big running days. My wife also bought me a grounding mat for my office to go under my feet whilst I work for my birthday (nothing to report here yet!). Grounding can be achieved through direct contact with the ground (walking around outside in bare feet) or by sleeping/standing on specific grounding sheets or mats plugged into a grounded wall socket. But with all that said, what does the research say? With my newfound curiosity, I took a little dive into some of the research in the area with specific reference to athlete recovery and muscle soreness.
In 2019, Erich Müller and Thomas Stöggl led a study assessing the effectiveness of a “grounded sleeping” recovery intervention in the period after a bout of muscle-damaging downhill running (2). The research was published in the journal Frontiers in Physiology. The authors led an Austrian team affiliated with the University of Salzburg and the Austrian Olympic Training Center.
The effect of grounding on human physiology has seen little empirical research. Therefore, Müller, Stöggl, and the team conducted their study to see if it affected recovery from downhill running. Where muscle damage and ROS accumulation would be expected to be substantial.
To that end, the researchers recruited 22 healthy undergraduate students. They randomly allocated them to either a grounded sleeping group or a sham-treatment control group. The study was impressively blinded, such that the participants, researchers, and data analysts did not know who was in what group.
As indicated, the participants first performed a 20-min bout of downhill running at 12 km.h-1 or 5:00 min per km pace. Whilst that doesn’t sound like much, the participants were running down an impressive -25% gradient. This means that for every four metres they ran forward, they descended by a metre. That’s a hefty gradient and one that would be expected to generate a fair bit of muscle damage!
Participants subsequently slept with a grounded sleeping sheet for 10 days. In the control/sham-treatment group, the plugs used were manipulated and masked, such that they did not deliver grounding to the sheet. As noted by the authors, there was no direct connection to electricity, so this means of grounding was perfectly safe. A testing battery was performed before downhill running and then at various points throughout the 10-day recovery period. The testing battery included jump performance as an assessment of lower body power, maximum voluntary. Isometric contractions as an assessment of force production capacity. And blood draws for analysis of a range of muscle damage-associated variables and perceptions of muscle soreness.
Interestingly, and perhaps surprisingly, the authors reported a coordinated set of responses that suggest the grounded sleeping intervention accelerated the recovery process. The participants in the grounded sleeping group exhibited a lesser reduction in power and force production capacity and, notably, lower concentrations of creatine kinase in the blood during the recovery period. Creatine kinase is a commonly assessed marker of muscle damage. In addition, other markers of inflammation were reduced in the recovery period in the grounded sleeping group.
Aside from grounding, another striking observation reported in this study was that none of the measured variables returned to their baselines values in ten days. That proves just how demanding the short 20-min downhill running intervention was for the participants!
Perhaps these results suggest that when recovery from intense, muscle-damaging exercise needs to be expedited. For example, if there is a short time between two races, grounded sleeping maybe an intervention worth considering. Remember, as discussed in previous blogs, muscle damage takes a long time to recover from. More research to come in this space, I’m sure! In the meantime, this is certainly something I’m pretty interested in, as I sit here writing this blog with my feet directly on a grounding mat :)! Every morning, I have started going outside and standing on the grass for 3 minutes – bare feet and skin exposed to as much sun as possible. I do feel like it gives me a little energy boost to get the day going. As they say, “do no harm”, so why not give it a try yourself!
1. Merry TL, Ristow M. Do antioxidant supplements interfere with skeletal muscle adaptation to exercise training? J Physiol 594: 5135–5147, 2016. doi: 10.1113/JP270654.
2. Müller E, Pröller P, Ferreira-Briza F, Aglas L, Stöggl T. Effectiveness of grounded sleeping on recovery after intensive eccentric muscle loading. Front Physiol 10: 35, 2019. doi: 10.3389/fphys.2019.00035.
3. Reid MB. Free radicals and muscle fatigue: Of ROS, canaries, and the IOC. Free Radic Biol Med 44: 169–179, 2008.
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