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Brief (10 min) weekly exposure to low energy pulsed electromagnetic fields (PEMFs) has been shown to improve human muscle mitochondrial bioenergetics and attenuate systemic lipotoxicity following anterior cruciate ligament surgical reconstruction. Here we present data generated from 101 participants, 62% female, aged 38-91 years, recruited from the QuantumTx Demo Centre in Singapore, wherein 87% of participants (n = 88) presented with pre-existing mobility dysfunction and 13% (n = 13) were healthy volunteers. Participants were recruited if: (i) not pregnant; (ii) above 35 years of age and; (iii) without surgical implants. All participants completed mobility testing, pre-and post-PEMF intervention for 12 weeks, whereas bioelectrical impedance analysis was conducted in a subgroup of 42 and 33 participants at weeks 4 and 8, respectively.Weekly PEMF exposure was associated with significant improvements in mobility (Timed Up and Go, 5 times Sit-to-Stand, and 4m Normal Gait Speed) and body composition (increased skeletal muscle mass and reduced total and visceral fat mass), particularly in the older participants. Perception of pain was also significantly reduced. PEMF therapy may provide a manner to counteract age-associated mobility and metabolic disruptions and merits future investigation in randomized controlled trials to elucidate its clinical benefits in the frail and older adult populations.

Muscle function reflects muscular mitochondrial status, which, in turn, is an adaptive response to physical activity, representing improvements in energy production for de novo biosynthesis or metabolic efficiency. Differences in muscle performance are manifestations of the expression of distinct contractile-protein isoforms and of mitochondrial-energy substrate utilization. Powerful contractures require immediate energy production from carbohydrates outside the mitochondria that exhaust rapidly. Sustained muscle contractions require aerobic energy production from fatty acids by the mitochondria that is slower and produces less force. These two patterns of muscle force generation are broadly classified as glycolytic or oxidative, respectively, and require disparate levels of increased contractile or mitochondrial protein production, respectively, to be effectively executed. Glycolytic muscle, hence, tends towards fibre hypertrophy, whereas oxidative fibres are more disposed towards increased mitochondrial content and efficiency, rather than hypertrophy. Although developmentally predetermined muscle classes exist, a degree of functional plasticity persists across all muscles post-birth that can be modulated by exercise and generally results in an increase in the oxidative character of muscle. Oxidative muscle is most strongly correlated with organismal metabolic balance and longevity because of the propensity of oxidative muscle for fatty-acid oxidation and associated anti-inflammatory ramifications which occur at the expense of glycolytic-muscle development and hypertrophy. This muscle-class size disparity is often at odds with common expectations that muscle mass should scale positively with improved health and longevity. Brief magnetic-field activation of the muscle mitochondrial pool has been shown to recapitulate key aspects of the oxidative-muscle phenotype with similar metabolic hallmarks. This review discusses the common genetic cascades invoked by endurance exercise and magnetic-field therapy and the potential physiological differences with regards to human health and longevity. Future human studies examining the physiological consequences of magnetic-field therapy are warranted.