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Over the course of the physical activity transition, machines have largely replaced skeletal muscle as the source of work for locomotion and other forms of occupational physical activity in industrial environments. To better characterize this transition and its effect on back muscles and the spine, we tested to what extent typical occupational activities of rural subsistence farmers demand higher magnitudes and increased variability of back muscle activity and spinal loading compared to occupational activities of urban office workers in Rwanda, and whether these differences were associated with back muscle endurance, the dominant risk factor for back pain. Using electromyography, inertial measurement units, and OpenSim musculoskeletal modeling, we measured back muscle activity and spinal loading continuously while participants performed occupational activities for one hour. We measured back muscle endurance using electromyography median frequency analysis. During occupational work, subsistence farmers activate their back muscles and load their spines at 390% higher magnitudes and with 193% greater variability than office workers. Partial correlations accounting for body mass show magnitude and variability response variables are positively associated with back muscle endurance (R= 0.39–0.90 [P< 0.001–0.210] andR= 0.54–0.72 [P= 0.007–0.071], respectively). Body mass is negatively correlated with back muscle endurance (R= -0.60,P= 0.031), suggesting higher back muscle endurance may be also partly attributable to having lower body mass. Because higher back muscle endurance is a major factor that prevents back pain, these results reinforce evidence that under-activating back muscles and under-loading spines at work increases vulnerability to back pain and may be an evolutionary mismatch. As sedentary occupations become more common, there is a need to study the extent to which occupational and leisure time physical activities that increase back muscle endurance helps prevent back pain. 

Abstract Three binuclear species [LCo^III₂(μ‐Pz)₂](ClO₄)₃(1), [LNi^II₂(CH₃OH)₂Cl₂]ClO₄(2), and [LZn^II₂Cl₂]PF₆(3) supported by the deprotonated form of the ligand 2,6‐bis[bis(2‐pyridylmethyl) amino‐methyl]‐4‐methylphenol were synthesized, structurally characterized as solids and in solution, and had their electrochemical and spectroscopic behavior established. Species1–3had their water reduction ability studied aiming to interrogate the possible cooperative catalytic activity between two neighboring metal centers. Species1and2reduced H₂O to H₂effectively at an applied potential of −1.6 V_Ag/AgCl, yielding turnover numbers of 2,820 and 2,290, respectively, after 30 minutes. Species3lacked activity and was used as a negative control to eliminate the possibility of ligand‐based catalysis. Pre‐ and post‐catalytic data gave evidence of the molecular nature of the process within the timeframe of the experiments. Species1showed structural, rather than electronic cooperativity, while species2displayed no obvious cooperativity. DFT methods complemented the experimental results determining plausible mechanisms.