Influence of upper limb training and analyzed muscles on estimate of physical activity during cereal grinding using saddle quern and rotary quern

Experimental grinding has been used to study the relationship between human humeral robusticity and cereal grinding in the early Holocene. However, such replication studies raise two questions regarding the robusticity of the results: whether female nonathletes used in previous research are sufficiently comparable to early agricultural females, and whether previous analysis of muscle activation of only four upper limb muscles is sufficient to capture the stress of cereal grinding on upper limb bones. We test the influence of both of these factors. Electromyographic activity of eight upper limb muscles was recorded during cereal grinding in an athletic sample of 10 female rowers and in 25 female nonathletes and analyzed using both an eight- and four-muscle model. Athletes had lower activation than nonathletes in the majority of measured muscles, but except for posterior deltoid these differences were non-significant. Furthermore, both athletes and nonathletes had lower muscle activation during saddle quern grinding than rotary quern grinding suggesting that the nonathletes can be used to model early agricultural females during saddle and rotary quern grinding. Similarly, in both eight- and four-muscle models, upper limb loading was lower during saddle quern grinding than during rotary quern grinding, suggesting that the upper limb muscles may be reduced to the previously used four-muscle model for evaluation of the upper limb loading during cereal grinding. Another implication of our measurements is to question the assumption that skeletal indicators of high involvement of the biceps brachii muscle can be interpreted as specifically indicative of saddle quern grinding.


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The experimental reconstruction of habitual tasks of past populations is often used to test   [4]. These similarities between rowers and grinding females suggest that rowers 105 might help us understand the effect of cereal grinding on human muscle activity better than 106 the previously used nonathletic females.

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In addition to the question of the appropriate modern population sample for experimental 108 testing is the issue of the choice of muscles to measure. The relationship between cereal 109 grinding and muscle activation during grinding was previously measured in four muscles with   As the first goal, we aim to compare muscle activation during grinding in athletes and 126 nonathletes using electromyography. We expect athletes to have lower muscle activation 127 during grinding than nonathletes. The second goal is to compare upper limb loading during 7 128 saddle and rotary quern grinding estimated using the eight-and four-muscle models. We  The first sample used in this study was an athletic sample consisting of 10 female rowers (age,   ground on the saddle quern using both hands in a to-and-fro movement. Saddle quern grinding 193 may also be performed using a circular movement, but the shape of the lower stone used in 194 this study suggests a to-and-fro bimanual movement [4,30]. Rotary quern grinding was 10 195 performed using the right hand in a circular motion in clockwise and anticlockwise directions.

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The same movements for saddle and rotary quern grinding were used previously by Sládek et 197 al. [4]. One cycle of saddle quern grinding was defined as one complete to-and-fro motion, 198 and one cycle of rotary quern grinding was defined as complete revolution of the upper stone.

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Grinding was performed in standardized tempo controlled by metronome, which was 175 and

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The values of maxEMG of athletes and nonathletes are shown in Table 1 Table 1 for abbreviations of muscles. The values of iEMG of athletes and nonathletes are shown in Table 2   The differences of coactivation index between athletes and nonathletes are shown in S1-S3  Our first goal was to compare muscle activation during cereal grinding between athletes and 310 nonathletes. We expected athletes to have lower muscle activation than nonathletes during 311 grinding due to lower antagonistic coactivation in athletes. While there was a trend of lower 312 activation in athletes than in nonathletes, most differences in activation were not significant.

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Similarly, coactivation was lower in athletes than nonathletes in most muscle pairs, but 314 significant difference occurred only in one muscle pair, which was not antagonistic. Our between athletes and nonathletes could be also associated with similar timing of muscle 341 activation in both samples (Fig 3). In any case, the similar levels of antagonistic coactivation 342 in athletes and nonathletes support the use of nonathletes in experimental cereal grinding. and colored areas indicate the means and ± standard deviations, respectively. See Table 1 for 347 abbreviations of muscles.

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Another possibility is that lower activation of the upper limb muscles in our athletic than  Fig 4).  We would like to thank the participants from Charles University and from the rowing teams 468 Český veslařský klub Praha, Veslařský klub Smíchov, and SK HAMR. We also wish to thank 469 the coaches and staff of the participating rowing teams. We would like to thank Iva

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Electromyography data was full wave rectified and smoothed using root mean square 587 function. See Table 1 for abbreviations of muscles.  Electromyography data was full wave rectified and smoothed using root mean square 591 function. See Table 1 for abbreviations of muscles. 592 S1