Sex efficiency through exercises : special physical culture for women / by Th. H. van de Velde ; [photos, by E. Steinemann].
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The image contains the following text:
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FILM 3.
VERTICAL
PELVIC ROTA-
T I O N ON
HANDS AND
KNEES. " The
M a c h i n e "
Exercise (Third
Phase).
Arch the lumbar
vertebra?, draw
the abdominal
muscles tense
and the pelvis
backwards.