Fig. 5.

Loading of the tibia–metatarsus joint of the hunting spider Cupiennius salei a as reconstructed from the measurements of the ground reaction forces during slow locomotion (10 m/s; midstance; Fig. 4) upside up (upright) at level ground and b upside down with forces as assumed (fictive) to be necessary to generate compression at the dorsal tibia (>< ; Fig. 5). Forces: black—resultant vector of the ground reaction force (GRF); green: proximad component of GRF (in b negative, i.e., distad); magenta—dorsad component of GRF; red—muscle force (Fl. met. longus and Fl. met. acc.); yellow—resulting joint force. Dashed: vectors defining the resultant joint load (inertia and weight of the distal segment neglected); dashed black: resultant ground reaction force; dashed red: muscle force. Strain calculated based on ground reaction force and geometry: − 23.4 µε. For details see "Appendix 5", Eqs. (5, 6). b Calculated strain: − 22 µε