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The extrusion of food for human and animal consumption is a unit operation that includes mixing, shearing, and force to the materials related to the rheological properties of the materials in the extruder. The present work aims to study the rheological behavior of an extruded fish diet incorporating hydrolyzed protein flour (HPF) processed by extrusion. The measurement was carried out online with a slit die rheometer, defining the rheological models and parameters that fit the process. During the extrusion process, the raw materials used were hydrolyzed protein flour, fish meal, and cassava starch. For the results, the evaluated treatments were adjusted to the Power Law, where an increase in the shear rate decreases the viscosity of the material, corresponding to a pseudoplastic behavior. The incorporation of hydrolyzed protein flour presented a significant effect on the value of n and Klp, increasing the viscosity with the increase in the percentage of inclusion of HPF. The models obtained for the prediction of the viscosity are adjusted to the system’s changes in shear rate, temperature, and humidity. The importance of the study lies in the fact that the diet developed can be applied to feed fish, and production is currently being scaled up to pilot plants for direct use by some producer communities.

Some studies show interest in measuring heart rate variability (HRV) during post-exercise recovery. It is known that the parasympathetic system is relevant during this process, where one of the factors of this modulation is the interaction of acetylcholine and cholinesterases (ChE). However, the behavior of ChE and its relationship during recovery is little known; therefore, the objective of this study was to analyze the behavior of ChE and its relationship with recovery evaluated in HRV indicators in volleyball players. An exercise protocol with long-term and intermittent high-intensity phases was applied in nine volleyball players. HRV measurements were made, and blood samples were drawn to evaluate the ChE before exercise and after 24 and 48 h post-exercise. The results show a modification of the variables after exercises with respect to the baseline values (ChE: 1818.4 ± 588.75 to 2218.78 ± 1101.58; RMSSD: 42.64 ± 12.86 to 17.72 ± 12.55 (p < 0.05); SS: 8.76 ± 1.93 to 21.93 ± 10.05 (p < 0.01); S/PS Ratio: 0.32 ± 0.14 to 3.26 ± 3.28 (p < 0.01)), as well as recovery after 24 and 48 h with respect to postexercise (ChE: 1608.81 ± 546.88 (p < 0.05) and 1454.54 ± 580.45 (p < 0.01); RMSSD: 43.83 ± 24.50 and 46.18 ± 33.22 (p < 0.01); SS; 10.93 ± 5.16 and 11.86 ± 4.32 (p < 0.01); S/PS Ratio: 0.46 ± 0.32 and 0.50 ± 0.28 (p < 0.01)). ChE correlations (p < 0.001) were found with moderate (SS: r = 0.465) and large (RMSSD: r = −0.654; S/PS Ratio: r = 0.666) HRV indexes. In conclusion, ChE modifications are related to changes in HRV showing a very similar behavior in the case of the study subjects.