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Post-stroke patients exhibit distinct muscle activation electromyography (EMG) features in sit-to-stand (STS) due to motor deficiency. Muscle activation amplitude, related to muscle tension and muscle synergy activation levels, is one of the defining EMG features that reflects post-stroke motor functioning and motor impairment. Although some qualitative findings are available, it is not clear if and how muscle activation amplitude-related biomechanical attributes may quantitatively reflect during subacute stroke rehabilitation. To better enable a longitudinal investigation into a patient's muscle activation changes during rehabilitation or an inter-subject comparison, EMG normalization is usually applied. However, current normalization methods using maximum voluntary contraction (MVC) or within-task peak/mean EMG may not be feasible when MVC cannot be obtained from stroke survivors due to motor paralysis and the subject of comparison is EMG amplitude. Here, focusing on the paretic side, we first propose a novel, joint torque-based normalization method that incorporates musculoskeletal modeling, forward dynamics simulation, and mathematical optimization. Next, upon method validation, we apply it to quantify changes in muscle tension and muscle synergy activation levels in STS motor control units for patients in subacute stroke rehabilitation. The novel method was validated against MVC-normalized EMG data from eight healthy participants, and it retained muscle activation amplitude differences for inter- and intra-subject comparisons. The proposed joint torque-based method was also compared with the common static optimization based on squared muscle activation and showed higher simulation accuracy overall. Serial STS measurements were conducted with four post-stroke patients during their subacute rehabilitation stay (137 ± 22 days) in the hospital. Quantitative results of patients suggest that maximum muscle tension and activation level of muscle synergy temporal patterns may reflect the effectiveness of subacute stroke rehabilitation. A quality comparison between muscle synergies computed with the conventional within-task peak/mean EMG normalization and our proposed method showed that the conventional was prone to activation amplitude overestimation and underestimation. The contributed method and findings help recapitulate and understand the post-stroke motor recovery process, which may facilitate developing more effective rehabilitation strategies for future stroke survivors.

In present research, differences in the number of seeds per berry (NSB), berry fresh weight (BW), days to ripening from flowering (DRF), and the duration of a slow growth phase (DS II) among pollen sources were investigated in highbush blueberry (Vaccinium corymbosum). NSB, as well as BW and DRF, were significantly different among the pollen sources. Analysis of covariance (ANCOVA) with NSB as the covariate showed significant interaction between the NSB and pollen sources on BW and DRF when self-pollination was included. However, ANCOVA without self-pollination showed no significant effect of the pollen source on BW and DRF. On the other hand, DS II was negatively correlated with NSB, and no significant interaction between NSB and pollen sources was found, even though self-pollination was included. Although the relationship between NSB and DS II appeared not to be statistically influenced by the different pollen sources, there seemed to be some difference between self- and cross-pollination. DS II shortened as the NSB increased, which may have led to a decrease in DRF.