Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans

The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 x 30 s). No changes were observed in a nonexercising control group (n = 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n = 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (-9.9%; P = 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in Hmax:Mmax (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (-18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability

Novel mechanisms of range of motion improvement in response to plantar flexor stretch training in men

The process of neuromuscular adaptation in response to muscle stretch training has not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity and the excitability of the motor neurone pool were examined during plantar flexor stretches after 3 wk of twice-daily stretch training (4 × 30-s straight-knee calf muscle stretches; 41.0 ± 1.2 sessions). No changes were observed in a control group (N=9), however stretch training elicited a 19.9% increase in dorsiflexion range (ROM) and 28% increase in passive joint moment at volitional stretch termination (N=12). Only a trend toward a decrease in passive moment during stretch (-9.9%, p=0.15) was observed and no changes in maximum EMG amplitude, EMG amplitude at stretch termination or joint angle at EMG onset were detected during a maximal stretch. Decreases in Hmax:Mmax elicited by tibial nerve stimulation were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed (i.e. with the muscle on stretch). There was an increase in muscle (12.2%) and fascicle (22.6%) strain and a decrease in muscle stiffness (-18%) during stretch to a target joint angle, and an increase in muscle length at stretch termination (13%) without a change in fascicle rotation, tendon elongation or tendon stiffness after the training. A lack of change in peak active joint moment and RFD at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. These results indicate that improvements in ROM were underpinned by increases in the maximum tolerated passive joint moment (‘stretch tolerance’) and muscle/fascicle elongation rather than by changes in volitional muscle activation or motor neurone pool excitability. Changes in the muscles’ passive elastic properties are not likely to be explained by changes within the series elastic component

Novel mechanisms of range of motion improvement in response to plantar flexor stretch training in men

The process of neuromuscular adaptation in response to muscle stretch training has not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity and the excitability of the motor neurone pool were examined during plantar flexor stretches after 3 wk of twice-daily stretch training (4 × 30-s straight-knee calf muscle stretches; 41.0 ± 1.2 sessions). No changes were observed in a control group (N=9), however stretch training elicited a 19.9% increase in dorsiflexion range (ROM) and 28% increase in passive joint moment at volitional stretch termination (N=12). Only a trend toward a decrease in passive moment during stretch (-9.9%, p=0.15) was observed and no changes in maximum EMG amplitude, EMG amplitude at stretch termination or joint angle at EMG onset were detected during a maximal stretch. Decreases in Hmax:Mmax elicited by tibial nerve stimulation were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed (i.e. with the muscle on stretch). There was an increase in muscle (12.2%) and fascicle (22.6%) strain and a decrease in muscle stiffness (-18%) during stretch to a target joint angle, and an increase in muscle length at stretch termination (13%) without a change in fascicle rotation, tendon elongation or tendon stiffness after the training. A lack of change in peak active joint moment and RFD at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. These results indicate that improvements in ROM were underpinned by increases in the maximum tolerated passive joint moment (‘stretch tolerance’) and muscle/fascicle elongation rather than by changes in volitional muscle activation or motor neurone pool excitability. Changes in the muscles’ passive elastic properties are not likely to be explained by changes within the series elastic component

Comparative analyses of the complete genome sequences of Pierce's disease and citrus variegated chlorosis strains of Xylella fastidiosa

Xylella fastidiosa is a xylem-dwelling, insect-transmitted, gamma-proteobacterium that causes diseases in many plants, including grapevine, citrus, periwinkle, almond, oleander, and coffee. X. fastidiosa has an unusually broad host range, has an extensive geographical distribution throughout the American continent, and induces diverse disease phenotypes. Previous molecular analyses indicated three distinct groups of X.fastidiosa isolates that were expected to be genetically divergent. Here we report the genome sequence of X. fastidiosa (Temecula strain), isolated from a naturally infected grapevine with Pierce's disease (PD) in a wine-grape-growing region of California. Comparative analyses with a previously sequenced X.fastidiosa strain responsible for citrus variegated chlorosis (CVC) revealed that 98% of the PD X.fastidiosa Temecula genes are shared with the CVC X. fastidiosa strain 9a5c genes. Furthermore, the average amino acid identity of the open reading frames in the strains is 95.7%. Genomic differences are limited to phage-associated chromosomal rearrangements and deletions that also account for the strain-specific genes present in each genome. Genomic islands, one in each genome, were identified, and their presence in other X.fastidiosa strains was analyzed. We conclude that these two organisms have identical metabolic functions and are likely to use a common set of genes in plant colonization and pathogenesis, permitting convergence of functional genomic strategies.18531018102