Electromyographic activities.

<p>The root-mean-square (RMS) values of electromyographic activities of the three superficial knee extensor muscles during maximal voluntary isomeric contractions of knee extension (open bar) and hip flexion (closed bar). A: absolute RMS values (RMS_MVC), B: RMS values normalized to the peak-to-peak amplitude of the maximal compound muscle action potential of each region (RMS_MVC/AMP_Mwave), C: RMS values normalized to the RMS values of the maximal compound muscle action potential of reach region (RMS_MVC/RMS_Mwave). Results are presented as the mean ± SD (n = 12). *Significant difference (P<0.05) between the two tasks. †Significant difference (P<0.05) from distal region.</p

Electromyographic activities.

<p>The root-mean-square (RMS) values of electromyographic activities of the three superficial knee extensor muscles during maximal voluntary isomeric contractions of knee extension (open bar) and hip flexion (closed bar). A: absolute RMS values (RMS_MVC), B: RMS values normalized to the peak-to-peak amplitude of the maximal compound muscle action potential of each region (RMS_MVC/AMP_Mwave), C: RMS values normalized to the RMS values of the maximal compound muscle action potential of reach region (RMS_MVC/RMS_Mwave). Results are presented as the mean ± SD (n = 12). *Significant difference (P<0.05) between the two tasks. †Significant difference (P<0.05) from distal region.</p

Effect of knee alignment on the quadriceps femoris muscularity: Cross-sectional comparison of trained versus untrained individuals in both sexes

<div><p>Knee alignment is suggested to be a factor affecting each quadriceps femoris muscle size, and knee alignment such as Q-angle differs between men and women. Also, training can induce inhomogeneous hypertrophy among the quadriceps femoris, thereby leading to different component characteristics of the muscles. If Q-angle is a major determinant of the quadriceps femoris muscularity, it is hypothesized that the sex-related difference in the quadriceps femoris muscularity, if any, is further highlighted in trained individuals, being associated with Q-angle. We tested this hypothesis. Magnetic resonance images of the right thigh were obtained from 26 varsity rowers as trained subjects (13 for each sex) and 34 untrained individuals as controls (17 for each sex). From the images, muscle volume of each constituent of the quadriceps femoris (vastus lateralis, VL; medialis, VM; intermedius; rectus femoris) was determined. The Q-angle was measured during quiet bilateral standing with hand support as needed. Percent volume of VM to the total quadriceps femoris was greater in female rowers than male rowers and female controls, and that of VL was greater in male rowers than male controls. There were no correlations between Q-angle and percent muscle volume in any muscles regardless of rowing experience or sex. The current study revealed that well-trained rowers have sex-related quadriceps femoris muscularity but no significant correlations between percent muscle volume in any muscles and Q-angle. Our findings suggest that Q-angle is not a major determinant of the quadriceps femoris muscularity in either well-trained or untrained individuals.</p></div

Examples of T1-weighted magnetic resonance images of the mid-thigh.

<p>The outline of individual muscles of the quadriceps is indicated by white dotted lines. VM, vastus medialis; VL, vastus lateralis; VI, vastus intermedius; RF, rectus femoris.</p

Relationship between Q-angle and percent muscle volume of each muscle to the total quadriceps femoris.

<p>Relationship between Q-angle and percent muscle volume of each muscle to the total quadriceps femoris.</p

Statistical results of the difference between rowers and untrained control subjects, and between males and females.

<p>Statistical results of the difference between rowers and untrained control subjects, and between males and females.</p

The percent muscle volume of each muscle to the total quadriceps femoris.

<p>* indicates a significant difference between male and female rowers. † indicates a significant difference between rowers and control subjects within each sex. VM, vastus medialis; VL, vastus lateralis; VI, vastus intermedius; RF, rectus femoris.</p

Muscle volume of each muscle normalized to body mass.

<p>* indicates a significant difference between male and female rowers or between male and female control subjects. † indicates a significant difference between rowers and control subjects within each sex. VM, vastus medialis; VL, vastus lateralis; VI, vastus intermedius; RF, rectus femoris.</p

Pearson's correlation coefficient matrix of titin, muscle damage markers, and muscle symptoms.

<p>Pearson's correlation coefficient matrix of titin, muscle damage markers, and muscle symptoms.</p

Detection of titin fragments in urine in response to exercise-induced muscle damage

<div><p>Many studies have attempted to determine the associations between blood biomarkers and exercise-induced muscle damage. However, poor correlations between the changes in biomarker levels and the magnitude of muscle symptoms have been reported. Recent advances in proteomic tools offer a strategy for the comprehensive analysis of protein expression, which can be used to identify biomarkers. Here, we used a proteomic analysis to identify urinary proteins that appear in response to a calf-raise exercise, including repetitive eccentric muscle contractions, and found that a titin (also known as connectin) N-terminal fragment molecule appears in the urine after eccentric exercise. We measured the titin fragment in urine samples from nine individuals before and after eccentric exercise using a newly-established enzyme-linked immunosorbent assay and found that the titin fragment excretion rate increased 96 h after the exercise (5.1 to 77.6 pg/min, p <0.01). The changes in the titin fragment excretion rate were correlated strongly with blood markers of muscle damage and with muscle symptoms. These findings suggest that the urinary titin fragment is potentially a noninvasive biomarker of muscle damage.</p></div