Relation Between Scouting Combine and Game Performance Among Defensive National Players in the Canadian Football League.

ABSTRACT: Pincivero, DM and Vandeweerd, J. Relation between scouting combine and game performance among defensive national players in the Canadian Football League. J Strength Cond Res 35(12S): S5-S10, 2021-The objective of this study was to examine the relation between fitness testing and draft order on professional performance of defensive national players in the Canadian Football League. A retrospective analysis (2006-2019) was completed for all subjects at the National Scouting Combine (NSC) and included height, body mass, 40 yard (38 m) dash, bench press, vertical jump, broad jump, and the shuttle run. A compiled variable for all NSC results was derived by calculating averaged Z-scores (Zavg). Multiple regression analyses revealed that the draft order was significantly predicted by the 40 yard dash and Zavg for the defensive linemen, Zavg for the linebackers, and the broad jump for the defensive backs. The broad jump and the 40 yard dash were significant predictors of total and special teams tackles per game for the defensive linemen. The draft order significantly predicted games played and defensive tackles per game, whereas the broad jump predicted total tackles per game for the linebackers. None of the NSC results or draft order significantly predicted defensive back league performance. The findings suggest that NSC testing can provide low-to-moderate levels of predictability for future performance in national-categorized defensive linemen and linebackers.

Non-Linear Relation Between Upper Arm Volume and Maximal Effort Force Production.

The objective of the present study was to examine the relationship between maximal effort force production and anthropometric measures of upper arm volume. Thirty healthy young participants (15 women) performed five isokinetic concentric and eccentric maximal-effort elbow flexor/extensor contractions, on separate days. Measures of arm length, circumference, and skinfold/subcutaneous fat thickness were used to obtain a measure of arm volume, modeled as two separate right-angle frustra. Single variable regression analyses demonstrated significant (p<0.001) second-order polynomial relationships between maximal effort elbow flexor and extensor force with arm volume (r2 = 0.63 - 0.86). The major findings demonstrated that strong and positive relations between maximal force production and estimates of limb volume can be observed using non-linear modeling and a closer geometric representation of the exercising limb.

Contraction mode and intensity effects on elbow antagonist muscle co-activation.

INTRODUCTION: Agonist muscle contraction mode and intensity effects on antagonist co-activation was examined between men and women. METHODS: Fifteen healthy young men (mean ±â€¯standard deviation age = 24.9 ±â€¯4.2 years, body mass index = 23.17 ±â€¯2.34) and 15 women (mean ±â€¯standard deviation age = 21.8 ±â€¯2.3 years, body mass index = 24.16 ±â€¯2.91) performed five isokinetic concentric and eccentric maximal-effort elbow flexor/extensor contractions to establish their peak torque. Participants then performed a series of randomly ordered sub-maximal (10-90% of peak torque, 10% increments) elbow flexor contractions over two separate experimental sessions. All sub-maximal elbow flexor contractions were concentric during the first session, while eccentric contractions were performed during the second session. Antagonist co-activation was quantified as the elbow extensor surface electromyogram (EMG) magnitude during all flexor contractions, normalized to its' respective MVC level, when acting as an agonist. RESULTS: The results demonstrated significant contraction intensity (p < 0.001), gender (p < 0.001) and contraction mode (p < 0.001) main effects, indicating that co-activation: (1) increased from 10-90% MVC (5.40% to 12.01%), (2) was greater in women than men (12.06% vs 3.68%), and (3) was greater during concentric than eccentric contractions (9.82% vs 5.92%), without correcting for skinfold thickness. A significant gender by contraction intensity interaction demonstrated that women displayed greater increases in co-activation, as compared to the men, across 10-90% MVC. Following correction for skinfold thickness, the gender difference was not found to be statistically significant. DISCUSSION: The major findings demonstrated that antagonist muscle co-activation demonstrated a dependency on contraction intensity and mode; however, a gender difference was not observed when corrected for skinfold thickness.

The Effects of Knee Joint Angle and Contractor Intensity on Perceived Exertion.

This study examined knee joint angle and knee muscle contraction intensity effects on perceived exertion during isometric contractions. Fourteen healthy young adults participated in five experimental exercise sessions in which knee angles varied randomly (10°, 30°, 50°, 70°, and 90°), each separated by one week. During each session, subjects performed five isometric maximal voluntary contractions (MVCs) of knee extension, followed by nine, randomly ordered submaximal contractions (10%-90% MVC, 10% increments). The participants repeated the identical procedure for the knee flexor muscles. Immediately following each submaximal contraction, participants rated their perceived exertion using a modified Borg category-ratio scale. We found that the participants' overall ratings of perceived exertion were significantly ( p < .05) greater at the 90° than at the 70° and 10° positions during the knee extensor contractions. There were also several significant angle by contraction intensity interactions in that perceived exertion was significantly greater across 60% to 70% MVC at 30° than at 50° ( p < .01), while the opposite pattern was observed across 70% to 80% MVC ( p < .01). During knee flexor contractions, perceived exertion was significantly greater ( p < .05) at 90°, when compared with all other knee angles. There were also significant ( p < .05) angle by contraction intensity interactions between the 50° and 70° knee positions across contraction intensities of 30-40%, 40-50%, 50-60%, and 60-70% MVC. We conclude that the higher perceived exertion rating at 90° during knee extension and flexion contractions suggests different peripheral and central contributors between both muscle groups, due to differences in muscle length.

Older adults underestimate RPE and knee extensor torque as compared with young adults.

PURPOSE: The purpose of this study was to examine knee extensor muscle recruitment, torque, and perceived exertion between healthy young and old adults. METHODS: During the first experimental session, subjects performed 6-s isometric knee extension contractions to intensities ranging from 10% to 90% (10% increments, random order) of three maximal voluntary contractions (MVC), during which RPE were obtained. During the second session, subjects performed 6-s isometric contractions to perceived exertion intensities corresponding to 1, 2, 3, 4, 5, 6, 7, 8, 9, and "maximal" on a modified Borg category-ratio scale, in a random order, to obtain the produced torque. Surface EMG were recorded from the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles. RESULTS: Perceived exertion was significantly (P < 0.05) greater for young than for old adults across 10%-90% MVC. Significantly (P < 0.05) greater VL and RF muscle EMG than the VM across 10%-90% MVC was observed for the young adults, whereas the old adults demonstrated no significant differences between the muscles. The produced torque across the perceived exertion levels was significantly (P < 0.05) greater in old than that in young adults. VL and RF muscle EMG was significantly greater than the VM muscle across the perceived exertion levels in the young adults. Recruitment of the VM, VL, and RF muscles was not significantly different across the perceived exertion levels in the old adults. CONCLUSIONS: The major findings demonstrated that healthy older adults underestimate voluntary knee extensor torque as compared with young adults, which may be driven by differential patterns of muscle recruitment.

Differences in ratings of perceived exertion between the sexes during single-joint and whole-body exercise.

The objective of the present study was to examine ratings of perceived exertion (RPE) between adult men (n = 10) and women (n = 10) during two different modes of fatiguing exercise. Participants provided their rating of perceived exertion (6-20 scale) while performing single-leg heel raises and exercise on a rowing ergometer, during two separate experimental sessions. During the heel raise exercise, ratings of perceived exertion were reported for the exercising calf muscles, while a single undifferentiated and two differentiated ratings were obtained during the rowing exercise. Perceived exertion responses were standardized across the exercise duration between participants, via linear interpolation and power function modelling. No significant differences were observed between the sexes in number of heel raises; however, women exercised significantly (P < 0.05) longer during the rowing exercise. No significant differences were observed between the sexes for ratings of perceived exertion obtained via linear interpolation. However, power function modelling revealed greater (P < 0.05) increases for women during the heel raises. The findings of the present study suggest the presence of a subtle difference in the perceived exertion response between the sexes when modelled as a power function during single-joint exercise.

EMG-torque relationship and reliability of the medial and lateral hamstring muscles.

PURPOSE: The objectives of the present investigation were to examine the EMG-joint torque relation and day-to-day reliability of the medial (MH) and lateral hamstring (LH) muscles during isometric contractions. METHODS: Twenty young adults performed five maximal voluntary isometric hamstring contractions (MVC) followed by contractions at 10%-90% MVC, in a random order. Full-wave-rectified and -integrated EMG during the middle 3 s of each contraction was expressed as a percent of the EMG during the three highest averaged MVC. A three-factor ANOVA (muscle x intensity x gender) with repeated measures was performed on normalized EMG activity. Reliability coefficients were determined for 10 randomly selected subjects that repeated the testing procedures 1 wk after the first session. RESULTS: The MH and LH EMG were observed to be significantly greater than equivalent percent MVC values at all intensity levels. A significant linear increase in MH and LH EMG was observed across contraction intensity levels, with no muscle or gender differences. Reliability was high for MH EMG across contraction intensities of 10%-60% MVC (intraclass correlation (ICC) = 0.70-0.82), moderate for the LH across 10%-30% MVC (ICC = 0.57-0.68) and the MH at 70% MVC (ICC = 0.52), and unreliable across all other contraction intensities for both muscles. CONCLUSIONS: The linear increase in MH and LH EMG, as a function of contraction intensity, was similar between both muscles but was highly reliable only for the MH during low to moderate intensities.

The effects of localized muscle and whole-body fatigue on single-leg balance between healthy men and women.

The purpose was to examine the effects of localized muscle and whole-body fatigue on indices of single-leg balance between healthy young men (n=10) and women (n=10). Subjects performed 10, 10-s single-leg balance trials on a force platform prior to performing each of three conditions (local, whole-body, and control), in a randomized order, on separate days. Localized muscle and whole-body fatigue consisted of single-leg, weight-bearing heel raises on an inclined platform, and exercise on a rowing ergometer, respectively, to the point of volitional failure. During the control condition, subjects remained in a seated position for 5 min. Immediately following each condition, five, 10-s, single-leg balance trials were performed. The localized muscle and whole-body fatigue protocols produced significant (p<0.05) increases in medial/lateral (M/L) and total sway (TS). Men experienced a greater (p<0.05) increase in anterior/posterior (A/P) sway following the localized muscle, than whole-body, fatigue protocol, whereas A/P sway increased more following the whole-body, than localized muscle, fatigue protocol for the women. Total sway variability increased significantly (p<0.05) more following the localized muscle fatigue protocol than the whole-body fatigue protocol for both men and women. The major findings of the present investigation demonstrated that measures of postural control, namely M/L, A/P sway and total sway, were adversely affected following fatiguing exercise, with differential effects between men and women.

The effect of arm abduction angle and contraction intensity on perceived exertion.

The objective of the present investigation was to examine the effects of voluntary contraction intensity and arm elevation angle on ratings of perceived exertion in healthy young adults. Twelve healthy young adults participated in six separate experimental sessions, during which maximal and sub-maximal arm abduction contractions were performed at one of the following randomly assigned arm angles: 15 degrees , 30 degrees , 45 degrees , 60 degrees , 75 degrees , and 90 degrees arm angles (degrees). The sub-maximal arm abduction contractions (10 s) were performed to target intensities ranging from 10 to 90% of the maximal voluntary contraction (MVC), in randomly ordered 10% increments. Perceived exertion was sampled with a modified Borg category-ratio scale immediately, following each sub-maximal contraction. Voluntary arm abduction torque was significantly (p < 0.05) lower at 45 degrees , 60 degrees , 75 degrees and 90 degrees , as compared to 15 degrees . The ratings of perceived exertion increased significantly (p < 0.05) across the range of contraction intensities, with no significant differences between arm angles. The perceived exertion response, as a function of contraction intensity, was best described as linear across the 30 degrees -90 degrees , while a power function described the response at 15 degrees . The major findings demonstrated that arm position plays a minimal role in mediating the growth in the perceived exertion response, as a function of contraction intensity.

Test-retest reliability of cardinal plane isokinetic hip torque and EMG.

The objective of the present study was to establish test-retest reliability of isokinetic hip torque and prime mover electromyogram (EMG) through the three cardinal planes of motion. Thirteen healthy young adults participated in two experimental sessions, separated by approximately one week. During each session, isokinetic hip torque was evaluated on the Biodex Isokinetic Dynamometer at a velocity of 60 deg/s. Subjects performed three maximal-effort concentric and eccentric contractions, separately, for right and left hip abduction/adduction, flexion/extension, and internal/external rotation. Surface EMGs were sampled from the gluteus maximus, gluteus medius, adductor, medial and lateral hamstring, and rectus femoris muscles during all contractions. Intraclass correlation coefficients (ICC - 2,1) and standard errors of measurement (SEM) were calculated for peak torque for each movement direction and contraction mode, while ICCs were only computed for the EMG data. Motions that demonstrated high torque reliability included concentric hip abduction (right and left), flexion (right and left), extension (right) and internal rotation (right and left), and eccentric hip abduction (left), adduction (left), flexion (right), and extension (right and left) (ICC range=0.81-0.91). Motions with moderate torque reliability included concentric hip adduction (right), extension (left), internal rotation (left), and external rotation (right), and eccentric hip abduction and adduction (right), flexion (left), internal rotation (right and left), and external rotation (right and left) (ICC range=0.49-0.79). The majority of the EMG sampled muscles (n=12 and n=11 for concentric and eccentric contractions, respectively) demonstrated high reliability (ICC=0.81-0.95). Instances of low, or unacceptable, EMG reliability values occurred for the medial hamstring muscle of the left leg (both contraction modes) and the adductor muscle of the right leg during eccentric internal rotation. The major finding revealed high and moderate levels of between-day reliability of isokinetic hip peak torque and prime mover EMG. It is recommended that the day-to-day variability estimates concomitant with acceptable levels of reliability be considered when attempting to objectify intervention effects on hip muscle performance.

Contraction mode shift in quadriceps femoris muscle activation during dynamic knee extensor exercise with increasing loads.

The objective of the present study was to examine the superficial quadriceps femoris (QF) muscle electromyogram (EMG) during dynamic sub-maximal knee extension exercise between young adult men and women. Thirty subjects completed, in a random order, 2 sub-maximal repetitions of single-leg knee extensions at 20-90% of their one-repetition maximum (1RM). Vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) muscle integrated EMG (IEMG) during each sub-maximal lift was normalized to the respective 1RM for concentric, isometric and eccentric modes. The EMG median frequency (f(med)) was determined over the isometric mode. Men attained a significantly (p<0.05) greater knee angular velocity than the women during the concentric mode (83.6+/-19.1 degrees /s and 67.4+/-19.8 degrees /s, respectively). RF IEMG was significantly lesser than the VM (p=0.014) and VL (p<0.001) muscles, when collapsed across all contraction modes, loads, and sex. Overall IEMG was significantly greater during the concentric (p<0.001) and isometric (p<0.001) modes, than the eccentric mode. Men generated significantly (p=0.03) greater VL muscle IEMG than the women, while the opposite pattern emerged for the RF muscle. VM f(med) (105.1+/-11.1Hz) was significantly lesser than the VL (180.3+/-19.5Hz) and RF (127.7+/-13.9Hz) muscles across all lifting intensities, while the men (137.7+/-10.7Hz) generated greater values than the women (129.0+/-11.4Hz). The findings demonstrate a reduction in QF muscle activation across the concentric to eccentric transition, which may be related to the mode-specific velocity pattern.

Forearm blood flow responses to fatiguing isometric contractions in women and men.

Previous studies suggest that women experience less vascular occlusion than men when generating the same relative contractile force. This study examined forearm blood flow (FBF) in women and men during isometric handgrip exercise requiring the same relative force. Thirty-eight subjects [20 women and 18 men, 22.8 +/- 0.6 yrs old (means +/- SE)] performed low- and moderate-force handgrip exercise on two occasions. Subjects performed five maximum voluntary contractions (MVC) before exercise to determine 20% and 50% MVC target forces. Time to task failure (TTF) was determined when the subject could not maintain force within 5% of the target force. Mean blood velocity was measured in the brachial artery with the use of Doppler ultrasonography. Arterial diameter was measured at rest and used to calculate absolute FBF (FBFa; ml/min) and relative FBF (FBFr; ml.min(-1).100 ml(-1)). Women generated less (P < 0.05) absolute maximal force (208 +/- 10 N) than men (357 +/- 17 N). The TTF was longer (P < 0.05) at 20% MVC for women (349 +/- 32 s) than for men (230 +/- 23 s), but no difference between the sexes was observed at 50% MVC (women: 69 +/- 5 s; men: 71 +/- 8 s). FBFa and FBFr increased (P < 0.05) from rest to TTF in both women and men during 20% and 50% MVC trials. FBFr was greater in women than in men at > or =30% TTF during 50% MVC. At exercise durations > or =60% of TTF, FBFa was lower (P < 0.05) in women than in men during handgrip at 20% MVC. Despite the longer exercise duration for women at the lower contraction intensity, FBFr was similar between the sexes, suggesting that muscle perfusion is matched to the exercising muscle mass independent of sex.

Relationship between hip and knee strength and knee valgus during a single leg squat.

The purpose of this study was to determine the relationship between hip and knee strength, and valgus knee motion during a single leg squat. Thirty healthy adults (15 men, 15 women) stood on their preferred foot, squatted to approximately 60 deg of knee flexion, and returned to the standing position. Frontal plane knee motion was evaluated using 3-D motion analysis. During Session 2, isokinetic (60 deg/sec) concentric and eccentric hip (abduction/adduction, flexion/extension, and internal/external rotation) and knee (flexion/extension) strength was evaluated. The results demonstrated that hip abduction (r2=0.13), knee flexion (r2=0.18), and knee extension (r2=0.14) peak torque were significant predictors of frontal plane knee motion. Significant negative correlations showed that individuals with greater hip abduction (r=-0.37), knee flexion (r=-0.43), and knee extension (r=-0.37) peak torque exhibited less motion toward the valgus direction. Men exhibited significantly greater absolute peak torque for all motions, excluding eccentric internal rotation. When normalized to body mass, men demonstrated significantly greater strength than women for concentric hip adduction and flexion, knee flexion and extension, and eccentric hip extension. The major findings demonstrate a significant role of hip muscle strength in the control of frontal plane knee motion.

Quadriceps femoris electromyogram during concentric, isometric and eccentric phases of fatiguing dynamic knee extensions.

The objective of this study was to examine the superficial quadriceps femoris (QF) muscle electromyogram (EMG) during fatiguing knee extensions. Thirty young adults were evaluated for their one-repetition maximum (1RM) during a seated, right-leg, inertial knee extension. All subjects then completed a single set of repeated knee extensions at 50% 1RM, to failure. Subjects performed a knee extension (concentric phase), held the weight with the knee extended for 2s (isometric phase), and lowered the weight in a controlled manner (eccentric phase). Raw EMG of the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) muscles were full-wave rectified, integrated and normalized to the 1RM EMG, for each respective phase and repetition. The EMG median frequency (f(med)) was computed during the isometric phase. An increase in QF muscle EMG was observed during the concentric phase across the exercise duration. VL EMG was greater than the VM and RF muscles during the isometric phase, in which no significant changes occurred in any of the muscles across the exercise duration. A significant decrease in EMG across the exercise duration was observed during the eccentric phase, with the VL EMG greater than the VM and RF muscles. A greater decrease in VL and RF muscle f(med) during the isometric phase, than the VM muscle, was observed with no gender differences. The findings demonstrated differential recruitment of the superficial QF muscle, depending on the contraction mode during dynamic knee extension exercise, where VL muscle dominance appears to manifest across the concentric-isometric-eccentric transition.

Angle- and gender-specific quadriceps femoris muscle recruitment and knee extensor torque.

The objectives were to examine knee angle-, and gender-specific knee extensor torque output and quadriceps femoris (QF) muscle recruitment during maximal effort, voluntary contractions. Fourteen young adult men and 15 young adult women performed three isometric maximal voluntary contractions (MVC), in a random order, with the knee at 0 degrees (terminal extension), 10 degrees, 30 degrees, 50 degrees, 70 degrees, and 90 degrees flexion. Knee extensor peak torque (PT), and average torque (AT) were expressed in absolute (N m), relative (N m kg(-1)) and allometric-modeled (N m kg(-n)) units. Vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscle EMG signals were full-wave rectified and integrated over the middle 3 s of each contraction, averaged over the three trials at each knee angle, and normalized to the activity recorded at 0 degrees. Muscle recruitment efficiency was calculated as the ratio of the normalized EMG of each muscle to the allometric-modeled average torque (normalized to the values at 0 degrees flexion), and expressed as a percent. Men generated significantly greater knee extensor PT and AT than women in absolute, relative and allometric-modeled units. Absolute and relative PT and AT were significantly highest at 70 degrees, while allometric-modeled values were observed to increase significantly across knee joint angles 10-90 degrees. VM EMG was significantly greater than the VL and RF muscles across all angles, and followed a similar pattern to absolute knee extensor torque. Recruitment efficiency improved across knee joint angles 10-90 degrees and was highest for the VL muscle. VM recruitment efficiency improved more than the VL and RF muscles across 70-90 degrees flexion. The findings demonstrate angle-, and gender-specific responses of knee extensor torque to maximal-effort contractions, while superficial QF muscle recruitment was most efficient at 90 degrees, and less dependent on gender.

The effects of rest interval length on ratings of perceived exertion during dynamic knee extension exercise.

The objective of this study was to examine the effects of rest interval length on perceived exertion and during 3 sets of 10 inertial knee extension repetitions. Thirty healthy men (n = 15) and women (n = 15) volunteers were randomly assigned to 1 of 3 groups (1-, 2-, or 3-minute rest interval length) following the establishment of each subject's 1 repetition maximum (1RM) for inertial knee extension exercise. Subjects in each group performed 3 sets of 10 repetitions at 70% of a theoretical 10RM (based on each subject's 1RM), with a 1-, 2-, or 3-minute rest interval between each set. Perceived exertion was recorded, via the Borg category-ratio scale, from each subject after each repetition of each set. The results demonstrated no significant rest interval length effect on perceived exertion across the 3 sets of 10 repetitions. The results revealed a significantly higher perceived exertion value following the first repetition in set 3 as compared to sets 2 and 1 in all groups. The increase in perceived exertion within each set, as described by the slope, was found to be significantly lowest in set 1, as compared to sets 2 and 3. The major findings of this study demonstrate that perceived exertion significantly increases in a similar manner across 3 sets of 10 knee extension repetitions, despite rest interval lengths of 1-3 minutes.

Gender differences in perceived exertion during fatiguing knee extensions.

PURPOSE: To examine gender differences in knee extensor strength, fatigue, and perceived exertion during a single set of continuous dynamic knee extensor contractions. METHODS: Fifteen men and 15 women were evaluated for their one-repetition maximum (1RM) during a single-leg, inertial knee extension with their right leg. All subjects then completed a single set of repeated knee extensions with a load equivalent to 50% of their 1RM to failure. Subjects lifted the weight by performing a knee extension, held the weight with the knee extended for 1-2 s, and then lowered the weight in a slow and controlled manner. Perceived exertion was measured after completion of each repetition, by viewing a modified Borg category-ratio (CR-10) scale. Perceived exertion responses were standardized across subjects via linear interpolation and power function modeling. The linear interpolated perceived exertion estimates were then examined for linear, quadratic, and cubic trends across the repetitions. RESULTS: Men lifted a significantly greater amount of mass than women, when corrected for body mass. Men and women did not differ significantly in the number of repetitions performed to failure. Women displayed significantly higher power function exponents for the perceived exertion response than men (0.72 +/- 0.16 and 0.57 +/- 0.16, respectively) and demonstrated statistically nonsignificant greater increases in perceived exertion than men across the repetitions. CONCLUSIONS: The major findings of this study indicated that: 1) men inherently possessed greater knee extensor strength than women; 2) submaximal fatiguing knee extensor performance did not differ between genders; 3) model selection had a significant impact on standardizing perceived exertion estimates; and 4) subtle gender differences in the perceived exertion response may have existed during submaximal, fatiguing resistance exercise.

Knee flexor torque and perceived exertion: a gender and reliability analysis.

PURPOSE: The objectives of the present study were to examine gender differences and between-day variability of isometric hamstring muscle peak torque and perceived exertion. METHODS: Subjects included 20 healthy, college-aged male (N = 10) and female (N = 10) volunteers. Each subject completed five maximal voluntary isometric hamstring muscle contractions (MVC), in a prone position, with their knee at 30 degrees flexion. Subjects then completed, in random order, isometric contractions at 10, 20, 30, 40, 50, 60, 70, 80, and 90% of their three highest averaged MVC. Perceived exertion was measured with a modified Borg CR-10 scale after each contraction. Ten randomly chosen subjects were asked to return approximately 1 wk after the initial evaluation to repeat the same procedure. Peak hamstring muscle torque was examined in absolute (N.m), relative (N.m.kg-1), and allometric-scaled (N.m.kg-n) units. Perceived exertion across the contraction intensities was modeled to a power function in order to determine the exponent and proportionality constant. RESULTS: Males generated significantly greater hamstring muscle torque than females in absolute, relative, and allometric-scaled units (P < 0.05). No significant differences in perceived exertion occurred across the submaximal contraction intensities between females and males, nor for the derived exponents and proportionality constants. Perceived exertion ratings were observed to be significantly lower (P < 0.05) across the contraction intensity range on the second day. CONCLUSIONS: The major findings demonstrated that perceived exertion did not differ between healthy young female and male adults, despite males generating significantly more hamstring muscle torque, and perceived exertion ratings decreased at similar relative contraction intensity levels across testing days.

Knee extensor torque, work, and EMG during subjectively graded dynamic contractions.

We examined knee extensor peak torque, work, and electromyogram (EMG) during dynamic contractions to perceived exertion levels in men and women. Thirty subjects performed three maximal effort isokinetic knee extensions (60 deg x s(-1)), followed by three contractions to each of nine separate levels of perceived exertion. Surface EMG of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF), and knee extensor peak torque and work were normalized to a percent of each respective value obtained during the maximal effort contractions. The results demonstrated a significant linear increase in voluntary knee extensor peak torque and work across perceived exertion levels. Knee extensor peak torque and work were less than 70%, 80%, and 90% maximal voluntary contraction (MVC) at perceived exertion levels 7, 8, and 9, respectively. A significant increase in VM, VL, and RF muscle EMG was observed across perceived exertion levels 1 through 9, with EMG increase highest for the VL. The findings demonstrate that dynamic contractions guided by perceived exertion are underproduced at relatively high perceptual intensities, and that reliance on VL activation occurs across submaximal torque levels. The overestimation of knee extensor peak torque and work at relatively high perceptual intensities may suggest the presence of a subconscious mechanism aiming to reduce high muscle and joint forces.