RPE angle effects in young and middle-aged adults.

The purpose of this study was to examine contraction intensity and arm abduction angle effects on perceived exertion between healthy young (n=14) and middle-aged (n=13) adults. Subjects participated in three separate experimental sessions during which, maximal (MVC) and sub-maximal (10-90% MVC, 10% increments, random order) arm abduction contractions were performed at one of the following randomly assigned angles: 30, 60 and 90 degrees Perceived exertion was sampled with a modified Borg category-ratio scale following each sub-maximal contraction. Voluntary arm abduction torque was significantly (p<0.05) greatest at 30 degrees , as compared to 60 degrees and 90 degrees , while no significant differences were observed between the young and middle-aged adults. Perceived exertion was significantly (p<0.05) greatest at 90 degrees abduction, as compared to 30 degrees and 60 degrees , and was not different between the two age groups. Power function modeling revealed that perceived exertion was significantly (p<0.05) fit to negatively accelerating non-linear trends for the middle-aged adults at all arm angles and at 90 degrees for the young adults. The findings demonstrated greater ratings of perceived exertion at elevated arm positions, while middle-aged adults displayed a non-linear contraction intensity dependency at the lower arm elevation angles.

Gender and contraction mode on perceived exertion.

The purpose of this study was to examine perceived exertion responses during concentric and eccentric elbow flexor contractions between young adult men and women. Thirty healthy young adults participated in two experimental sessions. During the first session, subjects performed five concentric isokinetic maximal voluntary contractions (MVC) of elbow flexion, followed by nine, randomly-ordered sub-maximal contractions (10-90% MVC). The same procedures were repeated during the second session, with the exception that eccentric contractions were performed. Subjects rated their perceived exertion following the sub-maximal contractions with the Borg category-ratio scale. Perceived exertion was significantly (p<0.05) less than equivalent values on the CR-10 scale at intensities greater than, and equal to, 30% MVC. A three-factor interaction between 30-40% MVC indicated that perceived exertion increased more during the eccentric, than concentric, contractions in women, while the opposite pattern was evident for the men. There were no significant contraction mode or gender differences. Power function modeling revealed that perceived exertion increased in a negatively accelerating manner, except for the men performing eccentric exercise. Perceived exertion increases in a similar non-linear manner between men and women during concentric contractions, while men exhibited a statistically linear pattern during eccentric contractions.

Influence of contraction intensity, muscle, and gender on median frequency of the quadriceps femoris.

The purpose of this study was to assess the effects of contraction intensity, gender, and muscle on median frequency of the three superficial portions of the quadriceps femoris muscle. Thirty healthy volunteers were assessed for isometric electromyogram activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles with the knee at 60 degrees flexion. Subjects performed 5-s isometric contractions at 10, 20, 30, 40, 50, 60, 70, 80, and 90% of the average of three maximal voluntary contractions. Median frequency (f(med)) of the three muscles was assessed through a power spectral analysis performed over 11 consecutive 512-ms epochs overlapping each other by one-half their length. The f(med) for each of the 11 epochs was then determined, followed by calculation of the mean and SD. The major findings of this study demonstrated that overall f(med) was significantly highest for the VL and lowest for the VM, whereas RF f(med) was between that of the other two muscles. Similar findings were observed for f(med) variability as the VL was significantly higher than the VM and RF, with no gender differences or differences between the latter two muscles. The results demonstrate that the largest change in f(med) as a function of contraction intensity occurred for the VL in men (18.6%) and women (7.6%). These findings suggest that muscle fiber-type homogeneity may exist in the VM and RF, which displayed negligible changes in f(med), whereas the VL may possess greater morphological variability.

A physiological review of American football.

American football has been one of the most popular sports in North America within the past century and has recently received support and increased participation from European nations. Two of the biggest concerns regarding participation in American football are the high incidence of injury and the physical demand for preparation. A basic understanding of the physiological systems utilised in the sport of football is necessary in order to develop optimal training programmes geared specifically for preparation as well as the requirements of individual field positions. Previously, it has been assumed that football relies primarily on an anaerobic source of energy for adenosine triphosphate (ATP) resynthesis with approximately 90% coming from the phosphocreatine (PCr) energy system. In lieu of research conducted specifically with football players, it appears that the energy contribution from the anaerobic glycolytic pathway in this sport has been underestimated. The elevated blood lactate levels observed in football players following game participation cast doubt on this hypothesis. Identifying position specific characteristics may also enhance the development of training programmes based on the requirements of the different positions. It appears that offensive and defensive linemen are generally larger, have higher levels of percent body fat and have greater absolute strength scores than all other positions. Offensive backs, defensive backs and wide receivers tend to display the lowest percentages of body fat, lower absolute strength scores, fastest times over 5, 10, 40 and 300m and the highest relative VO2max values. Linebackers appeared to represent a transition group mid way between the backs and linemen for size, body composition, strength, speed and endurance as well as positional duties. Findings within the literature suggest that a lack of cardiovascular development of university and professional football players may prove to be a hindrance to performance with specific regards to thermal regulation. Additional aerobic conditioning as well as the reduction of percent body fat would not only enhance performance, but might play a key role in preventing injuries and allowing a smoother transition into life after football.

Medial elbow stability. Clinical implications.

Medial elbow injuries of athletes, such as baseball pitchers and javelin throwers, can prove to be debilitating and may have a negative effect on performance. The most significant injury to the elbow occurs is an ulnar collateral ligament (UCL) sprain or rupture, which compromises the medial stability of the elbow joint. It has been found that the anterior oblique portion of the UCL is the primary stabiliser of the elbow, and that trauma to this complex may significantly hinder normal elbow function. An accurate diagnosis will dictate the degree of injury to the elbow as well as determine the most appropriate means of treatment.

Proprioception of the ankle and knee.

Proprioception and accompanying neuromuscular feedback mechanisms provide an important component for the establishment and maintenance of functional joint stability. Neuromuscular control and joint stabilisation is mediated primarily by the central nervous system. Multisite sensory input, originating from the somatosensory, visual and vestibular systems, is received and processed by the brain and spinal cord. The culmination of gathered and processed information results in conscious awareness of joint position and motion, unconscious joint stabilisation through protective spinal-mediated reflexes and the maintenance of posture and balance. Clinical research aimed at determining the effects of articular musculoskeletal injury, surgery and rehabilitation, on joint proprioception, neuromuscular control and balance has focused on the knee and ankle joints. Such studies have demonstrated alterations in proprioception subsequent to capsulo-ligamentous injury, partial restoration of proprioceptive acuity following ligamentous reconstruction, and have suggested beneficial proprioceptive changes resulting from comprehensive rehabilitation programmes.

The effects of joint angle and reliability on knee proprioception.

PURPOSE: The purpose of this study was to examine the reliability and effects of knee angle on the detection and subsequent response to passive knee movement. METHODS: Twenty college-aged male and 20 female volunteers were evaluated for proprioception by a newly developed perturbation test. Subjects were in a prone position on an isokinetic chair with their right lower leg attached to a freely moving resistance adapter. The knee was placed in a starting position of 15, 30, or 60 degrees of flexion. While relaxed, the knee was dropped into extension, and the subjects were instructed to "catch their leg" when movement was perceived. Five trials were completed at each angle, in a random order. An electrogoniometer was secured to the lateral portion of the knee in order to measure angular displacement after perturbation in two specific phases: detection (displacement from leg release to movement cessation) and response (displacement from movement cessation to peak knee flexion). A three-factor ANOVA (two repeated factors (knee angle and proprioception phase) and one between factor (gender)) was performed on the average and standard deviation of the five trials for significant main effects and interactions. RESULTS: The results demonstrated a significant phase by angle interaction, and no gender effect. It was shown that at a more extended knee joint position (15 degrees), significantly less knee movement occurred before perception, followed by a greater response, than in a more flexed position (30 and 60 degrees). CONCLUSION: The major findings of this study suggest that the detection of passive knee movement, and the subsequent voluntary response, may be dependent on joint angle. Considerations of the present method for proprioception assessment are warranted to enhance test-retest reliability.

Assessment of the reliability of high-intensity quadriceps femoris muscle fatigue.

OBJECTIVE: The purpose of this study was to evaluate test-retest reliability of two different measures of isokinetic quadriceps muscle fatigue. METHODS: Subjects for this study included 16 healthy, college age volunteers. Each subject performed 30 maximal, concentric repetitions on the Biodex System II Isokinetic Dynamometer at a preset angular velocity of 180 degrees.s(-1) for both the dominant and nondominant legs. Quadriceps work was evaluated between an angular range of 10 degrees and 60 degrees of flexion for each repetition. Quadriceps muscle fatigue was calculated through a fatigue index (work performed last 5 repetitions/work performed first five repetitions x 100) and the linear slope (beta) across the 30 repetitions. The subjects participated in two test sessions separated by one to two weeks. Intraclass correlation coefficients (ICC) and standard errors of measurements (SEM) were calculated for each fatigue measure on both legs. RESULTS: The findings demonstrated moderate to high ICCs for the nondominant leg (ICC = 0.78--0.92) and high ICCs for the slope and y-intercept for the dominant leg (ICC = 0.82 and 0.89, respectively). The fatigue index for the dominant leg was found to be low (ICC = 0.26). CONCLUSIONS: The findings of this study suggest that the quantification of muscle fatigue during high-intensity, short-term exercise is more reliably described by the slope, which is related to the magnitude of force output.

The role of proprioception in the management and rehabilitation of athletic injuries.

Rehabilitation continues to evolve with the increased emphasis on patient management and proprioceptive training. Proprioception can be defined as a specialized variation of the sensory modality of touch that encompasses the sensation of joint movement (kinesthesia) and joint position (joint position sense). Numerous investigators have observed that afferent feedback to the brain and spinal pathways is mediated by skin, articular, and muscle mechanoreceptors. Examining the effects of ligamentous injury, surgical intervention, and proprioceptively mediated activities in the rehabilitation program provides an understanding of the complexity of this system responsible for motor control. It appears that this neuromuscular feedback mechanism becomes interrupted with injury and abnormalities, and approaches restoration after surgical intervention and rehabilitation. Rehabilitation programs should be designed to include a proprioceptive component that addresses the following three levels of motor control: spinal reflexes, cognitive programming, and brainstem activity. Such a program is highly recommended to promote dynamic joint and functional stability. Thus far, current knowledge regarding the basic science and clinical application of proprioception has led the profession of sports medicine one step closer to its ultimate goal of restoring function.

Gender and muscle differences in EMG amplitude and median frequency, and variability during maximal voluntary contractions of the quadriceps femoris.

The purpose of this study was to evaluate gender and muscle differences in electromyographic (EMG) amplitude and median frequency mean and standard deviation during maximal voluntary contractions of the quadriceps femoris. Thirty recreationally active volunteers were assessed for isometric EMG activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles during three 5-s maximal isometric voluntary contractions (MVCs). Median frequency of the three muscles was assessed through a power spectral analysis (fast Fourier transformation, Hanning window processing, 512 points). The power spectral analysis was performed during the middle 3 s of each contraction over 11 consecutive, 512 ms epochs overlapping each other by half their length (256 ms). The median frequency (F(med)) for each of the 11 windows was determined for each muscle. The mean and standard deviation of the F(med) across the 11 overlapping windows were then calculated for each contraction and muscle. EMG amplitude was determined by calculating the root mean square (RMS-50 ms time constant) over the same contraction period for each muscle. The mean amplitude and standard deviation about the mean value were then determined. A three-factor ANOVA with repeated measures was performed on the calculated F(med) mean and standard deviation values, and RMS standard deviations, to assess any gender, muscle, or trial differences, or interactions. A two-factor (gender by muscle) ANOVA with repeated measures was performed on the RMS mean amplitude for each muscle. Intraclass correlation coefficients (ICCs-2,1), standard errors of measurement (SEMs), and associated 95% confidence intervals were then calculated for maximal quadriceps torque and F(med) for each muscle. The results from this study demonstrated that the VL muscle displayed significantly higher F(med) values than the RF and VM muscles. The RF muscle showed significantly higher F(med) values (mean of 11 overlapping windows) than the VM muscle. Intrasession reliability was found to be high for the calculated mean values (ICC=0.85-0.96), but was shown to be low for variability (ICC=0.13-0.45). The major findings of this study support the notion that the EMG signal is "quasi-random" in nature, as demonstrated by the reproducible F(med) means and unreliable variability.

Knee extensor torque and quadriceps femoris EMG during perceptually-guided isometric contractions.

The aim of this study was to examine superficial quadriceps femoris (QF) EMG and torque at perceived voluntary contraction efforts. Thirty subjects (15 males, 15 females) performed 9, 5 s, sub-maximal contractions at prescribed levels of perceived voluntary effort at points 1-9 on an 11-point scale (0-10), in a random order. Surface electromyograms (EMG) of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles, as well as QF peak torque (PT), average torque (AT), and torque coefficient of variation (C.V.), were sampled. The raw EMG signals were full-wave rectified and integrated over the middle three s of each contraction. The sampled EMG signals, and PT and AT at each perceived exertion level were normalized to the average of three maximal voluntary contractions. The normalized EMG and torque values at each perceived exertion level were then compared to equivalent percent values (i.e., 10% at a perceived level of 1). The results demonstrated that at all perceived exertion levels, with the exception of the RF at a level of 2 which was equivalent to 20%, and the VL and RF muscles at a level 1 in which activation was greater than 10%, activation was significantly less than the equivalent percent value at each point on the scale. VM EMG was found to be less than the VL and RF from contraction levels 3-9. PT was shown to be less than the equivalent percent values at contraction levels 6-9. The AT was found to be lower than the expected percent value at perceived effort levels 2-9. Torque C.V. was not found to be different across the range of perceived effort. The major findings of this study suggested that humans over-estimate voluntary QF muscle torque when guided by perceptual sensations. It is also suggested that the produced EMG signals revealed a reliance on the VL muscle for knee extensor torque generation at sub-maximal levels.

Changes in forearm blood flow during single and intermittent cold application.

STUDY DESIGN: Two-factor repeated measures design. OBJECTIVES: To compare the effects of a 20-minute cold application to the effects of a 20-minute cold application followed by 20 additional minutes of intermittent cold on forearm blood flow over a 60-minute period. BACKGROUND: The appropriate duration of cold application as a therapeutic modality following soft tissue trauma is an important clinical question because the goal of using this modality is to limit edema, decrease pain, and produce effective muscle relaxation without causing cold-induced reactive vasodilatation or nerve damage. METHODS AND MEASURES: Thirteen subjects (mean age, 21.46 +/- 4.01 years) volunteered to participate in this study. A bilateral tetrapolar impedance plethysmograph was used with venous occlusion to measure changes in local limb blood volume at the forearm for a period of 60 minutes under 2 conditions: Condition 1: Prolonged intermittent cold application (20 minutes ice application; 10 minutes off; 10 minutes ice on; 10 minutes off; 10 minutes ice on); Condition 2: Cold followed by application of a room-temperature pack of equal weight to the ice bag (20-minute ice application; 10 minutes off; 10 minute room-temperature pack on; 10 minutes off; 10-minute room-temperature pack on). RESULTS: A significantly lower blood flow was noted during the last 10 minutes of Condition 1 compared with Condition 2. CONCLUSIONS: The findings of this study indicate that blood flow is reduced when a prolonged intermittent cold application (Condition 1) is used compared to a single cold application (Condition 2).

The effect of sudden inversion stress on EMG activity of the peroneal and tibialis anterior muscles in the chronically unstable ankle.

Residual symptoms resulting from recurrent episodes of inversion-type ankle sprains may be attributed to a decreased neuromuscular response of the peroneal or tibialis anterior muscles, thereby increasing the probability for reinjury. The purpose of this study was to examine the electromyographic (EMG) response time of the peroneal and tibialis anterior muscles in response to sudden plantar flexion/inversion stress in the chronically functional unstable and normal ankle. Subjects for this study consisted of 13 athletically active individuals (five males and eight females, mean age = 19.2 +/- 1.51 years) with a previous history of a unilateral inversion-type ankle sprain. A specially designed platform that allows each foot to drop into plantar flexion/inversion from a standing neutral position was used. Reaction time in milliseconds for the peroneal and tibialis anterior muscles to sudden plantar flexion/inversion was measured via surface EMG. A paired t test was performed with the Bonferroni-Dunn correction factor to determine differences between the peroneal and tibialis anterior as well as between the chronically unstable and contralateral normal ankle. The results indicated no significant differences between the stable and unstable ankles for the peroneal or the tibialis anterior muscles. The results also indicated no significant differences existed between the tibialis anterior and peroneal muscles in either the stable or unstable ankles. The findings from the present study suggest that self-reported functional ankle instability may not result in a diminished reflex response time of the peroneal and tibialis anterior muscles to sudden plantar flexion/inversion stress.

The effects of ACL injury on lower extremity activation during closed kinetic chain exercise.

AIM: Injury to the anterior cruciate ligament (ACL) has been suggested to alter the neuromuscular mechanism in the lower extremity. However, conclusive evidence regarding this occurrence has yet to be established during closed kinetic chain exercise. The purpose of this study was to assess differences in muscle activation during slideboard exercise between non-injured, ACL deficient, and ACL reconstructed individuals. EXPERIMENTAL DESIGN: comparative study. SETTING: research laboratory. PARTICIPANTS: subjects for this study included 10 healthy, non-injured (NI) individuals, 7 uni-lateral ACL deficient (ACLD) individuals, and 6 uni-lateral ACL reconstructed (ACLR) individuals. INTERVENTIONS: EMG activity was measured from the vastus medialis (VM), vastus lateralis (VL), medial hamstring (MH), lateral hamstring (LH), tibialis anterior (TA), and medial gastrocnemius (MG) muscles during slideboard performance. MEASURES: EMG for each muscle during each of 6 phases of 1 average slideboard cycle was expressed as a percentage of EMG during a maximal voluntary contraction. RESULTS: The results demonstrated that during slideboard phase I the VM, VL, and TA muscles generated the greatest amount of activity as compared to the other muscles. Vastus medialis muscle activation was found to be significantly higher than the other muscles in the involved/dominant limb, as compared to the non-involved/non-dominant limb during slideboard phase II. During slideboard phases III-VI, tibialis anterior muscle activation was found to be consistently higher than the other muscles, while hamstring muscle activity was consistently the lowest. CONCLUSION: It is concluded that adaptive changes following ACL injury during a dynamic, closed kinetic chain activity such as the slideboard exercise, may be a restoration of a bi-lateral balance in muscle activation.

The effects of rest interval length and training on quadriceps femoris muscle. Part I: knee extensor torque and muscle fatigue.

AIM: The purpose of this study was to examine the effects of rest interval on quadriceps femoris (QF) muscle strength and fatigue during short-term, high-intensity training. METHODS: Fifteen healthy males were assessed for isokinetic QF strength, via peak torque (PT), work (WK) and power (PW), at a pre-set angular velocity of 180 deg x s(-1). Quadriceps femoris muscle fatigue was evaluated as the decline in isokinetic work and power (slope) across 30 maximal concentric contractions. Subjects were randomly assigned to 1 of 3 groups: Group 1 (short rest interval), Group 2 (long rest interval), and Group 3 (control-no training). Subjects in Group 1 received a rest period of 40 s in between exercise sets corresponding to a 2:1 rest:work ratio. Subjects in Group 2 received a rest period of 160 s corresponding to an 8:1 rest:work ratio. Groups 1 and 2 performed isokinetic knee extension contractions at 180 deg x s(-1) 2 days per week for 6 weeks. RESULTS: The results demonstrated a significant increase in QF muscle PT across the 6 week training period in the long rest interval group, and no significant changes in the short rest interval and control groups. Quadriceps femoris muscle work and power were observed to not change significantly across the training period in all 3 groups. The reduction in QF muscle work across the single set of 30 repetitions was observed to decrease significantly in the control group across the 6 week duration; no other significant changes in QF muscle fatigue for work and power were observed. CONCLUSION: The major findings of this study suggests that the possibility of different physiological mechanisms of adaptation exist for QF muscle peak torque, work and power, while changes in muscle fatigue resistance may be present when assessed across multiple, rather than a single, bouts of activity.

The effects of rest interval and resistance training on quadriceps femoris muscle. Part II: EMG and perceived exertion.

AIM: The purpose of this study was to examine the effects of rest interval on quadriceps femoris muscle activation and perceived exertion, during short-term resistance training. METHODS: Vastus medialis (VM) and vastus lateralis (VL) muscle electromyograms (EMG) were assessed in 15 males during a sustained 80% maximal voluntary contraction (MVC). During the pre-training evaluation, the absolute value of the 80% MVC (N.m) and contraction duration (s) was performed at 2, 4, and 6 weeks during the training period. Perceived exertion was measured via the Borg category-ratio scale every 5 s during the 80% MVC. Subjects were randomly assigned to 3 groups: group 1 received a 40 s rest interval in between exercise sets, group 2 received a rest period of 160 s, and the control group did not participate in training. Groups 1 and 2 performed isokinetic knee extensions at 180 deg.s(-1) 2 days per week for 6 weeks. RESULTS: The results demonstrated a significant decrease in VM EMG within the initial portion of the 80% MVC across the training period in the short rest interval group. The long rest interval and control groups showed no significant changes in VM EMG during 1st part of the contraction across the training period, whereas the control group exhibited a significant reduction in VL EMG across weeks 4 to 6. VL EMG increased during the 80% MVC in the control group across the training period. VM EMG increased during the sustained contractions in the long rest interval and control groups across the training period. The perceived exertion response was lower in the 1st part of the 80% MVC in the short and long rest interval groups, but not in the control group, across the training period. The results also showed a significant decrease in perceived exertion at the end of the sustained contraction in the short rest interval group, but not in the long rest interval group or the control group. CONCLUSIONS: The findings from this study suggest that the application of relatively short rest intervals in between sets of resistance exercise induced a greater neuromuscular response of the VM muscle during short-term training.

Perceived exertion during isometric quadriceps contraction. A comparison between men and women.

BACKGROUND: 1) To examine the validity and accuracy of the CR-10 scale for evaluating perceived exertion, and 2) to assess gender differences in perceived exertion across different levels of contraction intensity. EXPERIMENTAL DESIGN: cross-sectional, comparative design. SETTING: Human Performance and Fatigue Laboratory, Eastern Washington University. SUBJECTS: 30 healthy, college age volunteers (15 males, 15 females). MEASURES: All subjects were assessed for isometric torque and perceived exertion of the quadriceps femoris muscles, via the CR-10 scale. One low anchor was applied under resting conditions with the knee flexed to 60 degrees, and a high anchor was applied during a maximal voluntary muscle contraction (MVC). SUBJECTS performed five-second isometric contractions equivalent to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their MVC, in a random order, and were assessed for perceived exertion by visually observing the CR-10 scale. One sample "t"-tests and 95% confidence intervals were calculated for perceived exertion at each relative torque level. A single factor ANOVA with repeated measures was performed across al levels of exercise intensity. Linearity for perceived exertion was assessed via regression analysis. RESULTS: Perceived exertion at each exercise intensity were as follows: 10%: 1.87+/-1.14, 20%: 2.43+/-1.19, 30%: 3.5+/-1.36, 40%: 3.97+/-1.52, 50%: 4.73+/-1.28, 60%: 5.53+/-1.28, 70%: 6.73+/-1.62, 80%: 7.57+/-1.72, and 90%: 8.6+/-1.52. The increase in perceived exertion across the intensity spectrum was found to fit both linear and quadratic trends. There were no gender differences in perceived exertion across all levels of exercise intensity. CONCLUSIONS: The findings demonstrate that the CR-10 scale closely approximates perceived exertion of the quadriceps femoris muscles during sub-maximal, static contractions, and is not gender specific.

Physiologic response to a prescribed rating of perceived exertion on an elliptical fitness cross-trainer.

AIM: Perceived exertion during physical exercise is a major intrinsic factor for making decisions regarding intensity levels. The use of perceptual indices as a prescriptive guide of exercise intensity may be a valuable tool, should it be concomitant with physiological responses. The purpose of this study was to evaluate the physiologic response during exercise on an elliptical fitness cross-trainer at a prescribed level of perceived exertion. METHODS: Twenty, recreational exercisers (8 males, 12 females) were habituated to the elliptical cross-trainer and then assessed for their peak oxygen utilization (VO(2)) and peak heart rate (HR) using an incremental protocol. The point of volitional fatigue during the maximal test was used to anchor a modified Borg Category Ratio (CR-10) scale. Following a rest period of 48-72 hours, a second exercise session was performed at a prescribed perceived exertion level of 6. The subjects were instructed to manipulate the resistance and striding cadence to maintain the prescribed perceived exertion level for 15 min, during which VO(2) and HR were analyzed. RESULTS: The results from this study demonstrated that at exercise steady state, which occurred 4 min after the start of the protocol, relative VO(2) averaged 75.2+/-12.9% and relative HR was 91+/-.01%. Oxygen utilization and HR values were found to be significantly higher than a corresponding relative RPE in 20 recreational exercises when exercising on an elliptical fitness cross-trainer. CONCLUSION: This response has implications when using RPE as a prescriptive means of intensity regulation.

The effects of rest interval on quadriceps torque and perceived exertion in healthy males.

BACKGROUND: The ability to generate maximal muscular force is dependent upon time mediated mechanisms of fatigue. Interset rest interval length may not only affect force production but may also manifest changes in ratings of perceived exertion (RPE). The purpose of this study was to examine the effects of rest interval on quadriceps torque and RPE during multiple sets of resisted knee extensions. METHODS: 14 healthy male volunteers were assessed for concentric isokinetic quadriceps peak torque, total work, and average power on the Biodex System II Isokinetic Dynamometer at a preset angular velocity of 180 deg.sec-1. Perceived exertion was measured with a modified category-ratio scale (CR-10). Under isometric conditions the perceptual range was anchored with one high and two low anchors. Subjects were randomly assigned to one of two groups: short rest interval (Group 1, 40 sec) and long rest interval (Group 2, 160 sec). All subjects performed 4 sets of 20 maximal isokinetic contractions with an inter-set rest interval that corresponded to their group assignment. Following the completion of each set subjects were asked to assign a rating out of 10 to the feelings in their quadriceps by visually observing a chart of the CR-10 scale. RESULTS: The results demonstrated a significantly greater decline in quadriceps peak torque (p < 0.05), total work (p < 0.05), and average power (p < 0.05) by Group 1 as compared to Group 2. Changes in RPE across the 4 sets of exercise did not show a significant difference between the 2 groups. CONCLUSIONS: The generation of quadriceps torque is a function of rest interval length, whereas perceived exertion appears to be unaffected.

The effects of a functional elbow brace on medial joint stability: a case study.

Medical elbow ligament sprains in athletics can be traumatic and disabling. In this case report, we outline the effect of a prototype functional elbow brace on joint stability in a female collegiate javelin thrower with an ulnar collateral ligament sprain. A valgus force to both elbows was applied using graded stress radiography (Telos GA-II/E stress device) at 0, 5, 10, and 15 kiloPascals (kPa) of pressure. The increase in gap width between the coronoid process and the medial epicondyle was measured from anteroposterior radiographs to determine medial displacement. The brace resulted in less displacement in both injured and noninjured ulnar collateral ligament; injured ulnar collateral ligament demonstrated greater displacement regardless of condition. The brace restored medial stability to the elbow joint by 49%, 38%, and 35% at 5, 10, and 15 kPa of pressure, respectively. The application of the brace may be useful in athletes with ulnar collateral ligament injuries.