Danny M. Pincivero

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 special ized variation of the sensory modality of touch that encompasses the sensation of joint movement (kines thesia) and joint position (joint position sense). Numer ous 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 proprioceptiveiy mediated activities in the rehabil itation program provides an understanding of the com plexity 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 de signed to include a proprioceptive component that ad dresses 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 pro fession of sports medicine one step closer to its ulti mate goal of restoring function.

Proprioception of the Ankle and Knee

SummaryProprioception 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 capsuloligamentous injury, partial restoration of proprioceptive acuity following ligamentous reconstruction, and have suggested beneficial proprioceptive changes resulting from comprehensive rehabilitation programmes.

Relation Between Open and Closed Kinematic Chain Assessment of Knee Strength and Functional Performance

ObjectiveTo assess the relationship between concentric isokinetic quadriceps and hamstring strength values with the single leg hop for distance test, a closed kinematic chain activity. DesignCorrelational study. SettingNeuromuscular Research Laboratory, University of Pittsburgh. ParticipantsSubjects for this study consisted of 37 college-aged volunteers (21 men, 16 women: mean age = 22.76 ± 3.52 years, height = 169.90 ± 10.60 cm, weight = 69.31 ± 14.60 kg) with no previous history of injury to the lower extremity. InterventionEach subject performed three trials of a single leg hop for distance lest for the dominant and nondominant limbs followed by isokinetic evaluation. Isokinetic strength was assessed with the Biodex System II Isokinetic Dynamometer (Biodex Medical Inc., Shirley, NY, U.S.A.) for the quadriceps and hamstrings at preset angular velocities of 60°/s (5 repetitions) and 180°/s (30 repetitions). Before testing, each subject completed a dynamic warm-up period that consisted of submaximal cycling at a fixed cadence of 60 revolutions/min followed subsequently by quadriceps and hamstring muscle stretching. Main outcome measuresThe distance hopped in centimeters was converted to a ratio of the distance hopped to the individual leg length measured from the anterior superior iliac spine to the medial malleolus. Isokinetic values were obtained for peak torque (Nm), peak torque/body weight (%), total work (Nm), and average power (W). Main resultsLow to moderate significant relationships were found to exist between the single leg hop for distance test and the isokinetic variables for the quadriceps and hamstrings of both limbs at each test velocity. Significant correlation coefficients ranged from r = 0.33 to r = 0.69 at 60°/s and r = 0.33 and r = 0.67 at 180°/s. Correlation coefficients were found to be statistically greater for the hamstrings than the quadriceps for total work and average power at 60°/s and for peak torque/body weight, total work, and average power at 180°/s (p < 0.05). ConclusionsConcentric quadriceps and hamstring strength seem to demonstrate a significant contribution to the single leg hop for distance test; however, the hamstring muscles may play a more important role during the propulsive phase, thereby enabling subjects to jump further.

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.

A Physiological Review of American Football

SummaryAmerican 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 V̇O2max 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.

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

&NA; Woods, S., T. Bridge, D. Nelson, K. Risse, and D.M. Pincivero. The effects of rest interval length on ratings of perceived exertion during dynamic knee extension exercise. J. Strength Cond. Res. 18(3):540–545. 2004.—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 subjects 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 subjects 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.

Activation linearity and parallelism of the superficial quadriceps across the isometric intensity spectrum.

The purpose of this study was to assess neuromuscular activation of the three superficial portions of the quadriceps femoris muscles during linearly increasing isometric contraction intensities. Thirty healthy volunteers were assessed for isometric electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles with the knee at 60° of flexion. For 5 s, subjects performed isometric contractions equivalent to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the average of three maximal voluntary contractions (MVC), in random order. Full‐wave rectified and integrated EMG signals over the middle 3 s of each contraction were expressed as a percentage of the activity recorded during the three averaged MVCs. One sample t‐tests and 95% confidence intervals were calculated at each relative torque level. A two‐factor analysis of variance (muscle by intensity) with repeated measures was performed to evaluate parallel activation across the intensity levels. Activation linearity was assessed via regression analysis for each muscle. VM activation was shown to be significantly lower than expected at 20–70% MVC. VL and RF activations were significantly higher than expected at 10% MVC, and RF EMG was less than expected at 40–70% MVC. EMG of VM was shown to increase significantly more than VL and RF from 80% to 90% MVC. Significant linear and quadratic relations were also demonstrated for all three muscles. Parallel activation of the superficial quadriceps muscles occurred from low to moderate intensities, whereas convergence was noted at near maximal intensities.

The effects of voluntary contraction intensity and gender on perceived exertion during isokinetic quadriceps exercise.

Abstract The objectives of the present study were to: (1) examine perceived exertion across different target voluntary contraction intensities, (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. The subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Each subject completed five maximal isokinetic, concentric quadriceps contractions in a seated position at 60° · s−1 to determine their single, highest peak torque. All subjects then completed, in a random order, 3–5 submaximal isokinetic contractions at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their single, highest peak torque. Each relative contraction level (i.e., percentage) was achieved by having the subjects attempt to match the peak of their torque curve to a horizontal line on a computer monitor. Perceived exertion was measured by asking the subjects to provide a number that corresponded to the feelings in their quadriceps during exercise by viewing a modified category-ratio (CR-10) scale. The results of a two-factor (gender × intensity) analysis of variance revealed a significant, intensity main effect (F8,232=92.19, P < 0.001, η2=0.77, 1–β=0.99) and no significant gender main effect (F8,232=2.66, P = 0.11, η2=0.09, 1–β=0.35) or interactions (F8,232 = 1.01, P=0.43, η2=0.04, 1–β=0.46). The findings of this study demonstrate that perceived exertion is significantly (P < 0.05) different from the specific target values on the CR-10 scale at 10%, and 50–90% maximum voluntary contraction. The results revealed that the increase in perceived exertion across the contraction intensities could be fit to both linear (F1,29=205.41, P < 0.001, η2=0.88, 1–β=0.99) and quadratic (F1,29=10.05, P=0.004, η2=0.26, 1–β=0.87) trends. These findings suggest that perceived exertion is underestimated during submaximal isokinetic exercise, and is not different between males and females.

The Effects of Muscular Fatigue on Shoulder Proprioception

ObjectiveTo assess the influence of muscular fatigue on active and passive shoulder proprioception within the midrange of rotation. DesignA randomized controlled, before-and-after design. SettingNeuromuscular research laboratory. ParticipantsTwenty recreationally active men (mean age, 23.81 ± 2.77 years) were randomly assigned to either a control or a fatigue group. Exclusion criteria were any history of upper extremity injury or pathology, cardiovascular disease, or disease affecting the sensory system. InterventionShoulder proprioception was assessed by active reproduction of passive positioning (ARPP), active reproduction of active positioning (ARAP), reproduction of passive positioning (RPP), and threshold to detect passive motion (TTDPM). For each test direction, the experimental group performed two bouts of maximal reciprocal concentric isokinetic internal and external contractions at 180°/s until peak torque decreased to 50% of the established maximum voluntary contraction. After two bouts of the fatigue protocol, subjects were randomly assessed for proprioception into internal or external rotation. Main Outcome MeasuresThe absolute angular error for active and passive proprioception was measured on the Biodex System II Isokinetic Dynamometer (Biodex Medical Inc., Shirley, NY, U.S.A.) and a proprioception testing device, respectively. Main ResultsA two-factor repeated measures analysis of variance revealed no significant interactions between the experimental and control groups for ARPP, ARAP, RPP, or TTDPM. ConclusionsShoulder proprioception was not affected by the short-duration, high-intensity protocol used in this study. This may be due to the lack of an extended recovery period observed with this type of fatigue regimen.

Quadriceps activation and perceived exertion during a high intensity, steady state contraction to failure

The ability to sustain a high‐intensity, steady‐state muscle contraction may have differential effects on neuromuscular activation and perceived exertion. The purpose of this study was to examine changes in neuromuscular activation and perceived exertion at a near‐maximal steady‐state contraction of the quadriceps in healthy men. Seventeen healthy, college‐aged male volunteers were studied during isometric contractions equivalent to 80% of the maximum voluntary contraction (MVC). Perceived exertion was measured with a modified category‐ratio scale (CR‐10). The CR‐10 scale was anchored with one high anchor at 100% MVC and one low anchor at 10% MVC. Subjects then performed an 80% MVC for as long as they could sustain it. Subjects were asked to rate the feelings in their quadriceps every 5 s during the contraction. The results demonstrated significant increases in neuromuscular activation of the vastus medialis and vastus lateralis muscles (P < 0.05) during the 80% MVC, but there were no significant muscle by time interactions. The results also demonstrated a significant increase (P < 0.05) in perceived exertion during the 80% MVC. Neuromuscular activation of both muscles, and perceived exertion, were found to increase in linear (P < 0.05) and quadratic (P < 0.05) trends. Alterations in motor unit discharge properties or impairments in muscle fiber membrane excitability may account for nonlinear increases in vastii muscle activation and perceived exertion.