Eccentric Torque Research Articles

Energy cost and metabolic power of Australian football

Rhodes University, South Africa Introduction: The objective of the current investigation was to determine the strength changes within the lower limb musculature of specialised batsmen induced by twowork bouts of differing intensities. Methods: Twenty cricket batsmen (age 22.6±4.74 years; stature 179.5±6.38 cm; mass 80.7±11.77kg) were tested. Two experimental conditions, representative of a high(HVR representing twelve sprints per over) and moderate-volume running (MVR representing six sprints per over) batting protocol were compared in a laboratory setting. Muscle strength measures were collected prior to, and following both protocols using the Cybex 6000 Isokinetic Dynamometer, and included; concentric and eccentricmeasures of both knee flexors and extensors. Peak torque, total work, average power and the hamstring to quadriceps ratio were the isokinetic strength parameters under study with sampling conducted at speeds of 60 and 270◦ s−1. Results and discussion: Both the HVR and MVR conditions resulted in significant (p<0.05) reductions in concentric and eccentric extensor and eccentric flexor peak torque at 60◦ s−1. However, expectedly, the largest changes were seen following the HVR condition. For example, peak concentric and eccentric knee extensor (EXT) (−17.17% and -16.07% respectively) and eccentric flexor (FLEX) (−17.49%) values decreased significantly (p<0.05) following the HVR condition at 60◦ s−1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR condition. In contrast, the MVR condition elicited significant (p<0.05) reductions in concentric extensor average power values at speeds of 60◦ s−1, whereas the HVR protocol revealed no changes in average power for concentric or eccentric flexor and extensor values at both speeds. Thus, although strength was negatively compromised followingboth conditions, thiswas to a greater extent following the high volume sprinting condition. In conclusion, the isokinetic concentric strength decrementwas particularly exaggerated following the HVR condition while eccentric strength decrements were evident following both conditions.

Impact of a simulated one day international century on batting performance in cricket

Rhodes University, South Africa Introduction: The objective of the current investigation was to determine the strength changes within the lower limb musculature of specialised batsmen induced by twowork bouts of differing intensities. Methods: Twenty cricket batsmen (age 22.6±4.74 years; stature 179.5±6.38 cm; mass 80.7±11.77kg) were tested. Two experimental conditions, representative of a high(HVR representing twelve sprints per over) and moderate-volume running (MVR representing six sprints per over) batting protocol were compared in a laboratory setting. Muscle strength measures were collected prior to, and following both protocols using the Cybex 6000 Isokinetic Dynamometer, and included; concentric and eccentricmeasures of both knee flexors and extensors. Peak torque, total work, average power and the hamstring to quadriceps ratio were the isokinetic strength parameters under study with sampling conducted at speeds of 60 and 270◦ s−1. Results and discussion: Both the HVR and MVR conditions resulted in significant (p<0.05) reductions in concentric and eccentric extensor and eccentric flexor peak torque at 60◦ s−1. However, expectedly, the largest changes were seen following the HVR condition. For example, peak concentric and eccentric knee extensor (EXT) (−17.17% and -16.07% respectively) and eccentric flexor (FLEX) (−17.49%) values decreased significantly (p<0.05) following the HVR condition at 60◦ s−1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR condition. In contrast, the MVR condition elicited significant (p<0.05) reductions in concentric extensor average power values at speeds of 60◦ s−1, whereas the HVR protocol revealed no changes in average power for concentric or eccentric flexor and extensor values at both speeds. Thus, although strength was negatively compromised followingboth conditions, thiswas to a greater extent following the high volume sprinting condition. In conclusion, the isokinetic concentric strength decrementwas particularly exaggerated following the HVR condition while eccentric strength decrements were evident following both conditions.

A two- and five-year follow-up of clinical outcome after ACL reconstruction using BPTB or hamstring tendon grafts: a prospective intervention outcome study

The aim of the present study was to evaluate and compare objective and subjective outcome in patients 2 and 5 years after anterior cruciate ligament (ACL) reconstruction with either bone-patellar tendon-bone (BPTB) or hamstring grafts. The second aim was to report the prevalence of re- and contralateral ACL ruptures. Sixty-eight patients (BPTB, n = 34 and hamstring graft, n = 34) were evaluated preoperatively, 2 and 5 years after ACL reconstruction. Anterior knee laxity and rotational knee joint stability, muscle torque, hop length, anterior knee pain, activity level and self-reported knee function and quality of life were evaluated within and between groups. The prevalence of re- and contralateral ACL ruptures was also recorded. No significant difference in anterior knee laxity, rotational knee joint stability, hop length anterior knee pain or knee function and quality of life were noted at the 5-year follow-up. No significant differences in concentric or eccentric quadriceps torque at 90°/s and 230°/s were found at any of the follow-ups between and within grafts. A significant group difference in hamstring torque 1.05 (0.02) for BPTB and 0.89 (0.02) for hamstring grafts, and in hop length (leg symmetry index) follow-up 0.94 (0.07) for BPTB compared to 0.99 (0.07) for hamstring grafts (P = 0.002) was found at the 2 year follow-up in favour of the BPTB graft, but not at the 5 year follow-up. A significant improvement over time, irrespective of graft, was found in the KOOS's subscales Sport/Rec and quality of life (P < 0.001). None of the patients, irrespective of group, returned to their pre-injury level of sport (P < 0.05). Over the five postoperative years, one man and eight women (13 %) (hamstring graft, n = 5 and BPTB graft, n = 4), sustained a total of 11 (16.2 %) new ACL ruptures: seven (10.2 %) re-ruptures and four (5.9 %) ruptures of the contralateral ACL. At the 5-year follow-up, there were no significant differences in terms of anterior knee laxity, rotational knee joint stability, muscle torque, anterior knee pain, hop performance, quality of life or activity level between patients who had undergone reconstruction with BPTB or hamstring grafts. None of the patients, irrespective of group, had returned to their pre-injury level of activity. Eight out of the nine patients who had sustained a second ACL rupture were women.

Mechanomyographic and Electromyographic Responses During Fatiguing Eccentric Muscle Actions of the Leg Extensors

The purpose of the current study was to examine the patterns of responses for torque, mechanomyographic (MMG) amplitude, MMG frequency, electromyographic (EMG) amplitude, and EMG frequency across 30 repeated maximal eccentric muscle actions of the leg extensors. Eleven moderately trained females performed an eccentric fatigue protocol at 30°/s with MMG and EMG signals recorded from the vastus lateralis. The results indicated there were significant (P<.05) decreases in MMG frequency (linear, r2=.395), EMG frequency (linear, r2=.177), and torque (linear, r2=.570; % decline=9.8±13.3%); increases in MMG amplitude (linear, r2=.783); and no change in EMG amplitude (r2=.003). These findings suggested that the neural strategies used to modulate torque during fatiguing eccentric muscle actions involved de-recruitment of motor units, reduced firing rates, and synchronization. In addition, the decreases in eccentric torque were more closely associated with changes in MMG frequency than EMG frequency. Thus, these findings indicated that MMG frequency, compared with EMG frequency, more accurately tracks fatigue during repeated maximal eccentric muscle actions.

Effect of Hypohydration on Peripheral and Corticospinal Excitability and Voluntary Activation

We investigated whether altered peripheral and/or corticospinal excitatory output and voluntary activation are implicated in hypohydration-induced reductions in muscle isometric and isokinetic (90°.s−1) strength. Nine male athletes completed two trials (hypohydrated, euhydrated) comprising 90 min cycling at 40°C, with body weight losses replaced in euhydrated trial. Peripheral nerve and transcranial magnetic stimulations were applied during voluntary contractions pre- and 40 min post-exercise to quantify voluntary activation and peripheral (M-wave) and corticospinal (motor evoked potential) evoked responses in m. vastus medialis. Both maximum isometric (−15.3±3.1 vs −5.4±3.5%) and isokinetic eccentric (−24.8±4.6 vs −7.3±7.2%) torque decreased to a greater extent in hypohydrated than euhydrated trials (p<0.05). Half relaxation time of the twitch evoked by peripheral nerve stimulation during maximal contractions increased after exercise in the hypohydrated (21.8±9.3%) but stayed constant in the euhydrated (1.6±10.7%; p = 0.017) condition. M-wave amplitude during maximum voluntary contraction increased after exercise in the heat in hypohydrated (10.7±18.0%) but decreased in euhydrated condition (−17.4±16.9%; p = 0.067). Neither peripheral nor cortical voluntary activation were significantly different between conditions. Motor evoked potential amplitude increased similarly in both conditions (hypohydrated: 25.7±28.5%; euhydrated: 52.9±33.5%) and was accompanied by lengthening of the cortical silent period in euhydrated but not hypohydrated condition (p = 0.019). Different neural strategies seem to be adopted to regulate neural drive in the two conditions, with increases in inhibitory input of either intracortical or corticospinal origin during the euhydrated trial. Such changes were absent in the hypohydrated condition, yet voluntary activation was similar to the euhydrated condition, perhaps due to smaller increases in excitatory drive rather than increased inhibition. Despite this maximal isometric and eccentric strength were impaired in the hypohydrated condition. The increase in peripheral muscle excitability evident in the hypohydrated condition was not sufficient to preserve performance in the face of reduced muscle contractility or impaired excitation-contraction coupling.

Influence of the Hip Flexion Angle on Isokinetic Hip Rotator Torque and Acceleration Time of the Hip Rotator Muscles

The purpose of this study was to verify the influence of the hip flexion angle on isokinetic rotator torque and acceleration times of the hip medial and lateral rotator muscles. Twenty-one healthy women were included in this study. The hip rotator function was evaluated at 3 different hip flexion angles (10°, 40°, and 90°). The results showed that both eccentric and concentric hip lateral rotator torques were greater at 40° of hip flexion when compared with 90°. Moreover, both the eccentric and concentric hip medial rotator torques were greater at 90° of hip flexion than at 40° and 10°, and greater at 40° than at 10°. In addition, both the eccentric and concentric hip medial to lateral rotator torque ratios were greater at 90° of hip flexion than at 40° and 10°, and greater at 40° than at 10°. Finally, the acceleration times of the hip medial rotator muscles were smaller at 90° of hip flexion than at 10° and smaller at 40° than at 10°. The current results highlight the importance of evaluating the hip rotator muscles at different hip flexion angles to comprehensively assess their functions.

Adaptive changes in the dominant shoulders of female professional overhead athletes

The aim of our study was to evaluate adaptive changes in the dominant shoulders of female professional overhead athletes, their mutual association, and relation between adaptive changes and shoulder injury. Thirty-six female professional volleyball and handball players were divided into two groups: 14 athletes were included in the symptomatic group (positive shoulder injury history and specific shoulder tests) and 22 athletes were included in the asymptomatic group (negative shoulder injury history and specific shoulder tests). Clinical examinations with specific shoulder tests, evaluation of rotational mobility, and symptoms of malposition and dyskinesis of the dominant scapula (SICK scapula syndrome) were performed. Glenohumeral rotators were isokinetically tested at 60 and 150°/s, with evaluation of stability ratios and rotator fatigability. On average, the participants had decreased internal rotation (P<0.001) and increased external rotation (P<0.001), lower spiking (P<0.01 at 60 and 150°/s) and conventional ratios (P≤0.01 at 60 and 150°/s), lower eccentric external rotator peak torques (eER) (P≤0.05 at 60 and 150°/s), and marginally lower eccentric internal rotator peak torques at 60°/s (P=0.061) on the dominant side compared with the nondominant side. The symptomatic group showed decreased ER (P=0.021), higher deficit of dominant eER at 60°/s (P=0.049), and higher fatigability of internal (P=0.013) and external rotators (P=0.028). The athletes with increased ER had more scapular lateralization (ρ=0.340, P=0.042), higher spiking ratios at 60°/s (ρ=0.349, P=0.037) and 150°/s (ρ=0.330, P=0.049), and lower cocking ratios at 60°/s (ρ=-0.477, P=0.003). Decreased dominant ER, higher deficit of dominant eccentric ER peak torques, and higher dominant rotator fatigability correlate with previous shoulder pain/injury. Different adaptive changes (rotational mobility, SICK scapula signs, and glenohumeral muscular imbalance) are inter-related. As a form of both prevention and rehabilitation for the athletes at risk, we recommend individually adjusted shoulder training on the basis of clinical and isokinetic testing.

Can glenohumeral joint isokinetic strength and range of movement predict injury in professional rugby league

ObjectiveTo isokinetically record shoulder strength scores and range of motion in a professional rugby league squad. To prospectively monitor injuries over a season looking for associations between measured variables and injury. DesignA cohort study design involving prospective screening of risk factors with subsequent injury surveillance. SettingUniversity Sports Science Laboratory and Professional Rugby League Club. ParticipantsAll players participating in the clubs reserve team squad for the 2011 season (n = 20). Main outcome measuresConcentric (Con) and eccentric (Ecc) peak torque values; ratio of Ecc internal rotation IR to Con external rotation ER, also known as the dynamic control ratio (DCR), shoulder range of IR and ER. ResultsEight players (36%) received a total of eleven injuries over the season. There were no statistically significant differences between injured and non-injured shoulders. IR range of movement was significantly lower in injured versus non-injured groups with left (p = 0.022) and right (p = 0.024). Left IR range of movement was predictive of injury using binary logistic regression (p = 0.046). No isokinetic strength parameters reached statistical significance (p > 0.05) for prediction of injury; however size effects were apparent for reduced con IR of the left shoulder and Ecc IR of both shoulders. ConclusionReduced shoulder IR range appears predictive of future shoulder injury although caution is drawn due to small participant numbers. Injury prevention strategies for rugby league players should include exercises to improve shoulder IR and possibly Ecc IR strength.

Neuromechanical properties of the triceps surae in young and older adults

The aim of this study was to compare voluntary and involuntary force generating capacity of the triceps surae muscles in healthy young and older adult participants during isometric and isokinetic contractions. Ultrasound was used to measure medial gastrocnemius (MG) fascicle length during maximal voluntary isometric contractions and supra-maximal isometric twitch contractions at five ankle angles throughout the available range of motion, as well as isokinetic concentric and eccentric contractions at four ankle velocities. Maximum voluntary activation of the plantar flexors was assessed using the twitch interpolation technique. Peak plantar flexor torque was significantly lower in older adults compared to young participants by 42%, 28% and 43% during maximal voluntary isometric contractions, supra-maximal isometric twitch and concentric contractions respectively. No age-related differences in eccentric torque production were detected. When age-related differences in triceps surae muscle volume determined from MRI were taken into account, the age-related peak plantar flexor torque deficits for maximum voluntary isometric, supra-maximal twitch, and concentric contractions were 24%, 19% and 24% respectively. These age-related differences in torque were not explained by torque–length–velocity behaviour of the MG muscle fascicles, passive plantar flexor torque–angle properties, decreased neural drive of the plantar flexor muscles or antagonistic co-activation of the tibialis anterior muscle. The residual deficit in isometric and concentric plantar flexor torques in healthy older adults may involve reduced muscle quality. A significant reduction in supra-maximal twitch torque at longer MG fascicle lengths as well as a lower MG fascicle velocity during eccentric contractions in older adults was detected, which could possibly be a function of the reported increased Achilles tendon compliance in older adults.

Performance Enhancement Effects of Fédération Internationale de Football Association’s “The 11+” Injury Prevention Training Program in Youth Futsal Players

To evaluate if Fédération Internationale de Football Association's "The 11+" injury prevention program improves physical fitness and technical performance in youth futsal players. Randomized cohort study. Futsal club. Thirty-six futsal players (17.3 ± 0.7 years). Players were randomized to an intervention group (n = 18) or a control group (n = 18). Intervention group performed "The 11+" twice per week for 12 weeks. Isokinetic testing to access maximal quadriceps (Q) and hamstring (H) strength, vertical jump (squat jump, SJ; countermovement jump, CMJ), 5-m and 30-m sprint, agility, slalom, and balance performances were also measured. Intervention group increased (P < 0.05) quadriceps concentric (14.7%-27.3%) and hamstrings concentric (9.3%-13.3%) and eccentric (12.7%) peak torque. Intervention group improved functional H:Q ratio by 1.8% to 8.5% (P < 0.05). Intervention group improved (P < 0.05) SJ (13.8%) and CMJ (9.9%) and 5-m and 30-m sprint (8.9% and 3.3%, respectively), agility (4.7%), and slalom (4.8%) performances. Intervention group also improved balance, by decreasing the number of falls by 30% in the nondominant limb. No changes were observed in control group. The results suggest that 'The 11+' can be used as an effective conditioning means for improving physical fitness and technical performance of youth futsal players.

The influence of forefoot varus on eccentric hip torque in adolescents

Hip strength impairments have been established as risk factors for lower limb injuries. Hip muscles strength might be influenced by foot misalignments, however this has not yet been verified. Forefoot varus (FV) has been shown to cause subtalar joint hyperpronation. Subtalar hyperpronation has been associated with excessive lower limb internal rotation in weight-bearing activities. Also, subtalar hyperpronation might result in greater ground reaction force dissipation at the foot. Consequently, there would be less demand for force dissipation at the hip joint, which could reduce the capacity for hip eccentric torque in these subjects. Therefore, the purpose of this study was to determine if FV influences the eccentric hip torque generation of young subjects. Forty-four sedentary, healthy adolescents were divided into 2 groups: subjects with FV (VG, n = 22) and subjects with neutral forefoot alignment (CG, n = 22). An isokinetic dynamometer was used to assess the eccentric torque generated in hip extension and external rotation in these subjects. Group differences were assessed using a one-way multivariate analysis of variance. The VG presented smaller eccentric torque for hip extension (P = 0.014) when compared to the CG, with no difference between groups in external rotation torque (P = 0.433). These results indicate that FV influences hip eccentric torque generation of young subjects. Considering that the muscles involved in hip extension are related to the stabilization of the lumbar spine, hip and knee, these findings bring further enlightenment to the role of foot misalignments as risk factors for injuries in the lower limbs and lumbo-pelvic complex in young subjects.

Enhanced force production in old age is not a far stretch: an investigation of residual force enhancement and muscle architecture

In older adults, isometric force production is enhanced following a voluntary lengthening contraction when compared with isometric force produced at the same muscle length without a prior lengthening contraction. This phenomenon is termed residual force enhancement (RFE), and appears to be related to the age-related maintenance of eccentric (ECC) strength. However, it is unknown whether age-related changes in muscle architecture contribute to greater RFE at short and long muscle lengths in old age. Neuromuscular properties of the knee extensors were assessed on a HUMAC NORM dynamometer. Torque was examined in young (26 ± 3 year, n = 11) and old men (77 ± 6 year, n = 11) during brief maximal voluntary isometric contractions (MVC) at 80° and 120° (180° representing full knee extension) and then compared with torque during a steady-state phase at the same joint angle following a maximal voluntary lengthening contraction at 30°/sec over a 60° joint excursion; either from 140 to 80° (long), or from 180 to 120° (short). Ultrasound images were obtained from the vastus lateralis during the isometric phase for each condition. When comparing the ECC torque with the MVC isometric torque, old men had 17% greater ECC:MVC ratios than young men, confirming an age-related maintenance of ECC strength. The extent of RFE was greater at long versus short but independent of age. At rest, old had shorter (∼18%) and less pennated (∼22%) fascicles. However, changes in fascicle length and pennation during contraction did not contribute to RFE in either group. Thus, age-related changes in muscle architecture may not contribute to RFE.

Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running

The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180° s(-1) was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180° s(-1) (+2 %), being significantly reduced compared to before IERT (p < 0.05), however, RFD loss remained at -11 % (p > 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training.

Men with early degrees of knee OA have alterations in voluntary activity of the vastus lateralis muscle and decreases in eccentric knee extensor torque

Men with early degrees of knee OA have alterations in voluntary activity of the vastus lateralis muscle and decreases in eccentric knee extensor torque

Time Course of Neuromuscular Adaptations to Knee Extensor Eccentric Training

This study investigated the chronology of neural and morphological adaptations to knee extensor eccentric training and their contribution to strength gains in isometric, concentric and eccentric muscle actions. 20 male healthy subjects performed a 12-week eccentric training program on an isokinetic dynamometer, and neuromuscular evaluations of knee extensors were performed every 4 weeks. After 12 training weeks, significant increases were observed for: isometric (24%), concentric (15%) and eccentric (29%) torques; isometric (29%) and eccentric (33%) electromyographic activity; muscle thickness (10%) and anatomical cross-sectional area (19%). Eccentric and isometric torques increased progressively until the end of the program. Concentric torque and muscle mass parameters increased until the eighth training week, but did not change from this point to the twelfth training week. Eccentric and isometric activation increased at 4 and 8 training weeks, respectively, while no change was found in concentric activation. These results suggest that: 1) the relative increment in concentric strength was minor and does not relate to neural effects; 2) eccentric and isometric strength gains up to 8 training weeks are explained by the increased neural activation and muscle mass, whereas the increments in the last 4 training weeks seem to be associated with other mechanisms.

Stair descending exercise increases muscle strength in elderly males with chronic heart failure

BackgroundPrevious studies from our group have shown that "pure" eccentric exercise performed on an isokinetic dynamometer can induce health-promoting effects that may improve quality of life. In order to investigate whether the benefits of "pure" eccentric exercise can be transferred to daily activities, a new and friendlier way to perform eccentric exercise had to be invented. To this end, we have proceeded to the design and construction of an automatic escalator, offering both stair descending (eccentric-biased) and stair ascending (concentric-biased) exercise.FindingsTwelve elderly males (60-70 yr) with chronic heart failure participated in the present study. Participants carried out six weeks of stair descending or ascending training on the novel SmartEscalator device. Muscle damage and performance indices were evaluated before and at day 2 post exercise at the first and sixth week of training. Both training regimes increased, albeit not significantly in some cases, eccentric, concentric and isometric torque. After six weeks of stair descending exercise, eccentric, concentric and isometric peak torque increased 12.3%, 7.7% and 8.8%, respectively, whereas after stair ascending exercise eccentric, concentric and isometric peak torque increased 7.1%, 9.6% and 5.9%, respectively.ConclusionsStair descending exercise appears to be a pleasant and mild activity that can be easily followed by the elderly. Compared to the more demanding stair ascending exercise, changes in muscle strength are similar or even greater. Elderly or people with impaired endurance wishing to increase their muscle strength may be benefited by participating in activities with strong eccentric component, such as stair descending.

The Eccentric Torque Production Capacity of the Ankle, Knee, and Hip Muscle Groups in Patients with Unilateral Chronic Ankle Instability

The aim of this study was to investigate eccentric torque production capacity of the ankle, knee and hip muscle groups in patients with unilateral chronic ankle instability (CAI) as compared to healthy matched controls. In this case-control study, 40 participants (20 with CAI and 20 controls) were recruited based on convenient non-probability sampling. The average peak torque to body weight (APT/BW) ratio of reciprocal eccentric contraction of ankle dorsi flexor/plantar flexor, ankle evertor/invertor, knee flexor/extensor, hip flexor/extensor and hip abductor/adductor was determined using an isokinetic dynamometer. All subjects participated in two separate sessions with a rest interval of 48 to 72 hours. In each testing session, the torque production capacity of the ankle, knee, and hip muscle groups of only one lower limb was measured. At first, 3 repetitions of maximal eccentric-eccentric contraction were performed for the reciprocal muscles of a joint in a given movement direction. Then, the same procedure of practice and testing trials was repeated for the next randomly-ordered muscle group or joint of the same limb. There was no significant interaction of group (CAI and healthy controls) by limb (injured and non-injured) for any muscle groups. Main effect of limb was not significant. Main effect of group was only significant for eccentric torque production capacity of ankle dorsi flexor and hip flexor muscle groups. The APT/BW ratio of these muscles was significantly lower in the CAI group than the healthy controls (P<0.05). CAI is associated with eccentric strength deficit of ankle dorsi flexor and hip flexor muscles as indicated by reduction in torque production capacity of these muscles compared to healthy controls. This strength deficit appeared to exist in both the injured and non-injured limbs of the patients.

Indirect measures of substrate utilisation following exercise-induced muscle damage

This study investigated whether exercise-induced muscle damage (EIMD) resulted in changes to whole-body substrate utilisation during exercise performed during the subsequent 48 hours. Eight males (31±6 years) performed 30 minutes of bench-stepping exercise. One leg performed eccentric contractions (Ecc) by lowering the body whilst the control leg performed concentric contractions (Con) by raising the body. On the two days following bench-stepping exercise participants performed measures of muscle function on an isokinetic dynamometer and undertook a bout of one leg cycling exercise, at two differing workloads, with the first workload (WL1) at 1.5±0.25 W/kg and the second workload (WL2) at 1.8±0.25 W/kg with each leg. Expired respiratory gases were collected during cycling to estimate whole body substrate utilisation. There were significant decrements in measures of muscular performance (isometric force, concentric and eccentric torque) and increased perception of soreness in Ecc compared with Con (P < 0.05). The effect of the Ecc treatment on substrate utilisation during one-legged cycling revealed a significant trial×time interaction with higher rates of CHO oxidation in the Ecc condition compared with Con that were further increased 48 hours later (P = 0.02). A significant treatment×time×effort interaction (P < 0.01) indicated the effect of the treatment altered as workload increased with higher rates of CHO oxidation occurring in WL2. This is consistent with greater reliance upon muscle glycogen. Suggesting that in EIMD, reductions in strength and increased feelings of soreness can be associated with greater reliance upon intramuscular CHO oxidation, than lipid, during subsequent concentric work.

The torque–velocity relationship in large human muscles: Maximum voluntary versus electrically stimulated behaviour

The in vivo maximum voluntary torque–velocity profile for large muscle groups differs from the in vitro tetanic profile with lower than expected eccentric torques. Using sub-maximal transcutaneous electrical stimulation has given torque–velocity profiles with an eccentric torque plateau ∼1.4 times the isometric value. This is closer to, but still less than, the in vitro tetanic profiles with plateaus between 1.5 and 1.9 times isometric. This study investigated the maximum voluntary and sub-maximum transcutaneous electrical stimulated torque–angle–angular velocity profiles for the knee extensors and flexors in a group of healthy males. Fifteen male subjects performed maximum voluntary and sub-maximum electrically stimulated (∼40% for extensors and ∼20% for flexors) eccentric and concentric knee extension and flexions on an isovelocity dynamometer at velocities ranging from ±50°s−1 to ±400°s−1. The ratio of peak eccentric to peak isometric torque (Tecc/T0) was compared between the maximum voluntary and electrically stimulated conditions for both extensors and flexors, and between muscle groups. Under maximum voluntary conditions the peak torque ratio, Tecc/T0, remained close to 1 (0.9–1.2) while for the electrically stimulated conditions it was significantly higher (1.4–1.7; p<0.001) and within the range of tetanic values reported from in vitro studies. In all but one case there was no significant difference in ratios between the extensors and flexors. The results showed that even the largest muscle groups have an intrinsic Tecc/T0 comparable with in vitro muscle tests, and it can be ascertained from appropriate in vivo testing.

Eccentric Peak Torque Analysis of Subjects Suffering from Chronic Ankle Instability

The purpose of this study was to examine the effect of chronic ankle instability (CAI) on eccentric peak torque of the ankle musculature. The study included fifty participants divided into two groups; the first group consisted of twenty five subjects suffering from CAI, the second group consisted of twenty five subjects with no prior history of ankle injury as control group. Eccentric peak torque of invertors, evertors, plantar-flexors and dorsiflexors was recorded for each participant at angular velocities 30 and 90o/sec by using (Biodex Medical Systems, Inc, Shirley, NY, USA). Analysis of variance (ANOVA) revealed that there was a significant deficit for eccentric inversion, eversion, and plantar flexion peak torques between CAI group and control group at both angular velocities (p 0.05). There was no significant increase in eccentric torque of invertors, evertors, plantar-flexors and dorsiflexors when the angular velocity increased from 30 to 90°/sec for normal and CAI group (p> 0.05). Eccentric strengthening of invertors, evertors, and plantar-flexors must be considered during rehabilitation of subjects suffering from chronic ankle instability.