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Harleen Mangat Tajamul Hussain C Sundaram MP JS Anandaraj 《Indian journal of clinical biochemistry : IJCB》2002,17(2):74-79
Poly A RNA status and itsin vitro translation in a rabbit reticulolysate cell free system, were assessed in the skeletal muscle of young boys with Duchenne
muscular dystrophy. Compared to normals there is a significant 48% increase in poly A RNA content of dystrophic muscle and
its translatability was increased by 56% based on35S methionine incorporation into total protein systhesised. Immunoprecipitation of the translated products with monospecific
antibodies showed that there is a 2.6 fold and a 2 fold increase in m and μ calpains respectively. This underlines the importance
of both synthetic and degenerative activities in the early pathology in DMD muscle. 相似文献
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Purpose: Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability. Method: In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries. Results: Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies. Conclusion: We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries. 相似文献
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Liebenberg J Scharf J Forrest D Dufek JS Masumoto K Mercer JA 《Journal of sports sciences》2011,29(2):207-214
The aim of this study was to investigate how lower extremity muscles are influenced by body weight support during running at different speeds. Nine participants (age 24 ± 2 years, height 1.75 ± 0.12 m, mass 73.5 ± 15.7 kg) ran at 100%, 115%, and 125% of preferred speed at 100%, 90%, 80%, 70%, and 60% of body weight on a treadmill that provided body weight support. Preferred speed was self-selected by each participant and represented a speed that he or she could sustain if going for a 30 min run. Electromyography (EMG) data were recorded (1000 Hz, 1 min) from the bicep femoris, rectus femoris, tibialis anterior, and gastrocnemius for each condition together with knee angle (electrogoniometer). Average and root mean square EMG were calculated across 30 s. Muscle patterns were determined by smoothing (low-pass filter, 4 Hz) and extracting patterns for 49 cycles defined by consecutive maximum knee flexion angles. Repeated-measures analyses of variance were used to compare average and root mean square across body weight and speeds. Correlations were computed between the 100% speed/100% body weight condition and all other conditions per muscle. There was no interaction between body weight and speed (P > 0.05). Average and root mean square decreased as body weight decreased for all muscles (P < 0.05) and increased across speeds for all muscles (P < 0.05). Correlations for all muscles between conditions were high (range: 0.921-0.999). Although a percent reduction in body weight did not lead to the same reduction in muscle activity, it was clear that reducing body weight leads to a reduction in muscle activity with no changes in muscle activity patterns. 相似文献
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Andrew D. Nordin Janet S. Dufek C. Roger James Barry T. Bates 《Journal of sports sciences》2017,35(18):1858-1863
Our purpose was to use group and single-case methods to examine inter-individual variability in the context of factors related to landing injuries. We tested the load accommodation strategies model (An exploration of load accommodation strategies during walking with extremity-carried weights. Human Movement Science, 35, 17–29) using landing impulse, revealing pre-landing strategies following height and external load manipulations. Ten healthy volunteers (8 male, 2 female, 24.0 ± 1.4 years, 1.72 ± 0.06 m, 73.5 ± 8.7 kg) were analysed across 12 trials in each of three load conditions (100% body weight [BW], 110% BW, 120% BW) from two landing heights (30 cm, 60 cm). Landing impulse (BW ? s) was computed for each participant-condition-trial, using impulse ratios (unit-less; BW ? s/BW ? s) to evaluate load accommodation strategies between adjacent load conditions (110%/100%, 120%/110%) at each landing height. Load accommodation strategy classifications were based on 95% confidence intervals (CIs) containing mechanically predicted impulse ratios (1.10 and 1.09 for 110/100% BW and 120/110% BW, respectively; α = 0.05). Mean group impulse ratios matched and exceeded predicted impulse ratios. Single-case analyses revealed a range of individual landing strategies that might be overlooked during group analyses, possibly uncovering individuals at greater risk of injury during landing activities. 相似文献
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ABSTRACT Loading rates have been linked to running injuries, revealing persistent impact features that change direction among three-dimensional axes in different footwear and footstrike patterns. Extracting peak loads from ground reaction forces, however, can neglect the time-varying loading patterns experienced by the runner in each footfall. Following footwear and footstrike manipulations during laboratory-based overground running, we examined three-dimensional loading rate-time features in each direction (X, Y, Z) using principal component analysis. Twenty participants (9 M, 11 F, age: 25.3 ± 3.6 y) were analysed during 14 running trials in each of two footwear (cushioned and minimalist) and three footstrike conditions (forefoot, midfoot, rearfoot). Two principal components (PC) captured the primary loading rate-time features (PC1: 42.5% and PC2: 22.8% explained variance) and revealed interaction among axes, footwear, and footstrike conditions (PC1: F (2.1, 40.1) = 5.6, p = 0.007, η 2 = 0.23; PC2: F (2.0, 38.4) = 62.3, p < 0.001, η 2 = 0.77). Rearfoot running in cushioned footwear attenuated impact loads in the vertical direction, and forefoot running in minimalist footwear attenuated impact loads in the anterior-posterior and medial-lateral directions relative to forefoot running in cushioned shoes. Loading patterns depend on footwear and footstrike interactions, which require shoes that match the runner’s footstrike pattern. 相似文献
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Joshua P. Bailey Janet S. Dufek Julia Freedman Silvernail James Navalta John Mercer 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(5):618-632
ABSTRACT During the course of a training programme, runners will typically increase running velocity and volume possibly encountering fatigue during a run, which is characterised as a feeling of general tiredness. The purpose of the current study was to identify whether or not level of perceived fatigue affects coordination and coordination variability in healthy runners during the recovery velocity of an endurance interval run. A total of 20 endurance runners completed a 1-hour run that included running velocity intervals at 75% of estimated 10 k race pace (5 minutes) and estimated 10 k race pace (1 minute). After each run, participants completed a fatigue questionnaire and were grouped based on their post-run self-reported perceived fatigue. 3D motion capture data were collected during the run and analysed to generate coordination patterns and variability of the patterns as dependent variables. Multiple mixed model ANOVAs were conducted to test for differences between perceived fatigue groups. Coordination and variability differences were reported in a number of couplings during transition phases (late and early stance) and events (toe-off and foot contact) of the gait cycle. It was concluded that the level of perceived fatigue affected coordination and coordination variability during the recovery velocity of a 1-hour interval run. 相似文献
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Characteristics of shock attenuation during fatigued running 总被引：1，自引：1，他引：0
The aim of this study was to examine shock attenuation before and after completing a maximal effort graded exercise test while running on a treadmill. Ten individuals ran before and after a maximal graded exercise test with running speed controlled between conditions. Transfer functions were calculated using surface-mounted accelerometers to represent shock attenuation. An accelerometer was mounted on the distal aspect of the tibia and another on the anterior aspect of the forehead. Ten strides were analysed in each condition for all participants. Paired t-tests were used to compare each dependent variable (shock attenuation, stride length, rate of oxygen consumption) between conditions (running before vs after the exercise test). Oxygen consumption was 16% greater when running after the graded exercise test (47.9 +/- 5.0 ml x kg(-1) x min(-1); mean+/-s) than when running before it (41.1 +/- 2.7 ml x kg(-1) x min(-1)) (P < 0.05). Stride length was similar during running before (2.71 +/- 0.15 m) and after (2.75 +/- 0.17 m) the graded exercise test (P > 0.05). Shock attenuation was, on average, 12% lower during running after (-9.8 +/- 2.6 dB) than before (-11.3 +/- 2.7 dB) the graded exercise test (P < 0.05). We conclude that less shock was attenuated during fatigued than non-fatigued running and that only subtle changes in stride length were made while fatigued. 相似文献
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The purpose of this study was to examine changes in landing performance during fatigue that could result in increased stress fracture injury risk. Five participants performed nonfatigued and fatigued drop landings (0.60 m), while ground reaction force (GRF), electromyographic (EMG) activity, and kinematics were recorded. Fatigue was defined as a 5-20% reduction in vertical jumping performance. Single-subject analyses revealed that all participants were affected (p < or = .05) by fatigue. Post hoc comparisons revealed a group effect (p < or = .05) for selected variables. Participants landed with (a) less joint flexion at contact and used a greater range of motion, (b) greater GRF peaks and loading rates, and (c) less EMG activity. These changes were consistent with greater risk of stress fracture. 相似文献
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P. Aruna Prabhavathi Tajamul Hussain G. N. Mallikarjuna Rao MP JS Anandaraj 《Indian journal of clinical biochemistry : IJCB》2002,17(1):94-98
The efficacy of two intragenic polymorphic markers of factor VIII gene has been examined in Andhra Pradesh population with
a view to confirm/revise the strategy for carrier detection that would be precise and economical. The haemophilia A carrier
was detected using Bcl I and Xba I polymorphic sites in intron 18 and 22 respectively. The cumulative efficiency of these
two sites for detection of carriers is 100% since all 15 families tested were informative for one of these polymorphisms,
thus confirming their usefulness for factor VIII gene mutations found in Andhra Pradesh. 相似文献
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