Running Mechanics Research Articles

IMPROVEMENT IN ELEMENTARY STUDENTS PREFERENCE FOR PHYSICAL ACTIVITY ENGAGEMENT FOLLOWING PHYSICAL LITERACY PROGRAMMING

How children perceive their physical ability and body image can impact their involvement in physical activities. Teaching children basic mechanics and exposing them to new activities may increase the likelihood of selecting a physically active option versus a passive option. PURPOSE: The purpose of this research was to examine the relationship between body mass index (BMI) and self-perception of adequacy in and enjoyment of physical activity following implementation of a six-week physical literacy (PL) intervention. METHODS: Students (n=82) in grades 2-5 completed the Children’s Self-Perceptions of Adequacy and Predilection for Physical Activity (CSAPPA) scale pre- and post- PL intervention. The PL intervention program consisted of a once weekly, 30-minute program conducted by trained individuals during the school day. This program was designed to focus on the mechanics of running, jumping, and throwing. Height and weight were measured pre- intervention to calculate BMI using the Center for Disease Control’s Youth and Teen calculator. RESULTS: A significant interaction between CSAPPA score and BMI category was found, (F (1,82) = 4.948, p < 0.05). Further evaluation of the interaction indicated that students in the unhealthy BMI category were more likely to choose an active over a passive physical activity option following the PL intervention. CONCLUSION: Based on the aforementioned results, PL programming seems favorable in improving self-perception of physical activity selection in children with abnormal BMIs. Previous research has shown that students who do not feel confident performing a task are less likely to participate. Following the trend of decreased exposure to physical activity during school, students with unhealthy BMIs are not getting proper exposure to the mechanics of movement. This may lead to less physical activity participation and increases in unhealthy BMI ranges. By teaching children that they can move proficiently, children are making more active choices possibly leading to improvements in self-perception.

Influence Of Running Speed On Muscle Activity During Backward Running With Body Weight Support

A change in running speed influences gait mechanics of running. PURPOSE: The purpose of this study was to investigate the influence of a change in running speed on muscle activity during forward and backward running at different body weight support (BWS) conditions. METHODS: Eleven participants (29.7 ± 12.3 years) ran forward and backward on a lower body positive pressure treadmill at 0%BWS, 20%BWS, and 50%BWS conditions. The running speed conditions consisted of forward and backward running at preferred speed (PS), PS+10%, and PS-10%. Muscle activity from the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius and stride frequency were measured. Muscle activity and stride frequency were analyzed using a 2 (running direction) x 3 (BWS) x 3 (running speed) repeated measures analysis of variance (α = 0.05). RESULTS: Muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.01) were significantly different between running speeds. For example, muscle activity from the rectus femoris (P<0.05) and gastrocnemius (P<0.05) during running at PS were significantly greater than when running at PS-10%, regardless of running direction and BWS. Furthermore, muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.05) during running at PS+10% were significantly greater than when running at PS, regardless of running direction and BWS. Stride frequency was influenced by the interaction of running direction and running speed (P<0.05). Using the pairwise comparisons, stride frequency during running at PS was significantly higher than that of running at PS-10% only when running forward and backward at 0%BWS (e.g., 84.5 strides/min and 82.0 strides/min for backward running at PS and PS-10% conditions, respectively: P<0.05). Furthermore, stride frequency during running at PS+10% was significantly higher than that of running at PS during forward and backward running at 0%BWS (P<0.05). CONCLUSIONS: Muscle activity from the rectus femoris and gastrocnemius during running may increase with increasing running speed, regardless of BWS and running direction. However, unique biomechanical strategies for the increased muscle activity from the lower extremity may exist for running with BWS.

Influence Of A Novel Music App On Spatiotemporal Mechanics During Running

An increased running step rate (i.e., cadence) can decrease lower extremity joint loads and potentially reduce running-related injury (RRI) risk. Many gait interventions have significantly increased a runner’s cadence through a variety of external stimuli (e.g., metronome). Runners have been shown to spontaneously manipulate their cadence when listening to music with a tempo that differed ±3% from their baseline cadence. However, no study has determined whether a runner will subconsciously increase cadence > 3% when listening to up-tempo music. PURPOSE: To determine if music tempo (beats per minute, bpm) set 10% higher than baseline cadence affects spatiotemporal running mechanics. METHODS: Utilizing a blinded experimental design, twenty-two runners (15F, 7M, 18-40 yo) were recruited, granted informed consent, were randomly assigned to a control (C) or experimental (E) group, and picked four motivational songs. The Brunel Music Rating Inventory was used to rate song motivational level. Subjects ran three 5-min trials (5/10 effort) on a pressure-sensitive treadmill (Noraxon U.S.A., 100 Hz) with vertical ground reaction force and pressure recorded during the last 45 sec and lowpass filtered (40 Hz). Five-min of rest was given between trials. During the second trial, subjects listened to music via headphones with the bpm set to baseline cadence (C) or 10% higher (E). Music was administered via a novel smartphone application that permitted song tempo to be adjusted and maintained in one bpm increments. The last trial was completed without music with velocity held constant across all trials. A mixed design analysis of variance was run in JASP with a significance set apriori at 0.05. RESULTS: Baseline cadence was not significantly different between groups (C: 165.4±9.5 steps per minute, E 167.2±6.8, p=0.61). There was not a significant main effect (p=0.54, p=0.32, p=0.152, p=0.70) of music tempo between groups for cadence (F (1,20)=0.39), step width (F(1,20)=1.02), stance phase (F (1,20)=2.22), or foot rotation (F(1,20)=0.16). CONCLUSION: Spatiotemporal running mechanics do not spontaneously adjust when runners listen to motivational music set at a tempo 10% greater than baseline cadence. Listening to up-tempo music should not be considered an effective external stimulus to promote increased running cadence.

A Case Study on Influence of Utilizing Hill-Type Muscles on Mechanical Efficiency of Biped Running Gait

The presence of compliant elements in biped running mechanisms generates a smoother motion and decreases the impact forces. Biological creatures that have a complicated actuation system with parallel and series elastic elements in their muscles demonstrate very efficient and robust bipedal gaits. The main difficulty of implementing these systems is duplicating their complicated dynamics and control. This paper studies the effects of an actuation system, including Hill-type muscles on the running efficiency of a kneed biped robot model with point feet. In this research, we implement arbitrary trajectories compatible with the initial condition of the robot, and we calculate the necessary muscle forces using an analytical inverse dynamics model. To verify the results, we execute the direct dynamics of the robot with the calculated control inputs to generate the robot’s trajectory. Finally, we calculate the contractile element force of the muscles and its cost of transport, and we investigate the effects of the muscles’ elements on reducing or increasing the cost of transport of the gait and maximum actuating forces.

Running mechanics adjustments to perceptually-regulated interval runs in hypoxia and normoxia

ObjectivesWe determined whether perceptually-regulated, high-intensity intermittent runs in hypoxia and normoxia induce similar running mechanics adjustments within and between intervals. DesignWithin-participants repeated measures. MethodsNineteen trained runners completed a high-intensity intermittent running protocol (4×4-min intervals at a perceived rating exertion of 16 on the 6–20 Borg scale, 3-min passive recoveries) in either hypoxic (FiO2=0.15) or normoxic (FiO2=0.21) conditions. Running mechanics were collected over 10 consecutive steps, at constant velocity (∼15.0±2.0km.h−1), at the beginning and the end of each 4-min interval. Repeated measure ANOVA were used to assess within intervals (onset vs. end of each interval), between intervals (interval 1, 2, 3 vs. 4) and FiO2 (0.15 vs. 0.21) main effects and any potential interaction. ResultsParticipants progressively reduced running velocity from interval 1–4, and more so in hypoxia compared to normoxia for intervals 2, 3 and 4 (P<0.01). There were no between intervals (across all intervals P>0.298) and FiO2 (across all intervals P>0.082) main effects or any significant between intervals×within intervals×FiO2 interactions (all P>0.098) for any running mechanics variables. Irrespective of interval number or FiO2, peak loading rate (+10.6±7.7%; P<0.001) and duration of push-off phase (+2.0±3.1%; P=0.001) increased from the onset to the end of 4-min intervals, whereas peak push-off force decreased (−4.0±4.0%; P<0.001). ConclusionsWhen carrying out perceptually-regulated interval treadmill runs, runners adjust to progressively slower velocities in hypoxia compared to normoxia. However, only subtle constant-velocity modifications of their mechanical behaviour occurred within each set, independently of FiO2 or interval number.

Assessing the Vulnerability of Logistics Service Supply Chain Based on Complex Network

The reliable operation of a logistics service supply chain (LSSC) is a key factor for improving logistics efficiency and service level, and vulnerability is an important indicator of reliable LSSC operation. Based on complex network theory, we reconstructed the running mechanism of logistics service providers, integrators, and demanders. We constructed an improved structure model of LSSC. By observing the selected three indicators (clustering coefficient, maximum connectivity, and network connectivity efficiency), the influence caused by the problem will continue to spread to more subjects along the network when a problem exists in one part of the network. The results showed that the destructive power of deliberate attacks is far greater than the damage caused by random attacks, and the disruption of logistics service integrators will considerably increase the vulnerability of the LSSC. However, even if logistics service integrators are removed completely, the LSSC still can operate at low efficiency. Through a case analysis, we identified the vulnerable nodes in logistics service, clarify the vulnerable mechanism in LSSC, and provide guidance for the operation of LSSC in real life.

Effects of a foot strengthening program on foot muscle morphology and running mechanics: A proof-of-concept, single-blind randomized controlled trial

ObjectivesTo investigate the effects of a foot training program on muscle morphology and strength as well as running biomechanics in healthy recreational runners. DesignProof-of-concept, single-blind randomized controlled trial. SettingsRunners were allocated to a control (CG) or an intervention (IG) group. The intervention focused on strengthening the intrinsic foot muscles and their activation during weight-bearing activities. All participants were assessed at baseline and after 8-weeks. ParticipantsTwenty-eight healthy recreational long-distance runners not habituated to minimalist running shoes or barefoot running. Main outcomes measuresOutcomes were hallux and toes strength; foot function, cross-sectional area and volume of the abductor hallucis (ABH), abductor digiti minimi (ABV), flexor digitorum brevis (FDB), and flexor hallucis brevis; medial longitudinal arch range of motion and stiffness; vertical and antero-posterior propulsive impulses during running. ResultsCompared to the CG, an increase was found in the IG for the volume of all muscles investigated and for vertical propulsive impulse during running. Correlations were found between vertical propulsive impulse and volume of ABH(r = 0.40), ABV(r = 0.41), and FDB(r = 0.69). ConclusionThe foot exercise protocol effectively increased intrinsic foot muscle volume and propulsive forces in recreational runners. This shows that intrinsic muscle strengthening affects running mechanics and suggests that it may improve running performance.

The influence of sagittal trunk lean on uneven running mechanics.

The role of trunk orientation during uneven running is not well understood. This study compared the running mechanics during the approach step to and the step down for a 10 cm expected drop, positioned halfway through a 15 m runway, with that of the level step in 12 participants at a speed of 3.5 m s-1 while maintaining self-selected (17.7±4.2 deg; mean±s.d.), posterior (1.8±7.4 deg) and anterior (26.6±5.6 deg) trunk leans from the vertical. Our findings reveal that the global (i.e. the spring-mass model dynamics and centre-of-mass height) and local (i.e. knee and ankle kinematics and kinetics) biomechanical adjustments during uneven running are specific to the step nature and trunk posture. Unlike the anterior-leaning posture, running with a posterior trunk lean is characterized by increases in leg angle, leg compression, knee flexion angle and moment, resulting in a stiffer knee and a more compliant spring-leg compared with the self-selected condition. In the approach step versus the level step, reductions in leg length and stiffness through the ankle stiffness yield lower leg force and centre-of-mass position. Contrariwise, significant increases in leg length, angle and force, and ankle moment, reflect in a higher centre-of-mass position during the step down. Plus, ankle stiffness significantly decreases, owing to a substantially increased leg compression. Overall, the step down appears to be dominated by centre-of-mass height changes, regardless of having a trunk lean. Observed adjustments during uneven running can be attributed to anticipation of changes to running posture and height. These findings highlight the role of trunk posture in human perturbed locomotion relevant for the design and development of exoskeleton or humanoid bipedal robots.

Design of an experiment for the biomechanical and thermal analysis of athletes during prolonged running exercise

Biomechanics and thermoregulation of human running are key aspects playing an important role in the training of professional athletes. In the case of a prolonged exercise, as occurs during the marathon race, the intensity and duration of the exercise (in concert with environmental conditions) can affect the thermoregulatory response and the running mechanics. The aim of this study is the design of a novel experiment able to simultaneously capture information concerning the biomechanics of lower limbs and the surface temperature map of the whole body during a prolonged running exercise on treadmill. Kinematics quantities, such as linear and angular displacement, velocity and acceleration of relevant body markers are recorded by a video system, while surface temperature evolution on time is detected by an infrared thermal camera. A group of five amateur athletes, with long experience in long-distance running competitions, was involved in this study. Results for the sample group, in terms of kinematic (displacements and angles) and thermal (local and total-body skin temperatures) quantities, revealed features related to individual response to the effort. Even though the relatively little number of athletes does not permit to infer general conclusions, the combined mechanical and thermal experiment is deemed to be a useful tool for the investigation of endurance running characteristics.

Exercise Program Reduces Inter-Recti Distance in Female Runners Up to 2 Years Postpartum

Background: Pregnancy and childbirth are associated with increased inter-recti distance (IRD)/diastasis recti abdominis (DRA), pelvic joint laxity, and decreased physical activity levels. Recreational running is an accessible, popular form of exercise that may challenge pelvic stability in postpartum women. Objectives: To assess the impact of an 8-week abdominal muscle retraining program on IRD and pelvic running mechanics in women up to 2 years postpartum. Study Design: Pre/posttest single-arm intervention study. Methods: Thirteen postpartum women (32.8 ± 2.7 years of age; 1-3 pregnancies; 7 weeks to 2 years postpartum) who were recreational runners participated. Ultrasound imaging measured IRD above and below the umbilicus. Thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles was assessed with ultrasonography at rest and during performance of an abdominal draw-in maneuver. Participants underwent an 8-week abdominal muscle retraining program utilizing ultrasonography as biofeedback. Running gait was assessed with 3-dimensional motion capture at study enrollment (baseline), end of the intervention, and 6-week follow-up. Results: Inter-recti distance below the umbilicus decreased from baseline to end of intervention (P = .013) and remained stable at follow-up (P = .459). Inter-recti distance above the umbilicus, IO and TrA activation ratio, and running mechanics did not change (P > .05). Women reported increased running speed following the intervention (P = .021). Conclusion: An 8-week abdominal muscle retraining program reduced IRD below the umbilicus in recreational runners up to 2 years postpartum, suggesting therapeutic exercise may be part of conservative management for DRA.

An Organizational Structure and Self-Adaptive Mechanism for Holonic Multi-Agent Systems

A holonic multi-agent system combines the concept of a holon with a multi-agent system; this combination has been proven to be an effective way to build a complex system. Great progress has been made in this area, but previous studies are fragmented and lack of a task-based perspective to model different systems in the real world. Therefore, this article proposes a formalistic model for HMAS from a task-based perspective. Not only the static organizational structure is designed, but also the dynamic running mechanism, including the self-adaptive mechanism and the task assignment mechanism based on the proposed holonic structure, are also discussed. Finally, a case study is provided to verify the self-adaptive mechanism. The experimental results show that our proposed DHMAS has the ability to adapt to the changing environment, and performs better in terms of the success rate and the response time when the system is heavily loaded.

Sub/micro-structural evolution of a Co–Al–W–Ta–Ti single crystal superalloy during creep at 900 °C and 420 MPa

In order to clarify the high temperature strengthening mechanism of Co–Al–W-base superalloys, the tensile creep behavior of a Co–Al–W–Ta–Ti single crystal alloy was investigated at 900 °C and 420 MPa and sub/micro-structural evolutions were analyzed in detail using interrupted creep tests by transmission electron microscopy (TEM). Four distinct creep stages were observed during the creep process. The sharp decrease of strain rate in the deceleration stage should be attributed to the activation of run and stop mechanism of dislocations. Detailed analysis revealed that the planar defects, which were enclosed by 1/6[1‾1‾2] partial dislocations in numerous isolated and contiguous γ′ precipitates, resulted in the increase of strain rate in the first acceleration stage. The planar defects are then activated on multiple {111} planes to form Lomer-Cottrell locks (L-C lock), which were responsible for the increase of creep resistance in the steady-state stage combined with the γ/γ′ interfacial dislocation networks and the topological inversion of γ/γ′ microstructures. This indicates both advantages and disadvantages of planar defects as one of the major dislocation configurations in Co-base superalloys.

Running mechanics during 1600 meter track runs in young adults with and without chronic ankle instability

ObjectiveTo evaluate biomechanical measures in runners with and without chronic ankle instability (CAI) using wearable sensors during two 1600 m track runs at a slow- and fast-pace. DesignObservational case-control. SettingField. Participants18 recreational runners (CAI: n = 9; Healthy: n = 9) with rearfoot strike patterns. Main outcome measuresPronation excursion, maximum pronation velocity, peak braking g, peak impact g, contact time, cycle time, and stride length of every step of two 1600 m runs were collected using RunScribe™ sensors and binned to each 400 m lap (Lap 1 to Lap 4). ResultsSignificant group-by-lap interactions were identified for contact time (p = .05) during the slow-intensity run. The CAI group had greater contact time (p = 0.05) that progressively increased with distance completed. CAI group also had higher impact g than the control group throughout the slow-intensity run (p = .03). During the fast-intensity run, significant group by lap interaction was observed for pronation excursion with the CAI group exhibiting less pronation excursion than the healthy group as the run progressed (p = .002). ConclusionsRegardless of speed, runners with CAI demonstrated altered gait mechanics compared to healthy controls. During the higher intensity run, decreased pronation excursion was observed in the CAI group and differences became more prominent as the distance increased.

Conversion to a rearfoot strike pattern during running for prevention of recurrent calf strains: A case report

BackgroundRunning-related injuries are prevalent musculoskeletal complaints in the United States military. Although, run retraining is an extensively researched method for reducing pain and improving function in runners, its clinical utility remains low. Case descriptionThe patient had a seven-year history of recurrent right calf strains. Prior conventional physical therapy failed to resolve symptoms. A biomechanical running analysis revealed a right forefoot strike during running. The patient underwent run retraining that included real-time visual feedback and a faded feedback strategy focused on converting foot strike pattern to rearfoot. Running mechanics were reassessed post-training, and at one and six months post-training. OutcomesFoot strike pattern was successfully converted to rearfoot strike and was maintained up to six months post-training. Reductions in peak ankle dorsiflexion moment and dorsiflexion velocity were noted up to six months post-training. Self-reported function also improved by 20–30% and no calf strains were reported up to six months post-training. DiscussionThis case report details the clinical reasoning and evidence-informed interventions involved in treatment of a patient with chronic calf strains. The management strategy was intended to reduce eccentric calf demands, which allowed the patient to tolerate increased running frequency without any further episodes of calf strains up to six months post-training.

The effect of concurrent strength and endurance training on running performance and mechanics: a randomised controlled trial

The effect of concurrent strength and endurance training on running performance and mechanics: a randomised controlled trial

The number of strides required for treadmill running gait analysis is unaffected by either speed or run duration

Participation in running events has increased recently, with a concomitant increase in the rate of running related injuries (RRI). Mechanical overload is thought to be a primary cause of RRI, it is often detected using motion analysis to examine running mechanics during either overground or treadmill running. In treadmill running, no clear consensus for the number of strides required to establish stable kinematic data exists. The aim of this study was to establish the number of strides needed for stable data when analysing gait kinematics in the stance phase of treadmill running. Twenty healthy, masters age group, club runners completed a high intensity interval training run (HIIT) and an energy-expenditure matched medium intensity continuous run (MICR). Thirty consecutive strides at start and end of each run were identified. Sequential averaging was employed to determine the number of strides required to establish a stable value. No significant differences existed in the number of strides required to achieve stable values. Twenty consecutive strides are required to be 95% confident stable values exist for maximum angle, angle at initial foot contact, and range of motion at the ankle, knee, and hip joints variables at the ankle, knee, and hip joints, in all three planes of motion, and spatiotemporal regardless of running speed and time of capture.

Data‐driven control for combustion process of circulating fluidised bed boiler

Owing to the advantages of burning low-quality coal (coal slime and coal gangue), furnace desulfurisation, low N O x emission and deep load adjustment, the circulating fluidised bed (CFB) combustion technology becomes one of the few fossil fuel utilisation technologies funded continuously by the Chinese government. However, compared with the pulverised coal boiler, the combustion process of CFB boiler is more complicated because of the larger time delay, significant uncertainty and more coupled variables. In this study, a data-driven proportional–integral-derivative (DD-PID) control strategy is presented for the combustion control of CFB boiler to improve the operating performance under full operating conditions. By analysing the running mechanism of combustion process, an inverse decoupler is introduced to transfer the combustion object to the generalised controlled object, which has relatively independent input–output relationship. After that, a normative procedure of DD-PID, including PID-parameter database establishment, information-vector neighbourhood selection, active PID-parameter determination, database update, and redundant vector deletion, is given. Finally, a series of case study, including numerical tests applied to the proposed combustion model and application test employed on 330 MW CFB simulation platform proves the feasibility of DD-PID control strategy.

The Effect of EVA and TPU Custom Foot Orthoses on Running Economy, Running Mechanics, and Comfort.

Custom made foot orthoses (CFO) with specific material properties have the potential to alter ground reaction forces but their effect on running mechanics and comfort remains to be investigated. We determined if CFO manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), improve running economy (RE), running mechanics, and comfort at two running speeds. Eighteen well-trained, male athletes ran on an instrumented treadmill for 6 min at high (HS) and low (LS) speeds corresponding to and 15% lower than their first ventilatory threshold (13.8 ± 1.1 and 11.7 ± 0.9 km.h−1, respectively) in three footwear conditions (CON, EVA, and TPU). RE, running mechanics and comfort were determined. Albeit not reaching statistical significance (P = 0.11, η2 = 0.12), RE on average improved in EVA (+2.1 ± 4.8 and +2.9 ± 4.9%) and TPU (+0.9 ± 5.9 and +0.9 ± 5.3%) compared to CON at LS and HS, respectively. Braking force was decreased by 3.4 ± 9.1% at LS and by 2.7 ± 9.8% at HS for EVA compared to CON (P = 0.03, η2 = 0.20). TPU increased propulsive loading rate by 20.2 ± 24 and 16.4 ± 23.1% for LS and HS, respectively compared to CON (P = 0.01, η2 = 0.25). Both arch height (P = 0.06, η2 = 0.19) and medio-lateral control (P = 0.06, η2 = 0.16) showed a trend toward improved comfort for EVA and TPU vs. CON. Compared to shoes only, mainly EVA tended to improve RE and comfort at submaximal running speeds. Specific CFO-related running mechanical adjustments included a reduced braking impulse occurring in the first 25% of contact time with EVA, whereas wearing TPU increased propulsive loading rate.

The relationship between performance and biomechanics in middle-distance runners

ABSTRACT The present study aimed to identify movement patterns most related to running performance among highly trained middle-distance runners. Eleven male runners performed overground running trials on an indoor running track, and three-dimensional analyses techniques were used to measure running kinematics and kinetics. Performance was measured as season and personal best time over 1500 m. The average velocity during the running trials was 7.2 ± 0.3 m/s. The average season and personal best 1500 m race times were 3:49.7 ± 0:05.8 and 3:46.0 ± 0:08.3 minutes, respectively. Regression analysis revealed that a smaller range of sagittal-plane hip motion during swing, less thorax flexion at toe-off and a smaller ankle plantarflexion angle at contact accounted for 95.7% (p < 0.001) of the variation in season best running performance. Less sagittal-plane hip motion during swing and a smaller ankle plantarflexion angle at contact also explained 79% of the variance in personal best time. Slower middle-distance runners make initial ground contact with a more plantarflexed ankle and greater forward lean of the trunk. We recommend that coaches and runners pay attention to ankle, shank and thorax angles during technical development and training to identify opportunities to optimise middle-distance running mechanics and performance.

Symmetry Degree Measurement and its Applications to Anomaly Detection

Anomaly detection is an important technique used to identify patterns of unusual network behavior and keep the network under control. Today, network attacks are increasing in terms of both their number and sophistication. To avoid causing significant traffic patterns and being detected by existing techniques, many new attacks tend to involve gradual adjustment of behaviors, which always generate incomplete sessions due to their running mechanisms. Accordingly, in this work, we employ the behavior symmetry degree to profile the anomalies and further identify unusual behaviors. We first proposed a symmetry degree to identify the incomplete sessions generated by unusual behaviors; we then employ a sketch to calculate the symmetry degree of internal hosts to improve the identification efficiency for online applications. To reduce the memory cost and probability of collision, we divide the IP addresses into four segments that can be used as keys of the hash functions in the sketch. Moreover, to further improve detection accuracy, a threshold selection method is proposed for dynamic traffic pattern analysis. The hash functions in the sketch are then designed using Chinese remainder theory, which can analytically trace the IP addresses associated with the anomalies. We tested the proposed techniques based on traffic data collected from the northwest center of CERNET (China Education and Research Network); the results show that the proposed methods can effectively detect anomalies in large-scale networks.