Running Trials Research Articles

No immediate effects of highly cushioned shoes on basic running biomechanics

The aim of the study was to investigate the effects of highly cushioned shoes on running biomechanics. Sixteen recreational runners (8 males, 8 females) participated and ran at a self-selected pace across the force platform in the research laboratory wearing either the standard or highly cushioned shoes, in randomized order. Impact peak (IP), loading rate to IP (LR), active peak (AP), contact time (CT), strike index (SI), running velocity, and knee and ankle kinematics at initial contact (IC) and AP were recorded during the running trials. Overall, there was no effect of footwear on IP, LR, AP, CT and velocity (p>.05) with small effect sizes (ES<0.2). The highly cushioned shoes resulted in a more anterior foot strike pattern, based on the slightly higher SI (p=.03, ES=0.5), although the runners demonstrated a rearfoot strike pattern regardless of shoe condition. No kinematic differences were observed at IC or AP, across shoe conditions (p>.05). Our results indicate that the highly cushioned shoes did not show immediate changes in running biomechanics.

Potential Relationship between Passive Plantar Flexor Stiffness and Running Performance.

The present study aimed to determine the relationship between passive stiffness of the plantar flexors and running performance in endurance runners. Forty-eight well-trained male endurance runners and 24 untrained male control subjects participated in this study. Plantar flexor stiffness during passive dorsiflexion was calculated from the slope of the linear portion of the torque-angle curve. Of the endurance runners included in the present study, running economy in 28 endurance runners was evaluated by measuring energy cost during three 4-min trials (14, 16, and 18 km/h) of submaximal treadmill running. Passive stiffness of the plantar flexors was significantly higher in endurance runners than in untrained subjects. Moreover, passive plantar flexor stiffness in endurance runners was significantly correlated with a personal best 5000-m race time. Furthermore, passive plantar flexor stiffness in endurance runners was significantly correlated with energy cost during submaximal running at 16 km/h and 18 km/h, and a trend towards such significance was observed at 14 km/h. The present findings suggest that stiffer plantar flexors may help achieve better running performance, with greater running economy, in endurance runners. Therefore, in the clinical setting, passive stiffness of the plantar flexors may be a potential parameter for assessing running performance.

The use of real-time feedback to improve kinematic marker placement consistency among novice examiners

Marker placement deviation has been shown to be the largest source of error in gait kinematic data, limiting the ability of clinicians and researchers to conduct between-day or between-center investigations. Prior marker-placement standardization methods are either impractical for a clinical setting or rely on expert marker placement. However, a recently developed, real-time feedback tool has been developed and shown to improve marker placement and downstream kinematic calculations. The purpose of this study was to determine whether this real-time marker-placement tool could improve the consistency of gait kinematic data collected by a group of novice examiners. Twelve novice examiners identified anatomical landmarks and placed retroreflective markers on a single subject. For each examiner, a running trial was analyzed separately using two static trials: (1) PRE and (2) POST implementation of the feedback tool. The protocol was repeated a second time, one week later. Between-examiner consistency was represented by the 95% confidence interval (CI) of the mean joint angles for the entire stride, and compared between the PRE and POST conditions. The POST feedback trials showed an average 27.45% reduction of the 95%CI range for eight out of nine joint angles on day one, and an average 24.73% for five out of nine joint angles on day two, compared to POST. The results indicate a real-time feedback tool improves the consistency in marker placement for novice users.

Effects of prolonged running in the heat and cool environments on selected physiological parameters and salivary lysozyme responses

IntroductionLysozyme is one of the salivary antimicrobial proteins which act as the “first line of defence” at the mucosal surface. The effects of prolonged exercise in the hot and cool environments among recreational athletes on salivary lysozyme responses are very limited in the literature, especially in the Asian countries. ObjectiveTo determine the effects of prolonged running in the hot and cool environments on selected physiological parameters and salivary lysozyme responses among recreational athletes. MethodsRandomised and cross-over study design. Thirteen male recreational athletes (age: 20.9 ± 1.3 years old) from Universiti Sains Malaysia participated in this study. They performed two separate running trials; 90 min running at 60% of their respective maximum oxygen uptake (V˙O2max) One running trial was performed in the hot (31ºC) while the other was in the cool (18ºC) environment and this sequence was randomised. Each running trial was started with a 5 min warm-up at 50% of participant's respective V˙O2max Recovery period between these two trials was one week. In the both trials, saliva samples, blood samples, heart rate, ratings of perceived exertion, skin and tympanic temperatures, oxygen consumption, nude body weight, room temperature, and relative humidity were collected. ResultsParticipants' skin temperature, tympanic temperature, body weight changes, heart rate, ratings of perceived exertion, and plasma volume changes were significantly higher (p < 0.05) in the hot trial compared to the cool trial. Saliva flow rate was not significantly (p = 0.949) different between the hot (0.32 ± 0.08 ml/min) and cool (0.27 ± 0.05 ml/min) trials. However, in each trial, it significantly decreased (p < 0.05) at post-exercise as compared to pre-exercise but it returned to baseline value at 1 h post-exercise. In addition, there were no significant differences between and within hot and cool trials in salivary lysozyme concentration (p = 0.925; 4.79 ± 1.37 and 4.44 ± 1.11 μg/ml respectively) and secretion rate (p = 0.843; 1.67 ± 1.1 and 1.17 ± 1.0 μg/min respectively). ConclusionThis study found similar lysozyme responses between both hot and cool trials. Thus, room/ambient temperature did not affect lysozyme responses among recreational athletes. Nevertheless, the selected physiological parameters were significantly affected by room temperature.

Changes in gluteal muscle forces with alteration of footstrike pattern during running

Gait retraining is a common form of treatment for running related injuries. Proximal factors at the hip have been postulated as having a role in the development of running related injuries. How altering footstrike affects hip muscles forces and kinematics has not been described. Thus, we aimed to quantify differences in hip muscle forces and hip kinematics that may occur when healthy runners are instructed to alter their foot strike pattern from their habitual rear-foot strike to a forefoot strike. This may gain insight on the potential etiology and treatment methods of running related lower extremity injury. Twenty-five healthy female runners completed a minimum of 10 running trials in a controlled laboratory setting under rear-foot strike and instructed forefoot strike conditions. Kinetic and kinematic data were used in an inverse dynamic based static optimization to estimate individual muscle forces during running. Within subject differences were investigated using a repeated measures multi-variate analysis of variance. Peak gluteus medius and minimus and hamstring forces were reduced while peak gluteus maximus force was increased when running with an instructed forefoot strike pattern. Peak hip adduction, hip internal rotation, and heel-COM distance were also reduced. Therefore, instructing habitual rearfoot strike runners to run with a forefoot strike pattern resulted in changes in peak gluteal and hamstring muscle forces and hip kinematics. These changes may be beneficial to the development and treatment of running related lower extremity injury.

Relationship between Achilles tendon length and running performance in well-trained male endurance runners.

This study aimed to determine the relationship between Achilles tendon (AT) length and running performance, including running economy, in well-trained endurance runners. We also examined the reasonable portion of the AT related to running performance among AT lengths measured in three different portions. The AT lengths at three portions and cross-sectional area (CSA) of 30 endurance runners were measured using magnetic resonance imaging. Each AT length was calculated as the distance from the calcaneal tuberosity to the muscle-tendon junction of the soleus, gastrocnemius medialis (GMAT ), and gastrocnemius lateralis, respectively. These AT lengths were normalized with shank length. The AT CSA was calculated as the average of 10, 20, and 30mm above the distal insertion of the AT and normalized with body mass. Running economy was evaluated by measuring energy cost during three 4-minutes submaximal treadmill running trials at 14, 16, and 18km/h, respectively. Among three AT lengths, only a GMAT correlated significantly with personal best 5000-m race time (r=-.376, P=.046). Furthermore, GMAT correlated significantly with energy cost during submaximal treadmill running trials at 14km/h and 18km/h (r=-.446 and -.429, respectively, P<.05 for both), and a trend toward such significance was observed at 16km/h (r=-.360, P=.050). In contrast, there was no correlation between AT CSA and running performance. These findings suggest that longer AT, especially GMAT , may be advantageous to achieve superior running performance, with better running economy, in endurance runners.

Superficial plantar cutaneous sensation does not trigger barefoot running adaptations

It has long been proposed that the gait alterations associated with barefoot running are mediated by alterations in sensory feedback, yet there has been no data to support this claim. Thus, the purpose of this study was to examine the role of superficial plantar cutaneous feedback in barefoot and shod running. Methods10 healthy active subjects (6 male, 4 female); mass: 65.2+9.7kg; age: 27+7.1years participated in this study. 10 over-ground running trials were completed in each of the following conditions: barefoot (BF), shod (SHOD), anesthetized barefoot (ANEST BF) and anesthetized shod (ANEST SHOD). For the anesthetized conditions 0.1–0.3mL of 1% lidocaine was injected into the dermal layer of the plantar foot below the metatarsal heads, lateral column and heel. 3-dimensional motion analysis and ground reaction force (GRF) data were captured as subjects ran over a 20m runway with a force plate at 12m. Kinematic and kinetic differences were analyzed via two-way repeated measure ANOVAs. ResultsThe differences in gait between the BF and SHOD conditions were consistent with previous research, with subjects exhibiting a significant decrease in stride length and changing from rearfoot strike when SHOD to fore/midfoot strike when BF. Additionally, BF running was associated with decreased impact peak magnitudes and peak vertical GRFs. Despite anesthetizing the plantar surface, there was no difference between the BF and ANEST BF conditions in terms of stride length, foot strike or GRFs. ConclusionSuperficial cutaneous sensory receptors are not primarily responsible for the gait changes associated with barefoot running.

Peak medial (but not lateral) hamstring activity is significantly lower during stance phase of running. An EMG investigation using a reduced gravity treadmill

The hamstrings are seen to work during late swing phase (presumably to decelerate the extending shank) then during stance phase (presumably stabilizing the knee and contributing to horizontal force production during propulsion) of running. A better understanding of this hamstring activation during running may contribute to injury prevention and performance enhancement (targeting the specific role via specific contraction mode). Twenty active adult males underwent surface EMG recordings of their medial and lateral hamstrings while running on a reduced gravity treadmill. Participants underwent 36 different conditions for combinations of 50%–100% altering bodyweight (10% increments) & 6–16km/h (2km/h increments, i.e.: 36 conditions) for a minimum of 6 strides of each leg (maximum 32). EMG was normalized to the peak value seen for each individual during any stride in any trial to describe relative activation levels during gait. Increasing running speed effected greater increases in EMG for all muscles than did altering bodyweight. Peak EMG for the lateral hamstrings during running trials was similar for both swing and stance phase whereas the medial hamstrings showed an approximate 20% reduction during stance compared to swing phase. It is suggested that the lateral hamstrings work equally hard during swing and stance phase however the medial hamstrings are loaded slightly less every stance phase. Likely this helps explain the higher incidence of lateral hamstring injury. Hamstring injury prevention and rehabilitation programs incorporating running should consider running speed as more potent stimulus for increasing hamstring muscle activation than impact loading.

Knee Loading Deficits During Dynamic Tasks in Individuals Following Anterior Cruciate Ligament Reconstruction

Study Design Controlled laboratory study, cross-sectional. Background Well-documented deficits in sagittal plane knee loading during dynamic tasks indicate that individuals limit the magnitude of knee loading following anterior cruciate ligament reconstruction (ACLR). It is unknown how these individuals modulate the speed of knee flexion during loading, which is particularly important as they progress to running during rehabilitation. Objective To investigate how individuals following ACLR perform dynamic knee loading tasks compared to healthy controls. Methods Two groups of recreationally active individuals participated: 15 healthy controls and 15 individuals post-ACLR (ACLR group). Participants performed 3 trials of overground running and a single-limb loading (SLL) task. Sagittal plane range of motion, peak knee extensor moment, peak knee flexion angular velocity, peak knee power absorption, and rate of knee extensor moment were calculated during deceleration. A mixed-factor multivariate analysis of variance was performed to compare differences in variables between groups (ACLR and control), limbs (within ACLR), and tasks (within control). Results Knee power absorption, knee flexion angular velocity, and rate of knee extensor moment were lower in reconstructed limbs (for the SLL task: 5.6 W/kg, 325.8°/s, and 10.5 Nm/kg/s, respectively; for running: 11.8 W/kg, 421.4°/s, and 38.2 Nm/kg/s, respectively) compared to nonsurgical limbs (for the SLL task: 9.7 W/kg, 432.0°/s, and 19.1 Nm/kg/s, respectively; for running: 18.8 W/kg, 494.1°/s, and 72.8 Nm/kg/s, respectively) during both tasks (P<.001). The magnitudes of between-limb differences in knee flexion angular velocity were similar in both tasks. Conclusion Despite lower loading demands during SLL, individuals post-ACLR exhibit deficits in knee dynamics during SLL and running, suggesting an inability or reluctance to dynamically accommodate forces at the knee when progressing to running in rehabilitation. J Orthop Sports Phys Ther 2017;47(6):411-419. doi:10.2519/jospt.2017.6912.

Factors determining 800-m running performance in young male athletes.

BACKGROUNDː The aim of the present study was to identify determinant variables on 800-m running performance in young male athletes derived from field tests and biological maturity. METHODSː A total of 89 athletes, aged between 13 and 15 years old, performed a 800-m running trial and a battery of tests which involved anthropometric measurements, a running anaerobic test (RAST), a flexibility test (sit-and-reach), a counter movement jump test and progressive test for aerobic fitness evaluation. A stepwise multiple regression model selected three independent variables to explain the variance in 800-m running performance trial: peak of aerobic speed (PAS), total time of all sprints (RAST) and predicted mature stature (PMS). RESULTSː The PAS speed explained 73.6% (P<0.01) of the variance, whereas the RAST and PMS accounted for additional 7.7% (P<0.01) and 0.9% (P<0.05), respectively. Taken together, these variables explained 82.2% of the overall 800-m running performance. CONCLUSIONSː The results indicate that the 800-m running performance might be explained mainly by aerobic (PAS) and anaerobic metabolisms (RAST). Beyond the traditional variables of performance in 800-m running trial, the biological maturity must be considered in regard of endurance performance of young athletes.

Validation of Single Sensor Wireless In-shoe Force Insoles during Running

Assessment of lower extremity loading during running is often completed either overground or on an instrumented treadmill in a biomechanics lab. A new product has been developed to allow for the acquisition of plantar loading on an iPod using Bluetooth, which could allow for the assessment of running in an outdoor setting. PURPOSE: To validate a single sensor in-shoe force insole (pedoped, Novel Electronics, St. Paul, MN) against a force plate during various running conditions. METHODS: The study included 12 subjects (age 25.3±4.2, height 68.7±4.1 cm, weight 758.9±173.9 N) each fitted with a pair of pedoped insoles (100Hz) and a pair of New Balance shoes. Each subject completed a 20 second running trial for 6 different conditions on an instrumented treadmill (1200 Hz). These conditions include running at a 9, 10 and 11 min/mi pace, running uphill at 10 min/mi, running with an exaggerated heel strike and a wide gait pattern at 11 min/mi (R9, R10, R11, RU, RHS, and RW respectively). A Matlab program was created to calculate peak vertical ground reaction forces (vGRF), loading rate (LR), and impulse (I) for each step. The interclass correlation (ICC 3,k) comparing the pedoped insoles with the force plate was calculated in SPSS. The ranges used for the ICC are: fair 0.40-0.59, good 0.6-0.74, and excellent 0.75-1.00. RESULTS: The average peak vGRF, LR and I are presented in Table 1 along with the specific ICC values. For the vGRF the ICC values are considered excellent (0.81-0.91), LR ICC values are good to excellent (0.74-0.95), and I ICC values are excellent (0.84-0.91). CONCLUSIONS: Loading differences between the pedoped and force plate could result from differences in measurement location. These results indicate that these single sensor wireless insoles (pedoped) are a valid alternative to assessing lower extremity loading parameters during running allowing researchers to expand testing to a variety of settings outside of the lab.Table 1: Comparisons between pedoped and force plate loading parameters.

Smaller Compressive and Anteroposterior Joint Reaction Forces in Older Compared to Young Runners

Age-related changes in bone structure and mechanics may increase the risk of injury when performing exercise such as running. Joint-related injury such as osteoarthritis is a primary concern for older runners. A contributing factor to bony injury is joint loading. However, it is not known whether increased loading exists in older runners. PURPOSE: To compare anteroposterior and compressive joint reaction forces (JRFs) in the lower extremities during running in healthy young and older runners. METHODS: Nine healthy young runners (YA) and 10 healthy older adult runners (OA) performed fifteen over ground running trials at a fixed velocity (3.35 m/s). Running velocity was maintained (+ 5%) using an infrared timing gate. Three-dimensional kinematics and ground reaction forces were recorded simultaneously using an 8-camera motion capture system (240 Hz, Qualisys, Inc.) and force platform (960 Hz, AMTI, Inc.), respectively. Visual 3D was used to calculate ankle, knee and hip JRFs (compressive and anterior/posterior) during the stance phase of the gait cycle. Independent samples t-tests were used to compare mean JRFs in both directions. RESULTS: YA exhibited significantly larger mean JRFs at the ankle (p=0.04; YA: -13.2±1.0 BW; OA: -12.6±0.7 BW) and knee (p=0.04; YA: -13.0±0.9 BW; OA: -12.3±0.9 BW) while no differences were observed at the hip (p=0.08; YA: -12.0±1.0 BW; OA: -11.1±1.4 BW). In the anterior/posterior direction, older adults had significantly smaller ankle JRFs compared to young adults (p=0.01; YA: 5.1±0.7 BW; OA: 4.5±0.4 BW) while no differences were observed at the knee (p=0.20; YA: -3.0±1.2 BW; OA: -2.7±0.8 BW) or hip (p=0.37; YA: 2.4±2.0 BW; OA: 2.2±1.9 BW). CONCLUSIONS: These data demonstrate that OA have smaller compressive JRFs and anteroposterior shear forces than YA. Therefore, it can be suggested that the greater incidence of bony and cartilage injuries experienced by older runners is not due to greater forces applied to the lower extremity joints during running.

Middle-distance running acutely influences the concentration and composition of serum bile acids: Potential implications for cancer risk?

BackgroundThis study was aimed to investigate the acute effect of medium-distance running on bile acids concentration and composition, in order to verify whether the positive impact of physical exercise on cancer risk may also be mediated by variation of bile acids concentration and composition in serum.MethodsThe concentration and composition of serum bile acids was analyzed in 30 middle-aged and healthy recreational athletes with a reference liquid chromatography-mass spectrometry technique, immediately before and shortly after the end of the running trial. The concentration of bile acids after the run was adjusted for plasma volume change.ResultsAll athletes successfully completed the trial. After correction of values for the individual plasma volume change calculated after the run, the serum concentration of total bile acids was found to be significantly reduced by approximately 46%. A statistically significant decrease was observed for cholic, deoxycholic, chenodeoxycholic, ursodeoxycholic, glycoursodeoxycholic and hyodeoxycholic acids, whereas the concentration of the remaining compounds remained unvaried after the run. A considerable variation of bile acids profile was also observed. No significant association was found between running performance and variation of bile acids concentrations.ConclusionThese results show that middle distance running acutely decreases the concentration of total bile acids in serum, especially that of the more mutagenic and carcinogenic compounds, so providing an intriguing support to the favorable effects of physical exercise for lowering the risk of many gastrointestinal cancers.

Predicting mountain ultra‐marathon performance using the critical velocity model

PURPOSECritical Velocity (CV) and D′ were evaluated as predictors of mountain ultra marathon finishing times in cool conditions.HYPOTHESISIt was hypothesized that CV and D′ would both predict mountain ultra‐marathon performance.METHODSNine healthy males volunteered to participate in the study. Their average age was 37.9 ± 10.0 y, height 1.79 ± 0.05 m, body mass 76.6 ± 11.2 kg, BMI 23.8 ± 3.0 kg•m−2. The SFU Office of Research Ethics approved the study and each volunteer gave a signed consent prior to participation. Each volunteer completed a 50‐km mountain ultra‐marathon and then each volunteer's CV and D′ was evaluated using a series of maximal‐effort timed 1200, 2400 and 3600 m running trials on the same day with 30 min rest before trials 2 and 3. A Latin square design was employed to determine the orders of the tests. Maximal aerobic capacity was also assessed using indirect calorimetry and a graded treadmill test.RESULTSThe mean CV was 3.5 ± 0.5 m•s−1, D′ was 197.2 ± 83.2 m and mean absolute and relative aerobic powers were 4.8 ± 0.8 L min−1 and 63.5 ± 6.7 mL•kg−1•min−1, respectively. Stepwise multiple linear regression identified CV as the sole significant predictor of the mountain ultra‐marathon performance time (r=−0.88, p&lt;0.05). Correlation analysis of the independent variables with finishing time indicated that aerobic power was significantly and positively correlated with finishing times (r=−0.72, p=0.002).CONCLUSIONThese preliminary results suggest that CV explains both a significant fraction of the variance in mountain marathon finishing time and that CV obtained via running track tests is an appropriate method for predicting these finishing times.Support or Funding InformationSupported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canadian Foundation for Innovation (CFI)

Prosthetic model, but not stiffness or height, affects the metabolic cost of running for athletes with unilateral transtibial amputations.

Running-specific prostheses enable athletes with lower limb amputations to run by emulating the spring-like function of biological legs. Current prosthetic stiffness and height recommendations aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, it is unclear how different prosthetic configurations influence the biomechanics and metabolic cost of running. Consequently, we investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic cost of running. Ten athletes with unilateral transtibial amputations each performed 15 running trials at 2.5 or 3.0 m/s while we measured ground reaction forces and metabolic rates. Athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. Use of an Ottobock 1E90 Sprinter prosthesis reduced metabolic cost by 4.3 and 3.4% compared with use of Freedom Innovations Catapult [fixed effect (β) = -0.177; P < 0.001] and Össur Flex-Run (β = -0.139; P = 0.002) prostheses, respectively. Neither prosthetic stiffness (P ≥ 0.180) nor height (P = 0.062) affected the metabolic cost of running. The metabolic cost of running was related to lower peak (β = 0.649; P = 0.001) and stance average (β = 0.772; P = 0.018) vertical ground reaction forces, prolonged ground contact times (β = -4.349; P = 0.012), and decreased leg stiffness (β = 0.071; P < 0.001) averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces (β = 0.007; P = 0.003) but was unrelated to stride kinematic symmetry (P ≥ 0.636). Therefore, prosthetic recommendations based on symmetric stride kinematics do not necessarily minimize the metabolic cost of running. Instead, an optimal prosthetic model, which improves overall biomechanics, minimizes the metabolic cost of running for athletes with unilateral transtibial amputations.NEW & NOTEWORTHY The metabolic cost of running for athletes with unilateral transtibial amputations depends on prosthetic model and is associated with lower peak and stance average vertical ground reaction forces, longer contact times, and reduced leg stiffness. Metabolic cost is unrelated to prosthetic stiffness, height, and stride kinematic symmetry. Unlike nonamputees who decrease leg stiffness with increased in-series surface stiffness, biological limb stiffness for athletes with unilateral transtibial amputations is positively correlated with increased in-series (prosthetic) stiffness.

Hull forms and straight forward CFD free running trials of high-speed shuttle vessels

Hull forms and straight forward CFD free running trials of high-speed shuttle vessels

Pacing Ability in Elite Runners with Intellectual Impairment.

To understand how athletes invest their energy over a race, differences in pacing ability between athletes with and without intellectual impairment (II) were explored using a novel field test. Well-trained runners (n = 67) participated in this study, including 34 runners with II (age = 24.4 ± 4.5 yr; IQ = 63.1 ± 7.7) and 33 runners without II (age = 31.4 ± 11.2 yr). The ability to perform at a preplanned submaximal pace was assessed. Two 400-m running trials were performed on an athletics track, with an individually standardized velocity. In the first trial, the speed was imposed by auditory signals given in 20-40 m intervals, in combination with coach feedback during the initial 200 m. The participant was instructed to maintain this velocity without any feedback during the final 200 m. In trial 2, no coach feedback was permitted. Repeated-measures analyses revealed a significant between-group effect. II runners deviated more from the target time than runners without II. The significant trial-group interaction effect (F = 4.15, P < 0.05) revealed that the ability to self-regulate the pace during the final 200 m improved for runners without II (trial 1, 1.7 ± 1.0 s; trial 2, 0.9 ± 0.8 s), whereas the II runners deviated even more in trial 2 (4.4 ± 4.3 s) than that in trial 1 (3.2 ± 3.9 s). Our findings support the assumption that intellectual capacity is involved in pacing. It is demonstrated that II runners have difficulties maintaining a preplanned submaximal velocity, and this study contributes to understanding problems II exercisers might experience when exercising. With this field test, we can assess the effect of II on pacing and performance in individual athletes which will lead to a fair Paralympic classification procedure.

Effects of compression garments on surface EMG and physiological responses during and after distance running

BackgroundThe few previous studies that focused on the effects of compression garments (CG) on distance running performance have simultaneously measured electromyogram, physiological, and perceptual parameters. Therefore, this study investigated the effects of CG on muscle activation and median frequency during and after distance running, as well as blood-lactate concentration and rating of perceived exertion (RPE) during distance running. MethodsEight healthy male recreational runners were recruited to randomly perform two 40 min treadmill running trials, one with CG, and the other with control garment made of normal cloth. The RPE and the surface electromyography (EMG) of 5 lower extremity muscles including gluteus maximus (GM), rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA), and gastrocnemius (GAS) were measured during the running trial. The blood-lactate levels before and after the running trial were measured. ResultsWearing CG led to significant lower muscle activation (p < 0.05) in the GM (decreased 7.40%–14.31%), RF (decreased 4.39%–4.76%), and ST (decreased 3.42%–7.20%) muscles; moreover, significant higher median frequency (p< 0.05) in the GM (increased 5.57%) and ST (increased 10.58%) muscles. Wearing CG did not alter the RPE values or the blood-lactate levels (p > 0.05). ConclusionWearing CG was associated with significantly lower muscle activation and higher median frequency in the running-related key muscles during distance running. This finding suggested that wearing CG may improve muscle function, which might enhance running performance and prevent muscle fatigue.

Effects of a 4-week high-intensity interval training on pacing during 5-km running trial.

This study analyzed the influence of a 4-week high-intensity interval training on the pacing strategy adopted by runners during a 5-km running trial. Sixteen male recreational long-distance runners were randomly assigned to a control group (CON, n=8) or a high-intensity interval training group (HIIT, n=8). The HIIT group performed high-intensity interval-training twice per week, while the CON group maintained their regular training program. Before and after the training period, the runners performed an incremental exercise test to exhaustion to measure the onset of blood lactate accumulation, maximal oxygen uptake (VO2max), and peak treadmill speed (PTS). A submaximal constant-speed test to measure the running economy (RE) and a 5-km running trial on an outdoor track to establish pacing strategy and performance were also done. During the 5-km running trial, the rating of perceived exertion (RPE) and time to cover the 5-km trial (T5) were registered. After the training period, there were significant improvements in the HIIT group of ∼7 and 5% for RE (P=0.012) and PTS (P=0.019), respectively. There was no significant difference between the groups for VO2max (P=0.495) or onset of blood lactate accumulation (P=0.101). No difference was found in the parameters measured during the 5-km trial before the training period between HIIT and CON (P>0.05). These findings suggest that 4 weeks of HIIT can improve some traditional physiological variables related to endurance performance (RE and PTS), but it does not alter the perception of effort, pacing strategy, or overall performance during a 5-km running trial.

A disparity between locomotor economy and territory-holding ability in male house mice.

Both economical locomotion and physical fighting are important performance traits to many species because of their direct influence on components of Darwinian fitness. Locomotion represents a substantial portion of the total daily energy budget of many animals. Fighting performance often determines individual reproductive fitness through the means of resource control, social dominance and access to mates. However, phenotypic traits that improve either locomotor economy or fighting ability may diminish performance in the other. Here, we tested for a predicted disparity between locomotor economy and competitive ability in wild-derived house mice (Mus musculus). We used 8week social competition trials in semi-natural enclosures to directly measure male competitive ability through territorial control and female occupancy within territories. We also measured oxygen consumption during locomotion for each mouse using running trials in an enclosed treadmill and open-flow respirometry. Our results show that territory-holding males have higher absolute and mass-specific oxygen consumption when running (i.e. reduced locomotor economy) compared with males that do not control territories. This relationship was present both before and after 8week competition trials in semi-natural enclosures. This disparity between physical competitive ability and economical locomotion may impose viability costs on males in species for which competition over mates is common and may constrain the evolution of behavioral and phenotypic diversity, particularly in natural settings with environmental and resource variability.