Stride Rate Research Articles

Effect of custom-made and prefabricated insoles on plantar loading parameters during running with and without fatigue

Controversy exists whether custom-made insoles are more effective in reducing plantar loading compared to prefabricated insoles. Forty recreational athletes ran using custom-made, prefabricated, and the original insoles of their running shoes, at rest and after a fatigue run. Contact time, stride rate, and plantar loading parameters were measured. Neither the insole conditions nor the fatigue state modified contact time and stride rate. Addressing prevention of running injuries, post-fatigue loading values are of great interest. Custom-made insoles reduced the post-fatigue loading under the hallux (92 vs. 130 kPa, P < 0.05), medial midfoot (70 vs. 105 kPa, P < 0.01), and lateral midfoot (62 vs 96 kPa, P < 0.01). Prefabricated insoles provoked reductions in post-fatigue loading under the toes (120 vs. 175 kPa, P < 0.05), medial midfoot (71 vs. 105 kPa, P < 0.01), and lateral midfoot (68 vs. 96 kPa, P < 0.01). Regarding both study insoles, custom-made insoles reduced by 31% and 54% plantar loading under the medial and lateral heel compared to the prefabricated insoles. Finally, fatigue state did not influence plantar loading regardless the insole condition. In long-distance races, even a slight reduction in plantar loading at each foot strike may suppose a significant decrease in the overall stress experienced by the foot, and therefore the use of insoles may be an important protective mechanism for plantar overloading.

Foot Strike Pattern and Gait Changes During a 161-km Ultramarathon

Foot strike pattern has not been examined during ultramarathons where fatigue or avoidance of impact might have greater effect on foot strike and other gait parameters than in shorter events. In this study, video analysis from 3 level sites at a 161-km ultramarathon was used to: (a) examine changes in foot strike pattern, stride rate, and stride length; (b) determine if foot strike pattern is related to performance; and (c) ascertain if post-race blood creatine phosphokinase (CK) concentrations differ by foot strike pattern. Rear-foot strike (RFS) prevalence was 79.9, 89.0, and 83.9% at 16.5, 90.3, and 161.1 km, respectively. There was a significant distance effect observed between the 90.3 and 161.1-km site for stride rate (p < 0.05) and across all distances for stride length (p < 0.0001), but stride rate and length were stable among the top 20 finishers. There was no effect (p = 0.3) of foot strike pattern on performance. However, top 20 finishers had greater use (p = 0.02) of a non-RFS pattern at 161.1 km than the remaining finishers. There was a trend toward greater post-race blood CK values among non-RFS runners compared with RFS runners, reaching significance at the 90.3 km site (p < 0.05). Thus, the increased RFS prevalence by race midpoint was likely because of greater muscular demands of non-RFS patterns as supported by the higher post-race blood CK concentrations among non-RFS runners. Faster runners maintained higher stride rates and lengths throughout the race and made greater use of a non-RFS pattern at the end of the race compared with the slower finishers.

Lower-Body Determinants of Running Economy in Male and Female Distance Runners

A variety of training approaches have been shown to improve running economy in well-trained athletes. However, there is a paucity of data exploring lower-body determinants that may affect running economy and account for differences that may exist between genders. Sixty-three male and female distance runners were assessed in the laboratory for a range of metabolic, biomechanical, and neuromuscular measures potentially related to running economy (ml·kg(-1)·min(-1)) at a range of running speeds. At all common test velocities, women were more economical than men (effect size [ES] = 0.40); however, when compared in terms of relative intensity, men had better running economy (ES = 2.41). Leg stiffness (r = -0.80) and moment arm length (r = 0.90) were large-extremely largely correlated with running economy and each other (r = -0.82). Correlations between running economy and kinetic measures (peak force, peak power, and time to peak force) for both genders were unclear. The relationship in stride rate (r = -0.27 to -0.31) was in the opposite direction to that of stride length (r = 0.32-0.49), and the relationship in contact time (r = -0.21 to -0.54) was opposite of that of flight time (r = 0.06-0.74). Although both leg stiffness and moment arm length are highly related to running economy, it seems that no single lower-body measure can completely explain differences in running economy between individuals or genders. Running economy is therefore likely determined from the sum of influences from multiple lower-body attributes.

Walking activity of children with cerebral palsy and children developing typically: a comparison between the Netherlands and the United States

Purpose: To compare walking activity of children with and without cerebral palsy (CP) between the Netherlands and the United States. Methods: A cross-sectional analysis on walking activity data from an international retrospective comparison study including a convenience sample of 134 walking children aged 7–12 years with spastic CP, classified as Gross Motor Function Classification System (GMFCS) level I (N = 64), II (N = 49) or III (N = 21), and 223 typically developing children (TDC) from the Netherlands and the United States. Walking activity was assessed during a one-week period using a StepWatch™ activity monitor. Outcomes were the daily number of strides, daily time being inactive and spent at low (0–15 strides/min), moderate (16–30 strides/min) and high stride rate (31–60 strides/min). Walking activity was compared between countries using multiple linear regression analyses. Results: Walking activity of TDC was not significantly different between countries. Compared to their American counterparts, Dutch children in GMFCS level I and II showed less walking activity (p < 0.05), whereas Dutch children in GMFCS level III showed more walking activity (p < 0.05). Conclusion: The absence of differences in walking activity between Dutch and American TDC, and the presence of differences in walking activity between Dutch and American children with CP suggest that between-country differences affect walking activity differently in children with CP.Implications for RehabilitationPhysical activity of children with CP should be promoted in both the United States and the Netherlands.The between-country differences in walking activity illustrate that apart from the severity of the CP walking activity seems to be influenced by environmental aspects.In the promotion of physical activity, practitioners should pay attention to environmental barriers that families may experience for increasing physical activity.

A Preliminary Kinematic Gait Analysis of a Strongman Event: The Farmers Walk

This study sought to obtain some preliminary sagittal plane kinematic data on a common strongman event (and conditioning exercise) ‘the farmers walk’ and gain some insight into its kinematic determinants. Five experienced resistance trained males performed three, 20 m farmers walks at maximal speed while carrying 90.5 kg in each hand. Farmers walk average velocity was significantly greater in the middle (8.5–11.5 m) and latter (17–20 m) than initial stage (0–3 m), with this also associated with significant increases in stride length and stride rate and reductions in ground contact time. Comparisons between each subject’s fastest and slowest trials revealed virtually no significant differences. In contrast, the fastest three trials (irrespective of subject) had significantly greater stride length, stride rate and reduced ground contact time than the slowest three trials. Based on the impulse-momentum relationship, the production of high anterior-posterior and vertical impulses over short ground contact times may be crucial for farmers walk performance. Future studies should utilise larger samples and investigate the ground reaction and joint kinetics of the farmers walk and compare these values to other forms of bipedal gait and resistance training exercises to get a more complete understanding of the biomechanics of this exercise.

Daily stride rate activity and heart rate response in children with cerebral palsy

To compare daily stride rate activity, daily exercise intensity, and heart rate intensity of stride rate in children with cerebral palsy with that of typically developing children. Forty-three children with cerebral palsy, walking without (Gross Motor Function Classification System (GMFCS) I and II) or with (GMFCS III) an aid and 27 typically developing children (age range 7-14 years) wore a StepWatch™ activity monitor and a heart rate monitor. Time spent and mean heart rate reserve at each stride rate activity level and time spent in each mean heart rate reserve zone was compared. Daily stride rate activity was lower in children with cerebral palsy (39%, 49% and 79% in GMFCS I, II and III, respectively) compared with typically developing children (p < 0.05), while there were no differences in time spent at different mean heart rate reserve zones. Mean heart rate reserve at all stride rate activity levels was not different between typically developing children, GMFCS I and II, while mean heart rate reserve was higher for GFMCS III at stride rates < 30 strides/min (p < 0.05). Stride rate activity levels reflect the effort of walking, in children with cerebral palsy who are walking without aids, similar to that of typically developing, whereas children with cerebral palsy using walking aids show higher effort of walking. Despite a lower stride rate activity in cerebral palsy, daily exercise intensity seems comparable, indicating that the StepWatch™ monitor and the heart rate monitor measure different aspects of physical activity.

Walking activity patterns in youth with cerebral palsy and youth developing typically

Purpose: To describe daily walking stride rate patterns of young children with cerebral palsy (CP) as compared to a typically developing youth (TDY) cohort relative to age and functional level. Method: A cross-sectional comparison cohort study compared 209 youth with CP with 368 TDY aged 2–13 years. Youth with CP had Gross Motor Function Classification System (GMFCS) levels I–III with 60% bilateral involvement and 79% spastic. Five days of StepWatch data were averaged and classified into low, moderate and high stride rates. Group differences were examined by t-test and analysis of variance. Results: Children with CP walk significantly less each day than TDY (F = 245, p ≤ 0.001) and differ by GMFCS (F = 1.51, p < 0.001). TDY walk a similar number of strides in low and moderate stride rates each day while youth with CP do not. TDY attained high stride rates (>60 strides/min) for 8 min/d with levels I–III at 4.0, 3.2 and 0.53 min/d, respectively. Conclusions: The relative relationship of walking intensity levels within total daily stride activity differs for youth with CP as compared to TDY. The influence of functional walking ability on walking stride activity levels and intensity does not appear to differ significantly across age groups.Implications for RehabilitationLimitation in the ability to attain moderate stride-rate intensity, regardless of total number of strides taken each day for ambulatory youth with CP, is a potential area of focus for intervention.Understanding of stride activity levels and intensity in youth with CP may be employed to focus rehabilitation strategies to enhance habitual walking activity.Community-based stride rate data has potential as an effectiveness outcome for rehabilitation strategies focused on walking (i.e. orthopedic surgery, orthoses and injections therapies).

Influence of stride frequency and length on running mechanics: a systematic review.

Context:A high number of recreational runners sustain a running-related injury each year. To reduce injury risk, alterations in running form have been suggested. One simple strategy for running stride frequency or length has been commonly advocated.Objective:To characterize how running mechanics change when stride frequency and length are manipulated.Data Sources:In January 2012, a comprehensive search of PubMed, CINAHL Plus, SPORTDiscus, PEDro, and Cochrane was performed independently by 2 reviewers. A second search of the databases was repeated in June 2012 to ensure that no additional studies met the criteria after the initial search.Study Selection:Inclusion criteria for studies were an independent variable including manipulation of stride frequency or length at a constant speed with outcome measures of running kinematics or kinetics.Study Design:Systematic review.Level of Evidence:Level 3.Data Extraction:Two reviewers independently appraised each article using a modified version of the Quality Index, designed for assessing bias of nonrandomized studies.Results:Ten studies met the criteria for this review. There was consistent evidence that increased stride rate resulted in decreased center of mass vertical excursion, ground reaction force, shock attenuation, and energy absorbed at the hip, knee, and ankle joints. All but 1 study had a limited number of participants, with several methodological differences existing among studies (eg, overground and treadmill running, duration of test conditions). Although speed was held constant during testing, it was individually self-selected or fixed. Most studies used only male participants.Conclusion:Despite procedural differences among studies, an increased stride rate (reduced stride length) appears to reduce the magnitude of several key biomechanical factors associated with running injuries.

Effects of shoeing on limb movement and ground reaction forces in Icelandic horses at walk, tölt and trot

Tölt is a symmetric four-beat gait with a speed range extending into that of trot and canter. Specific shoeing methods, such as unnaturally high and long hooves, are used to enforce individual gait predisposition. The aim of this study was to assess the consequences of this shoeing style on loading and movement of the limbs at walk, tölt and trot, and at different velocities. Simultaneous kinetic and kinematic gait analysis was carried out at walk (1.4m/s) and at two tölting and trotting speeds (3.3m/s and 3.9m/s) on an instrumented treadmill. Thirteen sound Icelandic horses were first measured with high, long front hooves (SH) and, 1week later, after trimming the hooves according to standard shoeing principles (SN). Comparing SH with SN, front hooves had 21±5mm longer dorsal hoof walls, and the shoeing material per hoof was 273±50g heavier. In all three gaits, gait quality, as it is currently judged, was improved with SH due to a lower stride rate, a longer stride length and a higher, but not wider, forelimb protraction arc, which were also positively associated with speed. Forelimb–hind limb balance remained unchanged, but limb impulses were higher. Apart from an increase of ⩽2.2% in the forelimbs at the faster speed of both tölt and trot, SH had little influence on vertical peak forces.

Effects of shoeing on intra- and inter-limb coordination and movement consistency in Icelandic horses at walk, tölt and trot

To enhance expressiveness of forelimb movement and improve the four-beat rhythm of the tölt, Icelandic horses are commonly ridden with excessively high and long hooves. The aim of this study was to objectively assess the effect of shoeing on intra- and inter-limb coordination and limb movement consistency (inter-stride variability) at walk, tölt and trot. Thirteen sound and fit Icelandic horses accustomed to exercise with a rider on a treadmill were assessed with long and high hooves commonly used for competition (SH) and with the hooves trimmed according to the standards of normal shoeing (SN). Limb timing variables were extracted from the four vertical ground reaction force curves measured with an instrumented treadmill. Measurements were taken at walk and at two tölting and trotting speeds. High hooves with long toes reduced stride rate and increased breakover duration. At the tölt, the footfall rhythm showed less tendency to lateral couplets. Movement consistency of the walk remained unchanged, whereas, at the tölt, stride-to-stride variability of selected time parameters increased in SH and/or at the higher velocity. At the faster trotting speed, variability of hind limb duty factor decreased, whereas variability of contralateral step duration in the forelimb increased. High hooves with long toes improve the clearness of the four-beat footfall rhythm of the tölt, but disturb the movement consistency of the gait. The prolonged breakover duration observed in all gaits may have negative implications for the health of the palmar structures of the distal foot.

Reply to Pancheva, Panchev, and Pancheva

TO THE EDITOR: We are pleased that our paper “Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung” (5) has stimulated critical thought on the role of inertia as a cause of the venous remodeling by Pancheva and coworkers (3). Our group has extensively considered the forces being imposed on the vein wall and their role in remodeling, and we acknowledge that we never considered the inertial forces resulting from the movement of the horse as a major factor determining venous wall stress. We are aware that in the high-velocity flow regime of large arteries, inertial forces outweigh viscous forces (1). Furthermore, inertial forces contribute to the flow and pulse wave form in the pulmonary veins (2). Certainly in the galloping horse that has a cardiac output in excess of 300 l/min, these inertial forces associated with the high flow velocity in large-bore pulmonary arteries and veins are likely to be considerable. However, in the very small veins in which remodeling is occurring, flow velocity is low and inertial forces arising from the movement of the blood are likely to be negligible (1). Pancheva and coworkers are not the first to suggest that forces from the limbs play an etiological role in exerciseinduced pulmonary hemorrhage (EIPH). In 1998, Schroter and coworkers (4) suggested that pressure waves resulting from forelimb impact with the ground transmitted through the lung parenchyma are responsible for the dorsocaudal location of EIPH lesions. It is also likely that inertial forces provided by the acceleration of the horse around its fore- and hindlimbs have effects on pressure waves within the large vessels of the pulmonary circulation where blood mass is greatest. Predicting and measuring the interactions of these limb forces with those imposed by the heart will be difficult, in part because of phase variations between the heart (220 beats/min) and stride rate (120/min) of the exercising horse. Even if that could be done in the large vessels, understanding the role of limb acceleration on vein wall stress in complexly branching very small pulmonary veins will be confounded by their varying geometric relationships to the force vectors arising from the motion of the limbs.

Stride Rate and Walking Intensity in Healthy Older Adults

The study investigated (a) walking intensity (stride rate and energy expenditure) under three speed instructions; (b) associations between stride rate, age, height, and walking intensity; and (c) synchronization between stride rate and music tempo during overground walking in a population of healthy older adults. Twenty-nine participants completed 3 treadmill-walking trials and 3 overground-walking trials at 3 self-selected speeds. Treadmill VO2 was measured using indirect calorimetry. Stride rate and music tempo were recorded during overground-walking trials. Mean stride rate exceeded minimum thresholds for moderate to vigorous physical activity (MVPA) under slow (111.41 ± 11.93), medium (118.17 ± 11.43), and fast (123.79 ± 11.61) instructions. A multilevel model showed that stride rate, age, and height have a significant effect (p < .01) on walking intensity. Healthy older adults achieve MVPA with stride rates that fall below published minima for MVPA. Stride rate, age, and height are significant predictors of energy expenditure in this population. Music can be a useful way to guide walking cadence.

Influence of midsole ‘actuator lugs’ on running economy in trained distance runners

Introduction: Previous investigations reported the influence of running shoe design on running economy (RE) and determined that both shoe weight and midsole properties (hardness, stiffness, comfort) can alter RE. External forefoot actuator lugs have been reported to provide enhanced energy return during shoe mechanical testing, but it was unclear if this design feature would provide any improvement of RE. The current investigation measured the effects of external forefoot actuator lugs on RE in 12 highly-trained male distance runners during four submaximal running velocities. Methods: All runners voluntarily completed a maximal graded exercise treadmill protocol followed 5–7 days later by eight randomised 6 min submaximal level-grade treadmill runs with two randomised footwear conditions (WL = with lugs, WOL = without lugs). Oxygen consumption, heart rate (HR), rating of perceived effort (RPE), and sagittal plane high-speed video were collected. RE (metres run per millilitre O2 per kg of body mass), stance duration (ST), stride rate (SR), and foot strike (FS) were computed for each trial. Data were analysed with factorial repeated-measures analysis of variance (ANOVA). Results: RE, averaged over all submaximal velocities, was significantly greater (p < 0.05) in the WL condition (4.96 ± 0.12 m·ml−1·kg−1) as compared to the WOL condition (4.91 ± 0.10 m·ml−1·kg−1). Only one subject displayed a lower RE in the WL condition. No significant differences were found between HR (p > 0.05), ST (p > 0.05), or SR (p > 0.05) between footwear conditions, but running in the WL condition lowered RPE (p < 0.05). Conclusions: The presence of external forefoot actuator lugs improved RE by ∼1%, although the mechanisms explaining this improvement are not clear.

Temporal variables of the Shackleford Banker horse intermediate gaits

s / Journal of Equine Veterinary Science 33 (2013) 321-399 322 cell proliferationwas reduced in response to the inhibitor of cellular proliferation, porcine Transforming Growth Factorbeta. The ability to fuse and formmultinucleated myotubes is one of the critical capabilities of differentiated myogenic cells. Fusion percentage was calculated as the ratio of the number of myotube nuclei (a myotube is identified by the presence of three or more nuclei within a continuous cell membrane) to total nuclei. After 144 – 168 hours in culture, the ESC fused into large, stable, multinucleated myotubes with resultant cultures exhibiting 75-80% fusion. Further characterization included establishing that the doubling time of the equine satellite cells is 17.7 hours, consistent with other muscle cells grown in culture. We have sucessfully isolated equine satellite cells that maintain their myogenic phenotype in culture. We have optimized cell culture conditions and demonstrated that equine satellite cells respond in the expected manner to both positive and negative components present in the culture media. In other species satellite cells play a key role in postnatal muscle growth and repair of injuredmuscle.We are now inposition to utilize the ESC to investigate the role of satellite cells in these important processes in equine muscle. Temporal variables of the Shackleford Banker horse intermediate gaits M.C. Nicodemus , J. Beranger , and L. Ward 1 Mississippi State University, Mississippi State, MS, 39762, 2 American Livestock Breeds Conservancy, Pittsboro, NC, 27312 Shackleford Banker horse (SBH) is a Spanish Colonial horse (SCH) breed listed on the American Livestock Breeds Conservancy (ALBC) critically endangered list. In accordance to the Shackleford Banks Wild Horses Protection Act, SBH are currently managed by the National Park Service and the Foundation for Shackleford Horses, a nonprofit organization, with Shackleford Island numbers maintained under 150 horses. Selection of horses maintained on the Shackleford Island is based on the health of the animal and the characteristics that will preserve the heritage of the breed. Since other SCH are classified as gaited, SBH are assumed to perform similar gaits despite the lack of research done to confirm this assumption. To better manage the soundness of the herd and to improve horse selection, the objective of this study was to measure the temporal variables of the SBH intermediate gaits. Subject selection was a cooperative effort consisting of experts from the ALBC and the Foundation for Shackleford Horses with their selection based on soundness and best representation of the breed type. Eight SBH were filmed at a slow (SV: 2.43 0.22 m/s) and fast (FV: 3.25 0.14 m/s) intermediate gait. Gait velocity ranges were based on the ranges found in previous gaited horse studies. Frame-byframe analysis was performed on 10 symmetrical strides for each horse for each velocity. Stride variables were given as a % of stride duration with Student paired t-tests applied to determine differences between velocities (P<0.05). At the slower velocity, the footfall sequence was lateral alternating between lateral (12 3%) and diagonal bipedal support (DBS) (88 3%), while the faster velocity had a diagonal footfall sequence alternating between suspension (23 4%) and DBS (77 5%). While stride length (SV: 1.75 +0.20 m, FV: 1.95 0.13 m) remained consistent between the two velocities, stride duration (SV: 0.73 0.03 s, FV: 0.60 0.03 s), fore (SV: 50 5%, FV: 39 3%) and hind (SV: 50 6%, FV: 39 4%) stance durations, diagonal advanced placements (SV: 6 2%, FV: 0 1%), and DBS decreased at the faster velocity as stride rate (SV: 1.38 0.06 strides/s, FV: 1.67 0.09 strides/s) increased (P<0.05). Similar to other SCH, the SBH has the ability to perform a 4-beat stepping intermediate gait, but this ability is limited to the slower velocity and may be an example of a transitional gait as the horse transitions from the walk to the trot. Nevertheless, the velocity and the limb support sequencing of this transitional gait is unique from other gaited and non-gaited horse breeds. In addition, the mechanism used for increasing velocity, limb pairing and increased stride rate instead of increased stride length, is distinctive from other horse breeds studied that exhibited a 4-beat stepping intermediate gait, and thus, can be applied in the understanding of this

Resonance in Human Walking Economy: How Natural Is It?

Abstract Locomotion and movement economy are cornerstone topics in movement science. Modeling the leg as ahybrid mass-spring pendulum shows walking economy should be optimized when stride frequency matchesthe resonant frequency of the limb. Human walking is described as self-optimizing because mean preferred(PSF) and modeled resonant (RSF) stride frequencies usually are statistically equivalent, but this depictionmay not be fully justified. Purpose: To more thoroughly examine the self-optimization characterization andthe consequences of obligating use of the RSF. Methods : Forty-seven individuals of diverse staturescompleted 3 consecutive days of preferred walking trials on a treadmill where stride rate, stride length,walking speed, heart rate and walking economy measures were made under steady state heart rate conditions.Anthropometric measures were taken to build a hybrid model of the leg and model the RSF. Reliability acrossdays was evaluated via repeated measures analysis of variance (ANOVA) and intra-class correlation (α=.05)and correlations were calculated for PSF and RSF. A separate sample of 20 participants walked under 3conditions, (1) completely preferred; (2) at the original preferred speed using the RSF; and (3) with theoption to establish a new preferred speed while using the RSF.

Maximal Physiological Parameters during Partial Body-Weight Support Treadmill Testing

This study investigated maximal cardiometabolic response while running in a lower body positive pressure treadmill (antigravity treadmill (AG)), which reduces body weight (BW) and impact. The AG is used in rehabilitation of injuries but could have potential for high-speed running, if workload is maximally elevated. Fourteen trained (nine male) runners (age 27 ± 5 yr; 10-km personal best, 38.1 ± 1.1 min) completed a treadmill incremental test (CON) to measure aerobic capacity and heart rate (VO(2max) and HR(max)). They completed four identical tests (48 h apart, randomized order) on the AG at BW of 100%, 95%, 90%, and 85% (AG100 to AG85). Stride length and rate were measured at peak velocities (V(peak)). VO(2max) (mL.kg(-1).min(-1)) was similar across all conditions (men: CON = 66.6 (3.0), AG100 = 65.6 (3.8), AG95 = 65.0 (5.4), AG90 = 65.6 (4.5), and AG85 = 65.0 (4.8); women: CON = 63.0 (4.6), AG100 = 61.4 (4.3), AG95 = 60.7 (4.8), AG90 = 61.4 (3.3), and AG85 = 62.8 (3.9)). Similar results were found for HR(max), except for AG85 in men and AG100 and AG90 in women, which were lower than CON. V(peak) (km.h(-1)) in men was 19.7 (0.9) in CON, which was lower than every other condition: AG100 = 21.0 (1.9) (P < 0.05), AG95 = 21.4 (1.8) (P < 0.01), AG90 = 22.3 (2.1) (P < 0.01), and AG85 = 22.6 (1.6) (P < 0.001). In women, V(peak) (km.h(-1)) was similar between CON (17.8 (1.1) ) and AG100 (19.3 (1.0)) but higher at AG95 = 19.5 (0.4) (P < 0.05), AG90 = 19.5 (0.8) (P < 0.05), and AG85 = 21.2 (0.9) (P < 0.01). The AG can be used at maximal exercise intensities at BW of 85% to 95%, reaching faster running speeds than normally feasible. The AG could be used for overspeed running programs at the highest metabolic response levels.

Hemodynamic impacts of entrainment of heart rate and stride rate

Synchronization of heart rate and step rate has been hypothesized to create a hemodynamically favorable situation where heart motion and bodily motion are in constant harmony so that stroke volume and cardiac output enhanced and oxygen delivery to the tissues is increased. The primary aim of the present investigation was to determine the impact of synchronization of step rate and heart rate on cardiovascular functions. Twenty-three apparently healthy subjects performed treadmill running in three different conditions, one that the step rate was matched with the heart rate (matched condition), one that the step rate was ∼10 steps greater or lower than heart rate (unmatched conditions). Beat-by-beat blood pressure was measured using the finger plethysmography, and stroke volume and cardiac output were calculated using the validated Model Flow method. Average heart rate and blood pressures were not different among the 3 conditions. There were no differences in double products among the 3 conditions. Stroke volume and cardiac output were greater (P < 0.05) in the matched condition than in the unmatched conditions. Our present results are consistent with the idea that synchronization of heart motion and bodily motion augments stroke volume and cardiac output, presumably through the mechanism similar to the arterial counterpulsation.

Sacrificing economy to improve running performance—a reality in the ultramarathon?

ultramarathons have become increasingly popular in recent years. Although complex tactical and psychological-motivational factors play important roles in performance ([Fig. 1][1]), running velocity sustained over a prolonged time is directly proportional to maximal sustainable Vo2 and inversely

Middle cerebral artery blood velocity during running: interactions of heart and stride impact rates

Vertical movement during running or treadmill exercise generates complex aortic blood pressure waveforms that are developed by the interactions of the cardiac and foot impact pressure pulses (&gt;120bpm). Heart rate (HR) and stride rate (SR) can be synchronized in and out of phase with beat frequencies (difference in the HR and SR). Large variations in phasic aortic pulse pressures (40–120 mmHg) occur during running. Transcranial Doppler (TCD) measures dynamic middle cerebral artery blood velocity (CBFv), an index of hemispheric cerebral blood flow. Due to technical limitations, CBFv during running has not been reported. We hypothesized that running would significantly modulate CBFv. We used a 2 MHz TCD and a form fitting headset to minimize motion artifact in 5 healthy subjects (26 ±8SD) during: upright rest; walking (4 mph, no vertical motion); and running (7 mph, 4–5 inch vertical motion). The resting and walking waveforms were similar to reported ergometer waveforms. Running CBFv waveforms were similar to reported pressure waveforms and exhibited beat frequencies with a range of maximal and minimal CBFv. During in phase HR and SR periods, CBFv was 78±8 cm/s. Out of phase CBFv was 56±6 cm/s (p&lt;0.05). Preliminary data suggest that CBFv is significantly modulated by the convolution of HR and SR during running. Dynamic cerebral blood flow may depend on the mode of exercise, and it could be optimized by timing of stride rate.

Effects of synchronous music use in ultra distance events

ntroduction: Music use during physical activity has been associated with enhanced psychological responses, reduced perceived exertion, improved performance and, to a lesser extent, physiological efficiency. Whether such benefits apply to ultra-distance athletes is unknown. The present study examined effects of music on a range of indices among athletes competing in 24 h and 48 h events. Method: Ten elite ultra-distance walkers and runners (male = 7, female = 3, age range = 39–63 yr.), competing in events in Brisbane, Caboolture and Melbourne, participated in a field experiment. Participants were provided with a 120 min intervention (30 min each of motivational music, neutral music, audio book, silence) pre-loaded onto iPods, to which they listened three times during pre-assigned 6 h blocks (i.e., hours 6–12, 18–24, 30–36, 42–48). Music tempo was individually synchronized to match stride rate, and motivational qualities of music were rated by each participant using the BMRI-2. Participants were monitored using the BRUMS, FS, RPE, and HR. Lap times were recorded for each participant. Results: As a group, participants derived a significant performance benefit from synchronous motivational music compared to the other three conditions during the crucial 18–24 h period (F3,556 = 15.1, p < .001), with each 400 m lap completed faster, on average, by 14 s (v no music, p = .003), 18 s (v neutral music, p < .001) or 27 s (v audio book, p < .001). No group differences in FS, RPE, and HR were found. Individual differences were very apparent, however, with some participants deriving benefits from motivational music and others deriving no benefits or, in some cases, a disadvantage. For example, Participant 7 completed laps 36 s to 62 s faster while listening to motivational music whereas Participant 3 was 18 s to 23 s slower with motivational music compared to the other three conditions. Conclusions: A performance benefit from listening to synchronous motivational music may accrue for some individuals in ultra-distance events but not for others. The enhanced psychological responses, reduced perceived exertion and improved physiological efficiency found in previous studies were not apparent among ultra-distance athletes in the present study.