Acute effects of footwear on running impact loading in the preschool years.

The aim of this study was to assess acute effects of footwear conditions (barefoot, minimalist and standard running shoes) on running impact loading in the preschool years. Fourty-eight habitually shod preschool children (26 males and 22 females) were divided into four age groups (3-, 4-, 5- and 6-year-old). Children performed a simple running game in three different conditions. Three-dimensional biomechanical analysis was carried out during overground running. Statistical parametric mapping was performed on the vertical ground reaction force profiles during the stance phase and one-way repeated measures ANOVA on the vertical instantaneous loading rate. Three-year-old children displayed significantly lower vertical ground reaction force values in the barefoot condition compared to minimalist (3-7% stance) and standard running shoes (7-11% stance). There were also differences in vertical instantaneous loading rate, where 3-year-olds had lower loading when barefoot than in minimalist (p = 0.010, d = 1.19) or running shoes (p = 0.045, d = 0.98), despite no differences in the footstrike pattern (mostly rearfoot-midfoot strike). No differences were found for the older children. Running in minimalist shoes did not imitate barefoot running in 3-year-old children. On the contrary, increased loading was observed in minimalist shoes in early running developmental stages.

The effect of exercise modality on age-related changes observed during running.

INTRODUCTION: With the increase in participation by older adults in endurance events, research is needed to evaluate how exercising throughout the lifespan can affect the aging process regarding gait and mobility. The purpose of this study was to determine how the type of exercise modality one participates in will affect age-related declines observed during running. METHODS: Fifty-six individuals between the ages of 18-65 who considered running, resistance training or cycling/swimming as their primary form of activity participated in this study. Kinematics were captured using a 10-camera motion capture system while participants ran at a controlled pace of 3.5 m/s (± 5%) over a 10-m runway with force platforms collecting kinetic data. Eight successful trials were chosen for analysis. A one-way ANOVA assessed differences in mean kinematic and kinetic variables of interest between physical activity groups (α = 0.05). RESULTS: Older resistance trainers exhibited greater maximal knee power compared to older runners. No other group differences were observed. CONCLUSION: Despite type of exercise modality, regularly participating in exercise has positive effects. This is evident through the preservation of the function of the lower extremity with age, specifically function of the ankle, and its contribution to healthy movement patterns.

Plantar fasciitis injury status influences foot mechanics during running.

BACKGROUND: The biomechanical factors related to plantar fasciitis are not well understood. A history of injury is considered a risk factor for subsequent injury, but it is unknown if differences in mechanics exist before, during, and after injury. This study compared gait mechanics among individuals with plantar fasciitis, resolved plantar fasciitis, and uninjured controls. METHODS: Thirty male and female runners were divided into three groups: 1) plantar fasciitis (n = 10, age 43 ± 11 years); 2) resolved plantar fasciitis (n = 10, age 43 ± 13 years); and 3) control (n = 10, age 38 ± 11 years). Participants ran at preferred velocity and 3.3 m/s while kinematics and kinetics were collected. Variables of interest include vertical loading rate, foot, ankle, knee, and hip kinematics, arch height index, arch rigidity index, and arch drop. Group differences were analyzed at each velocity using one-way analysis of variance. FINDINGS: The plantar fasciitis group exhibited less forefoot extension (P = 0.02), more midfoot inversion (P < 0.01), and more midfoot extension (P < 0.01) than the resolved plantar fasciitis group. Foot mechanics in controls did not differ. Sagittal knee range of motion was greater in the plantar fasciitis group than resolved or control (P = 0.01). No other variables were significantly different among groups. INTERPRETATION: The plantar fasciitis group exhibited dynamic foot mechanics which suggest a lower, more flexible arch compared to the resolved group, although static measures of foot structure and ankle motion did not differ. The differences between these groups indicate that the motion of the forefoot and midfoot during gait are important to consider for plantar fasciitis.

Dynamic stability in runners with and without plantar fasciitis.

BACKGROUND: Plantar fasciitis (PF) is a common overuse injury experienced by runners. PF may decrease the ability of the plantar fascia to create tension and reduce stability of the foot. Stability of the foot is necessary for whole-body dynamic stability during running which consists of cyclical periods of single leg stance. Given that a major risk factor for running-related injury is previous injury, evaluating dynamic stability in runners with PF, runners with resolved PF, and healthy runners may elucidate differences between these individuals and clarify risk for secondary injury in these groups. RESEARCH QUESTION: Is dynamic stability reduced in runners with PF and runners with resolved PF compared to healthy runners? METHODS: Thirty runners were recruited for this retrospective comparative study based on mileage and injury status: current PF (PF), resolved PF (RPF), or healthy (CON). Kinematic and kinetic data were collected during running and dynamic stability was determined by time-to-contact (TtC) analysis for early, mid, and late stance to the anterior, posterior, medial, and lateral boundary of the foot. Dynamic stability was compared between groups one-way ANOVAs (α = 0.05) and Tukey post-hoc tests conducted when appropriate. Cohen's d effect sizes (d) were reported for all TtC comparisons (small = 0.20, medium = 0.50, large = 0.80). RESULTS: TtC values were shorter in PF compared to the other groups to all boundaries during mid-stance. TtC was significantly greater in PF compared to RPF to the anterior boundary during late stance. SIGNIFICANCE: Shorter TtC observed in PF compared to the other groups during midstance may indicate reduced dynamic stability during the most stable portion of running which may lead to increased injury risk.

Age differences in running biomechanics during footstrike between preschool children and adults.

This study aimed to compare impact loading between two age groups of preschool children (3-4 and 5-6 years old) and one group of young adults representing mature level of running skill (n = 15 per group). Three-dimensional biomechanical data were collected during running barefoot, in minimalist and running shoes. A two-way mixed ANOVA was performed to assess age and footwear differences in vertical instantaneous loading rate (VILR). An interaction was found in VILR. Older (5-6) preschoolers had 30-31% lower VILR than younger (3-4) (p = 0.012, d = 1.02; p = 0.001, d = 1.18) and adults had 51-77% lower VILR than younger preschoolers (p = 0.001, d = 1.85; p = 0.001, d = 2.82) in minimalist and running shoes, respectively. Additionally, adults had lower VILR than older preschoolers in running shoes (p = 0.001, d = 2.68). No differences were found between older children and adults in barefoot and minimalist shoes. Loading decreased with increasing age, particularly in minimalist and running shoes. Unchanged cadence and running speed did not explain the decrease of VILR during preschool age. The explanation likely underlies in lower limb alignment during footstrike and developmental ontogenetic changes.

Running Footstrike Patterns and Footwear in Habitually Shod Preschool Children.

INTRODUCTION: Running skill develops during the preschool age. There is little research evidence as to how footstrike patterns are affected by footwear during this important developmental period. PURPOSE: The aim of this study was to compare footstrike patterns among different age groups of preschool children running in different footwear conditions. METHODS: Three-dimensional kinetics and kinematics were collected while 48 typically developing children age 3 to 6 yr ran overground at self-selected speed in a barefoot condition and in minimalist and standard running shoes. Children were divided into four age groups (n = 12 per group). The key dependent variables for this study included strike index and sagittal plane ankle angle at footstrike. A two-way mixed ANOVA (3 × 4) was performed to determine possible footwear and age differences in footstrike patterns. RESULTS: An interaction between footwear condition and age group was found in the ankle angle at footstrike (P = 0.030, η2 = 0.145). There was a main effect within the footwear condition across all age groups for strike index (P = 0.001, η2 = 0.337). The ankle was more plantar flexed in the barefoot and minimalist conditions compared with standard running shoes only in 6-yr-old children (P < 0.05, d > 0.8). In addition, 6-yr-old children had a more plantar flexed ankle than did 3-yr-old children when they ran barefoot (P = 0.008, d = 1.24). CONCLUSIONS: Footstrike pattern is affected by footwear in preschool children. As children get older, their footstrike pattern becomes more non-rearfoot with a more plantar flexed ankle in barefoot and minimalist shoes. On the contrary, the rearfoot-midfoot strike pattern did not change over preschool age when they wore standard running shoes.

Joint coordination when running in minimalist, neutral, and ultra-cushioning shoes.

Ultra-cushioning (ULTRA) shoes are new to the running shoe market. Several studies have evaluated kinematics and kinetics while running in ULTRA shoes, however it remains unknown how such shoes influence joint coordination. Therefore, the purpose of this study was to evaluate lower extremity coordination and coordination variability when running in minimalist (MIN), traditional (NEUT) and ULTRA shoes. Fifteen runners ran for ten minutes in each shoe type. Coordination patterns and coordination variability were assessed for rearfoot-tibia, rearfoot-knee, and tibia-knee couplings using a modified vector coding method during early, mid, and late stance periods. During late stance ULTRA shoes resulted in more antiphase coordination than MIN (p =.036) or NEUT (p =.047) shoes and less in-phase coordination than MIN (p =.048) or NEUT (p =.013) shoes. During late stance there was also more proximal phase rearfoot-knee coordination in ULTRA shoes than in either MIN (p =.039) or NEUT (p =.005) shoes and less in-phase coordination in ULTRA shoes than in NEUT shoes (p =.006). There were no differences in coordination variability between shoes during any phase. The differences in coordination may have implications for tissue loading and injury development when running in ULTRA shoes..

Understanding the influence of perceived fatigue on coordination during endurance running.

During the course of a training programme, runners will typically increase running velocity and volume possibly encountering fatigue during a run, which is characterised as a feeling of general tiredness. The purpose of the current study was to identify whether or not level of perceived fatigue affects coordination and coordination variability in healthy runners during the recovery velocity of an endurance interval run. A total of 20 endurance runners completed a 1-hour run that included running velocity intervals at 75% of estimated 10 k race pace (5 minutes) and estimated 10 k race pace (1 minute). After each run, participants completed a fatigue questionnaire and were grouped based on their post-run self-reported perceived fatigue. 3D motion capture data were collected during the run and analysed to generate coordination patterns and variability of the patterns as dependent variables. Multiple mixed model ANOVAs were conducted to test for differences between perceived fatigue groups. Coordination and variability differences were reported in a number of couplings during transition phases (late and early stance) and events (toe-off and foot contact) of the gait cycle. It was concluded that the level of perceived fatigue affected coordination and coordination variability during the recovery velocity of a 1-hour interval run.

Running status and history: A self-report study.

OBJECTIVES: The purpose of the current study was to compare injury and running history among current and former runners who consider themselves either injured or uninjured. DESIGN: Cross-sectional survey. SETTING: Online survey, available to any individuals over the age of 18 who currently run (runners) or who once ran regularly but are no longer running (former runners). PARTICIPANTS: 312 participants (age 38 ±â€¯12 years, 219 males, 89 females, 4 did not disclose) completed the survey. MAIN OUTCOME MEASURES: This study assessed injury incidence, consequences of injury such as time off, and reported injury diagnoses and treatments. Chi-square and frequency analyses were calculated to describe running status, injury counts, and response to injury. RESULTS: Most participants (80%) reported 1 + running injury. 775 total injuries were reported. The four most common injuries were iliotibial band syndrome (34%), plantar fasciitis (30%), strained thigh/hip muscle (25%), and medial tibial stress syndrome (22%). About 40% of participants continued to run with these injuries. CONCLUSIONS: Injury frequencies (80%) agreed with those reported in the literature. The results of this study also support the notion that running injuries exist on a continuum of severity and that the individual response to injury is complex and determined by various factors.

Effects of treadmill running velocity on lower extremity coordination variability in healthy runners.

With a growing interest in coordination variability and its role in endurance running, it is important to identify the effect of running velocity. The purpose of the current study was to investigate the effect of treadmill running velocity on the coordination and variability of coordination of lower extremity couplings of healthy runners during stance. Fourteen apparently healthy runners ran on a split-belt force instrumented treadmill at five different velocities. Continuous relative phase (CRP) was used to quantify coordination and variability (vCRP) between lower extremity couplings of the right limb (thigh-shank, thigh-foot, shank-foot) during three phases of stance (loading, mid stance, and propulsion). Multiple one-way repeated measure ANOVAs were conducted to identify differences among velocity conditions at each phase and discrete events (initial foot contact, peak knee flexion during stance, and toe-off). Thigh internal/external rotation (IR/ER)-Shank abduction/adduction (AB/AD) coupling was different during the propulsive phase (p = 0.02). Thigh flexion/extension-Shank flexion/extension showed the greatest differences in vCRP across velocity conditions with differences occurring during loading phase, mid stance, propulsive phase, and peak flexion (p < 0.05). Additionally, significant differences were seen in Thigh FL/EX-Shank FL/EX (toe-off, p = 0.01) and Thigh FL/EX-Foot inversion/eversion (IN/EV) (toe-off, p = 0.032). Interestingly, the decreases in vCRP values were accompanied by changes in center of mass vertical motion during stance, but not knee flexion angles. Increases in running velocity led to a more constrained running pattern through a reduction in degrees of freedom.

Bilateral Comparison of Vertical Jump Landings and Step-off Landings From Equal Heights.

Harry, JR, Silvernail, JF, Mercer, JA, and Dufek, JS. Bilateral comparison of vertical jump landings and step-off landings from equal heights. J Strength Cond Res 32(7): 1937-1947, 2018-The purpose of this investigation was to examine kinetic, kinematic, and temporal parameters during vertical jump landings (VJL) and step-off landings (STL) from equal heights. Five men (25.0 ± 1.6 years; 1.7 ± 0.4 m; 79.7 ± 7.1 kg) and 5 women (20.8 ± 1.6 years; 1.6 ± 0.4 m; 68.5 ± 7.1 kg) performed 15 VJL and 15 STL. Paired-samples t-tests (α = 0.05) compared impact velocity and the times to the first (F1) and second (F2) peak vertical ground reaction force magnitudes (tF1 and tF2) and the end of impact. Two-way analyses of variance (α = 0.05) compared limb and task differences in F1, F2, hip, knee, and ankle joint angles at ground contact, F1, F2, and the end of impact, and hip, knee, and ankle joint displacements between contact and F1, F1 and F2, and F2 and the end of impact. Impact velocity was not different between STL and VJL, although STL produced a greater F1 and a more rapid tF2. Greater hip, knee, and ankle flexion/dorsiflexion occurred during STL throughout the majority of impact regardless of limb. Lesser hip, knee, and ankle joint displacements occurred during STL regardless of limb between F1 and F2, whereas greater joint displacement occurred between F2 and the end of impact. Lastly, knee joint angles at ground contact differed between limbs during STL only. Strength and conditioning professionals aiming to improve an athlete's performance during sport-specific jump landings should consider the likely impact attenuation outcomes before selecting STL or VJL in training.

Comparisons of Segment Coordination: An Investigation of Vector Coding.

The development of a methodology to assess movement coordination has provided gait researchers a tool to assess movement organization. A challenge in analyzing movement coordination using vector coding lies within the inherent circularity of data garnered from this technique. Therefore, the purpose of this investigation was to determine if accurate group comparisons can be made with varying techniques of vector coding analyses. Thigh-shank coordination was analyzed using a modified vector coding technique on data from 2 groups of runners. Movement coordination was compared between groups using 3 techniques: (1) linear average completed with compressed data (0°-180°) and noncompressed data (0°-360°), (2) coordination phase binning analysis; and (3) a circular statistics analysis. Circular statistics (inferential) analysis provided a rigorous comparison of average movement coordination between groups. In addition, the binning analysis provided a metric for detecting even small differences in the time spent with a particular coordination pattern between groups. However, the linear analysis provided erroneous group comparisons. Furthermore, with compressed data, linear analysis led to misclassification of coordination patterns. While data compression may be attractive as a means of simplifying statistical analysis of inherently circular data, recommendations are to use circular statistics and binning methods on noncompressed data.

Comparison of pre-contact joint kinematics and vertical impulse between vertical jump landings and step-off landings from equal heights.

Although impact phase differences between vertical jump landings (VJL) and step-off landings (STL) may be related to task-specific pre-contact strategies, pre-contact mechanics are rarely examined. Thus, pre-contact kinematics and vertical ground reaction force (vGRF) impulse were examined between VJL and STL. Ten health adults (20.9 ±â€¯1.6 yrs; 167.8 ±â€¯4.2 cm; 68.5 ±â€¯7.15 kg) performed 15 VJL and 15 STL from equal heights. Limb (lead; trail) by task (VJL; STL) ANOVAs (α = 0.05) compared hip, knee, and ankle joint angles 150 ms pre-contact, 100 ms pre-contact, 50 ms pre-contact, and at ground contact. Joint angular displacement was also evaluated between 150 ms pre-contact and ground contact. vGRF impulse was compared during the loading (ground contact to peak vGRF) and attenuation (peak vGRF to end of impact) phases. Greater hip flexion angles occurred during STL versus VJL at each event except 150 ms pre-contact (p ≤ .004). Trail limb knee flexion angles were greater at each event when compared to the lead limb during STL (p ≤ .019). Greater trail limb knee flexion angles occurred during STL versus VJL at all four events (p ≤ .018), while greater plantarflexion angles occurred at all four events during VJL versus STL (p ≤ .034). During STL, greater trail limb plantarflexion angles were detected at each event versus the lead limb (p < .001). Lesser hip, lead and trail limb knee displacement occurred during STL versus VJL (p < .05). Greater vGRF impulse was detected during the loading phase of VJL (<.001), while greater vGRF impulse occurred during the attenuation phase of STL (p = .025). These tasks are characterized by distinct pre-contact kinematic strategies and post-contact kinetics. The task utilized in practice should reflect the requirements of the population of interest.

Age and sex influences on running mechanics and coordination variability.

The purpose of this study was to examine the impact of age on running mechanics separately for male and female runners and to quantify sex differences in running mechanics and coordination variability for older runners. Kinematics and kinetics were captured for 20 younger (10 male) and 20 older (10 male) adults running overground at 3.5 m · s-1. A modified vector coding technique was used to calculate segment coordination variability. Lower extremity joint angles, moments and segment coordination variability were compared between age and sex groups. Significant sex-age interaction effects were found for heel-strike hip flexion and ankle in/eversion angles and peak ankle dorsiflexion angle. In older adults, mid-stance knee flexion angle, ankle inversion and abduction moments and hip abduction and external rotation moments differed by sex. Older compared with younger females had reduced coordination variability in the thigh-shank transverse plane couple but greater coordination variability for the shank rotation-foot eversion couple in early stance. These results suggest there may be a non-equivalent aging process in the movement mechanics for males and females. The age and sex differences in running mechanics and coordination variability highlight the need for sex-based analyses for future studies examining injury risk with age.

Segment coupling and coordination variability analyses of the roundhouse kick in taekwondo relative to the initial stance position.

The initial stance position (ISP) has been observed as a factor affecting the execution technique during taekwondo kicks. In the present study, authors aimed to analyse a roundhouse kick to the chest by measuring movement coordination and the variability of coordination and comparing this across the different ISP (0°, 45° and 90°). Eight experienced taekwondo athletes performed consecutive kicking trials in random order from every of the three relative positions. The execution was divided into three phases (stance, first swing and second swing phase). A motion capture system was used to measure athletes' angular displacement of pelvis and thigh. A modified vector coding technique was used to quantify the coordination of the segments which contributed to the overall movement. The variability of this coordination (CV) for each ISP was also calculated. Comparative analysis showed that during the stance phase in the transverse plane, athletes coordinated movement of the trunk and thigh with a higher frequency of in-phase and lower frequency of exclusive thigh rotation in the 0° stance than the 90° stance position (P < 0.05). CV was also influenced by the different ISP. During the first swing and the majority of the second swing phase, predominant in-phase coordination of the pelvis and thigh was observed. Including exercises that require in-phase movement could not only help athletes to acquire coordination stability but also efficiency. The existence of a constraint such as ISP implies an increase of the variability when the athletes have to kick from ISP they are not used to adopt (i.e., 0° and 90° ISP) as an evidence of adaptability in the athletes' execution technique.

Changes in coordination and its variability with an increase in running cadence.

Alterations in joint mechanics have been associated with common overuse injuries. An increase in running cadence in healthy runners has been shown to improve several parameters that have been tied to injury, but the reorganisation of motion that produces these changes has not been examined. The purpose of this study was to determine if runners change their segment coordination and coordination variability with an acute increase in cadence. Data were collected as ten uninjured runners ran overground at their preferred cadence as well as a cadence 10% higher than preferred. Segment coordination and coordination variability were calculated for select thigh-shank and shank-foot couples and selected knee mechanics were also calculated. Paired t-tests were used to examine differences between the preferred and increased cadence conditions. With increased cadence, there was a decrease in peak knee flexion and a later occurrence of peak knee flexion and internal rotation and shank internal rotation. Segment coordination was altered with most changes occurring in mid-late stance. Coordination variability decreased with an increase in cadence across all couples and phases of gait. These results suggest examination of coordination and its variability could give insight into the risk of intervention-induced injury.

The role of running mileage on coordination patterns in running.

Injury rates among runners are high, with the knee injured most frequently. The interaction of running experience and running mechanics is not well understood but may be important for understanding relative injury risk in low vs higher mileage runners. The study aim was to apply a principal component analysis (PCA) to test the hypothesis that differences exist in kinematic waveforms and coordination between higher and low mileage groups. Gait data were collected for 50 subjects running at 3.5 m/s assigned to either a low (< 15 miles/wk) or higher (> 20 miles/wk, 1 year experience) mileage group. A PCA was performed on a matrix of trial vectors of all force, joint kinematic, and center of pressure data. The projection of the subjects' trial vectors onto the linear combination of PC7, PC10, PC13, and PC19 was significantly different between the higher and lower mileage groups (d = 0.63, P = .012). This resultant PC represented variation in transverse plane pelvic rotation, hip internal rotation, and hip and knee abduction and adduction angles. These results suggest the coordination of lower extremity segment kinematics is different for lower and higher mileage runners. The adopted patterns of coordinated motion may explain the lower incidence of overuse knee injuries for higher mileage runners.

The influence of body mass index and velocity on knee biomechanics during walking.

Obesity has been associated with both the development and progression of knee osteoarthritis. Being overweight or obese from a young age is likely to decrease the age of onset for co-morbidities of obesity such as osteoarthritis. However, research on osteoarthritis has thus far focused on older adults. Therefore, the purpose of this study was to determine whether young adults who are overweight or obese exhibit biomechanical risk factors for knee osteoarthritis at either their preferred walking velocity or at 1m/s, which was slower than the preferred velocity. Thirty healthy young adults formed three equal groups according to body mass index. Three dimensional kinetics and kinematics were collected while participants walked overground at both velocities. Joint moments were normalized to fat free weight and height. The preferred walking velocity of obese participants was slower than that of normal weight individuals. There were no differences in knee flexion excursion, peak knee flexion angle, normalized peak knee flexion moment or normalized peak knee adduction moment among groups. Obese participants walked with lower peak knee adduction angle than both overweight and normal body mass index participants and several shifted towards knee abduction. All groups had smaller knee flexion excursion, peak knee flexion angle, peak knee flexion moment and peak knee adduction moment at 1m/s compared to preferred walking velocity. Overall, young and otherwise healthy overweight and obese participants have knee biomechanics during gait at preferred and slow walking velocities that are comparable to normal weight adults.