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Effects of Treadmill Cushion and Running Speed on Plantar Force and Metabolic Energy Consumption in Running
Abstract
Background:
Repetitive loading with high impact forces are considered as a primary risk factor for overuse injuries. Cushion was proposed in running surface and shoe manufacturing to reduce impact forces and prevent injuries in running.
Research question:
To investigate the effects of treadmill cushion and running speed on plantar force and metabolic energy consumption in treadmill running.
Methods:
Plantar force data and metabolic data were collected for 20 men during running at 8 km/h and 10 km/h on the treadmill with and without cushion. Two-way ANOVAs with repeated measures were performed to determine the treadmill effects and the speed effects.
Results:
Participants significantly decreased peak plantar force on the fore foot at both 10 km/h (P = 0.001) and 8 km/h (P = 0.001) and peak plantar force on the mid foot only at 10 km/h (P = 0.011) while running on the treadmill with cushion compared to the treadmill without cushion. The reduction of peak plantar force at 10 km/h was greater than that at 8 km/h while running on the treadmill with cushion. Participants significantly increased metabolic energy consumption while running on the treadmill with cushion compared to the treadmill without cushion (P = 0.007).
Significance:
Running on the treadmill with cushion significantly decreased plantar force on the fore foot and mid foot, and increased metabolic energy consumption. Running on the treadmill with cushion may be a useful method in the prevention of fore foot injuries and increasing exercise effects.
... In this regard, the role of the belt dimensions and intra-belt speed fluctuations remains largely unclear but might be relatively small for modern treadmills with strong driving mechanisms that provide minimal intra-stride belt speed variability, including high-quality research-based treadmills [3]. On the other hand, the controversy in the field regarding the comparison of treadmill vs. overground running could also be caused by dissimilarities in the mechanical properties of the running surfaces used in the different studies [2,3,7,8]. Indeed, treadmills' mechanical properties have an important influence-and in fact, greater than that of the lack of air resistance-on physiological responses [2,9] and can also affect running biomechanics [3], since athletes adjust their leg stiffness and dynamics when running on surfaces with different mechanical properties [10][11][12][13]. ...
... Assessing the mechanical properties of treadmill surfaces is therefore an important issue, not only in sports but also from a clinical perspective. Indeed, treadmill surfaces' mechanical properties have a significant influence on peak plantar forces and metabolic energy consumption [8,18], and treadmill running has been associated with a lower risk of developing tibial stress fractures but an increased risk of overload injuries at the Achilles tendon compared to overground running [19][20][21], due to altered lower-extremity kinetics and kinematics. ...
The mechanical properties of the surfaces used for exercising can affect sports performance and injury risk. However, the mechanical properties of treadmill surfaces remain largely unknown. The aim of this study was, therefore, to assess the shock absorption (SA), vertical deformation (VD) and energy restitution (ER) of different treadmill models and to compare them with those of other sport surfaces. A total of 77 treadmills, 30 artificial turf pitches and 30 athletics tracks were assessed using an advanced artificial athlete device. Differences in the mechanical properties between the surfaces and treadmill models were evaluated using a repeated-measures ANOVA. The treadmills were found to exhibit the highest SA of all the surfaces (64.2 ± 2; p < 0.01; effect size (ES) = 0.96), while their VD (7.6 ± 1.3; p < 0.01; ES = 0.87) and ER (45 ± 11; p < 0.01; ES = 0.51) were between the VDs of the artificial turf and track. The SA (p < 0.01; ES = 0.69), VD (p < 0.01; ES = 0.90) and ER (p < 0.01; ES = 0.89) were also shown to differ between treadmill models. The differences between the treadmills commonly used in fitness centers were much lower than differences between the treadmills and track surfaces, but they were sometimes larger than the differences with artificial turf. The treadmills used in clinical practice and research were shown to exhibit widely varying mechanical properties. The results of this study demonstrate that the mechanical properties (SA, VD and ER) of treadmill surfaces differ significantly from those of overground sport surfaces such as artificial turf and athletics track surfaces but also asphalt or concrete. These different mechanical properties of treadmills may affect treadmill running performance, injury risk and the generalizability of research performed on treadmills to overground locomotion.
... Due to easy performance and excellent accessibility, running is recognized as one of the most popular sports activities in the world (1). In fact, running is one of the best training methods for athletes and coaches to increase important components of physical fitness such as strength and coordination (2). ...
Journal of Clinical Physiotherapy Research
... Running is one of the sports that is included in athletics and is divided into three main events, namely short, medium, and long-distance running (Callison &;Lowen, 2022), and is one of the most popular sports in the world, easy to do and has good accessibility (Shi et al., 2019), especially in Indonesia this sport is also always given in schools (Sobarna &;Hambali, 2020), where the fastest time is the main determining factor in achievement (Rivanta &;Agus, 2019), especially in sprints, the speed of a runner's feet and hands is the main factor to quickly get to the finish line (Macadam et al., 2018). ...
In running events, especially sprints, there have been many good forms of training in improving sprint performance, such as downhill sprint training, towing, elastic assists, and orders. This training is used to improve stride length and stride frequency quality. Although in this study we tried to see with one among these training that contributes the most to improving running speed. The research method is an experiment using a design in the form of a pretest - posttest group design. The research subjects involved as many as 60 students of the physical education, health and recreation study program STKIP Pasundan, divided into two groups (A & B), group A was given stride frequency exercises, group B was given stride length exercises. From the results of data calculations in reality there is a significant influence from stride frequency training and also from stride length training to sprint running performance. But because stride length training has a greater positive impact on sprinting compared to stride frequency training, we as researchers recommend sprint trainers so that the exercise provides a greater proportion of the amount for stride length training.
... Despite several more recent studies examining the interactions between surface compliance and running mechanics Shi et al., 2019), the overall effects remain unclear. Some studies have reported that running on hard concrete increased plantar pressure and tibial loading (Ueberschär et al., 2019), when compared to running on soft grass or dirt surfaces. ...
The surface upon which running is performed has been suggested as a potential cause of many running-related injuries. It remains unclear, however, what effect surface compliance has on running biomechanics. This study aimed to investigate the effect of surface compliance on overground running biomechanics through a systematic review and meta-analysis. Using the PRISMA Protocols Statement, a search was conducted in three electronic databases (CINAHL, EMBASE, EBSCO) using the following anchoring terms: running, overground surface, biomechanics, kinematics, tibial acceleration, pressure and force. Following de-duplication, title/abstract screening and full-text review, 25 articles (n = 492) were identified which met all inclusion criteria, 22 (n = 392) of which were subsequently included in quantitative synthesis. Random effects analysis found that peak tibial acceleration was significantly lower when running on softer surfaces (P = 0.01, Z = 2.51; SMD = -0.8; 95% CI =-1.42 to -0.18). However, peak vertical ground reaction force, loading rate and ground contact time were not significantly different when comparing hard and soft surfaces. Since peak tibial acceleration has been associated with an increased risk of tibial stress injuries, the results of this meta-analysis suggest that running on softer surfaces to reduce impact stress on the tibia is probably justified to lower the risk of running-related stress injuries.
... For instance, some authors have suggested that a more compliant behavior of the treadmill surface would enhance energy return to the runner and thereby reduce the metabolic cost of running [4,22]. By contrast, some studies have found that the metabolic cost of running increased as the treadmill surface became more compliant [19,39]. In this context, the fact that SA, VD, and ER have seldom been accounted for in previous research (which has focused more on compliance or stiffness), is a potential confounder of the reported results. ...
The aim of this study was to define a reliable and sensitive test method for assessing Shock Absorption (SA), Vertical Deformation (VD), and Energy Restitution (ER) in treadmill surfaces. A total of 42 treadmills belonging to four different models were included in the study: (a) Technogym Jog700 Excite (n = 10), (b) Technogym Artis Run (n = 12), (c) LifeFitness Integrity Series 97T (n = 11), and (d) LifeFitness Integrity Series DX (n = 9). An advanced artificial athlete (AAA) device was used to assess SA, VD, and ER at three different locations along the longitudinal axis of each treadmill and in the support area of the athletes' feet. For each location, our results show that the error assumed when performing one impact with the AAA instead of three (SA ≤ |0.1|%, VD ≤ |0.0| mm, and ER ≤ |0.2|%) is lower than the smallest changes that can be detected by the measuring device (SA = 0.4%, VD = 0.2 mm, and ER = 0.9%). Also, our results show the ability of the test method to detect meaningful differences between locations once the one-impact criterium is adopted, since absolute minimum differences between zones (SA: |0.6|%, VD: |0.3| mm, and ER: |1.2|%) were above the uncertainty of the measuring device. Therefore, performing a single impact with the AAA in each of the three locations described in this study can be considered a representative and reliable method for assessing SA, VD, and ER in treadmill surfaces.
... Using a simplified model of an instrumented MT, Willems, Gosseye [81] however mathematically demonstrated that both vertical and horizontal forces applied to the MT belt can be measured accurately by force sensors mounted under the MT, although compliance in the mechanical model can introduce some biomechanical differences [20,28,[81][82][83]. Related to this, several studies have showed reduced plantar pressure when running on more compliant surfaces [27,84], suggesting the decreased plantar force in MT running compared to running on a track found in this review could be due to differences in surface stiffness. However, no differences were found when comparing MT to concrete or lab runway surfaces, potentially due to the smaller groups and hence lack of statistical power. ...
Background
Treadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings.
Objective
This study aimed at comparing biomechanical outcomes between motorized treadmill and overground running.
Methods
Four databases were searched until June 2019. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18–65 years) and written in English were included. Meta-analyses and meta-regressions were performed where possible.
Results
33 studies (n = 494 participants) were included. Most outcomes did not differ between running conditions. However, during treadmill running, sagittal foot–ground angle at footstrike (mean difference (MD) − 9.8° [95% confidence interval: − 13.1 to − 6.6]; low GRADE evidence), knee flexion range of motion from footstrike to peak during stance (MD 6.3° [4.5 to 8.2]; low), vertical displacement center of mass/pelvis (MD − 1.5 cm [− 2.7 to − 0.8]; low), and peak propulsive force (MD − 0.04 body weights [− 0.06 to − 0.02]; very low) were lower, while contact time (MD 5.0 ms [0.5 to 9.5]; low), knee flexion at footstrike (MD − 2.3° [− 3.6 to − 1.1]; low), and ankle sagittal plane internal joint moment (MD − 0.4 Nm/kg [− 0.7 to − 0.2]; low) were longer/higher, when pooled across overground surfaces. Conflicting findings were reported for amplitude of muscle activity.
Conclusions
Spatiotemporal, kinematic, kinetic, muscle activity, and muscle–tendon outcome measures are largely comparable between motorized treadmill and overground running. Considerations should, however, particularly be given to sagittal plane kinematic differences at footstrike when extrapolating treadmill running biomechanics to overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews).
Background
Tibial stress fracture (TSF) is a common injury in basketball players. This condition has been associated with high tibial shock and impact loading, which can be affected by running speed, footwear condition, and footstrike pattern. However, these relationships were established in runners but not in basketball players, with very little research done on impact loading and speed. Hence, this study compared tibial shock, impact loading, and foot strike pattern in basketball players running at different speeds with different shoe cushioning properties/performances.
Methods
Eighteen male collegiate basketball players performed straight running trials with different shoe cushioning (regular-, better-, and best-cushioning) and running speed conditions (3.0 m/s vs. 6.0 m/s) on a flat instrumented runway. Tri-axial accelerometer, force plate and motion capture system were used to determine tibial accelerations, vertical ground reaction forces and footstrike patterns in each condition, respectively. Comfort perception was indicated on a 150 mm Visual Analogue Scale. A 2 (speed) × 3 (footwear) repeated measures ANOVA was used to examine the main effects of shoe cushioning and running speeds.
Results
Greater tibial shock ( P < 0.001; η² = 0.80) and impact loading ( P < 0.001; η² = 0.73–0.87) were experienced at faster running speeds. Interestingly, shoes with regular-cushioning or best-cushioning resulted in greater tibial shock ( P = 0.03; η² = 0.39) and impact loading ( P = 0.03; η² = 0.38–0.68) than shoes with better-cushioning. Basketball players continued using a rearfoot strike during running, regardless of running speed and footwear cushioning conditions ( P > 0.14; η ² = 0.13).
Discussion
There may be an optimal band of shoe cushioning for better protection against TSF. These findings may provide insights to formulate rehabilitation protocols for basketball players who are recovering from TSF.
The economy of running has traditionally been quantified from the mass-specific oxygen uptake; however, because fuel substrate usage varies with exercise intensity, it is more accurate to express running economy in units of metabolic energy. Fundamentally, the understanding of the major factors that influence the energy cost of running (Erun) can be obtained with this approach. Erun is determined by the energy needed for skeletal muscle contraction. Here, we approach the study of Erun from that perspective. The amount of energy needed for skeletal muscle contraction is dependent on the force, duration, shortening, shortening velocity, and length of the muscle. These factors therefore dictate the energy cost of running. It is understood that some determinants of the energy cost of running are not trainable: environmental factors, surface characteristics, and certain anthropometric features. Other factors affecting Erun are altered by training: other anthropometric features, muscle and tendon properties, and running mechanics. Here, the key features that dictate the energy cost during distance running are reviewed in the context of skeletal muscle energetics.
Objectives:
This study investigated the association between high-speed running (HSR) and sprint running (SR) and injuries within elite soccer players. The impact of intermittent aerobic fitness as measured by the end speed of the 30-15 intermittent fitness test (30-15VIFT) and high chronic workloads (average 21-day) as potential mediators of injury risk were also investigated.
Design:
Observational Cohort Study.
Methods:
37 elite soccer players from one elite squad were involved in a one-season study. Training and game workloads (session-RPE×duration) were recorded in conjunction with external training loads (using global positioning system technology) to measure the HSR (>14.4kmh(-1)) and SR (>19.8kmh(-1)) distance covered across weekly periods during the season. Lower limb injuries were also recorded. Training load and GPS data were modelled against injury data using logistic regression. Odds ratios (OR) were calculated with 90% confidence intervals based on 21-day chronic training load status (sRPE), aerobic fitness, HSR and SR distance with these reported against a reference group.
Results:
Players who completed moderate HSR (701-750-m: OR: 0.12, 90%CI: 0.08-0.94) and SR distances (201-350-m: OR: 0.54, 90%CI: 0.41-0.85) were at reduced injury risk compared to low HSR (≤674-m) and SR (≤165-m) reference groups. Injury risk was higher for players who experienced large weekly changes in HSR (351-455-m; OR: 3.02; 90%CI: 2.03-5.18) and SR distances (between 75-105-m; OR: 6.12, 90%CI: 4.66-8.29). Players who exerted higher chronic training loads (≥2584 AU) were at significantly reduced risk of injury when they covered 1-weekly HSR distances of 701-750m compared to the reference group of <674m (OR=0.65, 90% CI 0.27-0.89). When intermittent aerobic fitness was considered based on 30-15VIFT performance, players with poor aerobic fitness had a greater risk of injury than players with better-developed aerobic fitness.
Conclusions:
Exposing players to large and rapid increases in HSR and SR distances increased the odds of injury. However, higher chronic training loads (≥2584 AU) and better intermittent aerobic fitness off-set lower limb injury risk associated with these running distances in elite soccer players.
Adaptation of kinetics response when running on different surface has been commonly measured by the ground reaction force (GRF). GRF was extensively been used in studies related to surface characteristics such irregularity, incline and types. Since surface hardness effects on the ground reaction force response and the foot adaption is remain unclear, the present study was carried out to address this issue. Ten subjects among university students population was selected to perform running on three different surface hardness which is concrete, artificial grass and rubber, with three shod conditions (barefoot, minimally shoe and heeled shoe) in recreational mode. The GRF data of each trial was obtained using force plate and the stance time of running phase was recorded using motion tracking system. In barefoot running, the GRF and stance time were found decreased with increasing of surface hardness. However, the GRF and stance time were not in correlation with the surface hardness for running with minimally shoe and heeled shoe. The results showed surface types and shod conditions contributed to the foot adaptation particularly in viewpoint of GRF response and stance time of running phase. © 2006-2017 Asian Research Publishing Network (ARPN). All rights reserved.
Purpose: This study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration.
Methods: Thirteen male recreational runners were required to run at 12 km/h velocity on concrete, synthetic track, natural grass, a normal treadmill, and a treadmill equipped with an ethylene vinyl acetate (EVA) cushioning underlay (treadmill_EVA), respectively. An in-shoe plantar pressure system and an accelerometer attached to the tibial tuberosity were used to record and analyze the characteristics of plantar pressure and tibial impact during running.
Results: The results showed that there were no significant differences in the 1st and 2nd peak plantar pressures (time of occurrence), pressure–time integral, and peak pressure distribution for the concrete, synthetic, grass, and normal treadmill surfaces. No significant differences in peak positive acceleration were observed among the five tested surface conditions. Compared to the concrete surface, however, running on treadmill_EVA showed a significant decrease in the 1st peak plantar pressure and the pressure–time integral for the impact phase (p
Possible benefits of barefoot running have been widely discussed in recent years. Uncertainty exists about which footwear strategy adequately simulates barefoot running kinematics. The objective of this study was to investigate the effects of athletic footwear with different minimalist strategies on running kinematics. Thirty-five distance runners (22 males, 13 females, 27.9 ± 6.2 years, 179.2 ± 8.4 cm, 73.4 ± 12.1 kg, 24.9 ± 10.9 km.week-1) performed a treadmill protocol at three running velocities (2.22, 2.78 and 3.33 m.s-1) using four footwear conditions: barefoot, uncushioned minimalist shoes, cushioned minimalist shoes, and standard running shoes. 3D kinematic analysis was performed to determine ankle and knee angles at initial foot-ground contact, rate of rear-foot strikes, stride frequency and step length. Ankle angle at foot strike, step length and stride frequency were significantly influenced by footwear conditions (p<0.001) at all running velocities. Posthoc pairwise comparisons showed significant differences (p<0.001) between running barefoot and all shod situations as well as between the uncushioned minimalistic shoe and both cushioned shoe conditions. The rate of rear-foot strikes was lowest during barefoot running (58.6% at 3.33 m.s-1), followed by running with uncushioned minimalist shoes (62.9%), cushioned minimalist (88.6%) and standard shoes (94.3%). Aside from showing the influence of shod conditions on running kinematics, this study helps to elucidate differences between footwear marked as minimalist shoes and their ability to mimic barefoot running adequately. These findings have implications on the use of footwear applied in future research debating the topic of barefoot or minimalist shoe running.
No systematic review has identified the incidence of running-related injuries per 1000 h of running in different types of runners.
The purpose of the present review was to systematically search the literature for the incidence of running-related injuries per 1000 h of running in different types of runners, and to include the data in meta-analyses.
A search of the PubMed, Scopus, SPORTDiscus, PEDro and Web of Science databases was conducted.
Titles, abstracts, and full-text articles were screened by two blinded reviewers to identify prospective cohort studies and randomized controlled trials reporting the incidence of running-related injuries in novice runners, recreational runners, ultra-marathon runners, and track and field athletes.
Data were extracted from all studies and comprised for further analysis. An adapted scale was applied to assess the risk of bias.
After screening 815 abstracts, 13 original articles were included in the main analysis. Running-related injuries per 1000 h of running ranged from a minimum of 2.5 in a study of long-distance track and field athletes to a maximum of 33.0 in a study of novice runners. The meta-analyses revealed a weighted injury incidence of 17.8 (95 % confidence interval [CI] 16.7-19.1) in novice runners and 7.7 (95 % CI 6.9-8.7) in recreational runners.
Heterogeneity in definitions of injury, definition of type of runner, and outcome measures in the included full-text articles challenged comparison across studies.
Novice runners seem to face a significantly greater risk of injury per 1000 h of running than recreational runners.
In the natural world, legged animals regularly run across uneven terrain with remarkable ease. To gain understanding of how running on uneven terrain affects the biomechanics and energetics of locomotion, we studied human subjects (N=12) running at 2.3 m s(-1) on an uneven terrain treadmill, with up to a 2.5 cm height variation. We hypothesized that running on uneven terrain would show increased energy expenditure, step parameter variability and leg stiffness compared with running on smooth terrain. Subject energy expenditure increased by 5% (0.68 W kg(-1); P<0.05) when running on uneven terrain compared with smooth terrain. Step width and length variability also increased by 27% and 26%, respectively (P<0.05). Positive and negative ankle work decreased on uneven terrain by 22% (0.413 J kg(-1)) and 18% (0.147 J kg(-1)), respectively (P=0.0001 and P=0.0008). Mean muscle activity increased on uneven terrain for three muscles in the thigh (P<0.05). Leg stiffness also increased by 20% (P<0.05) during running on uneven terrain compared with smooth terrain. Calculations of gravitational potential energy fluctuations suggest that about half of the energetic increases can be explained by additional positive and negative mechanical work for up and down steps on the uneven surface. This is consistent between walking and running, as the absolute increases in energetic cost for walking and running on uneven terrain were similar: 0.68 and 0.48 W kg(-1), respectively. These results provide insight into how surface smoothness can affect locomotion biomechanics and energetics in the real world.
Hybrid air-cushion vehicles (ACVs) provide a solution to transportation on soft terrain, whereas they also bring a new problem of excessive energy consumption. In order to minimize energy consumption in a computational manner, a Genetic Algorithm (GA) - Neural Network (NN) joint optimization algorithm is proposed to online calculate the corresponding optimal vehicle running parameters for given soil conditions. This is realized in three steps. (1) The energy consumption index is firstly simplified as a constrained function with respect to only two independent vehicle running parameters. (2) The optimal solutions are figured out offline with respect to some specific soil conditions by the designed GA optimizer. (3) The optimal solutions are figured out online with respect to general soil conditions by the designed NN optimizer, which is trained using the above offline-obtained data. The feasibility of the joint algorithm is supported by experiments, whose results show an effective integration of the GA’s advantage in complex function optimization and the NN’s advantage in generalization ability and computing speed.
The aim of this study was to examine the effect of changes in speed and incline slope on plantar pressure distribution of the foot during treadmill jogging. Plantar pressure parameters were measured with the Pedar-X system in twenty healthy girls (mean age of 20.7 years, mean height of 1.60m, and a mean weight of 53.35kg). Because variations in walking speed or slope can significantly change the magnitude of plantar pressure, comparisons of plantar pressure distribution between the two independent protocols during treadmill jogging were considered in this study. First, the subjects ran at the same speed of 2 m·s-1 with different incline slopes of 0%, 5%, 10%, and 15%. Second, they ran on the same slope of 0% with different speeds of 1.5 m·s-1, 2.0 m·s-1, and 2.5 m·s-1. The peak pressure of the eight plantar surface areas, apart from the medial forefoot and the hallux, significantly increased (p < 0.05) with an increase of 33% of peak pressure from 1.5 m·s-1 to 2.5 m·s-1 (speed) at heel region. In contrast, the peak pressures at the heel, medial forefoot, toe and hallux decreased significantly (p < 0.05) with increasing incline slope. At the heel, peak pressure reduced by 27% from 0% to 15% incline, however, pressure at the lateral midfoot region increased as following. Different speeds and incline slopes during jogging were associated with changes in plantar pressures. By systematic investigation of foot kinematics and plantar pressure during jogging with varying incline slope and speed, the results of this study provided further insight into foot biomechanics during jogging.
Abstract The practice of running has consistently increased worldwide, and with it, related lower limb injuries. The type of running surface has been associated with running injury etiology, in addition other factors, such as the relationship between the amount and intensity of training. There is still controversy in the literature regarding the biomechanical effects of different types of running surfaces on foot-floor interaction. The aim of this study was to investigate the influence of running on asphalt, concrete, natural grass, and rubber on in-shoe pressure patterns in adult recreational runners. Forty-seven adult recreational runners ran twice for 40 m on all four different surfaces at 12 ± 5% km · h(-1). Peak pressure, pressure-time integral, and contact time were recorded by Pedar X insoles. Asphalt and concrete were similar for all plantar variables and pressure zones. Running on grass produced peak pressures 9.3% to 16.6% lower (P < 0.001) than the other surfaces in the rearfoot and 4.7% to 12.3% (P < 0.05) lower in the forefoot. The contact time on rubber was greater than on concrete for the rearfoot and midfoot. The behaviour of rubber was similar to that obtained for the rigid surfaces - concrete and asphalt - possibly because of its time of usage (five years). Running on natural grass attenuates in-shoe plantar pressures in recreational runners. If a runner controls the amount and intensity of practice, running on grass may reduce the total stress on the musculoskeletal system compared with the total musculoskeletal stress when running on more rigid surfaces, such as asphalt and concrete.
Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.
The type of surface used for running can influence the load that the locomotor apparatus will absorb and the load distribution could be related to the incidence of chronic injuries. As there is no consensus on how the locomotor apparatus adapts to loads originating from running surfaces with different compliance, the objective of this study was to investigate how loads are distributed over the plantar surface while running on natural grass and on a rigid surface--asphalt. Forty-four adult runners with 4+/-3 years of running experience were evaluated while running at 12 km/h for 40 m wearing standardised running shoes and Pedar insoles (Novel). Peak pressure, contact time and contact area were measured in six regions: lateral, central and medial rearfoot, midfoot, lateral and medial forefoot. The surfaces and regions were compared by three ANOVAS (2 x 6). Asphalt and natural grass were statistically different in all variables. Higher peak pressures were observed on asphalt at the central (p<0.001) [grass: 303.8(66.7)kPa; asphalt: 342.3(76.3)kPa] and lateral rearfoot (p<0.001) [grass: 312.7(75.8)kPa; asphalt: 350.9(98.3)kPa] and lateral forefoot (p<0.001) [grass: 221.5(42.9)kPa; asphalt: 245.3(55.5)kPa]. For natural grass, contact time and contact area were significantly greater at the central rearfoot (p<0.001). These results suggest that natural grass may be a surface that provokes lighter loads on the rearfoot and forefoot in recreational runners.
Exercise has been shown to improve many health outcomes and well-being of people of all ages. Long-term studies in older adults are needed to confirm disability and survival benefits of exercise.
Annual self-administered questionnaires were sent to 538 members of a nationwide running club and 423 healthy controls from northern California who were 50 years and older beginning in 1984. Data included running and exercise frequency, body mass index, and disability assessed by the Health Assessment Questionnaire Disability Index (HAQ-DI; scored from 0 [no difficulty] to 3 [unable to perform]) through 2005. A total of 284 runners and 156 controls completed the 21-year follow-up. Causes of death through 2003 were ascertained using the National Death Index. Multivariate regression techniques compared groups on disability and mortality.
At baseline, runners were younger, leaner, and less likely to smoke compared with controls. The mean (SD) HAQ-DI score was higher for controls than for runners at all time points and increased with age in both groups, but to a lesser degree in runners (0.17 [0.34]) than in controls (0.36 [0.55]) (P < .001). Multivariate analyses showed that runners had a significantly lower risk of an HAQ-DI score of 0.5 (hazard ratio, 0.62; 95% confidence interval, 0.46-0.84). At 19 years, 15% of runners had died compared with 34% of controls. After adjustment for covariates, runners demonstrated a survival benefit (hazard ratio, 0.61; 95% confidence interval, 0.45-0.82). Disability and survival curves continued to diverge between groups after the 21-year follow-up as participants approached their ninth decade of life.
Vigorous exercise (running) at middle and older ages is associated with reduced disability in later life and a notable survival advantage.
Oxygen uptake (VO2) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3-7 km.h-1) or running (7-14 km.h-1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of VO2 to speed and expressed in J.kg-1.m-1 assuming an energy equivalent of 20.9 J.ml O2-1. At the highest speeds C was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand, C increased linearly with speed from 3.1 J.kg-1.m-1 at 3 km.h-1 to 5.5 J.kg-1.m-1 at 7 km.h-1, whereas on a firm surface C attained a minimum of 2.3 J.kg-1.m-1 at 4.5 km.h-1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km.h-1, C was about 1.8 times greater on sand than on compact terrain. When running on sand C was approximately independent of the speed, amounting to 5.3 J.kg-1.m-1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.
Moving about in nature often involves walking or running on a soft yielding substratum such as sand, which has a profound effect on the mechanics and energetics of locomotion. Force platform and cinematographic analyses were used to determine the mechanical work performed by human subjects during walking and running on sand and on a hard surface. Oxygen consumption was used to determine the energetic cost of walking and running under the same conditions. Walking on sand requires 1.6-2.5 times more mechanical work than does walking on a hard surface at the same speed. In contrast, running on sand requires only 1.15 times more mechanical work than does running on a hard surface at the same speed. Walking on sand requires 2.1-2.7 times more energy expenditure than does walking on a hard surface at the same speed; while running on sand requires 1.6 times more energy expenditure than does running on a hard surface. The increase in energy cost is due primarily to two effects: the mechanical work done on the sand, and a decrease in the efficiency of positive work done by the muscles and tendons.
Mammals use the elastic components in their legs (principally tendons, ligaments, and muscles) to run economically, while maintaining consistent support mechanics across various surfaces. To examine how leg stiffness and metabolic cost are affected by changes in substrate stiffness, we built experimental platforms with adjustable stiffness to fit on a force-plate-fitted treadmill. Eight male subjects [mean body mass: 74.4 +/- 7.1 (SD) kg; leg length: 0.96 +/- 0.05 m] ran at 3.7 m/s over five different surface stiffnesses (75.4, 97.5, 216.8, 454.2, and 945.7 kN/m). Metabolic, ground-reaction force, and kinematic data were collected. The 12.5-fold decrease in surface stiffness resulted in a 12% decrease in the runner's metabolic rate and a 29% increase in their leg stiffness. The runner's support mechanics remained essentially unchanged. These results indicate that surface stiffness affects running economy without affecting running support mechanics. We postulate that an increased energy rebound from the compliant surfaces studied contributes to the enhanced running economy.
Length changes of the muscle-tendon complex (MTC) during activity are in part the result of length changes of the active muscle fibres, the contractile component (CC), and also in part the result of stretch of elastic structures [series-elastic component (SEC)]. We used a force platform and kinematic measurements to determine force and length of the human calf muscle during walking, running and squat jumping. The force-length relation of the SEC was determined in dynamometer experiments on the same four subjects. Length of the CC was calculated as total muscle-tendon length minus the force dependent length of the SEC. The measured relations between force and length or velocity were compared with the individually determined force-length and force-velocity relations of the CC. In walking or running the negative work performed in the eccentric phase was completely stored as elastic energy. This elastic energy was released in the concentric phase, at speeds well exceeding the maximum shortening speed predicted by the Hill force-velocity relation. Speed of the CC, in contrast, was positive and low, well within the range predicted by the measured force-velocity properties and compatible with a favourable muscular efficiency. These effects were also present in purely concentric contractions, like the squatted jump. Contractile component length usually started at the far end of the force-length relation. Inter-individual differences in series-elastic stiffness were reflected in the force and length recordings during natural activity.
To provide an extensive and up to date database for specific running related injuries, across the sexes, as seen at a primary care sports medicine facility, and to assess the relative risk for individual injuries based on investigation of selected risk factors.
Patient data were recorded by doctors at the Allan McGavin Sports Medicine Centre over a two year period. They included assessment of anthropometric, training, and biomechanical information. A model was constructed (with odds ratios and their 95% confidence intervals) of possible contributing factors using a dependent variable of runners with a specific injury and comparing them with a control group of runners who experienced a different injury. Variables included in the model were: height, weight, body mass index, age, activity history, weekly activity, history of injury, and calibre of runner.
Most of the study group were women (54%). Some injuries occurred with a significantly higher frequency in one sex. Being less than 34 years old was reported as a risk factor across the sexes for patellofemoral pain syndrome, and in men for iliotibial band friction syndrome, patellar tendinopathy, and tibial stress syndrome. Being active for less than 8.5 years was positively associated with injury in both sexes for tibial stress syndrome; and women with a body mass index less than 21 kg/m(2) were at a significantly higher risk for tibial stress fractures and spinal injuries. Patellofemoral pain syndrome was the most common injury, followed by iliotibial band friction syndrome, plantar fasciitis, meniscal injuries of the knee, and tibial stress syndrome.
Although various risk factors were shown to be positively associated with a risk for, or protection from, specific injuries, future research should include a non-injured control group and a more precise measure of weekly running distance and running experience to validate these results.
The purpose of this study was to present a systematic overview of published reports on the incidence and associated potential risk factors of lower extremity running injuries in long distance runners. An electronic database search was conducted using the PubMed-Medline database. Two observers independently assessed the quality of the studies and a best evidence synthesis was used to summarise the results. The incidence of lower extremity running injuries ranged from 19.4% to 79.3%. The predominant site of these injuries was the knee. There was strong evidence that a long training distance per week in male runners and a history of previous injuries were risk factors for injuries, and that an increase in training distance per week was a protective factor for knee injuries.
Background:
Running injuries are very common. Risk factors for running injuries are not consistently described across studies and do not differentiate between runners of long- and short distances within one cohort.
Objectives:
The aim of this study is to determine risk factors for running injuries in recreational long- and short distance runners separately.
Design:
A prospective cohort study.
Methods:
Recreational runners from four different running events are invited to participate. They filled in a baseline questionnaire assessing possible risk factors about 4 weeks before the run and one a week after the run assessing running injuries. Using logistic regression we developed an overall risk model and separate risk models based on the running distance.
Results:
In total 3768 runners participated in this study. The overall risk model contained 4 risk factors: previous injuries (OR 3.7) and running distance during the event (OR 1.3) increased the risk of a running injury whereas older age (OR 0.99) and more training kilometers per week (OR 0.99) showed a decrease. Models between short- and long distance runners did not differ significantly. Previous injuries increased the risk of a running injury in all models, while more training kilometers per week decreased this risk.
Conclusions:
We found that risk factors for running injuries were not related to running distances. Previous injury is a generic risk factor for running injuries, as is weekly training distance. Prevention of running injuries is important and a higher weekly training volume seems to prevent injuries to a certain extent.
We have shown that stress fractures can be induced in the tibial diaphysis of an animal model by the repeated application of non-traumatic impulsive loads. The right hind limbs of 31 rabbits were loaded for three to nine weeks and changes in the bone were monitored by radiography and bone scintigraphy. The presence of stress fractures was confirmed histologically in some cases. Most animals sustained a stress fracture within six weeks and there was a positive correspondence between scintigraphic change and radiological evidence. Microscopic damage was evident at the sites of positive bone scans. The progression, location, and time of onset of stress fractures in this animal model were similar to those in clinical reports, making the model a useful one for the study of the aetiology of stress fractures.
During locomotion, the lower limb tendons undergo stretch and recoil, functioning like springs that recycle energy with each step. Cadaveric testing has demonstrated that the arch of the foot operates in this capacity during simple loading, yet it remains unclear whether this function exists during locomotion. In this study, one of the arch’s passive elastic tissues (the plantar aponeurosis; PA) was investigated to glean insights about it and the entire arch of the foot during running. Subject specific computer models of the foot were driven using the kinematics of eight subjects running at 3.1 m/s using two initial contact patterns (rearfoot and non-rearfoot). These models were used to estimate PA strain, force, and elastic energy storage during the stance phase. To examine the release of stored energy, the foot joint moments, powers, and work created by the PA were computed. Mean elastic energy stored in the PA was 3.1±1.6 J, which was comparable to in situ testing values. Changes to the initial contact pattern did not change elastic energy storage or late stance PA function, but did alter PA pre-tensioning and function during early stance. In both initial contact patterns conditions, the PA power was positive during late stance, which reveals that the release of the stored elastic energy assists with shortening of the arch during push-off. As the PA is just one of the arch’s passive elastic tissues, the entire arch may store additional energy and impact the metabolic cost of running.
Considerable evidence has established the link between high levels of physical activity (PA) and all-cause and cardiovascular disease (CVD)-specific mortality. Running is a popular form of vigorous PA that has been associated with better overall survival, but there is debate about the dose-response relationship between running and CVD and all-cause survival. In this review, we specifically reviewed studies published in PubMed since 2000 that included at least 500 runners and 5-year follow-up so as to analyze the relationship between vigorous aerobic PA, specifically running, and major health consequences, especially CVD and all-cause mortality. We also made recommendations on the optimal dose of running associated with protection against CVD and premature mortality, as well as briefly discuss the potential cardiotoxicity of a high dose of aerobic exercise, including running (eg, marathons).
Background
Although running is a popular leisure-time physical activity, little is known about the long-term effects of running on mortality. The dose-response relations between running, as well as the change in running behaviors over time, and mortality remain uncertain.
Objectives
We examined the associations of running with all-cause and cardiovascular mortality risks in 55,137 adults, 18 to 100 years of age (mean age 44 years).
Methods
Running was assessed on a medical history questionnaire by leisure-time activity.
Results
During a mean follow-up of 15 years, 3,413 all-cause and 1,217 cardiovascular deaths occurred. Approximately 24% of adults participated in running in this population. Compared with nonrunners, runners had 30% and 45% lower adjusted risks of all-cause and cardiovascular mortality, respectively, with a 3-year life expectancy benefit. In dose-response analyses, the mortality benefits in runners were similar across quintiles of running time, distance, frequency, amount, and speed, compared with nonrunners. Weekly running even <51 min, <6 miles, 1 to 2 times, <506 metabolic equivalent-minutes, or <6 miles/h was sufficient to reduce risk of mortality, compared with not running. In the analyses of change in running behaviors and mortality, persistent runners had the most significant benefits, with 29% and 50% lower risks of all-cause and cardiovascular mortality, respectively, compared with never-runners.
Conclusions
Running, even 5 to 10 min/day and at slow speeds <6 miles/h, is associated with markedly reduced risks of death from all causes and cardiovascular disease. This study may motivate healthy but sedentary individuals to begin and continue running for substantial and attainable mortality benefits.
Purpose:
Knee pain and Achilles tendinopathies are the most common complaints among runners. The differences in the running mechanics may play an important role in the pathogenesis of lower limb overuse injuries. However, the effect of a runner's foot strike pattern on the ankle and especially on the knee loading is poorly understood. The purpose of this study was to examine whether runners using a forefoot strike pattern exhibit a different lower limb loading profile than runners who use rearfoot strike pattern.
Methods:
Nineteen female athletes with a natural forefoot strike (FFS) pattern and pair-matched women with rearfoot strike (RFS) pattern (n = 19) underwent 3-D running analysis at 4 m·s⁻¹. Joint angles and moments, patellofemoral contact force and stresses, and Achilles tendon forces were analyzed and compared between groups.
Results:
FFS demonstrated lower patellofemoral contact force and stress compared with heel strikers (4.3 ± 1.2 vs 5.1 ± 1.1 body weight, P = 0.029, and 11.1 ± 2.9 vs 13.0 ± 2.8 MPa, P = 0.04). In addition, knee frontal plane moment was lower in the FFS compared with heel strikers (1.49 ± 0.51 vs 1.97 ± 0.66 N·m·kg⁻¹, P =0.015). At the ankle level, FFS showed higher plantarflexor moment (3.12 ± 0.40 vs 2.54 ± 0.37 N·m·kg⁻¹; P = 0.001) and Achilles tendon force (6.3 ± 0.8 vs 5.1 ± 1.3 body weight; P = 0.002) compared with RFS.
Conclusions:
To our knowledge, this is the first study that shows differences in patellofemoral loading and knee frontal plane moment between FFS and RFS. FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries. On the other hand, parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries.
The objective of this study is to compare plantar loads during treadmill running and running on concrete and grass surfaces.
Crossover study design was used in the study.
A total of 16 experienced heel-to-toe runners participated in the study. Plantar loads data were collected using a Novel Pedar insole sensor system during running on the treadmill, concrete, and grass surfaces at 3.8m/s running speed and then analyzed.
Compared with running on the two other surfaces, treadmill running showed a lower magnitude of maximum plantar pressure and maximum plantar force for the total foot, maximum plantar pressure at two toe regions, and maximum plantar force for the medial forefoot region and two toe regions (p<0.0017). Treadmill running also showed a longer absolute contact time at two toe regions compared with running on the other two surfaces (p<0.0017).
Treadmill running is associated with a lower magnitude of maximum plantar pressure and a lower maximum plantar force at the plantar areas. These results suggest that the plantar load distribution in treadmill running is not the same as the plantar load distribution in running on overground surfaces. Treadmill running may be useful in early rehabilitation programs. Patients with injuries in their lower extremities may benefit from the reduction in plantar loads. However, the translation to overground running needs investigation.
The purpose of this study was to investigate the acute effects of progressive fatigue on the parameters of running mechanics previously associated with tibial stress fracture risk.
Twenty-one trained male distance runners performed three sets (Pre, Mid, and Post) of six overground running trials at 4.5 m·s (±5%). Kinematic and kinetic data were collected during each trial using a 12-camera motion capture system, force platform, and head and leg accelerometers. Between tests, each runner ran on a treadmill for 20 min at their corresponding lactate threshold (LT) speed. Perceived exertion levels (RPE) were recorded at the third and last minute of each treadmill run.
RPE scores increased from 11.8 ± 1.3 to 14.4 ± 1.5 at the end of the first LT run and then further to 17.4 ± 1.6 by the end of the second LT run. Peak rearfoot eversion, peak axial head acceleration, peak free moment and vertical force loading rates were shown to increase (P < 0.05) with moderate-large effect sizes during the progression from Pre to Post tests, although vertical impact peak and peak axial tibial acceleration were not significantly affected by the high-intensity running bouts.
Previously identified risk factors for impact-related injuries (such as tibial stress fracture) are modified with fatigue. Because fatigue is associated with a reduced tolerance for impact, these findings lend support to the importance of those measures to identify individuals at risk of injury from lower limb impact loading during running.
This study aimed to compare foot plantar pressure distribution while jogging and running in highly trained adolescent runners. Eleven participants performed two constant-velocity running trials either at jogging (11.2 ± 0.9 km/h) or running (17.8 ± 1.4 km/h) pace on a treadmill. Contact area (CA in cm(2)), maximum force (F(max) in N), peak pressure (PP in kPa), contact time (CT in ms), and relative load (force time integral in each individual region divided by the force time integral for the total plantar foot surface, in %) were measured in nine regions of the right foot using an in-shoe plantar pressure device. Under the whole foot, CA, F(max) and PP were lower in jogging than in running (-1.2% [p<0.05], -12.3% [p<0.001] and -15.1% [p<0.01] respectively) whereas CT was higher (+20.1%; p<0.001). Interestingly, we found an increase in relative load under the medial and central forefoot regions while jogging (+6.7% and +3.7%, respectively; [p<0.05]), while the relative load under the lesser toes (-8.4%; p<0.05) was reduced. In order to prevent overloading of the metatarsals in adolescent runners, excessive mileage at jogging pace should be avoided.
Play of physically active video games may be a way to increase physical activity and/or decrease sedentary behavior, but games are not universally active or enjoyable. Active games may differ from traditional games on important attributes, which may affect frequency and intensity of play. The purpose of this study was to investigate differences in energy expenditure and enjoyment across four game types: shooter (played with traditional controllers), band simulation (guitar or drum controller), dance simulation (dance mat controller), and fitness (balance board controller).
Energy expenditure (METs) and enjoyment were measured across 10 games in 100 young adults age 18-35 yr (50 women).
All games except shooter games significantly increased energy expenditure over rest (P < 0.001). Fitness and dance games increased energy expenditure by 322% (mean ± SD = 3.10 ± 0.89 METs) and 298% (2.91 ± 0.87 METs), which was greater than that produced by band simulation (73%, 1.28 ± 0.28 METs) and shooter games (23%, 0.91 ± 0.16 METs). However, enjoyment was higher in band simulation games than in other types (P < 0.001). Body mass-corrected energy expenditure was greater in normal weight than in overweight participants in the two most active game types (P < 0.001).
Active video games can significantly increase energy expended during screen time, but these games are less enjoyable than other more sedentary games, suggesting that they may be less likely to be played over time. Less active but more enjoyable video games may be a promising method for decreasing sedentary behavior.
The purpose of this study was to evaluate the metabolic cost of running (Cr) on natural grass (NG) and artificial turf (AT), compared with a hard surface (HS), that is, asphalted track. Eight amateur soccer players (mean ± SD: age 22.9 ± 2.3 years, body mass 69.0 ± 4.7 kg, and height 178 ± 5 cm) completed 9 runs (3 surfaces × 3 speeds, i.e., 2.22, 2.78, 3.33 m·s) of 6 minutes, in a random order on the different surfaces. Characteristics of the running surfaces were assessed at 3 points of each running track by measuring shock absorption and standard vertical deformation, via an 'artificial athlete' device according to FIFA protocol. No significant interactions (2-way ANOVA analysis; p = 0.38) were found between running surfaces and running speeds. A significant main effect for surface was found. The average Cr values were 4.02 ± 0.25 J·kg·L·m on HS, 4.22 ± 0.35 J·kg·L·m on NG, and 4.21 ± 0.31 J·kg·L·m on AT. The Cr was also higher at 3.33 m·s compared with the Cr measured at the other 2 running speeds. In conclusion, we found a Cr of ∼ 4.20 J·kg·L·m on both natural and artificial grass football pitches, in accordance with similar percentage shock absorption characteristics of these 2 tested surfaces. Our finding allows a better computation of the Cr on NG and AT, and supports the exclusion of the Cr as a potential factor for the higher physical effort in matches played on artificial turf, as reported by soccer players.
The term incidence is interpreted in many different ways in the literature. Running injury epidemiology should include denominator-based incidence rates, in which the number of new injuries observed during 1 year is related to the population of runners at risk. In 10 studies with denominator-based incidences selected from the literature, the annual incidence rates of injured runners vary from 24 to 65%. Comparison of denominator-based incidence rates from different studies requires a discussion of the denominator and of the numerator; i.e. the study population and the definition of running injury. Injury definitions differ from one study to another. Study populations are particular subgroups of the total running population and they differ from one study to another. Subgroups may differ in origin: volunteers, runners from a mailing list or entrants of a road race. Incidence rates are higher among supervised volunteers than among listed runners, and higher among both these groups than among race-entrants. The choice from the universe of the running population and the used injury definition are methodological issues. Incidence is dependently associated with the prevalence of predisposing running injury factors. There is consistent epidemiological support for the role of a few aetiological factors; i.e. higher mileage per week, previous running injury, higher running speed and lesser running experience. Higher mileage per week is probably the strongest predictor. In the selected injury studies, mileage per week differs from one study population to another. Differences in mileage per week do not explain differences in incidence rate between these studies. In conclusion, caution must be taken when comparing annual incidence rates of different studies. Methodological issues are at least as important as aetiological factors. Study populations may refer to different selections of the universe of the running population. The lengths of observation periods and 'running injury' definitions may differ from one study to another.
The foot and ankle is a complex structure made of many small bones with capsular and ligamentous constraints. The physiology, kinematics, and muscle interaction of the walking, jogging, and running cycles will be discussed and the current biomechanical literature reviewed. To analyze the pathologic state, one must be aware of the normal stresses and functions of the running cycle. This knowledge establishes a rational basis for the interpretation of problems in providing medical and orthotic treatment.
Using a computerized pendulum device for delivery of a moderate, reproducible impact on the surface of canine femoral cartilage, the lipids of the cartilage were analyzed by gas chromatography, and a four-fold increase in arachidonic acid was found in the phospholipid pool, as compared with controls. This is the first evidence presented thus far which clarifies the link between mechanical injury and the early biochemical changes of the osteoarthritic process. Electron microscopy of impacted cartilage cells showed an increase in lipids and microtubules and cytoplasmic derangement. There was a brief rise in hexosamine content soon after impaction, followed by a trend toward loss.
Ground reaction forces and center of pressure (C of P) patterns were studied in 17 subjects running at 4.5 ms−1. The subjects were classified as rearfoot or midfoot strikers according to the location of the C of P at the time of first contact between foot and ground. The C of P path in the rearfoot group showed a continuous anterior movement during support while the C of P in most of the midfoot group migrated posteriorly during the first 20 ms of the support phase. Variability in both groups was most marked during early support. The mean peak to peak force components were 3 BW, 1 BW and 0.3 BW in the vertical, anteroposterior and mediolateral directions respectively. Consistent differences between groups were noted in all three components, but individual differences within a given group were also considerable. The C of P patterns are presented in conjunction with ground reaction force data, and the implications of the results in the areas of running mechanics, shoe design and sports injury are discussed.
Athletes who participate in high-impact sports involving running, jumping, or contact are at risk for forefoot injury. These injuries occur as a result of acute trauma or chronic overuse. Some athletes may be predisposed to injury because of preexisting foot deformity, such as cavus, hallux valgus, or Achilles contracture. This article reviews the common causes of forefoot pain in the athlete. The most common causes of forefoot pain in the athlete are metatarsal stress fracture, interdigital neuroma, sesamoid pathology, metatarsalgia, hallux rigidus, hallux valgus, and turf toe. The pathophysiology, clinical presentation, and treatment of these conditions are discussed.
This study scientifically measures the dynamic gait characteristics and energy consumption of 16 male below-knee amputees, eight vascular and eight traumatic, while wearing solid ankle cushion heel (SACH), single axis and multiple axis prosthetic feet via six-camera motion analysis, metabolic measurement cart and heavy-duty treadmill. Subjective results are additionally determined via questionnaire after testing. Motion analysis showed statistically significant differences at P<0.05 between the SACH, single axis and multiple axis foot in the velocity, cadence, stride length and single limb stance. Significant differences were found in energy consumption between the traumatic and vascular groups, and significant changes in walking under different speeds and different inclines. Results provide quantitative and qualitative information about the dynamic performance of the various feet, which can be helpful in prescribing the optimal prosthetic foot for individual amputees.
Impact forces and muscle tuning: a new paradigm. Exerc. Sport Sci. Rev., Vol. 29, No. 1, pp 37-41, 2001. We propose that repetitive impact forces during physical activities are not important from an injury perspective but are the reason for changes in myoelectric activity (muscle tuning) to minimize soft tissue vibrations. Changes in myoelectric activity (intensity, frequency, timing), comfort, and performance provide supporting evidence for this new paradigm.
The primary aim of this study was to measure the energetics of six elite surf iron men (who participate in regular sand running training), performing steady-state running trials on grass in shoes at 8, 11 and 14 km x h(-1), and on sand bare foot and in shoes, at both 8 and 11 km x h(-1). The net total energy cost (EC, J x kg(-1) x m(-1)) was determined from the net steady-state oxygen consumption and respiratory exchange ratio (net aerobic EC) plus net lactate accumulation (net anaerobic EC). For the sand barefoot and sand in shoes running trials at 8 and 11 km x h(-1), net aerobic EC and total net EC (but not anaerobic EC) were significantly greater (P < 0.001) than the grass running trial values. No differences (P > 0.05) existed between the sand barefoot and sand in shoes trials. These measures were compared with data obtained from eight well-trained male recreational runners who performed the same protocol in a previous study, but who were not accustomed to running on sand. Comparisons of net aerobic EC between the two groups for the surface conditions were not significantly different (P > 0.05). For net anaerobic EC, the iron man values were significantly less (P < 0.02) than the recreational runner values. For net total EC, the iron man values were less than the recreational runner values, but the differences were only significant when both groups ran on sand barefoot (P < 0.03: on grass P = 0.158; on sand in shoes P = 0.103). The lower lactate accumulation values recorded for the iron men on both grass and sand may indicate that running on sand potentially reduces metabolic fatigue when running on firm or soft surfaces.
PBWSTT has emerged from an interesting idea to a well-accepted and scientifically supported treatment modality for gait training after stroke. PBWSTT offers a task-specific approach to functional gait retraining that is based on rehearsal of repetitive controlled gait cycles. Newer devices are being developed that will provide better mechanical control of the patient and reduce therapist effort.
Forces that are repeatedly applied to the body could lead to positive remodeling of a structure if the forces fall below the tensile limit of the structure and if sufficient time is provided between force applications. On the other hand, an overuse injury could result if there is inadequate rest time between applied forces. Running is one of the most widespread activities during which overuse injuries of the lower extremity occur. The purpose of this article is to review the current state of knowledge related to overuse running injuries, with a particular emphasis on the effect of impact forces. Recent research has suggested that runners who exhibit relatively large and rapid impact forces while running are at an increased risk of developing an overuse injury of the lower extremity. Modifications in training programs could help an injured runner return to running with decreased rehabilitation time, but it would be preferable to be able to advise a runner regarding injury potential before undertaking a running program. One of the goals of future research should be to focus on the prevention or early intervention of running injuries. This goal could be accomplished if some easily administered tests could be found which would predict the level of risk that a runner may encounter at various levels of training intensity, duration, and frequency. The development of such a screening process may assist medical practitioners in identifying runners who are at a high risk of overuse injury.
Repetitive impacts encountered during locomotion may be modified by footwear and/or surface. Changes in kinematics may occur either as a direct response to altered mechanical conditions or over time as active adaptations.
: To investigate how midsole hardness, surface stiffness, and running duration influence running kinematics.
In the first of two experiments, 12 males ran at metabolic steady state under six conditions; combinations of midsole hardness (40 Shore A, 70 Shore A), and surface stiffness (100 kN x m, 200 kN x m, and 350 kN x m). In the second experiment, 10 males ran for 30 min on a 12% downhill grade. In both experiments, subjects ran at 3.4 m x s on a treadmill while 2-D hip, knee, and ankle kinematics were determined using high-speed videography (200 Hz). Oxygen cost and heart rate data were also collected. Kinematic adaptations to midsole, surface, and running time were studied.
Stance time, stride cycle time, and maximal knee flexion were invariant across conditions in each experiment. Increased midsole hardness resulted in greater peak ankle dorsiflexion velocity (P = 0.0005). Increased surface stiffness resulted in decreased hip and knee flexion at contact, reduced maximal hip flexion, and increased peak angular velocities of the hip, knee, and ankle. Over time, hip flexion at contact decreased, plantarflexion at toe-off increased, and peak dorsiflexion and plantarflexion velocity increased.
Lower-extremity kinematics adapted to increased midsole hardness, surface stiffness, and running duration. Changes in limb posture at impact were interpreted as active adaptations that compensate for passive mechanical effects. The adaptations appeared to have the goal of minimizing metabolic cost at the expense of increased exposure to impact shock.
Increased numbers of circulating endothelial progenitor cells (EPC) are associated with improved vascular function. Exercise is a central component of the primary prevention of vascular diseases. The effect of physical activity on circulating EPC in healthy individuals is not known.
A prospective crossover study.
In order to study a potential link between the extent of physical exercise and progenitor cells in humans, EPC were quantified by flow cytometry and cell culture in 25 healthy volunteers undergoing three protocols of running exercise. Intensive running, defined as 30 min at 100% of the velocity of the individual anaerobic threshold (IAT; approximately 82% maximal oxygen consumption; VO2max), as well as moderate running with 30 min at 80% of the velocity of the IAT ( approximately 68% VO2max), increased circulating EPC numbers to 235+/-93% and 263+/-106% of control levels, respectively. However, moderate short-term running for 10 min did not upregulate EPC counts. The maximum increase in circulating EPC numbers was observed 10-30 min after intensive running. Exercise increased EPC migratory and colony-forming capacity.
Intensive and moderate exercising for 30 min, but not for 10 min, increased circulating levels of EPC, which may represent an important beneficial outcome of physical exercise. The data support the notion that increased numbers of EPC correlate with cardiovascular health and suggest EPC quantification as a novel surrogate parameter of the vascular effects of exercising.
This study investigated the time needed for familiarization to treadmill running. Seventeen young healthy adults, who were inexperienced on a treadmill, ran for 11 min on a treadmill at their self-selected speed. Discrete sagittal-plane angular kinematic parameters of the pelvis, hip, knee and ankle, and cadence and stride time data were captured with a three-dimensional motion analysis system at 0, 2, 4, 6, 8 and 10 min. Participants were considered familiarized to treadmill running by 6 min, as there were no significant changes in any dependent variables from this time. Furthermore, mean absolute difference scores between consecutive times were minimal (1.3 degrees ) and the average intraclass correlation coefficient [ICC(2,1)=.95] was maximal and highly reliable by this time. Future studies comparing treadmill and overground running need to provide an adequate treadmill familiarization time of at least 6 min prior to data capture of sagittal-plane kinematic events.
Tibial stress fractures (TSF) are among the most serious running injuries, typically requiring 6-8 wk for recovery. This cross-sectional study was conducted to determine whether differences in structure and running mechanics exist between trained distance runners with a history of prior TSF and those who have never sustained a fracture.
Female runners with a rearfoot strike pattern, aged between 18 and 45 yr and running at least 32 km.wk(-1), were recruited for this study. Participants in the study were 20 subjects with a history of TSF and 20 age- and mileage-matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected during overground running at 3.7 m.s(-1) using a six-camera motion capture system, force platform, and accelerometer. Variables of interest were vertical impact peak, instantaneous and average vertical loading rates, instantaneous and average loading rates during braking, knee flexion excursion, ankle and knee stiffness, and peak tibial shock. Tibial varum was measured in standing. Tibial area moment of inertia was calculated from tibial x-ray studies for a subset of runners.
The TSF group had significantly greater instantaneous and average vertical loading rates and tibial shock than the control group. The magnitude of tibial shock predicted group membership successfully in 70% of cases.
These data indicate that a history of TSF in runners is associated with increases in dynamic loading-related variables.