Downhill Grades Research Articles

Tibial strains are sensitive to speed perturbations, but not grade perturbations, during running.

A fatigue-failure process is hypothesized to govern the development of tibial stress fractures, where bone damage is highly dependent on the peak strain magnitude. To date, much of the work examining tibial strain during running has ignored uphill and downhill running despite the prevalence of this terrain. This study examined the sensitivity of tibial strain to changes in running grade and speed using a combined musculoskeletal-finite element modelling routine. Seventeen participants ran on a treadmill at ±10, ±5 and 0deg; at each grade, participants ran at 3.33 m s-1 and at a grade-adjusted speed of 2.50 and 4.17 m s-1 for uphill and downhill grades, respectively. Force and motion data were recorded in each grade and speed combination. Muscle and joint contact forces were estimated using inverse-dynamics-based static optimization. These forces were applied to a participant-adjusted finite element model of the tibia. None of the strain variables (50th and 95th percentile strain and strained volume ≥4000 με) differed as a function of running grade; however, all strain variables were sensitive to running speed (F1≥9.59, P≤0.03). In particular, a 1 m s-1 increase in speed resulted in a 9% (∼260 με) and 155% (∼600 mm3) increase in peak strain and strained volume, respectively. Overall, these findings suggest that faster running speeds, but not changes in running grade, may be more deleterious to the tibia.

Component sizing and sensitivity analysis of design parameters of a hydraulic-pneumatic regenerative braking system for heavy duty vehicles

A regenerative hydraulic-pneumatic braking system for trucks or busses must allow recovery of braking energy in both high energy/low power situations, such as long downhill grades, and low energy/high power situations, such as those typical of urban traffic. Proper component sizing must get the best out of both situations. The main contribution of this work is the development of a component sizing strategy that will greatly accelerate the development of designs for a given target. Once components are defined, subsequent studies can be performed under dynamic conditions to refine the design, including improving local and higher-level controls. The design strategy presented is applied to a 12-ton commercial vehicle and its behavior is then simulated using a full nonlinear dynamic numerical model previously validated against a laboratory prototype. The efficiencies predicted by the design method deviate only by 3.1% and 6.7% from the results of the dynamic model for urban and highway traffic, respectively, which is reasonable for the design phase of a hybrid hydraulic-pneumatic powertrain. The component equations and computational strategy can also be used for sizing other hydraulic or pneumatic system architectures.

Metabolic cost of level, uphill, and downhill running in highly cushioned shoes with carbon-fiber plates

BackgroundCompared to conventional racing shoes, Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by 4%. The reduction is attributed to their lightweight, highly compliant, and resilient midsole foam and a midsole-embedded curved carbon-fiber plate. We investigated whether these shoes also could reduce the metabolic cost of moderate uphill (+3°) and downhill (–3°) grades. We tested the null hypothesis that, compared to conventional racing shoes, highly cushioned shoes with carbon-fiber plates would impart the same ∼4% metabolic power (W/kg) savings during uphill and downhill running as they do during level running. MethodsAfter familiarization, 16 competitive male runners performed six 5-min trials (2 shoes × 3 grades) in 2 Nike marathon racing-shoe models (Streak 6 and Vaporfly 4%) on a level, uphill (+3°), and downhill (–3°) treadmill at 13 km/h (3.61 m/s). We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4–5 and calculated metabolic power (W/kg) for each shoe model and grade combination. ResultsCompared to the conventional shoes (Streak 6), the metabolic power in the Vaporfly 4% shoes was 3.83% (level), 2.82% (uphill), and 2.70% (downhill) less (all p < 0.001). The percent of change in metabolic power for uphill running was less compared to level running (p = 0.04; effect size (ES) = 0.561) but was not statistically different between downhill and level running (p = 0.17; ES = 0.356). ConclusionOn a running course with uphill and downhill sections, the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall, compared to the savings on a perfectly level race course.

Method for Estimating Speed of the Out-of-Control Tractor-Semitrailer on Downhill Grades

Speed estimation for the out-of-control truck on a downhill grade is essential for passive safety features like truck escape ramps to promote traffic safety. This paper presents a method for estimating the speed of out-of-control trucks based on Newton’s Laws of Motion. First of all, we analyze gravity effort, aerodynamics, and rolling resistance through a free body diagram of an out-of-control truck on a downhill grade. Further, we select the speed as the dependent variable, with the following road and vehicle characteristics as independent variables: road surface type, grade, grade length, truck size, truck weight, and tire type. Finally, we estimate the speed and acceleration according to Newton’s Laws of Motion. The results show that the factors that significantly affect the out-of-control truck’s speed include tire type, road surface coefficient, grade, and grade length. TruckMaker simulation results demonstrate that the model is valid at a 99% confidence level.

Virtual Point Control for Step-Down Perturbations and Downhill Slopes in Bipedal Running.

Bipedal running is a difficult task to realize in robots, since the trunk is underactuated and control is limited by intermittent ground contacts. Stabilizing the trunk becomes even more challenging if the terrain is uneven and causes perturbations. One bio-inspired method to achieve postural stability is the virtual point (VP) control, which is able to generate natural motion. However, so far it has only been studied for level running. In this work, we investigate whether the VP control method can accommodate single step-down perturbations and downhill terrains. We provide guidelines on the model and controller parameterizations for handling varying terrain conditions. Next, we show that the VP method is able to stabilize single step-down perturbations up to 40 cm, and downhill grades up to 20–40° corresponding to running speeds of 2–5 ms−1. Our results show that the VP approach leads to asymmetrically bounded ground reaction forces for downhill running, unlike the commonly-used symmetric friction cone constraints. Overall, VP control is a promising candidate for terrain-adaptive running control of bipedal robots.

Modular footwear that partially offsets downhill or uphill grades minimizes the metabolic cost of human walking.

Walking on different grades becomes challenging on energetic and muscular levels compared to level walking. While it is not possible to eliminate the cost of raising or lowering the centre of mass (COM), it could be possible to minimize the cost of distal joints with shoes that offset downhill or uphill grades. We investigated the effects of shoe outsole geometry in 10 participants walking at 1 m s−1 on downhill, level and uphill grades. Level shoes minimized metabolic rate during level walking (Psecond-order effect < 0.001). However, shoes that entirely offset the (overall) treadmill grade did not minimize the metabolic rate of walking on grades: shoes with a +3° (upward) inclination minimized metabolic rate during downhill walking on a −6° grade, and shoes with a −3° (downward) inclination minimized metabolic rate during uphill walking on a +6° grade (Pinteraction effect = 0.023). Shoe inclination influenced (distal) ankle joint parameters, including soleus muscle activity, ankle moment and work rate, whereas treadmill grade influenced (whole-body) ground reaction force and COM work rate as well as (distal) ankle joint parameters including tibialis anterior and plantarflexor muscle activity, ankle moment and work rate. Similar modular footwear could be used to minimize joint loads or assist with walking on rolling terrain.

Level, uphill and downhill running economy values are strongly inter-correlated.

Exercise economy is not solely an intrinsic physiological trait because economy in one mode of exercise (e.g., running) does not strongly correlate with economy in another mode (e.g. cycling). Economy also reflects the skill of an individual in a particular mode of exercise. Arguably, level, uphill and downhill running constitute biomechanically different modes of exercise. Thus, we tested the hypothesis that level running economy (LRE), uphill running economy (URE) and downhill running economy (DRE) would not be strongly inter-correlated. We measured the oxygen uptakes of 19 male trained runners during three different treadmill running speed and grade conditions: 238m/min, 0%; 167m/min, + 7.5%; 291m/min, - 5%. Mean oxygen uptakes were 46.8 (SD 3.9), 48.0 (3.4) and 46.9 (3.7) ml/kg/min for level, uphill and downhill running, respectively, indicating that the three conditions were of similar aerobic intensity. We reject our hypothesis based on the strong correlations of r = 0.909, r = 0.901 and r = 0.830, respectively, between LRE vs. URE, LRE vs. DRE and URE vs. DRE. Economical runners on level surfaces are also economical on uphill and downhill grades. Inter-individual differences in running economy reflect differences in both intrinsic physiology and skill. Individuals who have experience with level, uphill and downhill running appear to be equally skilled in all three modes.

Effect of downhill running grade on lower extremity loading in female distance runners

ABSTRACTHill running is often used as a foundational training mechanism to build strength and speed. Distance runners in particular are at an increased likelihood of encountering steep hills during training runs. There is limited research regarding downhill running, and there is no research available on the biomechanics of females specifically during downhill running. The purpose of this study was to quantify the differences in loading when running downhill at different grades compared to a level surface in female distance runners to determine the potential risk for injury. Fifteen female distance runners (age: 23.5 ± 4.9 y), who ran 56.3 ± 20.9 km a week participated in this study. Participants ran on a force-instrumented treadmill at 4.0 m/s for 2 min at 0%, −5%, −10%, −15%, and −20% grades, with 5 min of rest between conditions. Study findings showed increased impact forces (p < 0.001), and increased loading rates (p < 0.001) with increasing downhill grades compared to level. These results indicate a significantly greater risk of overuse injury to the lower extremity with steeper downhill grades. Individuals need to be aware of these risks to plan and implement training programmes that will increase performance while minimising injury risk.

Examining longitudinal train dynamics in ore car tipplers

ABSTRACTTrain simulation has been adapted in this paper to model the behaviour of indexing operations in ore car tippler operations. An important consideration in simulations at these low speeds (less than 4 km/h) is the increased rolling resistance transitioning from stationary conditions to motion. Most formulations of rolling resistance equations do not include this range although there are empirical values in some railway standards. The indexer control utilised here has a target trapezoidal velocity profile. The indexer to train connection was modelled as a stiff linear spring, a damper and a gap element. A sensitivity analysis was completed considering variations in wagon connections including wedge static friction, preload, coupling slack and tippler slack. Track topography including downhill grades of 0.1% and 0.2% and a valley profile were also investigated. Results showed high sensitivity to draft gear parameters of static friction and preload, but minimal benefit from downhill grades and changes in coupling slack.

The Effects of Load Carriage and Physical Fatigue on Cognitive Performance.

In the current study, ten participants walked for two hours while carrying no load or a 40 kg load. During the second hour, treadmill grade was manipulated between a constant downhill or changing between flat, uphill, and downhill grades. Throughout the prolonged walk, participants performed two cognitive tasks, an auditory go no/go task and a visual target detection task. The main findings were that the number of false alarms increased over time in the loaded condition relative to the unloaded condition on the go no/go auditory task. There were also shifts in response criterion towards responding yes and decreased sensitivity in responding in the loaded condition compared to the unloaded condition. In the visual target detection there were no reliable effects of load carriage in the overall analysis however, there were slower reaction times in the loaded compared to unloaded condition during the second hour.

Severity of urban cycling injuries and the relationship with personal, trip, route and crash characteristics: analyses using four severity metrics

ObjectiveTo examine the relationship between cycling injury severity and personal, trip, route and crash characteristics.MethodsData from a previous study of injury risk, conducted in Toronto and Vancouver, Canada, were used...

Comparing the effects of infrastructure on bicycling injury at intersections and non-intersections using a case–crossover design

BackgroundThis study examined the impact of transportation infrastructure at intersection and non-intersection locations on bicycling injury risk.MethodsIn Vancouver and Toronto, we studied adult cyclists who were injured and treated at...

Route Infrastructure and the Risk of Injuries to Bicyclists: A Case-Crossover Study

We compared cycling injury risks of 14 route types and other route infrastructure features. We recruited 690 city residents injured while cycling in Toronto or Vancouver, Canada. A case-crossover design compared route infrastructure at each injury site to that of a randomly selected control site from the same trip. Of 14 route types, cycle tracks had the lowest risk (adjusted odds ratio [OR] = 0.11; 95% confidence interval [CI] = 0.02, 0.54), about one ninth the risk of the reference: major streets with parked cars and no bike infrastructure. Risks on major streets were lower without parked cars (adjusted OR = 0.63; 95% CI = 0.41, 0.96) and with bike lanes (adjusted OR = 0.54; 95% CI = 0.29, 1.01). Local streets also had lower risks (adjusted OR = 0.51; 95% CI = 0.31, 0.84). Other infrastructure characteristics were associated with increased risks: streetcar or train tracks (adjusted OR = 3.0; 95% CI = 1.8, 5.1), downhill grades (adjusted OR = 2.3; 95% CI = 1.7, 3.1), and construction (adjusted OR = 1.9; 95% CI = 1.3, 2.9). The lower risks on quiet streets and with bike-specific infrastructure along busy streets support the route-design approach used in many northern European countries. Transportation infrastructure with lower bicycling injury risks merits public health support to reduce injuries and promote cycling.

The role of elastic energy storage and recovery in downhill and uphill running

In level running, humans and other animals store and recover elastic energy during each step. What role does elastic energy play during downhill and uphill running? We measured the fluctuations of the mechanical energy of the center of mass (CoM) of 15 human participants running at 3 m s(-1) on the level, downhill and uphill on a force-measuring treadmill mounted at 3, 6 and 9 deg. In level running, nearly symmetrical decreases and increases of the combined gravitational potential and kinetic (GPE+KE) energy of the CoM indicated equal possible elastic energy storage and recovery. However, asymmetrical fluctuations during hill running indicate reduced maximum possible elastic energy storage and return. We analyzed mechanical energy generation and dissipation during level and hill running by quantifying the anatomically estimated elastic energy storage (AEEE) in the arch and Achilles' tendon using peak ground reaction forces and anatomical characteristics. AEEE did not change with grade. At shallow downhill grades, the body must generate mechanical energy, though it dissipates more than it generates. At steeper downhill grades, little to no energy generation is required and only mechanical energy dissipation must occur. The downhill grade at which mechanical energy must no longer be generated occurs at approximately -9 deg, near the metabolically optimal running grade. At shallow uphill grades, mechanical energy must be generated to raise the CoM, and at steeper grades, additional energy must be generated to offset reduced elastic energy storage and return.

Mechanical work performed by the individual legs during uphill and downhill walking

Previous studies of the mechanical work performed during uphill and downhill walking have neglected the simultaneous negative and positive work performed by the leading and trailing legs during double support. Our goal was to quantify the mechanical work performed by the individual legs across a range of uphill and downhill grades. We hypothesized that during double support, (1) with steeper uphill grade, the negative work performed by the leading leg would become negligible and the trailing leg would perform progressively greater positive work to raise the center of mass (CoM), and (2) with steeper downhill grade, the leading leg would perform progressively greater negative work to lower the CoM and the positive work performed by the trailing leg would become negligible. 11 healthy young adults (6 M/5 F, 71.0±12.3kg) walked at 1.25m/s on a dual-belt force-measuring treadmill at seven grades (0, ±3, ±6, ±9°). We collected three-dimensional ground reaction forces (GRFs) and used the individual limbs method to calculate the mechanical work performed by each leg. As hypothesized, the trailing leg performed progressively greater positive work with steeper uphill grade, and the leading leg performed progressively greater negative work with steeper downhill grade (p<0.005). To our surprise, unlike level-ground walking, during double support the leading leg performed considerable positive work when walking uphill and the trailing leg performed considerable negative work when walking downhill (p<0.005). To understand how humans walk uphill and downhill, it is important to consider these revealing biomechanical aspects of individual leg function and interaction during double support.

Energy Balance During Backpacking

PURPOSE: The energy expenditure (EE) of backpacking has been described in only a few studies, and energy balance has never been reported. This study sought to evaluate EE and energy intake (EI) during an extended backpacking trip. METHODS: Three experienced, aerobically fit backpackers (32-yr old female, 57 ml.min-1.kg-1 VO2max; 34-yr old male, 73 ml.min-1.kg-1; 53-yr old male, 62 ml.min-1.kg-1) recorded their heart rate (HR) and food consumption during a five-day, 162-km trip on a rugged section of the Appalachian Trail. Body mass was recorded shortly before the trip began and immediately upon exiting the trail on day five, using the same scale. Resting EE was estimated as 1 kcal/hr per kg. Exercise EE was estimated two ways: (1) ACSM equation for walking, using distance traveled and gross elevation gained; EE of descents was considered equivalent to flat walking in accordance with past research showing that shallow downhill grades require less EE than flat walking, but steep downhill grades require more than flat walking; (2) the HR/VO2 relationship during treadmill testing was applied to average HR values for each subject for each day during walking. RESUITS: Gross EE using the ACSM equation averaged 4062 kcal on four full days, and 2733 kcal on the fifth day. Gross EE using HR/VO2 was 23% greater. EI averaged 2134 kcal on four full days, and 1117 kcal on the fifth day. The largest food source was snack bars and trail mix, which accounted for 62% of EI. Substrates were 52% carbohydrates, 17% protein and 31 % fat. Average HR during hiking was 105 bpm, or 37% of heart rate reserve. Expected average weight loss was 1.2 kg based on the ACSM walking equation and 1.8 kg based on HR/VO2. Actual weight loss averaged 1.7 kg. CONCLUSIONS: Subjects in this study did not maintain weight during extended backpacking. Their weight loss was more accurately predicted by estimating EE from HR/VO2 than from a walking equation.

Stiffness and Damping Response Associated with Shock Attenuation in Downhill Running

Studies on shock attenuation during running have induced alterations in impact loading by imposing kinematic constraints, e.g., stride length changes. The role of shock attenuation mechanisms has been shown using mass-spring-damper (MSD) models, with spring stiffness related to impact shock dissipation. The present study altered the magnitude of impact loading by changing downhill surface grade, thus allowing runners to choose their own preferred kinematic patterns. We hypothesized that increasing downhill grade would cause concomitant increases in both impact shock and shock attenuation, and that MSD model stiffness values would reflect these increases. Ten experienced runners ran at 4.17 m/s on a treadmill at surface grades of 0% (level) to 12% downhill. Accelerometers were placed on the tibia and head, and reflective markers were used to register segmental kinematics. An MSD model was used in conjunction with head and tibial accelerations to determine head/arm/trunk center of mass (HATCOM) stiffness (K1), and lower extremity (LEGCOM) stiffness (K2) and damping (C). Participants responded to increases in downhill grade in one of two ways. Group LowSAhad lower peak tibial accelerations but greater peak head accelerations than Group HighSA, and thus had lower shock attenuation. LowSAalso showed greater joint extension at heelstrike, higher HATCOMheelstrike velocity, reduced K1stiffness, and decreased damping than HighSA. The differences between groups were exaggerated at the steeper downhill grades. The separate responses may be due to conflicts between the requirements of controlling HATCOMkinematics and shock attenuation. LowSAneeded greater joint extension to resist their higher HATCOMheelstrike velocities, but a consequence of this strategy was the reduced ability to attenuate shock with the lower extremity joints during early stance. With lower HATCOMimpact velocities, the HighSArunners were able to adopt a strategy that gave more control of shock attenuation, especially at the steepest grades.

Oxygen consumption, heat production, and muscular efficiency during uphill and downhill walking

Oxygen consumption, heat production, and muscular efficiency for walking are parameters important to know for ergonomics models and equipment design. Most of these assume that the oxygen consumption and heat production of downhill walking are the same as for uphill walking. Eight subjects wearing insulating clothing walked on a treadmill at three uphill and three downhill grades, and at level grade at a rate of 1.1 m/s. Oxygen consumption V ̇ O 2 was calculated from steady state measurements of respiratory minute volume and oxygen percentage. Heat production ( q ̇ ) was calculated from the rate of heat storage in the body and clothing. Least-squares best fit equations for oxygen consumption and heat production found were to be V ̇ O 2 =0.813+0.0361G+0.000810G 2−0.0000302G 3 and q ̇ =6.55+0.185G+0.0114G 2−0.000190G 3 where G is percent grade. Approximations show that V ̇ O 2 (downhill)=0.5 V ̇ O 2 (uphill), q ̇ (downhill)=0.67 q ̇ (uphill), and muscular efficiency η (downhill)=−2 η (uphill).

ENERGY EXPENDITURE DURING RECREATIONAL SNOWSHOEING

329 The purpose of this study was to determine the energy expenditure of females during recreational snowshoeing and to assess the validity of HR-VO2 regression equations in predicting energy expenditure. Subjects(n=7) performed three exercise protocols: one maximal stress test, and two steady state protocols [treadmill speed (3.2, 4.8, 6.4 kmph) and grade (3, 6, 9%) were varied to ascertain the HR-VO2 regression equation which would give the most accurate prediction of VO2 in the field] on a treadmill. Subjects then snowshoed [walking] for a total of 30 minutes on uphill and downhill grades. Each subjects' VO2 in L·min-1 and ml·kg-1min-1, RER, HR, ECO2%, EO2%, and VEs were measured with the AeroSport KBI-C (AeroSport, Inc., Ann Arbor, MI). Energy expenditure for snowshoeing uphill was found to average 7.8±1.8 kcals/min. Downhill data determined that energy expenditure was less with a group mean of 5.5±1.3 kcals/min. Mean VO2 on an uphill grade and downhill grade averaged 63% and 44% of maximal VO2, respectively. Mean HR while snowshoeing uphill was at 80% of maximal and 68% of maximal while downhill snowshoeing. A repeated measures ANOVA was run to compare estimated VO2 in each regression equation to the VO2 as measured by the Aerosport KB1-C. Estimated uphill VO2 in each equation compared to actual values showed no significant difference among groups. Downhill VO2 estimations and actual values revealed significance F(3,18)=3.44, p=.039, accounting for 14% of the treatment effect (ω2), between actual VO2 and the HR-VO2 max regression and the grade-dependent steady state regression. Mean HR values for uphill and downhill were found to fall within the target heart zone established by the American College of Sports Medicine. Therefore, it is concluded that snowshoeing is an activity that can be utilized to achieve or maintain cardiovascular fitness.

ドライバーメンタルモデルによる下り坂惰性走行時の自動減速制御に関する一考察

ドライバーメンタルモデルによる下り坂惰性走行時の自動減速制御に関する一考察