Peak Loading Rate Research Articles

Abnormal Joint Moment Distributions and Functional Performance During Sit-to-Stand in Femoroacetabular Impingement Patients

BackgroundFemoroacetabular impingement (FAI) is a morphological abnormality of the hip joint that causes pain when performing a mechanically demanding activity of daily living such as the sit-to-stand (STS) task. Previous studies have assessed lower extremity joint mechanics during an STS task in various pathologies, yet the STS task has not been studied in FAI patients. ObjectiveThe objective of this study was to identify differences in joint kinetics and performance between FAI patients and healthy controls during a STS task. It was hypothesized that FAI patients would exhibit altered time needed to complete the STS task, as well as altered lower extremity biomechanics, when compared to healthy controls. DesignThis was a cross-sectional cohort study. SettingThe study took place at a motion capture laboratory at an institutional orthopedic facility. ParticipantsBiomechanical analysis was performed in 17 FAI patients and 31 age- and body mass index (BMI)−matched healthy controls during the STS task. MethodsSagittal plane joint moments, total support moment (TSM), joint contributions to the TSM, and functional measures during the STS task were compared between groups. Main Outcome MeasurementsPeak joint moments, TSM and joint contributions to the TSM were assessed during the STS task. In addition, the time to and value of the peak vertical ground reaction force (vGRF), limb symmetry index at peak vGRF, loading rate, and total time needed to perform the STS task were determined. ResultsCompared to the control participants, the FAI patients exhibited worse Hip Disability and Osteoarthritis Outcome Score (HOOS) pain and function subscores. No group differences were observed in peak sagittal joint moments during the STS task. However, when compared to controls, the FAI patients demonstrated reduced knee joint contributions to the TSM. In addition, the FAI patients exhibited increased time needed to perform the STS task, increased time to reach peak vGRF, and reduced lower extremity loading rate during the STS task. ConclusionsFAI patients demonstrated abnormal joint contributions to TSM and altered functional performance during the STS task. These altered movement patterns during the STS task may be compensatory mechanisms used by the FAI patients to reduce pain and to improve function. Level of EvidenceNot applicable.

Whole Body Vibration Immediately Decreases Lower Extremity Loading During the Drop Jump.

Chen, Z-R, Peng, H-T, Siao, S-W, Hou, Y-T, and Wang, L-I. Whole body vibration immediately decreases lower extremity loading during the drop jump. J Strength Cond Res 30(9): 2476-2481, 2016-The purpose of this study was to evaluate the acute effect of whole body vibration (WBV) on lower extremity loading during the drop jump (DJ). Fifteen male collegiate physical education students randomly completed 3 experimental sessions on 3 separate days with 4 days interval between sessions (performing 3 trials of DJ from 30-, 40-, and 50-cm drop heights before WBV and 4 minutes after WBV). Eight cameras and 2 force platforms were used to record kinematic and kinetic data, respectively. Peak impact force and loading rate significantly decreased after WBV during DJ from 40 and 50 cm. Knee angular displacements significantly increased after WBV during DJ from 30, 40, and 50 cm. Whole body vibration may help immediately reduce lower extremity loading.

Quadriceps Function and Gait Kinetics after Anterior Cruciate Ligament Reconstruction.

Chronic quadriceps dysfunction has been implicated as a contributor to knee osteoarthritis (OA) development after anterior cruciate ligament reconstruction (ACLR). This dysfunction potentially leads to impulsive/high-rate loading during gait, thus accelerating cartilage degradation. The purpose of this study was to examine relationships between several indices of quadriceps function and gait biomechanics linked to knee OA development in individuals with ACLR. Gait biomechanics and quadriceps function were assessed in 39 individuals with ACLR. Indices of quadriceps function included isometric peak torque and rate of torque development (RTD), isokinetic peak torque and power, and the central activation ratio. Gait biomechanics included the peak vertical ground reaction force and loading rate, and the heel strike transient (HST) magnitude and loading rate. Isometric peak torque was not associated with any of the gait biomechanical variables. However, greater RTD was associated with lesser peak vertical ground reaction force linear (r = -0.490, P = 0.003) and instantaneous (r = -0.352, P = 0.031) loading rates, as well as a lesser HST magnitude (r = -0.312, P = 0.049) and instantaneous loading rate (r = -0.355, P = 0.029). Greater central activation ratio was associated with greater HST instantaneous (r = 0.311, P = 0.050) and linear (r = 0.328, P = 0.033) loading rates. Isokinetic peak torque and power were not associated with any of the biomechanical variables. Poor quadriceps function, especially RTD, is associated with gait kinetics linked to cartilage degradation in individuals with ACLR. These results highlight the likely role of chronic quadriceps dysfunction in OA development after ACLR and the need to emphasize improving quadriceps function as a primary rehabilitation goal.

The Relationship Between Whole-Body External Loading and Body-Worn Accelerometry During Team-Sport Movements.

To investigate the relationship between whole-body accelerations and body-worn accelerometry during team-sport movements. Twenty male team-sport players performed forward running and anticipated 45° and 90° side-cuts at approach speeds of 2, 3, 4, and 5 m/s. Whole-body center-of-mass (CoM) accelerations were determined from ground-reaction forces collected from 1 foot-ground contact, and segmental accelerations were measured from a commercial GPS accelerometer unit on the upper trunk. Three higher-specification accelerometers were also positioned on the GPS unit, the dorsal aspect of the pelvis, and the shaft of the tibia. Associations between mechanical load variables (peak acceleration, loading rate, and impulse) calculated from both CoM accelerations and segmental accelerations were explored using regression analysis. In addition, 1-dimensional statistical parametric mapping (SPM) was used to explore the relationships between peak segmental accelerations and CoM-acceleration profiles during the whole foot-ground contact. A weak relationship was observed for the investigated mechanical load variables regardless of accelerometer location and task (R2 values across accelerometer locations and tasks: peak acceleration .08-.55, loading rate .27-.59, and impulse .02-.59). Segmental accelerations generally overestimated whole-body mechanical load. SPM analysis showed that peak segmental accelerations were mostly related to CoM accelerations during the first 40-50% of contact phase. While body-worn accelerometry correlates to whole-body loading in team-sport movements and can reveal useful estimates concerning loading, these correlations are not strong. Body-worn accelerometry should therefore be used with caution to monitor whole-body mechanical loading in the field.

Application of peak load for industrial water treatment plant design

Peak load rate(i.e., maximum daily flow/average daily flow) has not been considered for industrial water demand planning in Korea to date, while area unit method based on average daily flow has been applied to decide capacity of industrial water treatment plants(WTPs). Designers of industrial WTPs has assumed that peak load would not exist if operation rate of factories in industrial sites were close to 100%. However, peak load rates were calculated as 1.10~2.53 based on daily water flow from 2009 to 2014 for 9 industrial WTPs which have been operated more than 9 years(9-38 years). Furthermore, average operation rates of 9 industrial WTPs was less than 70% which means current area unit method has tendency to overestimate water demand. Therefore, it is not reasonable to consider peak load for the calculation of water demand under current area unit method application to prevent overestimation. However, for the precise future industrial water demand calculation more precise data gathering for average daily flow and consideration of peak load rate are recommended.

The Effect of Exertion and Sex on Vertical Ground Reaction Force Variables and Landing Mechanics.

The purpose of this investigation was to determine how exertion and sex affected a variety of vertical ground reaction force (VGRF) parameters during a jump-landing task, including peak VGRF, peak VGRF asymmetry, loading rate, and loading rate asymmetry. Additionally, we wanted to determine whether landing mechanics changed after exertion as measured by the Landing Error Scoring System (LESS). Forty recreationally active participants (20 men and 20 women) completed jump landings from a 30-cm-high box onto force plates before and after repeated bouts of an exercise circuit until a specific rating of perceived exertion was achieved. Three-way (sex × time × limb) analyses of variance were used to analyze variables pre-exertion to postexertion. No significant 3-way interactions were observed for peak VGRF (p = 0.31) or loading rate (p = 0.14). Time by sex interactions were observed for peak VGRF (p = 0.02) and loading rate (p = 0.008). Post hoc analysis revealed that men increased landing force and loading rate after exertion while women did not. Landing mechanics, as assessed by total LESS score, were worse after exertion (p < 0.001) with increased frequency of errors for knee flexion <30° at initial contact, lateral trunk flexion, and not flexing the hip during landing. Women may be more resistant to exertion compared with men and use different joint controls' strategies to cope with VGRF after exertion. However, VGRF asymmetry is not affected by sex and exertion. Limiting peak VGRF and addressing landing postures, especially after exertion, should be components of injury prevention strategies.

Cross Validation Of A Figure Skating Blade Instrumented To Measure Figure Skating Impact Forces.

Competitive figure skating requires a vast amount of athleticism with an artistic touch. Skaters spend hours each day on-ice mastering jumps, spins, and footwork. The high workload may be related to overuse injuries, which are very common in figure skating, especially at the elite level. To better understand the relationships between on ice training and injuries, it is important to understand the loading patterns acting on skaters. PURPOSE: To validate an instrumented figure skating blade that is designed to measure impact forces while skating. METHODS: Seven subjects (Age: 21.3±2.8 yrs, Ht: 166.9±2.5 cm, Mass: 64.7±7.9 kg) performed 20 landings each onto artificial ice while landing on the instrumented blade from heights of 17.5cm, 25cm, and 33cm. A custom instrumented blade calibrated to measure in forces in Newtons (N) was used to measure impact forces (1000Hz) during landings. These forces were compared to forces obtained while subjects landed on AMTI force plates located underneath the artificial ice surface. Boot angle (250Hz) and force plate data (1000Hz) were collected using Vicon Nexus. Custom LabVIEW programs were used to determine peak force, loading rate, impulse, and the correlation between the blade force data and the force plate data. Paired T-tests were used to compare peak force, loading rate, and impulse between the blade and force plate data. Alpha = 0.05. RESULTS: Correlations between the blade force data and force plate data were good to excellent: mean r (±SD) = .86 ± 0.08. No significant differences were found for peak force and impulse between the blade and force plate data. Peak force means (±SD) were 1353.7 ± 352.2 N for the blade and 1361.2 ± 309.7 N for the force plate (p=.86). The means (±SD) for impulse were 44.99 ± 21.2 Ns for the blade and 48.1 ± 17.7 Ns for the force plate (p=.125). Loading rate, calculated from impact to time of peak force, was significantly higher (p = 0.0004) for the blade data (28.88 ± 22.8 N/ms) as compared to the force plate data (9.77 ± 7.5 N/ms). CONCLUSION: The custom instrumented blade is a valid tool for measuring peak forces and impulse during landings. Current research is focused on increasing the gain of the instrumented blade to improve loading rate accuracy. Supported by US Figure Skating, Sports Science and Medicine Grant 2011

Assessment of Elasticity, Plasticity and Resistance to Machining-induced Damage of Porous Pre-sintered Zirconia Using Nanoindentation Techniques

Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai's series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for pre-sintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai–Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1–2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate (ANOVA, p > 0.05). The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia.

Comparison of ankle kinematics and ground reaction forces between prospectively injured and uninjured collegiate cross country runners

Biomechanical comparative studies on running-related injuries have included either currently or retrospectively injured runners. The purpose of this study was to prospectively compare ankle joint and ground reaction force variables between collegiate runners who developed injuries during the cross country season and those who did not. Running gait analyses using a motion capture system and force platform were conducted on 19 collegiate runners prior to the start of their cross country season. Ten runners sustained running-related injuries and 9 remained healthy during the course of the season. Strike index, peak loading rate of the vertical ground reaction force, dorsiflexion range of motion (ROM), eversion ROM, peak eversion angle, peak eversion velocity, and eversion duration from the start of the season were compared between injury groups. Ankle eversion ROM and peak eversion velocity were greater in uninjured runners while peak eversion angle was greater in injured runners. Greater ankle eversion ROM and eversion velocity with lower peak eversion angle may be beneficial in reducing injury risk in collegiate runners. The current data may only be applicable to collegiate cross country runners with similar training and racing schedules and threshold magnitudes of ankle kinematic variables to predict injury risk are still unknown.

Pressure Sensor Calibration for Measuring Stud-player Impacts

In rugby union, laceration injuries can occur from players stamping on opponents in the ruck. To measure the stud-skin interaction during stamping movements, pressure sensors can be used. Pressure sensor calibration techniques have highlighted the need to perform calibrations using appropriate impact dynamics. A pilot study with seven rugby players informed the expected peak forces and loading rates of rugby stamps. Subsequently, a custom calibration procedure was developed, using a drop hammer and force platform to replicate the experimentally observed forces and loading rates. The conventional calibration of the pressure sensor system, supplied by the manufacturer, overestimated total force by 132%. The method described in this paper resulted in a mean error of 7.5%. This study describes a simple and effective calibration procedure for using pressure sensors when measuring the peak force from stud-player impacts. The method has potential to be used as an improved calibration protocol when the expected peak force range of the measured event is between 1800 and 3000N. The calibrated pressure sensors will be used to obtain kinetic data from stamping events in the ruck in rugby union.

The Effect of High- and Low-Damping Prosthetic Foot Structures on Knee Loading in the Uninvolved Limb Across Different Walking Speeds.

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater knee loading in the frontal plane has been related to severity and rate of progression in knee osteoarthritis. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. However, little is known about specific effects that prosthetic foot damping may have on uninvolved limb loading. We hypothesized that uninvolved limb peak knee internal abduction moment (IAM) and loading rates would be greater when using a high-damping foot compared with a low-damping foot, across walking speeds. Eight healthy, young subjects walked in a prosthesis simulator boot using the experimental feet. Greater uninvolved limb first peak IAM (+16% in fast speed, P = .002; +11% in slow speed, P = .001) and loading rates (+11% in fast speed, P = .003) were observed when using the high-damping foot compared with low-damping foot. Within each foot, uninvolved limb first peak IAM and loading rates had a trend to increase with increased walking speed. These findings suggest that damping properties of prosthetic feet are related to uninvolved limb peak knee IAM and loading rates.

Establishing force and speed training targets for lumbar spine high-velocity, low-amplitude chiropractic adjustments.

We developed an adjusting bench with a force plate supporting the lumbar portion to measure loads transmitted during lumbar manual adjustment. It will be used to provide force-feedback to enhance student learning in technique labs. The study goal is to define the learning target loads and speeds, with instructors as expert models. A total of 11 faculty members experienced in teaching Gonstead technique methods performed 81 simulated adjustments on a mannequin on the force plate. Adjustments were along 9 lumbopelvic "listings" at 3 load levels: light, normal, and heavy. We analyzed the thrusts to find preload, peak load, duration, and thrust rate. Analysis of 891 thrusts showed wide variations between doctors. Peak loads ranged from 100 to 1400 N. All doctors showed clear distinctions between peak load levels, but there was overlap between high and low loads. Thrust rates were more uniform across doctors, averaging 3 N/ms. These faculty members delivered a range of thrusts, not unlike those seen in the literature for high velocity, low amplitude manipulation. We have established at least minimum force and speed targets for student performance, but more work must be done to create a normative adjustment to guide refinement of student learning.

Three-dimensional impact kinetics with foot-strike manipulations during running

BackgroundLack of an observable vertical impact peak in fore/mid-foot running has been suggested as a means of reducing lower extremity impact forces, although it is unclear if impact characteristics exist in other axes. The purpose of the investigation was to compare three-dimensional (3D) impact kinetics among foot-strike conditions in over-ground running using instantaneous loading rate–time profiles. MethodsImpact characteristics were assessed by identifying peak loading rates in each direction (medial–lateral (ML), anterior–posterior (AP), vertical, and 3D resultant) following foot-strike instructions (fore-foot, mid-foot, subtle heel, and obvious heel strike). Kinematic and kinetic data were analyzed among 9 male participants in each foot-strike condition. ResultsLoading rate peaks were observed in each direction and foot-strike condition, differing in magnitude by direction (3D resultant and vertical > AP > ML, p ≤ 0.031) and foot-strike: ML (fore-foot and mid-foot strike > obvious heel strike, p ≤ 0.032), AP (fore-foot and mid-foot strikes > subtle-heel and obvious heel strikes, p ≤ 0.023). In each direction, the first loading rate peak occurred later during heel strike running relative to fore-foot (p ≤ 0.019), with vertical and 3D resultant impact durations exceeding shear (ML and AP, p ≤ 0.007) in each condition. ConclusionLoading rate–time assessment identified contrasting impact characteristics in each direction and the 3D resultant following foot-strike manipulations, with potential implications for lower extremity structures in running.

The Immediate Effects of Arch Support Insole on Ground Reaction Forces during Walking

Introduction: Evaluation of ground reaction forces (GRF) and other kinetic parameters have clinical importance. These parameters may cover all possible interaction between shoe type and insole. This study aimed to investigate the immediate effects of arch support insole on GRF and their peak time, impulse, loading rate, and free moment during stance phase of gait in normal individuals. Materials and Methods: Sixteen healthy male subjects with mean ± SD age; 29.4 ± 4.8 years, mean ± SD mass; 77.9 ± 12.6 kg and mean ±SD height; 176.5 ± 5.8 cm were participated in this study. All parameters were measured using two adjacent Kistler force plates (1000Hz) during stance phase of walking in two different conditions: with and without shoe insole. Maximum GRF and their related peak time, impulse, loading rate, and free moment were recorded. Repeated measure ANOVA was used to analyze the data (α = 0.05). Results: Wearing insole caused reduction the peak vertical GRF (PvGRF) in heel contact phase by 6.9% of body weight (BW) (P = 0.001) and the loading rate (8.4%, P = 0.02). However, it increased the propulsive force (7% N/BW, P = 0.001), anterior-posterior impulse by 1.2% BW (P = 0.003) and normal impulse by 2% of BW (P = 0.032).

Clinical effects of buprenorphine on open field behaviour and gait symmetry in healthy and lame weaned piglets

Lameness in pigs decreases animal welfare and economic profit for the farmer. An important reason for impaired welfare in lame animals is pain due to lameness. No direct measurement of pain is possible in animals, and methods to indirectly detect and quantify the amount of pain an animal is experiencing are urgently needed. In this study, two methods to assess pain associated with lameness in pigs were evaluated to determine if they were sensitive enough to detect a lameness reduction as an effect of an experimental analgesic medication. Asymmetry associated with lameness was objectively quantified using pressure mat kinetic parameters: peak vertical force (PVF), load rate (LR), vertical impulse (VI) and peak vertical pressure (PVP). Locomotor activity was assessed in an open field test. A dose of 0.04 mg/kg buprenorphine, a strong analgesic, was used to treat 10 lame pigs, while eight other lame pigs, treated with physiological saline solution, served as controls.Buprenorphine decreased lameness-associated asymmetry for pressure mat LR (P = 0.002), VI (P = 0.003) and PVP (P = 0.001) and increased activity of the lame pigs in the open field (P = 0.023), while saline-treated animals did not show any changes in asymmetry and became less active in the open field (P < 0.001). It was concluded that measurement of gait asymmetry by pressure mat analysis and locomotor activity in an open field test are both sensitive enough to detect the analgesic effects of buprenorphine when used to treat moderate to severe clinical pain in a relatively small group of affected pigs. The methods used in this study may also provide promising additional tools for future research into early pain recognition and lameness treatment in pigs.

Lower limb reaction force asymmetry in rowers with and without a history of back injury

Back injury is common in rowers. Asymmetrical lower limb reaction force on the foot stretchers during rowing may compromise trunk biomechanics and lead to back injury. However, such a mechanism remains putative. Therefore, this study examined lower limb reaction force in experienced rowers with and without a history of back injury. Six rowers who suffered from back injury for more than one week in the past year and another 19 rowers who were never injured performed maximal exertion rowing on a fixed-head rowing machine for 30 strokes. Peak force, average and peak loading rate of the lower limb reaction force during the middle 10-stroke were recorded using strain-gauge transducers placed at the foot stretchers. Asymmetries and intra-limb variability were quantified as asymmetry indices and coefficients of variation, respectively. No significant asymmetry was observed in all selected kinetic parameters between the injured and healthy rowers (p = 0.448–0.722, Hedges' g = 0.162–0.310). Subgroup analyses also did not reveal any significant kinetic differences between injured and healthy scullers or sweepers (p = 0.194–0.855, Hedges' g = 0.203–0.518). Rowers with a history of back injury, regardless of the rowing types, did not demonstrate greater lower limb reaction force asymmetry when compared with healthy rowers.

Reduced knee flexion is a possible cause of increased loading rates in individuals with patellofemoral pain

BackgroundStair ascent is an activity that exacerbates symptoms of individuals with patellofemoral pain. The discomfort associated with this activity usually results in gait modification such as reduced knee flexion in an attempt to reduce pain. Although such compensatory strategy is a logical approach to decrease pain, it also reduces the normal active shock absorption increasing loading rates and may lead to deleterious and degenerative changes of the knee joint. Thus, the aims of this study were (i) to investigate whether there is reduced knee flexion in adults with PFP compared to healthy controls; and (ii) to analyze loading rates in these subjects, during stair climbing. MethodTwenty-nine individuals with patellofemoral pain and twenty-five control individuals (18–30years) participated in this study. Each subject underwent three-dimensional kinematic and kinetic analyses during stair climbing on two separate days. Between-groups analyses of variance were performed to identify differences in peak knee flexion and loading rates. Intraclass correlation coefficient was performed to verify the reliability of the variables. FindingsOn both days, the patellofemoral pain group demonstrated significantly reduced peak knee flexion and increased loading rates. In addition, the two variables obtained high to very high reliability. InterpretationReduced knee flexion during stair climbing as a strategy to avoid anterior knee pain does not seem to be healthy for lower limb mechanical distributions. Repeated loading at higher loading rates may be damaging to lower limb joints.

Strength Asymmetry and Landing Mechanics at Return to Sport after Anterior Cruciate Ligament Reconstruction.

Evidence-based quadriceps femoris muscle (QF) strength guidelines for return to sport after anterior cruciate ligament (ACL) reconstruction are lacking. This study investigated the effect of QF strength asymmetry on knee landing biomechanics at the time of return to sport after ACL reconstruction. Seventy-seven individuals (17.4 yr) at the time of return to sport after primary ACL reconstruction (ACLR group) and 47 uninjured control individuals (17.0 yr; CTRL group) participated. QF strength was assessed and quadriceps index was calculated (QI = [involved strength / uninvolved strength] × 100%). The ACLR group was subdivided based on QI: high quadriceps (HQ, QI ≥ 90%) and low quadriceps (LQ, QI < 85%). Knee kinematic and kinetic variables were collected during a drop vertical jump maneuver. Limb symmetry during landing and discrete variables were compared among the groups using multivariate analysis of variance and linear regression analyses. The LQ group demonstrated worse asymmetry in all kinetic and ground reaction force variables compared to the HQ and CTRL groups, including reduced involved limb peak knee external flexion moments (P < 0.001), reduced involved limb (P = 0.003) and increased uninvolved limb (P = 0.005) peak vertical ground reaction forces and higher uninvolved limb peak loading rates (P < 0.004). There were no differences in the landing patterns between the HQ and CTRL groups on any variable (P > 0.05). In the ACLR group, QF strength estimated limb symmetry during landing after controlling for graft type, meniscus injury, knee pain, and symptoms. At the time of return to sport, individuals after ACL reconstruction with weaker QF demonstrate altered landing patterns. Conversely, those with nearly symmetrical QF strength demonstrate landing patterns similar to uninjured individuals. Consideration of an objective QF strength measure may aid clinical decision making to optimize sports participation after ACL reconstruction.

Assessing the effectiveness of micro-spring technology to reduce initial and peak loading rates when integrated into running footwear

Running has long been one of the world’s most popular recreational activities. The current total of European runners exceeds 80 million, approximately, 36% of 15�65-year-old European population. Running is one of the most widespread activities during which overuse injuries of the lower extremity occur (Hreljac, 2004). It has been estimated that up to 70% of runners will sustain an overuse injury during any one year period (Caspersen et al., 1984). Previous work has shown that impact forces and high loading rates are linked to injury rates in runners (Davis, Bowser, & Mullineaux, 2010). Despite the apparent advances in footwear technology and the plethora footwear choices available, we are yet to see a reduction in injury rates amongst runners.

The effects of short-term jump training on bone metabolism in females using oral contraceptives

The purpose of this study was to determine the effect of oral contraceptive use on bone serum markers following a 3-week jumping protocol. Twenty-three females (18–25 years) were grouped as oral contraceptive users (OC+) or non-users (OC−). Following a 3-week observation period, participants completed a 3-week (15-day) jump protocol. Jump sessions consisting of ten 42 cm drop jumps with a 30 s rest interval between jumps were completed each day, 5 days per week. Peak vertical ground reaction force and loading rate were measured and the osteogenic index was calculated. Serum markers for bone formation, bone alkaline phosphatase (BAP) and bone resorption, C-terminal telopeptides of type I collagen (CTX) were measured at three time points (pre-, mid-, post-jump). BAP and CTX increased significantly (P = 0.0017, 0.0488) in both groups post-jump; however, bone metabolic markers were not different between the OC+ and OC− groups. Osteogenic index, ground reaction force and vertical jump height were similar between groups. Correlations between markers of bone metabolism and participants’ age at menarche, weight, loading rate and years on OC were not significant. A 3-week jumping protocol was found to be effective in stimulating bone metabolism in both OC+ and OC− groups.