Differences In Ground Reaction Forces Research Articles

Unimodal and bimodal curves of ground reaction force-time profiles identify the drop jump performance

ABSTRACT This study aimed to investigate the kinematics and kinetics differences in ground reaction force (GRF)-time profiles with uni- and bimodal curves (UNC and BIC) during the concentric phase of the drop jump (DJ). Twenty two male Physical Education college student who met UNC (N = 11) or BIC (N = 11) of the GRF-time profile of were recruited. Two force plates and eight infrared optical cameras were synchronised to collect the GRF and motion data during DJ from a 30-cm height. The Shapiro-Wilk test was used to assess the normality of data. The Wilcoxon test was used when data were not normally distributed. Otherwise, Independent t-tests were used to compare differences between the UNC and BIC groups for each dependent variable. The UNC group demonstrated shorter ground contact time, lower jump height, greater leg stiffness, greater peak power during the eccentric phase, less work during the eccentric and concentric phases, and greater hip and knee joint flexion and extension angle displacements (p < 0.05). No significant intergroup differences were found in reactive strength index (p > 0.05). The UNC and BIC of the GRF-time profiles can indicate whether athletes can practice DJ appropriately. UNC can be representative of a better DJ performance with an efficient stretch-shortening cycle function.

Walking speed differentially affects lower extremity biomechanics in individuals with anterior cruciate ligament reconstruction compared to uninjured controls

BackgroundWalking biomechanics are commonly affected after anterior cruciate ligament reconstruction and differ compared to uninjured controls. Manipulating task difficulty has been shown to affect the magnitude of walking impairments in those early after knee surgery but it is unclear if patients in later phases post-op are similarly affected by differing task demands. Here, we evaluated the effects of manipulating walking speed on between-limb differences in ground reaction force and knee biomechanics in those with and without anterior cruciate ligament reconstruction. MethodsWe recruited 28 individuals with anterior cruciate ligament reconstruction and 20 uninjured control participants to undergo walking assessments at three speeds (self-selected, 120%, and 80% self-selected speed). Main outcomes included sagittal plane knee moments, angles, excursions, and ground reaction forces (vertical and anterior-posterior). FindingsWe observed walking speed differentially impacted force and knee-outcomes in those with anterior cruciate ligament reconstruction. Between-limb differences increased at fast and decreased at slow speeds in those with anterior cruciate ligament reconstruction while uninjured participants maintained between-limb differences regardless of speed (partial η2 = 0.13–0.33, p < 0.05). Anterior cruciate ligament reconstruction patients underloaded the surgical limb relative to both the contralateral, and uninjured controls in GRFs and sagittal plane knee moments (partial η2 range = 0.13–0.25, p < 0.05). InterpretationOverall, our findings highlight the persistence of walking impairments in those with anterior cruciate ligament reconstruction despite completing formal rehabilitation. Further research should consider determining if those displaying larger changes in gait asymmetries in response to fast walking also exhibit poorer strength and/or joint health outcomes.

Does Nordic Walking technique influence the ground reaction forces?

BackgroundNordic Walking (NW) practice has increased during the last decade, generating great benefits related to the reduction of ground reaction forces (GRF). However, there is still limited evidence regarding how the NW technique could affect GRF. Research questionTo analyze the effect of the speed and the differences in ground reaction forces (GRF) between NW with Diagonal technique (DT) versus Alpha technique (AT) and compare them with normal walking (W) Methods29 male physically active sport science students were randomly assigned to one of the training groups: AT (n = 15) or DT (n = 14). After 5 technique familiarization sessions, participants performed 5 experimental trials on a walkway for both NW and W at two different walking speeds, previously randomized. A two-way repeated measures ANOVA analysis was carried out to find differences between speeds (preferred, fast) and gait (NW, W) as within-subject factors and NW techniques (DT vs AT) as between-subject factor. ResultsDuring NW, both technique groups (AT, DT) showed an increase in GRF variables compared to W, such as in stance time (2.9 % mean increment, p < 0.01, ES = 0.3; 95 %IC[−0.027, −0.008]), vertical force impact or vertical heel strike variables (4.9 % mean increment, p < 0.01, ES = 0.4; 95 %IC[0.101, 0.036]; 7.3 % mean increment, p < 0.01, ES = 0.8; 95 %IC[−0.133, −0.081] respectively). Moreover, AT group experienced significant lower forces at vertical force at midstance (10.1 % mean descent, p = 0.036, ES = 0.3; 95 %IC[−0.083, −0.009]) and higher forces at AP propulsive forces (23.7 % mean increment, p < 0.001, ES = 0.6; 95 %IC[0.078, 0.202) and ML max force (14.0 % mean increment, p = 0.045, ES = 0.3; 95 %IC[0.002, 0.026]) compared to DT group. Walking speed was significantly higher during NW (Preferred: 1.89 ± 0.18 m/s; Fast: 2.17 ± 0.21 m/s) compared to W (Preferred: 1.76 ± 0.15 m/s; Fast: 2.04 ± 0.19 m/s) in both speed conditions. SignificanceNW favours an increase in GRF and speed in comparison with Walking, independently of the technique, with no evidence that justifies the use of one technique or another.

Effect of Sex-Specific Running Shoes on Female Recreational Runners

Alterations in running shoe design have been studied and used in the prevention of injury and enhancement of performance allowing running shoe companies to market to a variety of runners based on skill level, foot-strike pattern, and even sex. These alterations have been shown to affect biomechanical and physiological variables associated with running. Some shoe companies have designed shoes specifically for biological female runners due to the morphological differences found between male and female feet. The purpose of this study is to determine if sex-specific running shoes can alter female runner biomechanics or physiology. Female runners were asked to run in the male and female models of the Altra Torin 4 Plush shoe to determine if there were differences in ground reaction forces (GRFs), sagittal plane joint angles and moments, oxygen consumption (VO2), respiratory exchange ratio (RER), and perceived level of comfort while running; There were no significant differences in GRFs, sagittal joint angles and moments, VO2, RER, or perceived comfort; There were no differences in measured biomechanical or physiological variables between the female and male version of the shoes suggesting that the alterations made to the female-specific shoe do not provide any additional benefit to female recreational runners.

Softball Pitching Propulsion and Performance Differences According to Body Fat Percentage.

Softball pitchers with a high body-fat percentage (bf%) can often be successful, despite the heightened risk of injury associated with high bf%. Given the importance of propulsion during pitching, those with high bf% may have an advantage performance-wise. Therefore, the purpose of this study was to examine the differences in ground reaction force (GRF) development between two groups of pitchers: those with a high-fat percentage (≥32 bf%) and a healthy-fat percentage (<32 bf%). Thirty-two female high-school softball pitchers (1.70±.06 m, 76.09±17.50 kg, 15±1 yrs) completed dual-energy x-ray absorptiometry (DEXA) scans. GRF data were collected during pitch propulsion via a force plate, pitch speed was captured using a radar gun, BMI was calculated from pitcher height and mass, and fat free mass index (FFMI) and fat mass index (FMI) were calculated using DEXA data and pitcher height. Multivariate analysis of variance revealed pitcher group GRFs differed significantly (F3,30=3.45, p=.030). Univariate follow-up analyses showed healthy bf% pitchers presented greater weight-normalized peak medial GRF (F1,30=7.17, p=.012). BMI and FFMI were positively associated with pitch speed while bf% and FMI were negatively associated with pitch speed. While pitchers can be successful and carry excess bf%, results indicate potential performance disadvantages associated with having an increased bf%.

Waveform analysis of shank loaded wearable resistance during sprint running acceleration

ABSTRACT Lower-limb wearable resistance (WR) provides a specific and targeted overload to the musculature involved in sprint running, however, it is unknown if greater impact forces occur with the additional limb mass. This study compared the contact times and ground reaction force waveforms between sprint running with no load and 2% body mass (BM) shank-positioned WR over 30 m. Fifteen male university-level sprint specialists completed two maximum effort sprints with each condition in a randomized order. Sprint running with shank WR resulted in trivial changes to contact times at 5 m, 10 m, and 20 m (effect size [ES] = <0.20, p > 0.05) and a small, significant increase to contact time at 30 m by 1.94% (ES = 0.25, p = 0.03). Significant differences in ground reaction force between unloaded and shank loaded sprint running were limited to the anterior-posterior direction and occurred between 20% and 30% of ground contact at 10 m, 20 m, and 30 m. Shank WR did not result in greater magnitudes of horizontal or vertical forces during the initial impact portion of ground contact. Practitioners can prescribe shank WR training with loads ≤2% BM without concern for increased risk of injurious impact forces.

Biomechanical Analysis of Long Distance Running on Different Sports Surfaces

Running is one of the most accessible physical activities and long-distance running has attracted extensive attention in the past several years. While the incidence of running injuries, especially to the lower extremities, has increased. The objective of this study was to investigate the differences in ground reaction forces (GRF) and kinematic param between long-distance runners before and after long-distance running on treadmill (TM), asphalt road (AR), and plastic track (PT). Eight-camera Vicon motion analysis system was used to measure the hip, knee and ankle motion param of 10 healthy male subjects at a speed of 2.8 ± 0.2m/s. The hip, knee and ankle kinematics and the relationship of joint angles of lower limbs in the sagittal plane, coronal plane and transversal plane were analyzed. Ground reaction force (GRF) was collected using an AMTI force platform. The results showed that there were no significant differences in GRF and average loading rate (VALR). There was no significant difference in the range of motion (ROM) of ankle and hip after long-distance running on three surfaces compared to pre-test. Compared with stance-period of pre-test, the stance-period of AR and PT were significantly longer. Post hoc analyses exhibited the stance-period of AR and PT were longer than TM. In conclusion, runners can adjust different joints angles to maintain a similar GRF during long-distance running on different sports surfaces.

Biomechanical Evaluation and Strength Test of 3D-Printed Foot Orthoses.

Foot orthoses (FOs) are commonly used as interventions for individuals with flatfoot. Advances in technologies such as three-dimensional (3D) scanning and 3D printing have facilitated the fabrication of custom FOs. However, few studies have been conducted on the mechanical properties and biomechanical effects of 3D-printed FOs. The purposes of this study were to evaluate the mechanical properties of 3D-printed FOs and determine their biomechanical effects in individuals with flexible flatfoot. During mechanical testing, a total of 18 FO samples with three orientations (0°, 45°, and 90°) were fabricated and tested. The maximum compressive load and stiffness were calculated. During a motion capture experiment, 12 individuals with flatfoot were enrolled, and the 3D-printed FOs were used as interventions. Kinematic and kinetic data were collected during walking by using an optical motion capture system. A one-way analysis of variance was performed to compare the mechanical parameters among the three build orientations. A paired t-test was conducted to compare the biomechanical variables under two conditions: walking in standard shoes (Shoe) and walking in shoes embedded with FOs (Shoe+FO). The results indicated that the 45° build orientation produced the strongest FOs. In addition, the maximum ankle evertor and external rotator moments under the Shoe+FO condition were significantly reduced by 35% and 16%, respectively, but the maximum ankle plantar flexor moments increased by 3%, compared with the Shoe condition. No significant difference in ground reaction force was observed between the two conditions. This study demonstrated that 3D-printed FOs could alter the ankle joint moments during gait.

Abstract 482: Differences in Ground Reaction Forces and Chest Compression Release Velocity in Professional and Lay Rescuers With and Without the Use of Real-Time CPR Feedback

Purpose: Chest compression release velocity (CCRV) has been associated with survival and favorable neurological outcome after cardiac resuscitation. Both complete chest release and high CCRV contribute to improved venous return during CPR. Differences in compression forces delivered by professional and lay rescuers are reported, which may contribute to differences in CCRV. The aim of this pilot study was to investigate differences in ground reaction force (GRF) and CCRV between professional and lay rescuers during CPR performed on a manikin with and without real-time feedback. Methods: Professional (n = 5) and lay rescuers (n = 11) performed two minutes of continuous compressions on a manikin positioned over a force plate for two trials. CPR feedback provided by a defibrillator was disabled in the first trial and enabled in the second. CPR pads containing an accelerometer were used to calculate individual compression characteristics. Relative maximum and minimum GRFs were calculated for each compression cycle and averaged over each trial. Paired and independent sample t tests and Pearson correlations were conducted in STATA 15.1. Results: CCRV was higher in professionals vs. lay rescuers with feedback disabled and enabled ( p &lt;0.05). Professionals had greater maximal and lower minimum forces than lay rescuers without feedback ( p &lt;0.05), though there were no differences between groups with feedback enabled (Table 1). CCRV was associated with minimum force (r = -0.63, p &lt;0.01) and force range (r = 0.78, p &lt;0.01) in all rescuers. Analysis of GRFs by CCRV for all rescuers indicated lower force minimum (9.71 + 3.16 N, p &lt;0.05) with CCRV &gt;400 mm/s in comparison to CCRV 300-400 mm/s (39.73 + 8.91 N) and CCRV 200-300 mm/s (63.82 + 16.98 N). Conclusions: CPR feedback attenuated differences in GRF between professional and lay rescuers. CCRV was greater in professionals and was associated with measures of GRF, and thus may serve as an indicator of both velocity and amount of chest release.

Relationship of an osteoarthritis of the knee and a knee pain of single-leg on the bilateral difference of ground reaction force in stepping

Relationship of an osteoarthritis of the knee and a knee pain of single-leg on the bilateral difference of ground reaction force in stepping

Sex and race related differences in ground reaction forces during walking and interactions with knee pain and osteoarthritis in a large cohort

Sex and race related differences in ground reaction forces during walking and interactions with knee pain and osteoarthritis in a large cohort

A comparison of the ground reaction forces of archers with different levels of expertise during the arrow shooting

Summary Objective The purpose of this study was to compare the differences in ground reaction forces (GRFs) of archers with different levels of expertise during arrow shooting. Material and methods Twenty-seven male archers were involved in this study. Anterior-posterior ground reaction force (APGRF-Fy) and medio-lateral ground reaction force (MLGRF-Fx) collected by force platform during the successful shots towards the target from a distance of 18 m. The center of pressure (CoP) excursion was computed during arrow shooting using the GRFs. All statistical analyses were completed using SPSS 22.0 for Windows software (SPSS Inc., Chicago, IL). The level of statistical significance was set as P Results Results demonstrated that elite group had the least CoP sway, APGRF and MLGRF during all phases comparing to both mid-level, beginner level archers. However the differences in APGRF and MLGRF between groups didn’t reach the significance level (P > 0.05). The sway range of CoP values of elite group were significantly smaller than the values of beginner group (P Conclusion In conclusion, it was observed that the relationship between body sway and expertise level. Therefore instantaneous visual force feedback training including APGRF, MLGRF and CoP sway values could be recommended in order to increase shooting performance.

Hinged ankle braces do not alter knee mechanics during sidestep cutting

Lateral ankle sprains are common injuries in quick, dynamic movements and are caused by rapid ankle inversion. Ankle braces are used to reduce ankle inversion, while allowing normal plantar and dorsiflexion ranges of motion. Knee injuries, such as anterior cruciate ligament injuries, are also common in dynamic movements. It is important to understand how ankle braces affect injury risk at other proximal joints. There is limited and conflicting results on how ankle braces affect knee mechanics during these types of movements. Additionally, it is unknown if sex differences exist when using an ankle brace. Therefore, the purpose of this study was to determine the effects of a hinged ankle brace and sex during a 45° cutting movement. Three-dimensional kinematics and ground reaction forces were collected using a motion capture system and force plate on ten men and eight women during cutting trials. 2 × 2 repeated measures ANOVAs were used to detect differences in ground reaction forces, as well as knee and ankle kinematics between brace conditions and sex (p < 0.05). The brace condition exhibited greater initial contact ankle dorsiflexion (p = 0.011), decreased peak ankle inversion (p < 0.01), and increased vertical loading rate (p = 0.040). Females performed the cutting movement with less initial contact (p = 0.019) and peak knee flexion (p = 0.023) compared to males. Ankle bracing had no impact on the observed sex differences. Females exhibited decreased knee flexion compared to males, which has been well documented in the literature. The use of an ankle braces reduced ankle injury risk variables while not adversely impacting knee mechanics during a 45° sidecutting movement.

How does body symmetry influence standing balance?

The aim of the study was to determine whether maintaining the standing balance position is influenced by athlete’s symmetric morphological characteristics. Thirty-two healthy sports students participated in this study (age 19.8±1.4 years, body height 182.9±6.8 cm, body weight 79.1±8.1 kg). Morphological characteristics are represented with differences between the left and the right body side of: forearm girth, upper arm girth, calf girth, thigh girth, long shoulder height, lean mass of legs and lean mass of arms. The standing balance result was calculated as a result of factor scores for 9 measurements of 30 seconds (3 measurements of normal standing, 3 measurements of blind standing, and 3 measurements of deaf standing) collected from the pressure insoles system and the difference in ground reaction force between the left and the right leg. Results show that the asymmetric leg load in maintaining standing balance depends on the side differences in the thigh girth and upper arm girth. The greater difference in the thigh girth in favour of the left side resulted in bigger ground reaction force on the right leg compared to the left leg and the greater difference in the upper arm girth in favour of the left side resulted in bigger ground reaction force on the left leg. To avoid one side overload, it is essential for all sports activities to be performed bilaterally.

Force measurements during running on different instrumented treadmills

One method to determine the forces produced during running is to conduct extensive kinematic and kinetic analysis. These analyses can be performed by having an individual perform repeated over-ground running trials or simply run continuously on an instrumented treadmill. The forces produced during over-ground running may not be the same as the forces during treadmill running and these differences could be attributed to a number of factors, including the design of the instrumented treadmill. The purpose of this paper was to determine whether there are differences in force measurements on different instrumented treadmill setups in comparison to over-ground running and to correct for any of these differences using a theoretical model. 11 participants ran on three different treadmills and performed over-ground running at 2.7, 3.6, and 4.5 m/s. Ground reaction forces were measured via force plates and an instrumented pressure insole. We found that the magnitude of the vertical ground reaction force differed between the three treadmills and over-ground running. The difference in ground reaction forces estimated by the pressure insole and the treadmill-force-plate system or instrumented treadmill can be explained by a three degree of freedom mechanical model of a person running on a treadmill and this model could potentially be used to correct for errors in force measurement from instrumented treadmills. The model included a force plate, a treadmill, and a wobbling mass with varying natural frequencies and damping characteristics, and constant masses. These findings provide researchers a method to correct forces from an instrumented treadmill set-up to determine a close approximation of the actual forces experienced by a participant during treadmill running.

Accelerations from wearable accelerometers reflect knee loading during running after anterior cruciate ligament reconstruction

BackgroundFollowing anterior cruciate ligament reconstruction, individuals exhibit sagittal plane knee loading deficits as they underload their injured limb during running. These between-limb biomechanical differences are difficult to clinically detect. Wearable accelerometers may aid in the development of early rehabilitation programs to improve symmetrical loading. This study aimed to identify whether segment accelerations from wearable accelerometers can predict knee loading asymmetry in an anterior cruciate ligament reconstructed population. Methods14 individuals 5-months post-anterior cruciate ligament reconstruction performed self-selected speed running. Data were collected concurrently using a marker-based motion system and accelerometers positioned on participants' shanks and thighs. Stepwise linear regression was used to determine predictive value of accelerometer data on biomechanical variables. FindingShank acceleration was not predictive of any biomechanical variable. Between-limb differences in thigh axial acceleration explained 30% of the variance in between-limb differences in knee power absorption (p = 0.045), suggesting that accelerometers placed on proximal joint segments may provide information regarding knee loading asymmetry. Between-limb differences in thigh axial acceleration also explained 38% of the variance in between-limb differences in ground reaction force (p = 0.002). InterpretationThese relationships indicate that accelerations from wearable accelerometers may provide some useful information regarding knee loading during running in individuals following anterior cruciate ligament reconstruction.

Differences in Ground Reaction Forces When Collegiate Quarterbacks Throw Using Different Drop Patterns

While there is limited research examining the kinematics of the quarterback passing throw, to date there have not been any studies reporting on ground reaction forces (GRF) during this type of throwing motion. Additionally, there have been no studies reporting how foot positions or drop patterns used by quarterbacks might change GRF parameters. This information would useful to both coaches and sports medicine professionals as it provides both performance and injury related insights. PURPOSE: Compare GRF parameters between three commonly used quarterback drop patterns: a one step (1S), a three step (3S), and a three plus one step (3P1) when performed with the rearfoot angled 90° relative to the throwing direction and 45° relative to the throwing direction. METHODS: Three NCAA Division I quarterbacks participated in this study. Participants performed three throws using each type of drop and each foot position. Two force plates were used to record GRF data at 1000 Hz. Trials were considered valid if both the front (FF) and rear (RF) feet landed on their respective force plates, with the RF foot in the appropriate orientation. For both the RF and FF, peak horizontal and vertical forces, and horizontal and vertical impulses were calculated. Differences between foot positions and drop patterns were evaluated using a 2x3 repeated measures ANOVA. RESULTS: There were no differences in any force metrics for the FF. For the RF, peak horizontal GRFs showed a main effect of drop (F2,4=43.9, p=.002), with peak forces being lower in the 3P1 (210.7 ± 13.5 N) than the 3S (476.7 ± 50.5 N) or 1S(378.7 ± 2.6 N) conditions. Peak vertical forces in the RF also showed a main effect of drop (F2,4=20.3, p=.008), with peak forces being lower in the 3P1 (1201.7 ± 39.8 N) than the 3S (1359.9 ± 105.8 N). Lastly, there was a main effect of drop for RF horizontal impulse (F2,4=55.7, p=.001), with impulses being lower in the 3P1 (58.2 ± 9.12 Ns) than the 3S(150.7 ± 4.5 Ns) or 1S (150.8 ± 5.1 Ns) conditions. CONCLUSION: A 3P1 drop pattern makes use of horizontal momentum, thus requiring the athlete to generate less force and smaller impulses with the RF during the throw. As such, coaches should emphasize pushing with the RF when using a 1S or 3S drop pattern. Changing foot positions does not appear to influence force parameters.

초등학생의 골프클럽 종류에 따른 스윙 구간별 양발의 지면반력 차이 비교

초등학생의 골프클럽 종류에 따른 스윙 구간별 양발의 지면반력 차이 비교

A comparison of running kinetics in children with and without genu varus: A cross sectional study.

IntroductionVarus knee alignment has been identified as a risk factor for the progression of medial knee osteoarthritis. However, the underlying mechanisms have not been elucidated yet in children. Thus, the aims of the present study were to examine differences in ground reaction forces, loading rate, impulses, and free moment values during running in children with and without genu varus.MethodsThirty-six boys aged 9–14 volunteered to participate in this study. They were divided in two age-matched groups (genu varus versus healthy controls). Body weight adjusted three dimensional kinetic data (Fx, Fy, Fz) were collected during running at preferred speed using two Kistler force plates for the dominant and non-dominant limb.ResultsIndividuals with knee genu varus produced significantly higher (p = .01; d = 1.09; 95%) body weight adjusted ground reaction forces in the lateral direction (Fx) of the dominant limb compared to controls. On the non-dominant limb, genu varus patients showed significantly higher body weight adjusted ground reaction forces values in the lateral (p = .01; d = 1.08; 86%) and medial (p < .001; d = 1.55; 102%) directions (Fx). Further, genu varus patients demonstrated 55% and 36% greater body weight adjusted loading rates in the dominant (p < .001; d = 2.09) and non-dominant (p < .001; d = 1.02) leg, respectively. No significant between-group differences were observed for adjusted free moment values (p>.05).DiscussionHigher mediolateral ground reaction forces and vertical loading rate amplitudes in boys with genu varus during running at preferred running speed may accelerate the development of progressive joint degeneration in terms of the age at knee osteoarthritis onset. Therefore, practitioners and therapists are advised to conduct balance and strength training programs to improve lower limb alignment and mediolateral control during dynamic movements.

Ground reaction forces produced by two different hockey skating arm swing techniques

The arm swing in hockey skating can have a positive effect on the forces produced by each skate, and the resulting velocity from each push off. The main purpose of this study was to measure the differences in ground reaction forces (GRFs) produced from an anteroposterior versus a mediolateral style hockey skating arm swing. Twenty-four elite-level female hockey players performed each technique while standing on a ground-mounted force platform, and all trials were filmed using two video cameras. Force data was assessed for peak scaled GRFs in the frontal and sagittal planes, and resultant GRF magnitude and direction. Upper limb kinematics were assessed from the video using Dartfish video analysis software, confirming that the subjects successfully performed two distinct arm swing techniques. The mediolateral arm swing used a mean of 18.38° of glenohumeral flexion/extension and 183.68° of glenohumeral abduction/adduction while the anteroposterior technique used 214.17° and 28.97° respectively. The results of this study confirmed that the mediolateral arm swing produced 37% greater frontal plane and 33% less sagittal plane GRFs than the anteroposterior arm swing. The magnitudes of the resultant GRFs were not significantly different between the two techniques; however, the mediolateral technique produced a resultant GRF with a significantly larger angle from the direction of travel (44.44°) as compared to the anteroposterior technique (31.60°). The results of this study suggest that the direction of GRFs produced by the mediolateral arm swing more closely mimic the direction of lower limb propulsion during the skating stride.