Ground Contact Research Articles

Improvement of postural control in the frail older adults through foot care: A pre- and post-intervention study

Frailty in older adults often leads to foot issues, increasing fall-related fracture risk. Mechanoreceptors, the pressure receptors in the foot sole, are pivotal for postural control. Foot problems can impair mechanoreceptor function, compromising balance. This study aimed to examine the effect of foot care on postural control in frail older adults. Forty-eight participants underwent a five-month monthly foot care intervention. Measurements were taken before and after this intervention. Participants stood for 45 s in a static, open-eyed position on a stabilometer. Center-of-pressure (CoP) analysis included total trajectory length, integrated triangle area, rectangular area, and range of motion in anterior–posterior and medio-lateral directions. Results indicated that foot care significantly increased toe ground contact area by 1.3 times and improved anterior–posterior motion control during static standing. Enhanced postural control resulted from improved skin condition due to foot care that intensified mechanoreceptor signal input and improved postural control output. These findings underscore the potential for reducing fracture risks in older adults through proactive foot care. The study highlights the vital role of foot care in enhancing postural control, with broader implications for aging population well-being and safety.

Effect of Thermal Modification on the Density, Durability, Dimensional Stability, and Mechanical Properties of Pinus caribaea

Pinus caribaea (Pine) is an underutilized timber species in Sri Lanka due to its low density, durability, dimensional stability, and undesirable colour. This research aims to examine the enhancements in the physical and mechanical properties of Pinewood through thermal modification (TM) and compare the properties of the TM wood with kiln-dried and untreated wood and with the properties of high-graded timbers of Tectona grandis (teak) and Koompassia malaccensi (kempas). TM is a process that involves heating wood to high temperatures (2000 C) in the absence of oxygen, which removes the moisture and creates changes in the wood at the cellular level. The effectiveness of the thermal modification on density, modulus of rupture (MOR), modulus of elasticity (MOE), moisture content, dimensional stability, durability, and colour was studied. Specific gravity of thermally modified wood was 6% higher than untreated wood, but lower than teak and kempas. MOR and MOE values were 35.75% and 46.46% respectively higher than untreated wood. Equilibrium moisture content was reduced after TM and volumetric shrinkage of TM was reduced to 2.16% and swelling under liquid water contact was reduced to 2.37%. Thermally modified timber was classified as not durable (DC 5) based on field test (EN 252, 2014) results. However, TM timber was slightly durable (DC 4) according to laboratory tests and showed better fungal resistance. The wood underwent a darkening effect as a result of thermal modification, resembling the colour of teak. The cost of TM was 13.1% higher than kiln drying. Improved dimensional stability, enhanced bending strength, and attractive appearance demonstrate the potential of thermal modification as a promising alternative for transforming P. caribaea wood into high-value raw material. TM timber finds suitable applications in indoor furniture and joinery projects. However, due to its lack of termite resistance, preservative treatment is recommended for outdoor ground contact usage.
 
 Keywords: Thermally modified timber, Mechanical properties, Dimensional stability, Durability,
 Pinus caribaea

Longer Ground Contact Time Is Related to a Superior Running Economy in Highly Trained Distance Runners.

Tanji, F, Ohnuma, H, Ando, R, Yamanaka, R, Ikeda, T, and Suzuki, Y. Longer ground contact time is related to a superior running economy in highly trained distance runners. J Strength Cond Res 38(5): 985-990, 2024-Running economy is a key component of distance running performance and is associated with gait parameters. However, there is no consensus of the link between the running economy (RE), ground contact time, and footstrike patterns. Thus, this study aimed to clarify the relationship between RE, ground contact time, and thigh muscle cross-sectional area (CSA) in highly trained distance runners and to compare these parameters between 2 habitual footstrike patterns (midfoot vs. rearfoot). Seventeen male distance runners ran on a treadmill to measure RE and gait parameters. We collected the CSAs of the right thigh muscle using a magnetic resonance imaging scanner. The RE had a significant negative relationship with distance running performance ( r = -0.50) and ground contact time ( r = -0.51). The ground contact time had a significant negative relationship with the normalized CSAs of the vastus lateralis muscle ( r = -0.60) and hamstrings ( r = -0.54). No significant differences were found in RE, ground contact time, or normalized CSAs of muscles between midfoot ( n = 10) and rearfoot ( n = 7) strikers. These results suggest that large CSAs of knee extensor muscles results in short ground contact time and worse RE. The effects of the footstrike pattern on the RE appear insignificant, and the preferred footstrike pattern can be recommended for running in highly trained runners.

Stryd biomechanical parameters as indicators of running economy and performance

The interplay of biomechanical and neuromuscular aspects aids in the conversion of power production in running performance, and when combined with metabolic factors, these aspects may lead to improved running economy (RE). Therefore, the purpose of this study is to determine the association between the Stryd Power Meter foot pod metrics with RE and performance. Fifteen high-caliber male athletes completed two treadmill running sessions. First, RE was determined at 10 and 12 km/h. Second, two all-out efforts of nine and three minute duration were completed. At 10 km/h, the simple and stepwise multiple linear regression analysis revealed that form power (FP) was the best RE predictor (adjusted R2 = 0.464; p = 0.005) followed by vertical oscillation (VO) ( R2 = 0.424; p = 0.005) and ground contact time (GCT) ( R2 = 0.363; p = 0.010). At 12 km/h, such regressions confirmed that GCT was the best RE indicator (adjusted R2 = 0.222; p = 0.043) followed by FP (adjusted R2 = 0.213; p = 0.047). During the nine and three minute all-out effort sessions, GCT was the best performance predictor ( R2 = 0.491; p = 0.002 and R2 = 0.380; p = 0.014, respectively). The biomechanical factors of GCT and FP are good indicators of RE and running performance.

An 8-week injury prevention exercise program combined with change-of-direction technique training limits movement patterns associated with anterior cruciate ligament injury risk

Knee ligament sprains are common during change-of-direction (COD) maneuvers in multidirectional team sports. This study aimed to compare the effects of an 8-week injury prevention exercise program containing COD-specific exercises and a similar program containing linear sprint exercises on injury- and performance-related variables during a 135° COD task. We hypothesized that the COD-specific training would lead to (H1) stronger reductions in biomechanical variables associated with anterior cruciate ligament (ACL) injury risk during COD, i.e. knee abduction moment and angle, hip internal rotation angle and lateral trunk lean, and (H2) more effective improvements in COD performance according to the COD completion time, executed angle, ground contact time, and approach speed. Twenty-two sports science students (40% female) completed biomechanical assessments of COD movement strategies before and after participating in two supervised 25-min training sessions per week over 8 weeks. We observed significant ‘training x group’ interaction effects in support of H1: the COD-specific training but not the linear sprint training led to reduced peak knee abduction moments (interaction, p = 0.027), initial knee abduction (interaction, p < 0.001), and initial lateral trunk lean angles (interaction, p < 0.001) compared to baseline. Although the COD-specific training resulted in sharper executed angles (interaction, p < 0.001), the sprint-specific training group showed reduced COD completion (interaction, p = 0.037) and ground contact times (interaction, p < 0.001). In conclusion, a combination of generic and COD-specific injury prevention training resulted in COD technique adaptations that can help to avoid ACL injury-prone COD movements but may negatively affect COD speed.

Replacement of tibialis cranialis tendon with polyester, silicone-coated artificial tendon preserves biomechanical function in rabbits compared to tendon excision only

BackgroundArtificial tendons may be an effective alternative to autologous and allogenic tendon grafts for repairing critically sized tendon defects. The goal of this study was to quantify the in vivo hindlimb biomechanics (ground contact pressure and sagittal-plane motion) during hopping gait of rabbits having a critically sized tendon defect of the tibialis cranialis and either with or without repair using an artificial tendon.MethodsIn five rabbits, the tibialis cranialis tendon of the left hindlimb was surgically replaced with a polyester, silicone-coated artificial tendon (PET-SI); five operated control rabbits underwent complete surgical excision of the biological tibialis cranialis tendon in the left hindlimb with no replacement (TE).ResultsAt 8 weeks post-surgery, peak vertical ground contact force in the left hindlimb was statistically significantly less compared to baseline for the TE group (p = 0.0215). Statistical parametric mapping (SPM) analysis showed that, compared to baseline, the knee was significantly more extended during stance at 2 weeks post-surgery and during the swing phase of stride at 2 and 8 weeks post-surgery for the TE group (p < 0.05). Also, the ankle was significantly more plantarflexed during swing at 2 and 8 weeks postoperative for the TE group (p < 0.05). In contrast, there were no significant differences in the SPM analysis among timepoints in the PET-SI group for the knee or ankle.ConclusionsOur findings suggest that the artificial tibialis cranialis tendon effectively replaced the biomechanical function of the native tendon. Future studies should investigate (1) effects of artificial tendons on other (e.g., neuromuscular) tissues and systems and (2) biomechanical outcomes when there is a delay between tendon injury and artificial tendon implantation.

A Pilot Study in Sensor Instrumented Training (SIT) - Ground Contact Time for Monitoring Fatigue and Curve Running Technique

Abstract This study examines the possibilities of sensor-instrumented training (SIT) in mid-distance running training sessions. Within this framework, variations of ground contact time (GCT) between straight and curved running, as well as GCT as a fatigue indicator, are explored. Seven experienced runners, with two elite female athletes, participated in two training protocols: 15 sets of 400 m with 1-minute rest and five sets of 300 m with 3-minute rest. GCT was calculated using two inertial measurement units (IMU) attached to the athletes’ feet. The running speed of all athletes was measured with wearable GPS devices. GCT showed variations between inner and outer feet, notably during curve running (300m: 2.56%; 400m: 2.35%). However, for the 300m runs, statistically insignificant GCT differences were more pronounced in straight runs (3.54%) than in curve runs (2.56%), contrasting with the typical assumption of higher differences in curve running. A fatigue-indicating pattern is visible in GCT, as well as speed curves. Other data of this study are consistent with prior research that has observed differences between the inner and outer foot during curve running, while our understanding of the development throughout the training session is enhanced. Using SIT can be a valuable tool for refining curve running technique. By incorporating novel sensing technology, the possibilities enhance our understanding of running kinematics and offer an excellent application of SIT in sports.

Effects of Prophylactic Lace-Up Ankle Braces on Kinematics of the Lower Extremity During a State of Fatigue

Background: Prophylactic lace-up braces are commonly used in athletics regardless of ankle injury history to reduce lateral ankle sprains (LAS). Objectives: The purpose of the study was to assess ankle and knee kinematics associated with chronic knee pathologies during a 90° cutting maneuver before and after a state of fatigue. Methods: Using a randomized crossover design, thirteen, active adults (6 males and 7 females) engaged in a 15-m beep test fatigue protocol with a 90° cutting maneuver test before and after the fatigue protocol, both with and without brace. Results: Brace condition significantly reduced Ankle Sagittal Displacement (ASD; 52°) compared to no brace condition (62°) (p .05). Peak knee flexion was significantly greater in brace (56°) compared to no brace condition (47°) and, likewise, took longer to reach it (10 ms) (p .05). Conclusions: Prophylactic ankle braces limiting ASD can cause the foot to land in a more dorsiflexed position at initial ground contact causing more rearfoot strike, which may contribute to chronic knee pathologies.

Configuration design and kinematic performance analysis of a parallel wheelset suspension for a multi-wheeled pressurized lunar rover

When a multi-wheeled pressurized lunar rover (MWPLR) travels over rough terrain, the ability of its suspension to maintain wheel–ground contact is critical for achieving heavy load distribution and increasing its payload capacity. If the MWPLR uses an independent suspension, increasing the number of wheels worsens the wheel-off-ground problem. If the MWPLR utilizes a rocker–bogie suspension with a planar open-loop kinematic chain, it will have difficulty withstanding lateral impacts. In this study, to solve the above problems, the configurations of the 4-SS parallel mechanism were enumerated based on the Grassmann line geometry and screw theory to design a two-degree-of-freedom parallel wheelset suspension. The suspension integrated two axially parallel wheels on the same moving platform. Kinematic analysis showed that no singularities occurred in the workspace. The moving platform enabled large vertical movement and rotation of ±30°. Simulations showed that the suspension dramatically improved the ride comfort and wheel–ground contact capability of the MWPLR.

Mathematical Modeling of the Optimal Cost for the Design of Strap Combined Footings

This paper presents a novel mathematical model to determine the minimum cost for the design of reinforced-concrete strap combined footings under biaxial bending, with each column using a genetic algorithm. The pressure is assumed to be linearly distributed along the contact area. This study comprises two steps: firstly, identifying the smallest ground contact area, and secondly, minimizing the cost. The methodology integrates moment, bending shear, and punching shear calculations according to the ACI standard. Some authors present a smaller area (but limited to one or two property lines) and the design considers that the thickness of the footings and beam are equal, and do not show the lower cost of a strap combined footing; generally, the beam has a greater thickness than the footings and therefore the footings would have an unnecessary thickness that would generate a higher cost. A numerical example is shown to find the lowest cost for the design of strap combined footings considering four different conditions such as square footings and other limitation at the ends of the footings. The minimum area does not guarantee that it is the lowest cost. The proposed model is versatile, applicable to T-shaped and rectangular combined footings, and is not restricted to specific property lines. The contributions include eliminating trial and error practices, accommodating various design conditions, and emphasizing equilibrium in the derived equations. The model is adaptable to different building codes, offering a comprehensive approach to achieving optimal design and cost considerations for strap combined footings.

Intra-Day and Inter-Day Reliability and Usefulness of Performance, Kinetic and Kinematic Variables during Drop Jumping in Hurling Players

The aim of this study was to estimate the intra-day and inter-day reliability and usefulness of performance (Jump height (JH), ground contact time (GCT) and reactive strength index (RSI)), kinetic (force, power, eccentric rate of force development [E-RFD] and leg stiffness [LS]) and kinematic (velocity) variables during drop jumping (DJ) in hurling players. Seventeen (n = 17; mean ± SD; age = 23.35 ± 5.78 years, height = 178.35 ± 6.30 cm, body mass = 78.62 ± 8.06 kg) male club-level hurling players completed two maximal DJs from 0.20, 0.30, 0.40, 0.50 and 0.60 m drop heights on three testing days separated by 5–9 days of rest. Reliability was assessed using the coefficient of variation percentage (CV% ≤ 15%) and intraclass correlation coefficient (ICC &gt; 0.70). For intra-day reliability, GCT (0.40 m, 0.50 m and 0.60 m), peak force (absolute and relative) (0.40 m and 0.50 m) and leg stiffness (0.40 m and 0.50 m) were found to be unreliable (ICC = 0.32–0.68 and CV% = 3.67–11.83%) from those specific drop heights. All other variables were found to be reliable (ICC = 0.72–0.98 and CV% = 1.07–14.02%) intra-day. All variables were found to be reliable (ICC = 0.72–0.96 and CV% = 2.57–14.68%) inter-day except for relative peak force and absolute and relative eccentric RFD (0.30 m and 0.40 m) (ICC = 0.68–0.90 and CV% = 7.76–16.47%). Practitioners have multiple reliable DJ performance, kinetic and kinematic variables for performance testing and training purposes.

Ground Reaction Forces, Asymmetries and Performance of Change of Direction Tasks in Youth Elite Female Basketball Players.

The magnitude and direction of inter-limb asymmetries in a change of direction (COD) have increased interest in scientific research in recent years. This present study aimed to investigate the magnitude of asymmetries in an elite youth female basketball sample (n = 18, age = 17.79 ± 0.67 y) and determine its directionality using force platform technology. Participants performed 70° and 180° COD tests analyzing the following variables: time, ground contact time (GCT) and ground reaction forces (GRF) along the anterior-posterior, mediolateral, and vertical axes. Inter-limb asymmetries were evident in both COD tests, with substantial differences observed between limbs (p < 0.01). The asymmetry values ranged from 3.02% to 24.31% in COD 180° and from 1.99% to 21.70% in COD 70°, with anterior-posterior GRF consistently exhibiting the highest asymmetry magnitude. Additionally, the directionality exhibited variability between the tests, indicating poor agreement and suggesting the independent directionality of asymmetries across tasks. Moreover, players required more time to complete the COD 180°, the GCT was noticeably longer for the COD 180° than for the COD 70°, and GRF varied across the axis, suggesting that players adapt uniquely to the specific demands of each task. The utilization of force platforms presents a comprehensive approach to assess asymmetries and COD variables performance variables which are "angle-dependent", which could have important implications for COD screening and effective training interventions.

Reliability of running parameters using fitness watches synced with accelerometers during outdoor runs

Background: To prevent running related injuries and return to sport activities, monitoring the running dynamic parameters (cadence, stride length, ground contact time and vertical oscillation) especially outdoor running is crucial. Previous studies investigated the reliability of these parameters in laboratory settings. However, the nature of outdoor runs is different (curve, uphill, other runners, etc.) and challenging in terms of equipment (simple) and environments (grass, asphalt, rubber, etc.). Therefore, the reliability of these parameters using a fitness watch synced with accelerometer needed to be investigated. Objective: To investigate the reliability of running parameters measured using fitness watches and accelerometers during outdoor runs. Materials and methods: 30 healthy volunteers (age 25.8±9.6 years, height 167.2±9.3 cm, weight 62.4±14.2 kg, and body mass index 22.2±3.8 kg/m2) participated in the study. They wore a fitness watch and attached a synced accelerometer at their pants. They completed 2 running laps (800 meters each) at their comfortable speeds. Resting periods were provided between laps. To control the speed for the second lap, the watch was set the maximum and minimum speed and set vibration and sound alarm mode. Running parameters include cadence, stride length, vertical oscillation, and ground contact time. Results: The reliability of the four running parameters (cadence, stride length, ground contact time, and vertical oscillation), indicated by the intraclass correlation coefficients (ICC (3,k)) was 0.94, 0.97, 0.98 and 0.99, respectively. Very high reliability values were confirmed. Conclusion: Using a fitness watch synced with an accelerometer during outdoor runs, running dynamic parameters (cadence, stride length, ground contact time, and vertical oscillation) illustrated very high levels of reliability.

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.

The acute effect of verbal instructions on performance and landing when dropping from different heights: the ground reaction force-time profile of drop vertical jumps in female volleyball athletes.

The drop vertical jump (DVJ) is extensively utilized for conditioning and evaluating physical performance, as well as reducing the likelihood of injury by enhancing joint stability through the coactivation of muscles acting on the joint. The execution of DVJ can be controlled by verbal instructions and evaluated by the vertical ground reaction force (vGRF)-time profile. Our hypothesis was that varying verbal instructions could have an impact on the DVJ's parameter, thereby optimizing vertical performance and minimizing the impact during landing in young female volleyball players. Sixteen female volleyball players volunteered to participate in this study (age: 21.3 ± 2.6 years; stature: 1.66 ± 0.1 m; body mass: 62.0 ± 8.1 kg and BMI: 22.2 ± 1.8). They executed DVJs following verbal instructions ranging from "jump as high as possible" (1A), "jump as quickly as possible" (2A), "jump as high as possible and during the landing attempt to dampen the impact at ground contact" (1B), and "jump as high as quickly as possible and during the landing attempt to damp the impact at ground contact" (2B). The reactive strength index (RSI), vGRF (1st and 2nd peaks), and flight time (FT) were evaluated. The verbal instructions 1A improved the FT and the first peak of the vGRF (P < 0.05), whereas 2A the RSI (P < 0.05). On the contrary, "the damping" required in the 1B, and 2B verbal instruction reduced the 2nd peak of vGRF (P < 0.05), without altering the task required during the jump (P < 0.05). The instructions provided for the final landing (the second peak of vGRF) have the potential to enhance safety by reducing the peak of vGRF without affecting the performance required during the jump. When designing DVJ training, coaches or kinesiologists must consider the use of verbal instructions to induce specific adaptation over time. The present study supports the use of specific verbal instructions to reduce impact forces in landing and injury risk.

Lower-Extremity Energetic Distribution During Rate-Controlled Ballet Jumps (Sautés) in Healthy Dancers.

Dancers frequently perform jumps in the context of a prolonged, continuous dance piece. The purpose of this study is to explore the lower-extremity energetics in healthy dancers performing repetitive dance jumps (sautés) before and after typical dance-specific choreography. Lower-extremity kinetic data were collected from 14 healthy female dancers during a series of sautés performed before and after 3minutes of dance. Percent contributions of the lower-extremity joints to the whole-limb mechanical energy expenditure during ground contact were calculated. The jumps performed at the beginning were compared with the jumps at the end of the dance choreography. Dancers maintained the jump rate and consistent whole-limb mechanical energy expenditure between the jump series. As expected, for both jump series, the sautés had greater relative energetic contribution from the ankle and knee as compared with lesser contribution from the hip and toe. However, we observed lesser contribution from the knee and greater contribution from the hip after a 3-minute dance. After performing typical dance choreography, the dancers demonstrated a distal to proximal redistribution of individual joints' contribution to whole-limb mechanical energy expenditure.

Switched Control of HyTAQs: A Framework of Stochastic Hybrid Fuzzy Systems With Variable Dimensions.

This article is concerned with the switched control of hybrid terrestrial and aerial quadrotors (HyTAQs) via stochastic hybrid fuzzy system methodology, in which the terrestrial and aerial mode switching is subject to a Markov process with lower-bounded sojourn time. For the first time, the bimodal nonlinear attitude dynamics of HyTAQs is analyzed and modeled based on the Takagi-Sugeno (T-S) fuzzy model, and switched fuzzy controllers are developed to stabilize the hybrid fuzzy system. The characteristic of state dimension switching caused by ground contact is modeled via the singular system presentation with mode-dependent singularity matrices, based on which numerically testable criteria of stability and stabilization in the stochastic sense are derived. Compared with the previous control approaches based on Markov jump systems, the proposed one is able to describe the deterministic dwelling duration in practice and integrate multiple subsystems with algebraic equations of different dimensions, while achieving lower conservatism. Illustrative examples are provided to demonstrate the effectiveness and potential of the designed variable-dimension fuzzy controllers.

The effects of single and combined jump exercises utilizing fast and slow stretch-shortening cycle on physical fitness measures in healthy adult males: A randomized controlled trial

This study aimed to compare the effects of six-week volume-equated jump training using drop jump (DJ), countermovement jump (CMJ), or a combination of both (COMB) on the physical fitness of adult males. Participants were randomly assigned to DJ (n=10), CMJ (n=9), or COMB (n=10) training groups or an active control group (n=7). Performance data were collected for 10-m and 30-m sprint, DJ, CMJ, standing long jump (SLJ), triple-hop jump, change of direction speed (CODS), and maximal isometric strength. The DJ demonstrated improvements in the 10-m sprint, CMJ, and SLJ (g=0.62–1.13, %Δ=3.0–10.8). The CMJ group improved in the 10-m and 30-m sprints, CODS, CMJ and SLJ (g=0.34–1.17, %Δ=3.4–10.5). The COMB group displayed progress in CMJ and SLJ (g=0.46–0.61, %Δ=6.4–8.6). In comparison to the control and COMB groups, the DJ and CMJ groups improved the 10-m sprint (p=0.008, ηp2=0.311), and in comparison to the control group, the CMJ group improved SLJ (p=0.037, ηp2=0.220). To conclude, the findings presented here deviate from the training principle of specificity, particularly in relation to ground contact time. This suggests that the classification of jump exercises into fast- and slow-SSC categories based solely on ground contact time might oversimplify a more intricate phenomenon.

Fast and Slow Jump Training Methods Induced Similar Improvements in Measures of Physical Fitness in Young Females

This study aimed to contrast the impacts of an exercise intervention using either bounce drop jump (DJ; fast stretch-shortening cycle exercise) or countermovement jump (CMJ; slow stretch-shortening cycle exercise) on measures of physical fitness in young females. A total of 23 young females (age: 19.7 ± 1.0 years, height: 159.8 ± 4.2 cm, body mass: 54.3 ± 14.3 kg) were randomly assigned to either DJ (n = 12) or CMJ (n = 11) training, which spanned 6 weeks. Pre- and posttraining assessments were conducted for 10 m and 30 m linear sprints, change-of-direction speed, CMJ, DJ (jump height, contact time, and reactive strength index), standing long jump, triple-hop distance, and isometric strength. Apart from the variance in jump technique, both interventions were standardized in terms of total repetitions, intensity, and surface type. No significant Group × Time effect was observed in any dependent variables (all p &gt; .05). A significant time effect was observed in 10 m (p &lt; .001, effect size [ES] = 0.70) and 30 m (p &lt; .001, ES = 0.79) linear sprint, CMJ height (p = .012, ES = 0.34), DJ contact time (p = .012, ES = 0.34), and triple-hop distance (p = .006, ES = 0.38). Both DJ and CMJ training interventions led to comparable improvements in linear sprints, CMJ height, DJ contact time, and triple-hop distance. These findings suggest that the duration of ground contact during intervention exercises (i.e., fast vs. slow stretch-shortening cycle) did not significantly influence initial (6 weeks) physical fitness adaptations in young females. However, extending these results to highly trained groups (e.g., athletes) warrants further investigation.

Comparison of Ladder Training Versus Plyometric Training on Agility &amp; Speed among Vadodara Cricket Players: An Experimental Study

Background: Cricket is the second most popular sport in the world, right behind football, and it is played between 105 nations that are members of the ICC. In cricket, speed plays an essential role as the faster the speed generation the more the number of singles taken &amp; saved during fielding. Agility is required in the infield of cricket because fielders are closer to the batsmen and have less time to react.Ladder drills improve footwork &amp; coordination in players performance level which makes players easy to catch, strike or block or tackle. In Agility Ladder, jumps are performed without obstacles &amp; in multidirectional ways with fast ground contact time. Aim: To compare the effect of Ladder Training versus Plyometric Training on agility &amp; speed among cricket players. Method: 38 male cricket players (under -19) were selected by convenient sampling. Participants who met the inclusion criteria were randomly allocated into two equal groups: Ladder Training group and Plyometric Training group. Baseline data was collected by Illinois agility test &amp; 40m Sprint test. The training duration was 3 sessions/week for 6 weeks. Results:The data was analyzed using paired – t test for within group and Unpaired – t test for between group. Results showed that both the training methods produced significant improvement in agility &amp; speed performance but ladder training method showed statistically significant difference in agility (p&lt;0.0001) &amp; speed (p&lt;0.0002) than plyometric training. Conclusion: The present study concludes that Ladder training has an added advantageous effect for improving speed and agility in cricket players over plyometric training.