Concurrent Validity and Reliability of In-Field Vertical Jump Performance Measures on Sand Surfaces.

ABSTRACT: Wirtz, S, Julian, R, Schmale, R, and Eils, E. Concurrent validity and reliability of in-field vertical jump performance measures on sand surfaces. J Strength Cond Res 38(4): 687-693, 2024-Beach sports, such as handball, volleyball, and soccer, involve dynamic actions, primarily jumps. Nonetheless, there is a need for more established measurement devices that are both valid and feasible in accurately evaluating jumping performance on sand surfaces. This study aims to assess the reliability and concurrent validity of MyJump2 and an inertial measurement unit (VERT) for quantifying countermovement jump performance on the sand. Twenty-one subjects performed 5 countermovement jumps on the sand. Jumping height was measured simultaneously by a force plate, VERT, and MyJump2. The VERT and MyJump2 reliability measures were evaluated using the intraclass correlation coefficients (ICC) for both absolute agreement (ICC 2,1 ) and consistency (ICC 3.1 ). The day-to-day reliability of both devices and the interrater and intrarater reliability of the MyJump2 were assessed. The concurrent validity of the VERT and MyJump2 was assessed using ICCs 2.1, 3.1 and Bland-Altman plots. A near-perfect agreement was seen for intrarater (ICC = 0.98) and interrater (ICC = 0.98) reliability of the MyJump2. Moreover, a near-perfect agreement was also observed when comparing the MyJump2 with the force plate (ICC = 0.92), with a mean bias of -2.31 cm. The VERT device only demonstrated a moderate agreement (ICC = 0.55) with a mean bias of 6.31 cm compared with the force plate, despite showing good day-to-day reliability (ICC = 0.79). The study's results indicate that MyJump2 is valid and reliable for assessing jump heights on sand surfaces, whereas VERT cannot be recommended.

Jumping on sand surfaces redistributes loading of the plantar surface to midfoot areas and reduces peak loading.

The purpose was to assess plantar mechanical loading on different surface conditions when performing jumps. Twenty subjects performed standardized drop jumps and countermovement jumps both in shoes and barefoot on a rigid surface and barefoot on a sand surface. Flexible insoles of the Pedar Mobile system (PedarX, Novel GmbH) were used for data collection. The foot was subdivided into eight regions where peak pressures and relative loads were derived. Significant differences were found for several foot areas for both, countermovement and drop jumps. For the sand surface, as compared to the rigid surface, peak pressures were significantly reduced in the hallux&2nd toe, medial/lateral forefoot, and heel but were increased in the medial/lateral midfoot. The relative load shifted significantly from the forefoot to the midfoot area. Substantially different plantar pressure distribution patterns between conditions were observed in jumping. The switch from a rigid to a sand surface is associated with a lower mechanical loading, whereas switching back from sand to an indoor surface potentially increases this loading. Our results show that the observed pressure distribution patterns for different surfaces align with other tasks like playing soccer/running, are in a typical range for these sports and entail a comparable mechanical loading.

A Group-Based 8-Week Functional Interval-Type Outdoor Training Program Improves Physical Performance in Recreationally Active Adults.

Even though physical activity is an important aspect of health, lack of time or motivation impede people from working out regularly. One type of training program that is both efficient and motivating is functional interval-type outdoor training. To evaluate this, our study had 81 participants complete a battery of physical performance tests (incremental treadmill test, core stability test and functional fitness test) before and after an 8-week outdoor interval-type training intervention. Training procedures included multimodal and high-intensity exercises performed in consistent, small groups. Results showed that the interval training program produced significant increases in the intervention group (n = 43) in functional and strength exercises (p < 0.001; squat (+27%), burpee (+24%), bridge (+39%), push-up (+34%), sit-up (+25%), high knees (+25%), row (+19%), effect sizes 0.4-0.11) for almost all parameters in comparison to a non-intervention control population (n = 38). Interestingly, trunk stability increased significantly (p < 0.001; flexion (+86%), extension (+43%), lateral left (+39%), lateral right (+32%), effect sizes 0.3-0.15) even though it was not explicitly trained; this was rather a secondary outcome of the functional exercises. Drop-out rates (Intervention group: 27%) suggest that this form of training seems to improve adherence to exercise and may help participants to stay committed to regular, intense activity. By simultaneously triggering adaptations in functional fitness, endurance and whole-body movements, this program can be used by people at different training levels.

The Implication of Wearables and the Factors Affecting Their Usage among Recreationally Active People.

Regular physical activity (PA) is associated with health and well-being. Recent findings show that PA tracking using technological devices can enhance PA behavior. Consumer devices can track many different parameters affecting PA (e.g., number of steps, distance, and heart rate). However, it remains unclear what factors affect the usage of such devices. In this study, we evaluated whether there was a change in usage behavior across the first weeks of usage. Further we investigated whether external factors such as weather and day of the week influence usage behavior. Thirty nine participants received a Fitbit Charge 2 fitness tracker for a nine-week period. All participants were asked to wear the device according to their wishes. The usage time and amount of PA were assessed, and the influencing factors, such as weather conditions and day of the week, were analyzed. The results showed that usage behavior differed largely between individuals and decreased after five weeks of usage. Moreover, the steps per worn hour did not change significantly, indicating a similar amount of activity across the nine-week period when wearing the device. Further influencing factors were the day of the week (the tracker was used less on Sundays) and the temperature (usage time was lower with temperatures >25°). Tracking peoples' activity might have the potential to evaluate different interventions to increase PA.

Vision adds to haptics when dyads perform a whole-body joint balance task.

When two or more people aim to produce joint action outcomes they need to coordinate their individual actions in space and time. Successful joint action performance has been reported to depend, among others, on visual and somatosensory information provided to the joint actors. This study investigated whether and how the systematic manipulation of visual information modulates real-time joint action when dyads performed a whole-body joint balance task. To this end, we introduced the Joint Action Board (JAB) where partners guided a ball through a maze towards a virtual hole by jointly shifting their weight on the board under three visual conditions: (1) the Follower had neither visual access to the Leader nor to the maze; (2) the Follower had no visual access to the maze but to the Leader; (3) the Follower had full visual access to both the Leader and to the maze. Joint action performance was measured as completion time of the maze task; interpersonal coordination was examined by means of kinematic analyses of both partners' motor behaviour. We predicted that systematically adding visual to the available haptic information would result in a significant increase in joint performance and that Leaders would change their coordination behavior depending on these conditions. Results showed that adding visual information to haptics led to an increase in joint action performance in a Leader-Follower relationship in a joint balance task. In addition, interpersonal coordination behavior (i.e. sway range of motion, time-lag between partner's bodies etc.) changed dependent on the provided visual information between partners in the jointly executed task.

Multistation proprioceptive exercise program prevents ankle injuries in basketball.

PURPOSE: To investigate the effectiveness of a multistation proprioceptive exercise program for the prevention of ankle injuries in basketball players using a prospective randomized controlled trial in combination with biomechanical tests of neuromuscular performance. METHODS: A total of 232 players participated in the study and were randomly assigned to a training or control group following the CONSORT statement. The training group performed a multistation proprioceptive exercise program, and the control group continued with their normal workout routines. During one competitive basketball season, the number of ankle injuries was counted and related to the number of sports participation sessions using logistic regression. Additional biomechanical pre­post tests (angle reproduction and postural sway) were performed in both groups to investigate the effects on neuromuscular performance. RESULTS: In the control group, 21 injuries occurred, whereas in the training group, 7 injuries occurred. The risk for sustaining an ankle injury was significantly reduced in the training group by approximately 65%. [corrected] The corresponding number needed to treat was 7. Additional biomechanical tests revealed significant improvements in joint position sense and single-limb stance in the training group. CONCLUSIONS: The multistation proprioceptive exercise program effectively prevented ankle injuries in basketball players. Analysis of number needed to treat clearly showed the relatively low prevention effort that is necessary to avoid an ankle injury. Additional biomechanical tests confirmed the neuromuscular effect and confirmed a relationship between injury prevention and altered neuromuscular performance. With this knowledge, proprioceptive training may be optimized to specifically address the demands in various athletic activities.

Passive stability characteristics of ankle braces and tape in simulated barefoot and shoe conditions.

BACKGROUND: Ankle sprains are among the most common injuries in barefoot sport activities such as dance, gymnastics, or trampoline. At present, the use of external ankle devices for prevention of ligament injuries for barefoot activities remains unclear. HYPOTHESIS: External ankle devices have a significant loss of passive stability when used without a shoe in barefoot activities. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-five healthy subjects participated in the project (mean age, 26.2 +/- 3.3 years; mean body mass, 71.2 +/- 10.3 kg; mean height, 178 +/- 7 cm). Passive range of motion measurements were performed with 3 different ankle stabilizers (a stirrup brace, a lace-up brace, and tape), as well as 2 different shoe conditions (cutout shoe [simulated barefoot] and normal shoe). RESULTS: In the simulated barefoot condition, a significantly reduced stabilizing effect for inversion and eversion (19% and 29%, respectively) was found for the stirrup ankle brace. Small decreases were noted with the soft brace and tape, but these were not statistically significant. CONCLUSION: The passive stability characteristics of ankle braces depend to a great extent on being used in combination with a shoe. This is especially true for semirigid braces with stirrup design. Therefore, it is recommended that soft braces (like the one tested in the present investigation) be used in barefoot sports for restricting passive range of motion of the foot and ankle complex. CLINICAL RELEVANCE: This study provides useful information for clinicians to select or recommend an external ankle stabilizing device in barefoot sports to restrict passive range of motion of the foot-ankle complex most effectively.

The influence of external ankle braces on subjective and objective parameters of performance in a sports-related agility course.

With lateral ankle sprains being the most frequent sports-related injury, there is an evident demand for the preventive measures in active individuals with chronic ankle instability. Braces are commonly used for prevention and treatment of ankle injuries. Various investigations-mostly performed with healthy subjects-focused on this problem, yet they often compared only a few models or used only limited testing procedures. However, controversy exists whether braces affect sports performance. The purpose of the present study was to compare the effects of ten different ankle braces-one rigid, five semirigid, four soft models-in a comprehensive evaluation with multiple testing procedures in 34 subjects with self-reported chronic ankle instability. The multiple testing procedures evaluated objective performance-related parameters and subjective parameters related to comfort and stability. The subjects performed an agility course with maximal effort. The course included a vertical jump and a cutting maneuver, both on a force platform, a single leg hopping test on level and inclined plates, a combined straight and curve sprint and sidesteps. Three valid trials were measured and averaged for each brace and every subject. Subjective aspects were evaluated with a questionnaire about handling, perceived restrictions, support and comfort; it was completed after each brace was worn and tried. With regard to the objective parameters, no significant differences were found between the braces except for the rigid brace which showed decreased values for the vertical jump and longer times for the other tests compared to all other braces. The subjective evaluation of the braces revealed significant differences with respect to comfort and handling and therefore, permitted a distinction between semirigid and soft braces. Although significant differences between braces were found in subjective performance restriction, no significant differences were revealed in the objective evaluation. From that point of view, patients could choose a brace model according to their individual needs. A comfortable brace might have a positive influence on the athlete's state of mind although other aspects like the brace's stabilizing effect play an additional role and should also be taken into account for recommendation of braces.

The influence of muscle fatigue on electromyogram and plantar pressure patterns as an explanation for the incidence of metatarsal stress fractures.

BACKGROUND: Stress fractures are common overuse injuries in runners and appear most frequently in the metatarsals. PURPOSE: To investigate fatigue-related changes in surface electromyographic activity patterns and plantar pressure patterns during treadmill running as potential causative factors for metatarsal stress fractures. STUDY DESIGN: Prospective cohort study with repeated measurements. METHODS: Thirty experienced runners volunteered to participate in a maximally exhaustive run above the anaerobic threshold. Surface electromyographic activity was monitored for 14 muscles, and plantar pressures were measured using an in-shoe monitoring system. Fatigue was documented with blood lactate measurements. RESULTS: The results demonstrated an increased maximal force (5%, P < .01), peak pressure (12%, P < .001), and impulse (9%, P < .01) under the second and third metatarsal head and under the medial midfoot (force = 7%, P < .05; pressure = 6%, P < .05; impulse = 17%, P < .01) toward the end of the fatiguing run. Contact area and contact time were only slightly affected. The mean electromyographic activity was significantly reduced in the medial gastrocnemius (-9%, P < .01), lateral gastrocnemius (-12%, P < .01), and soleus (-9%, P < .001) muscles. CONCLUSION: The demonstrated alteration of the rollover process with an increased forefoot loading may help to explain the incidence of stress fractures of the metatarsals under fatiguing loading conditions.

Reduced plantar sensation causes a cautious walking pattern.

The aim of this study was to investigate the influence of reduced plantar sensation on gait patterns during walking in 20 healthy subjects (25.9 +/- years, 61.6 +/- 11.5 kg, 178 +/- 9.5 cm) with no history of sensory disorders. Force plate measurements, electromyography (EMG) measurements and a three-dimensional movement analysis were performed simultaneously during barefoot walking before and after reduction of plantar sensation using an ice immersion technique. The results show that reduced plantar sensation leads to significant changes in gait patterns that are present at the ankle, knee and hip joint and indicate a more cautious ground contact and push-off with modified EMG and motion patterns.

Characteristic plantar pressure distribution patterns during soccer-specific movements.

PURPOSE: To characterize in-shoe pressure measurements during different soccer-specific maneuvers on two playing surfaces to identify the main loading areas of the foot. METHODS: Twenty-one experienced male soccer players participated in the study (25.5 +/- 1.8 years, 78.7 +/- 5.4 kg, and 182.9 +/- 5.7 cm). The Pedar Mobile system was used to collect plantar pressure information inside the soccer shoe. Four soccer-specific movements were performed (normal run, cutting maneuver, sprint, and goal shot) on both a grass and a red cinder surface. RESULTS: Results showed characteristic pressure distribution patterns with specific loading areas of the foot that correspond to the evaluated movements. In addition, loading patterns with higher pressure values than those observed during normal run were found. In cutting, the medial part of the foot; in sprinting, the first and second ray; and in kicking, the lateral part of the foot are predominantly loaded. No global effect of the two surfaces on pressure parameters was found. CONCLUSION: The results of the present investigation suggest that the high load in soccer in combination with a high repetition may have an important influence in the development of overuse injuries.

The main function of ankle braces is to control the joint position before landing.

The aim of the present investigation was to evaluate the stabilizing effect of 10 different ankle braces during simulated inversion on a tilting platform. Twenty-five subjects participated in the study (23 +/- 3 yrs, 71 +/- 12 kg, 177 +/- 9 cm). Ten commercially available ankle braces and a trapdoor in combination with a goniometer system that measured hindfoot inversion inside the shoe were used. Inversion was subdivided into a free fall and a maximum inversion phase. Results showed that all braces restricted inversion significantly between 51% and 15% compared to the no-brace condition but distinct differences between models were found. Maximum inversion angle and inversion velocity were lower for those braces that restricted inversion most effectively during the free fall phase. Reaction times of the peroneus longus did not appear to influence the degree of inversion. Relatively constant differences between free fall and maximum inversion angles for all models (between 6 degrees and 10 degrees) and a high correlation between these two parameters suggests that the main function of ankle braces is to restrict inversion during the free fall phase and not at the extremes of motion.

Changes in talocrural joint contact stress characteristics after simulated rotationplasty.

In order to assess the changes in talocrural joint contact stress after rotationplasty, 10 lower-leg cadaver specimens were axially loaded with 600 N and investigated in two loading situations: (1) Normal loading with a plantigrade foot; (2) in an equinus position of a simulated rotationplasty. Joint contact stress in the talar facet of the talocrural joint was determined with Fuji Prescale film cut to size and analyzed with digital image analysis for joint contact area, mean and peak pressure, contact force, and location of the load application on the trochlea tali. The results demonstrate a significant transfer on the loading zone to the posterior part of the talus (p = 0.005), a significant reduction of the contact area (p = 0.005) and force (p = 0.005), and a significant increase of the mean (p = 0.022) and maximum pressures (p = 0.013). These results indicate that the rotationplasty causes pronounced changes in joint loading characteristics.

Comprehensive testing of 10 different ankle braces. Evaluation of passive and rapidly induced stability in subjects with chronic ankle instability.

OBJECTIVE: The aim of the present investigation was to test the stability of 10 different ankle braces under passive and rapidly induced loading conditions in a population suffering from chronic ankle instability in order to provide objective information to choose or recommend an appropriate model for specific needs. In addition, the relationship between passive and rapidly induced testing of the stabilizing effect against inversion was evaluated to identify if passive support characteristics of braces are reflected under rapidly induced conditions. DESIGN: An experimental in vivo study with a repeated-measures design was used. BACKGROUND: Ankle braces are commonly used for treatment, rehabilitation, and prevention of ankle injuries. A variety of products exists but there is few information available to assist clinicians, physiotherapists and coaches as well as consumers in choosing a brace on a basis of objective information. Furthermore, there is a lack of studies that provide data for both passively and rapidly induced movement of the ankle joint when using different ankle braces. METHODS: Twenty-four subjects with chronic ankle instability participated in the project. Passive ankle range of motion measurements were performed in a custom-built fixture and simulated inversion sprains were elicited on a tilting platform. RESULTS: The tested braces restrict range of motion significantly compared to the no-brace condition for both the passively and rapidly induced inversion and marked differences between braces were revealed. A close relationship between passive and rapidly induced test results for inversion was found. CONCLUSIONS: Passive as well as rapidly induced stability tests provide a basis of objective information to describe the characteristics of different ankle braces. Combined results of passive and rapidly induced inversion as well as correlation between results demonstrate that passive support characteristics of braces are reflected under rapidly induced conditions but the amount of restriction is reduced. Therefore, caution should be taken when recommending braces for applications under dynamic circumstances only on the basis of passive support characteristics. RELEVANCE: A basis of information regarding the stability characteristics of different ankle braces under passive and rapidly induced conditions will help the clinician and consumer in choosing the most appropriate brace model for specific use. The results also provide more insights into factors that influence stability characteristics of ankle braces.

Modified pressure distribution patterns in walking following reduction of plantar sensation.

The aim of the present study was to investigate the influence of reduced plantar sensation on pressure distribution patterns during gait of 40 healthy subjects (25.3+/-3.3 yr, 70.8+/-10.6 kg and 176.5+/-7.8 cm) with no history of sensory disorders. Plantar sensation in the subjects was reduced by using an ice immersion approach, and reduced sensitivity was tested with Semmes-Weinstein monofilaments. All subjects performed six trials of barefoot walking over a pressure distribution platform under normal as well as iced conditions. Plantar cutaneous sensation was significantly reduced after the cooling procedure (p<0.0001). Pressure distribution analysis showed substantially modified plantar pressure distribution patterns during the roll-over process (ROP) under iced conditions. Analysis of peak pressures revealed significant reductions under the toes and under the heel (p<0.001). The contact time and the relative impulse for the whole foot did not change significantly between the two conditions. For the different areas, a significant load shift from the heel and toes towards the central and lateral forefoot and the lateral midfoot was observed. The results indicate the strong influence of reduced afferent information of the sole of the foot on the ROP in walking.