Body Harness Research Articles

Analysis of hazards associated with injuries to the employee’s head during fall arrest

A fall from a height is one of the most serious hazards faced by employees in the work environment. It is present mostly at workstations in such industries as construction, power engineering, mining, storage, etc. Using individual protective equipment against falls from a height is a basic method of protecting workers under such conditions. The choice of this method carries specific risks associated with the functioning of equipment during fall arrest. Hitting elements of the workstation during fall arrest associated with pendulum movement is a very serious threat. This paper presents conditions which trigger pendulum movement during fall arrest and the positions which a human equipped with a full body harness can assume then. Potential effects of the impact of the head against an obstacle during pendulum movement are discussed on the basis of the results of research with an anthropomorphic dummy. The article discusses methods of preventing swing movement and ways of mitigating the effects of collisions with obstacles within the workstation. It also presents the basic requirements for protective helmets intended for use with individual protection equipment against falls from a height.

Definition of the inspection criteria for personal protective equipment (for work at heights) on example of full body harnesses

Works at heights can be unit in the separate sector of works which requires increased risk control and labor protection measures. According to the accident statistics this sector is one of the most hazardous and problematic. The problem of application of full body harnesses to protect workers against the risks of falling from heights is considered in this article. Herewith the importance of operational aspects revealed after purchase of applicable certified personal protection equipment for work at heights (further PPE) is particularly noted. Features of technical/detailed inspections of PPE and training of experts in this field in Russian Federation are presented. The analytical part of the article contains basic information about main damages and standard defects of full body harnesses which could become the basis of a normative document (further ND) for PPE inspection. ND in turn would help to form the general inspection criteria for PPE of various types, and would become normative «foundation» to train specialists. It is shown that GOST R EN 365 need to be reformed in accordance with priorities of domestic market.

Utilization and Effectiveness of Harnesses and Lifelines in Grain Entrapment Incidents: Preliminary Analysis.

No previous studies have been found that document the level of use or validate the effectiveness of safety harnesses and lifelines in the prevention of or extrication from grain entrapments or engulfments. This article addresses that void via analysis of the data contained in the Purdue Agricultural Confined Space Incident Database. A total of 1,147 cases involving entrapments or engulfments in grain masses were mined for terms that might indicate the use of a safety harness, lifeline, fall restraint system, rope, or outside observer. Case information ranged from brief news accounts to comprehensive investigation results. The review turned up 38 incidents (< 5%) in which these safety devices were identified as having been used by either workers or rescuers during access to a storage structure. In 26 of the 38 cases (68%) where safety devices were identified, the entrapment or engulfment resulted in a fatality. The two most common reasons cited for failure of these devices were (1) that the lifeline or rope was too long (17 incidents) and (2) that the worker had removed the harness with the attached lifeline while in the structure (6 incidents). It was also determined that these devices, if used improperly, can lead to secondary injuries of the victim. The preliminary evidence suggests that use of these devices alone does not ensure the user's safety and may even provide a false sense of security if used without proper training. It was further found that an approved body harness and safety line provided little or no protection from either entrapment or falls if used in the presence of vertically crusted grain surfaces, without proper anchors, or not in conjunction with outside observers. The presented results are important for safety professionals to consider as they endeavor to reduce the risk of grain entrapment and engulfment incidents through training, education, selection of personal protective equipment, etc., and should contribute to the development of new structural standards for grain bins. It is the intent of this article to elucidate the importance of training and proper use of these safety devices.

The recovery response to a novel unannounced laboratory-induced slip: The “first trial effect” in older adults

BackgroundAfter a single slip, older adults rapidly make adaptive changes to avoid or eliminate further backward loss of balance or a fall. This rapid adaptation has been termed the “single trial effect”. The purpose of this study was to explore the relationship between the motor errors subjects experienced upon a novel slip and the selection and execution of corrective response by which they modified their ongoing gait pattern and turned it into a protective step. MethodsA forward slip was induced in the laboratory among 145 community-living older (≥65year old) adults who were protected by an overhead full body harness system. An eight-camera motion analysis system recorded subjects' kinematics, which was used to compute their instability (motor error), recovery step placement (response selection), and stability gain (motor correction). FindingsA linear relationship was found between the stability errors at recovery foot liftoff and the distance between the recovery foot and slipping foot at the time of its touchdown, reflecting an appropriate selection of response that was proportionate to the motor error. A linear relationship was also found between this step modification and resulting stability gain, indicating that greater step modification resulted in greater stability gain. This learning behavior was surprisingly consistent regardless whether the outcome was a recovery or a fall. InterpretationsThese results suggest that fallers and non-fallers all have an intact motor learning foundation that has enabled them to rapidly improve their stability in subsequent exposures.

Development of a 3D Gait Measurement Protocol for Amputees Walking on Treadmill

Walking motion is actually a complex activity since it involves many body parts, especially the lower limb. Due to the needs for gait analysis in many medical applications, Biomechanics Research Team at ITB has developed an affordable optical motion analyzer to measure motions of subject walking over ground. However, the needs for multicycles gait data is better met by measuring subjects walking on treadmill. This paper discusses the modification of the developed motion analyzer to accommodate data acquisition of subject walking on treadmill, including those of transfemoral amputees. Seven markers, two 95 fps cameras, a dual-channel Camera Link Acquisition NI PCIe-1430 frame grabber, and a workstation are employed in the optical motion analyzer system. The speed displayed on the treadmill is evaluated. Additional equipment such as the modified hydraulic engine crane and the body harness are introduced to ensure the safety of amputees and avoid the risk of falling down while walking on the treadmill. The modified motion analyzer system is then used to obtain gait parameters of normal (37 males and 31 females) and three amputee subjects. The gait parameters of normal subjects in the treadmill walking shows that there is a decrease in the stride length and range of motion, and increase in the cadence due to walking adaptation. There are also phase shifting and increase in the range of motion for amputee subjects compared to the normal subjects which imply that there is an extra work done by the residual limb in doing walking movement and the amputee subjects try to balance their walking on the treadmill.

RISK ASSESSMENT K3 PADA PROSES PENGOPERASIAN SCAFFOLDING PADA PROYEK APARTEMEN PT. X DI SURABAYA

ABSTRACTProblems that arised when employees works at height are worker did not wear full body harness, lanyard did not hanged perfectly to handrail, did not works according to the procedure, and using unsafe scaffolding. Hazard identification and risk assessment used as prevention for accident when operating scaffolding. This study was an observational study with cross sectional design and analyzed descriptively. The design used for the study carried out by observing cause and effect within a period of time and space. Objects of this study were frame scaffolding and scaffolding PCH, while subjects of this study were SHE Officer, SHE supervisor, workers section structure, finishing, plumbing hydrant, and mechanical engineering. Results of hazard identification using JSA method founds 43 potential hazards originating from 4 different types of work in this project. The results of the risk assessment of 43 potential hazards have been found that 1 hazard have low risk, 40 hazards have moderate risk , and high risk hazard are 2. The dominant risk from the operation of the scaffolding was 40 potential hazards or 93% of the total potential hazards and high-risk hazard eventhough only 5% of all potential hazards remains a top priority and should be controlled soon to reduce the high and medium risk becomes low risk. The likelihood-based control is more possible to reduce risk level than severity-based control.Keywords: risk assessment, scaffolding operation

Harness Suspension Stress: Physiological and Safety Assessment.

Evaluate hemodynamics, subjective discomfort, and biological markers of muscle damage during 30-minutes suspension; and evaluate differences between harness attachment (frontal or dorsal). Heart rate, blood pressure, biological markers of muscle damage, and subjective discomfort were measured. Trial time was shorter in the dorsal versus frontal point of attachment. Hemodynamic shift resulted in the dorsal trial which indicated possible perfusion abnormalities. Hemodynamic adjustments contributed to early termination observed in the dorsal trial. A frontal point of attachment may be more suitable for extended harness exposure.

Contrasting effects of GPS device and harness attachment on adult survival of Lesser Black‐backed Gulls Larus fuscus and Great Skuas Stercorarius skua

Telemetry has become an important method for studying the biology and ecology of animals. However, the impact of tracking devices and their method of attachment on different species across multiple temporal scales has seldom been assessed. We compared the behavioural and demographic responses of two species of seabird, Lesser Black‐backed Gull Larus fuscus and Great Skua Stercorarius skua, to a GPS device attached using a crossover wing harness. We used telemetry information and monitoring of breeding colonies to compare birds equipped with a device and harness, and control birds without an attachment. We assessed whether tagged birds have lower short‐term breeding productivity or lower longer term overwinter return rates (indicative of overwinter survival) than controls. For Great Skua, we also assessed whether territory attendance within the breeding season differed between tagged and control birds. As with previous studies on Lesser Black‐backed Gull, we found no short‐term impacts on breeding productivity or long‐term impacts on overwinter return rates. For Great Skua, there was no evidence for impacts of the device and harness on territory attendance or breeding productivity. However, as found by a previous study of Great Skuas using a different (body) harness design, there was strong evidence of reduced overwinter return rates. Consequently, a device attached using a wing harness was considered suitable for long‐term deployment on Lesser Black‐backed Gulls, but not on Great Skuas. These findings will inform the planning of future tracking studies.

Safety Performance of the Full Harness in Various Falling Postures of Wearer

Fundamental safety measure for falling is to prepare flat and effective wide workplace with guardrails. However, their countermeasures may be difficult to apply for short-duration works and disaster relief works. In such cases, the fall arrest system has been applied to the height workplaces. This study focuses on fundamental characteristics of full body harness in various postures of wearer during falling. Three kinds of situation, such as (1) leg first fall, (2) head first fall, and (3) stop falling when the wearer body in parallel to the ground, were considered to recognize the performance. Experiments were carried out using 735N of human dummy, called HybridIII pedestrian 50%tile model in the automobile industry. The shock-absorber of the Lanyards used in this study were designed about 4kN. Impact force acting on hook, head accelerations, and a chest displacement were measured during falling. From the results, not only the vertical acceleration of the human dummy but also horizontal were measured. Due to the horizontal acceleration, a huge bending moment acting on the dummy's neck observed in several situations. It indicates that the wearer may have risks of whiplash or more serious injuries such as dislocation of cervical vertebrae or spinal injuries. Chest deformations measured in this study were not also small for aged workers. It indicates that there are some risks of rid fractures or related chest injuries. The back of the head crashed aggressively to the D-ring of the full harness when the dummy rebounded due to stop falling by lanyard. Therefore, special helmet to resist the impact force due to D-ring, and the design force of shock-absorber should be reconsidered.

A randomized trial of functional electrical stimulation for walking in incomplete spinal cord injury: Effects on walking competency

BackgroundMulti-channel surface functional electrical stimulation (FES) for walking has been used to improve voluntary walking and balance in individuals with spinal cord injury (SCI).ObjectiveTo investigate short- and long-term benefits of 16 weeks of thrice-weekly FES-assisted walking program, while ambulating on a body weight support treadmill and harness system, versus a non-FES exercise program, on improvements in gait and balance in individuals with chronic incomplete traumatic SCI, in a randomized controlled trial design.MethodsIndividuals with traumatic and chronic (≥18 months) motor incomplete SCI (level C2 to T12, American Spinal Cord Injury Association Impairment Scale C or D) were recruited from an outpatient SCI rehabilitation hospital, and randomized to FES-assisted walking therapy (intervention group) or aerobic and resistance training program (control group). Outcomes were assessed at baseline, and after 4, 6, and 12 months. Gait, balance, spasticity, and functional measures were collected.ResultsSpinal cord independence measure (SCIM) mobility sub-score improved over time in the intervention group compared with the control group (baseline/12 months: 17.27/21.33 vs. 19.09/17.36, respectively). On all other outcome measures the intervention and control groups had similar improvements. Irrespective of group allocation walking speed, endurance, and balance during ambulation all improved upon completion of therapy, and majority of participants retained these gains at long-term follow-ups.ConclusionsTask-oriented training improves walking ability in individuals with incomplete SCI, even in the chronic stage. Further randomized controlled trials, involving a large number of participants are needed, to verify if FES-assisted treadmill training is superior to aerobic and strength training.

A trial of three harness attachment methods and their suitability for long-term use on Lesser Black-backed Gulls and Great Skuas

Tracking devices are useful in studying the movement and behaviour of birds throughout the year. However, the effects of device attachment must be monitored for bird welfare and the scientific veracity of information gathered. We report on a trial of three different harness types (leg-loop, body and wing) for attaching GPS devices to Lesser Black-backed Gulls Larus fuscus and of a leg-loop harness on Great Skuas Stercorarius skua. This trial evaluated the functionality of the device whilst deployed, harness retention and the effects of each harness on the birds. The leg-loop harness prevented the devices from charging, due to feathers overlapping their solar panels, and individuals of both species shed this attachment during the first breeding season. For Lesser Black-backed Gull, devices functioned properly when attached using body and wing harnesses; foraging behaviour and territory attendance of birds were similar to the findings of other studies. Despite small sample sizes, annual adult survival rates for Lesser Black-backed Gull were similar to published estimates, suggesting harnesses had no deleterious effects. The wing harness has a smaller amount of skin contact than the body harness, and a non-constricting fit that better accommodates changes in body size. The wing harness was therefore considered the most appropriate for long-term studies.

Effects of satellite transmitters on captive and wild mallards

ABSTRACTSatellite telemetry has become a leading method for studying large‐scale movements and survival in birds, yet few have addressed potential effects of the larger and heavier tracking equipment on study subjects. We simultaneously evaluated effects of satellite telemetry equipment on captive and wild mallards (Anas platyrhynchos) to assess impacts on behavior, body mass, and movement. We randomly assigned 55 captive ducks to one of 3 treatment groups, including a standard body harness group, a modified harness group, and a control group. Ducks in the control group were not fitted with equipment, whereas individuals in the other 2 groups were fitted with dummy transmitters attached with a Teflon ribbon harness or with a similar harness constructed of nylon cord. At the conclusion of the 14‐week captive study, mean body mass of birds in the control group was 40–105 g (95% CI) greater than birds with standard harnesses, and 28–99 g (95% CI) greater than birds with modified harnesses. Further, results of focal behavior observations indicated ducks with transmitters were less likely to be in water than control birds. We also tested whether movements of wild birds marked with a similar Teflon harness satellite transmitter aligned with population movements reported by on‐the‐ground observers who indexed local abundances of mid‐continent mallards throughout the non‐breeding period. Results indicated birds marked with satellite transmitters moved concurrently with the larger unmarked population. Our results have broad implications for field research and suggest that investigators should consider potential for physiological and behavioral effects brought about by tracking equipment. Nonetheless, results from wild ducks indicate satellite telemetry has the potential to provide useful movement data. © 2014 The Wildlife Society.

Evaluation of upper body muscle activity during cardiopulmonary resuscitation performance in simulated microgravity

Performance of efficient single-person cardiopulmonary resuscitation (CPR) is vital to maintain cardiac and cerebral perfusion during the 2–4min it takes for deployment of advanced life support during a space mission. The aim of the present study was to investigate potential differences in upper body muscle activity during CPR performance at terrestrial gravity (+1Gz) and in simulated microgravity (μG). Muscle activity of the triceps brachii, erector spinae, rectus abdominis and pectoralis major was measured via superficial electromyography in 20 healthy male volunteers. Four sets of 30 external chest compressions (ECCs) were performed on a mannequin. Microgravity was simulated using a body suspension device and harness; the Evetts–Russomano (ER) method was adopted for CPR performance in simulated microgravity. Heart rate and perceived exertion via Borg scores were also measured. While a significantly lower depth of ECCs was observed in simulated microgravity, compared with +1Gz, it was still within the target range of 40–50mm. There was a 7.7% decrease of the mean (±SEM) ECC depth from 48±0.3mm at +1Gz, to 44.3±0.5mm during microgravity simulation (p<0.001). No significant difference in number or rate of compressions was found between the two conditions. Heart rate displayed a significantly larger increase during CPR in simulated microgravity than at +1Gz, the former presenting a mean (±SEM) of 23.6±2.91bpm and the latter, 76.6±3.8bpm (p<0.001). Borg scores were 70% higher post-microgravity compressions (17±1) than post +1Gz compressions (10±1) (p<0.001). Intermuscular comparisons showed the triceps brachii to have significantly lower muscle activity than each of the other three tested muscles, in both +1Gz and microgravity. As shown by greater Borg scores and heart rate increases, CPR performance in simulated microgravity is more fatiguing than at +1Gz. Nevertheless, no significant difference in muscle activity between conditions was found, a result that is favourable for astronauts, given the inevitable muscular and cardiovascular deconditioning that occurs during space travel.

Impact of Harness Fit on Suspension Tolerance

This study investigated the effect of body size and shape and harness fit on suspension tolerance time. Fall victims may develop suspension trauma, a potentially fatal reduction of return blood flow from legs to the heart and brain, after a successfully arrested fall if they are not rescued quickly or the harness does not fit them well. For this study, 20 men and 17 women with construction experience were suspended from the dorsal D-ring of a full-body fall-arrest harness. Their suspension tolerance time, physical characteristics, and harness fit levels were assessed. Body characteristics (i.e., weight, stature, upper- and lower-torso depths) were associated with decreased suspension tolerance time (r = -.36 - -.45, p < or = .03). In addition, harness fit affected suspension tolerance time; workers with a torso angle of suspension greater than 35 degrees, a thigh strap angle greater than 50 degrees, or a poorly fitting harness size had shorter suspension tolerance time (mean differences = 14, 11, and 9.8 min, respectively, p < or = .05). Body size and harness fit were predictors of suspension tolerance time. Selecting well-fit harnesses and establishing a 9-min rescue plan are suggested to ensure that no more than 5% of workers would experience suspension trauma. The study provides a basis for harness designers, standards writers, and manufacturers to improve harness configurations and testing requirements for better worker protection against suspension trauma.

Plasticity of corticospinal neural control after locomotor training in human spinal cord injury.

Spinal lesions substantially impair ambulation, occur generally in young and otherwise healthy individuals, and result in devastating effects on quality of life. Restoration of locomotion after damage to the spinal cord is challenging because axons of the damaged neurons do not regenerate spontaneously. Body-weight-supported treadmill training (BWSTT) is a therapeutic approach in which a person with a spinal cord injury (SCI) steps on a motorized treadmill while some body weight is removed through an upper body harness. BWSTT improves temporal gait parameters, muscle activation patterns, and clinical outcome measures in persons with SCI. These changes are likely the result of reorganization that occurs simultaneously in supraspinal and spinal cord neural circuits. This paper will focus on the cortical control of human locomotion and motor output, spinal reflex circuits, and spinal interneuronal circuits and how corticospinal control is reorganized after locomotor training in people with SCI. Based on neurophysiological studies, it is apparent that corticospinal plasticity is involved in restoration of locomotion after training. However, the neural mechanisms underlying restoration of lost voluntary motor function are not well understood and translational neuroscience research is needed so patient-orientated rehabilitation protocols to be developed.

Effects of Different Elastic Cord Assistance Levels on Vertical Jump

Tran, TT, Brown, LE, Coburn, JW, Lynn, SK, Dabbs, NC, Schick, MK, Schick, EE, Khamoui, AV, Uribe, BP, and Noffal, GJ. Effects of different elastic cord assistance levels on vertical jump. J Strength Cond Res 25(12): 3472-3478, 2011-Currently, little research has been conducted using body weight reduction (BWR) as a means to enhance vertical jump. The purpose of this study was to determine the effects of different elastic cord assistance levels on vertical jump height (JH), takeoff velocity (TOV), relative ground reaction force (rGRF), relative impact force (RIF), and descent velocity (DV). Thirty recreationally trained college men and women (M = 15, W = 15) completed 3 testing sessions consisting of 5 conditions: 0, 10, 20, 30, and 40% BWR. In all BWR conditions, the subjects wore a full body harness while being attached to 2 elastic cords suspended from the ceiling and a linear velocity transducer. They then performed 3 maximal countermovement jumps with arm swing on a force plate. The results indicated no interaction of condition by sex for any variable; however, there was a significant (p < 0.05) main effect for condition for each variable. The JH significantly increased across all conditions (0%: 43.73 ± 1.62 cm, 40%: 64.77 ± 2.36 cm). The TOV at 30% (2.73 ± 0.34 m·s) was significantly greater than that at 0% (2.59 ± 0.39 m·s) and 10% (2.63 ± 0.34 m·s), whereas that at 40% (2.79 ± 0.43 m·s) was significantly greater than that at >0, 10, and 20%. The rGRF at 30% (18.62 ± 4.35 N·kg) was significantly greater than that at >0, 10, and 20%, whereas that at 40% (21.38 ± 5.21 N·kg) was significantly greater than in all conditions. The RIF at 20, 30, and 40% (40%: 61.60 ± 18.53 N·kg) was significantly greater than that at 0% (44.46 ± 9.12 N·kg). The DV at 20% (2.61 ± 0.31 m·s) was significantly greater than at 10%, whereas those at 30 and 40% (2.8 ± 0.41 m·s) were significantly greater than at 0, 10, and 20%. These results demonstrate that using different elastic cord levels to reduce body weight appears effective for increasing ascent and descent force and velocity variables. Future research should investigate greater BWR% and chronic training.

Data-loggers carried on a harness do not adversely affect sheep locomotion

The use of externally fitted motion sensors to animal subjects has the potential for allowing researchers to investigate subtle changes in animal movement that may occur with the onset of specific diseases. However, it is crucial to consider whether or not the use of such technology has an effect on the variables measured. Here, we examine the effect of a body harness data logging device on the locomotive patterns of female Merino sheep, Ovis aries. We extracted locomotion variables typical of motion sensor data (stride frequency, stride length, gait type, speed, and limb velocity) from high-definition video collected under controlled conditions. We found no significant difference between the variables measured in the harnessed and unharnessed conditions. Overall, our experiment demonstrates that data-loggers carried on a harness do not adversely affect sheep locomotion, and extended periods of habituation post-instalment of devices should ensure consistency and accuracy of data in future experiments.

Effect Of Elastic Assistance Vs. Bodyweight Training On Vertical Jump

Athletes who depend on vertical jump performance may benefit from integrating a training program that includes elastic assistance. Recent research has shown that training with low level elastic assistance may increase vertical jump height in comparison to training at body weight. PURPOSE: To determine the effects of 30% elastic assistance versus body weight training on vertical jump. METHODS: Sixteen recreationally trained male subjects (age 21.93 ± 2.04 yrs, height 173.64 ± 5.36 cm, mass 73.44 ± 3.90 kg) were divided into three groups: control (C), body weight (BW), or 30% body weight reduction (BWR). Training consisted of jumping 2 days a week for 6 weeks. In the BWR condition, subjects wore a full body harness that was attached to four elastic cords suspended from the ceiling as they completed maximal countermovement jumps with arm swing. Each group completed pre and post-tests of three maximal countermovement jumps in both conditions, (BW and BWR). All jumps were performed on a force plate. The training program progressively increased volume over the first five weeks, and then tapered on the 6th week. Maximum values for vertical jump height and relative ground reaction force (rGRF) were analyzed for each condition and time. RESULTS: Vertical jump collapsed across group demonstrated a significant (P<0.05) increase across time, (pre: 66.70 ± 2.20 cm, post: 69.54 ± 2.41 cm) and was significantly greater for BWR (75.92 ± 2.39 cm) than BW (59.76 ± 2.00 cm). For rGRF, there was a main effect for time and condition across group. The control group showed no significant (P>0.05) difference over time. The BW group significantly (P<0.05) increased over time, (pre: 16.65 ± 1.42 N/kg, post: 18.48 ± 1.27 N/kg) and it was significantly (P<0.05) greater with assistance, (BWR: 20.24 ± 1.96 N/kg, BW: 14.73 ±.82 N/kg). The BWR group significantly (P<0.05) increased over time, (pre: 18.25 ± 1.53 N/kg, post: 22.60 ± 2.41 N/kg) and it was significantly (P<0.05) greater with assistance, (BWR: 25.09 ± 2.1 N/kg, BW: 15.94 ± 1.3 N/kg). CONCLUSION: The greatest increases in rGRF were from the BWR group (∼24%) compared to the BW group (∼11%). Therefore, athletes who are dependent on the vertical jump for their specific sport should incorporate jumping with elastic assistance in their training program.

Effect of Different Levels of Assisted Jumping on Countermovement Unloading Force and Velocity

PURPOSE: The purpose of this study was to investigate the effect of elastic band assistance on VJ CM unloading force and velocity. METHODS: Thirty recreationally trained college men and women (M=15, W=15) completed three VJ testing sessions consisting of five conditions: 0%, 10%, 20%, 30%, and 40% body weight reduction (BWR). In all BWR conditions, subjects wore a full body harness while attached to two elastic cords suspended from the ceiling and performed three maximal VJ's with CM and arm swing on a force plate. In addition, a linear velocity transducer was attached to the subject's hip to determine the velocity-time curve. Percent unloading from body weight to minimal CM force and maximal CM velocity at each condition were recorded for analysis. RESULTS: Results indicated there were no sex by condition interactions (p>.05), but there were significant (p<.05) main effects for condition for both force and velocity. Countermovement unloading percentages were not different between 0% (64.62+22.51%) and 10% (70.75+14.41%), or between 20% (77.05+15.71%) and 30% (81.08+15.48%), or between 30% and 40% (83.88+13.79) BWR. Both 30% and 40% were greater than 10% and 0%, but only 40% was greater than 20%. CM velocities under all elastic conditions were significantly faster than 0% (0%=.99+.25 m/s, 10%=1.19+.26 m/s, 20%=1.24+.30 m/s, 30%=1.29+.26 m/s, 40%=1.23+.17 m/s). Only 30% was significantly faster than 10%. CONCLUSIONS: These data suggest that assisted jumping alters countermovement mechanics. Therefore, future research should investigate the chronic effects of assisted jumping on normal bodyweight VJ performance.

Effects of Assisted Jumping on Relative Impact Force and Descent Velocity

Unassisted increased jump height subsequently increases descending velocity resulting in increased impact forces. Increased impact forces produce greater eccentric forces, which may lead to greater muscular adaptations. This is less well understood during an assisted jump. PURPOSE: The purpose of this study was to investigate the effects of different assisted jumping conditions on relative impact forces (RIF) and descent velocity (DV). METHODS: Thirty recreationally trained subjects (male = 15, female = 15) completed three testing sessions consisting of five experimental conditions: body weight reduction (BWR) of 0%, 10%, 20%, 30%, or 40%. In all conditions, subjects wore a full body harness while attached to two elastic cords, suspended and bolted to the ceiling. Subjects performed three maximal countermovement jumps with arm swing on a force plate with a velocity transducer for each condition. Maximum jump height (JH) values using a vertec for each condition were used for analyses. RESULTS: JH significantly (p < 0.05) increased across conditions (0% = 35.14 ± 9.02 cm, 40% = 79.44 ± 14.12 cm). Additionally, DV at 30% and 40% were significantly greater than 0%, 10%, and 20%, however, no differences were found between 30% and 40% (0% = 2.57 ± 0.30 m/s, 40% = 2.78 ± 0.35 m/s). Lastly, RIF was significantly greater across conditions from 10–30% (0% = 44.46 ± 9.12 N/kg, 30% = 57.66 ± 19.16 N/kg) when compared to 0%. Conclusion: Increased DV coupled with decreased body weight greater than 30% results in increased relative eccentric forces. Practical Applications: Assisted jumping at BWR ≥ 30% may augment eccentric forces and enhance muscular adaptations.