Dr. Richard C. Nelson: An Important Multigenerational Father of Biomechanics.

Dr. Richard Nelson is internationally acknowledged in many countries as an extremely important leader in the emergence of biomechanics of human movement as a respected scientific discipline. As his PhD graduates, and, subsequently, their graduates, have become faculty members at many universities, Dr. Nelson's influence has grown for more than 50 years via several generations of his biomechanics "children." It was probably never known to him that he also had significant influence on all laboratory-based subdisciplines of the undergraduate and graduate education and faculty research programs of the then new (1967) Department of Kinesiology at the University of Waterloo, Canada. The teaching and research programs included not only biomechanics but also exercise and work physiology, anatomy, biochemistry, and neurophysiology of human movement.

Voluntary Muscle Relaxation Can Mitigate Fatigue and Improve Countermovement Jump Performance.

Pinto, BL and McGill, SM. Voluntary muscle relaxation can mitigate fatigue and improve countermovement jump performance. J Strength Cond Res 34(6): 1525-1529, 2020-When muscles contract, they create force and stiffness. Thus, muscle activation and relaxation must be strategically sequenced to coordinate and control movement, to enhance athletic variables such as speed and strength. However, research has favored investigation of muscle activation over relaxation. Athletes such as runners, swimmers, and boxers often shake their limbs to allow the muscle to oscillate freely, immediately before a bout. The purpose was to investigate whether shaking the lower limbs with the intention to voluntarily relax the muscles of the limb has an effect on countermovement jump (CMJ) performance. Subjects performed 10 maximal effort CMJs with 30 seconds of rest between each jump. During the rest period, they either performed the relaxation technique or control condition (standing still). Statistical significance was considered at p < 0.05. Subjects significantly improved jump height, compared with their first jump of the day, when performing the relaxation technique. To further investigate the mechanism of enhancement, subjects were grouped into responders and nonresponders. The responder group significantly decreased their jump height and concentric phase impulse (relative to the first jump) during the control condition compared with the nonresponder group, indicating fatigue. When performing the relaxation technique, the responder group improved their jump height and mitigated fatigue by significantly increasing their unweighting impulse and unweighting force. The relaxation technique improved CMJ performance, specifically in those that fatigue with consecutive bouts, by enhancing unweighting, that requires muscle relaxation, rather than propulsion that requires activation. This technique can be useful for training or competition.

Spine loading during laboratory-simulated fireground operations - inter-individual variation and method of load quantification.

Spine loading data are needed to design low-back health-preserving ergonomic interventions for firefighters. Study objectives were to quantify spine loads during simulated fireground operations using simple (polynomial) and advanced (EMG-assisted musculoskeletal model) methods and to describe the variation in spine loads between performers (N = 20). Spine compression forces differed by as much as 5.5 times bodyweight between individuals performing identical tasks. Anteroposterior and mediolateral shear forces varied by as much 3.2 and 2.1 times bodyweight between individuals performing the same tasks, respectively. Large variations in spine load magnitudes were documented regardless of whether simple or advanced quantification methods were used. Results suggest that low-back loading demands on the fireground would vary widely depending on the physical characteristics of individual firefighters, movement strategies employed, and tasks performed. Thus, personalised ergonomic interventions are warranted to regulate spine loading and load tolerance in firefighters. Practitioner summary: Even when performing the same work, the associated spine loading demands will vary widely across people due to differences in their body sizes, shapes, and movement strategies. Therefore, personalised interventions are needed to regulate spine loading and load tolerance in workers (e.g. obesity prevention, physical capacity-building exercise, and movement [re]training).

Evidence on the Ability of a Pneumatic Decompression Belt to Restore Spinal Height Following an Acute Bout of Exercise.

OBJECTIVE: The purpose of this study was to evaluate the ability of a pneumatic decompression belt to restore spinal height lost following an acute bout of exercise that induced compression. METHODS: This study implemented a test-retest repeated measures design in which twelve participants (male = 10, female = 2) age, 21.5 ± 1.0 years; height, 179.0 ± 7.70 cm; weight, 84.0 ±11.5 kg; were recruited from a university population and acted as their own control. All participants were healthy with no previous history of disabling back pain, and were frequent weight trainers. A stadiometer was used to measure spinal height at baseline, then following an acute bout of exercise and then again following the intervention (use of a pneumatic decompression belt for 20 minutes) or control (lying supine for 20 minutes). A 2-way repeated measures ANOVA was performed on the change in spinal height in order to evaluate differences between measurement phases and intervention conditions. RESULTS: The use of the decompression belt increased spinal height gain (4.3 ± 3.0 mm) significantly more than the control condition (1.8 ± 1.2 mm) following an acute bout of weightlifting exercises known to elicit high compressive loads on the lumbar spine. CONCLUSION: The pneumatic decompression belt restored spinal height faster than a non-belt wearing condition in young healthy asymptomatic participants.

Documenting female spine motion during coitus with a commentary on the implications for the low back pain patient.

PURPOSE: To describe female lumbar spine motion and posture characteristics during coitus and compare these characteristics across five common coital positions. Exacerbation of low back pain during coital movements and positions is a prevalent issue reported by female low back pain (LBP) patients. To address this problem, the first study to examine lumbar spine biomechanics during coitus was conducted. METHODS: Ten healthy males and females performed coitus in the following pre-selected positions and variations: QUADRUPED (fQUAD1 and fQUAD2 where the female is supporting her upper body with her elbows and hands, respectively), MISSIONARY (fMISS1 and fMISS2 where the female is minimally and more flexed at the hips and knees, respectively), and SIDELYING. An electromagnetic motion capture system was used to measure three-dimensional lumbar spine angles that were normalized to maximum active range of motion-a transmitter and receiver were affixed to the skin overlying the lateral aspect of the pelvis and the spinous process of the twelfth thoracic vertebra, respectively. To determine if each coital position had distinct spine kinematic profiles (i.e., amplitude probability distribution function and total range of lumbar spine motion), separate univariate general linear models followed by Tukey's honestly significant difference post hoc analysis were used. The presentation of coital positions was randomized. RESULTS: Female lumbar spine movement varied depending on the coital position; both variations of QUADRUPED, fQUAD1 and fQUAD2, were found to use a significantly greater range of spine motion than fMISS2 (p = 0.017 and p = 0.042, respectively). With the exception of both variations of MISSIONARY, fMISS1 and fMISS2, the majority of the range of motion used was in extension. These findings are most pertinent to patients with LBP that is exacerbated by motions or postures. Based on the spine kinematic profiles of each position, the least-to-most recommended positions for a female flexion-intolerant patient are: fMISS2, fMISS1, fQUAD1, fSIDE, and fQUAD2. These recommendations would be contraindicated for the extension-intolerant patient. CONCLUSIONS: The findings provided here may guide the clinician's specific recommendations, including alternative coital positions and/or movement patterns or suggesting a lumbar support, depending on the female LBP patient's specific motion and posture intolerances.

A six-week trial of hula hooping using a weighted hoop: effects on skinfold, girths, weight, and torso muscle endurance.

Novel ideas for core endurance training are continually being created. However, studies of their mechanism of action assist in evaluation of their potential as a training tool, for a variety of people and purposes. The specific purpose of this study was to evaluate a weighted hula hooping training program for its efficacy on improving core muscular endurance and influence on measures of body composition. Eighteen women participated in a weighted hula hooping trial lasting 6 weeks, although only 13 returned for posttrial re-assessment. Hip and waist circumferences, 5 torso muscle endurance tests, and 5 skinfold measurements ("sum of 5") were measured before and after the exercise program. Paired samples t-tests were performed to examine pre/post changes. On average, participants experienced a significant decrease in waist and hip circumference -3.4 cm (p < 0.01) and -1.4 cm (p ≤ 0.05), respectively and waist-to-hip ratio from 89.3 cm down to 87.3 cm (t = 3.312, p < 0.01). There were no significant changes in torso muscular endurance after the 6 weeks of hooping; however, the average "sum of 5" skinfold measurements increased by 10.5 cm (p ≤ 0.05). This study of weighted hula hooping suggested that regular hooping was associated with reduced waist and hip girth together with a redistribution of body mass; however, there were no improvements in torso muscular endurance as measured by isometric testing.

Effect of long-term isometric training on core/torso stiffness.

Although core stiffness enhances athletic performance traits, controversy exists regarding the effectiveness of isometric vs. dynamic core training methods. This study aimed to determine whether long-term changes in stiffness can be trained, and if so, what is the most effective method. Twenty-four healthy male subjects (23 ± 3 years; 1.8 ± 0.06 m; 77.5 ± 10.8 kg) were recruited for passive and active stiffness measurements before and after a 6-week core training intervention. Twelve subjects (22 ± 2 years; 1.8 ± 0.08 m; 78.3 ± 12.3 kg) were considered naive to physical and core exercise. The other 12 subjects (24 ± 3 years; 1.8 ± 0.05 m; 76.8 ± 9.7 kg) were Muay Thai athletes (savvy). A repeated-measures design compared core training methods (isometric vs. dynamic, with a control group) and subject training experience (naive vs. savvy) before and after a 6-week training period. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed through a quick release mechanism. Passive stiffness increased after the isometric training protocol. Dynamic training produced a smaller effect, and as expected, there was no change in the control group. Active stiffness did not change in any group. Comparisons between subject and training groups did not reveal any interactions. Thus, an isometric training approach was superior in terms of enhancing core stiffness. This is important since increased core stiffness enhances load bearing ability, arrests painful vertebral micromovements, and enhances ballistic distal limb movement. This may explain the efficacy reported for back and knee injury reduction.

FMS Scores Change With Performers' Knowledge of the Grading Criteria-Are General Whole-Body Movement Screens Capturing "Dysfunction"?

Deficits in joint mobility and stability could certainly impact individuals' Functional Movement Screen (FMS) scores; however, it is also plausible that the movement patterns observed are influenced by the performers' knowledge of the grading criteria. Twenty-one firefighters volunteered to participate, and their FMS scores were graded before and immediately after receiving knowledge of the movement patterns required to achieve a perfect score on the FMS. Standardized verbal instructions were used to administer both screens, and the participants were not provided with any coaching or feedback. Time-synchronized sagittal and frontal plane videos were used to grade the FMS. The firefighters significantly (p < 0.001) improved their FMS scores from 14.1 (1.8) to 16.7 (1.9) when provided with knowledge pertaining to the specific grading criteria. Significant improvements (p < 0.05) were also noted in the deep squat (1.4 [0.7]-2.0 [0.6]), hurdle step (2.1 [0.4]-2.4 [0.5]), in-line lunge (2.1 [0.4]-2.7 [0.5]), and shoulder mobility (1.8 [0.8]-2.4 [0.7]) tests. Because a knowledge of a task's grading criteria can alter a general whole-body movement screen score, FMS or otherwise, observed changes may not solely reflect "dysfunction." The instant that individuals are provided with coaching and feedback regarding their performance on a particular task, the task may lose its utility to evaluate the transfer of training or predict musculoskeletal injury risk.

Exercise-Based Performance Enhancement and Injury Prevention for Firefighters: Contrasting the Fitness- and Movement-Related Adaptations to Two Training Methodologies.

Using exercise to enhance physical fitness may have little impact on performers' movement patterns beyond the gym environment. This study examined the fitness and movement adaptations exhibited by firefighters in response to 2 training methodologies. Fifty-two firefighters were assigned to a movement-guided fitness (MOV), conventional fitness (FIT), or control (CON) group. Before and after 12 weeks of training, participants performed a fitness evaluation and laboratory-based test. Three-dimensional lumbar spine and frontal plane knee kinematics were quantified. Five whole-body tasks not included in the interventions were used to evaluate the transfer of training. FIT and MOV groups exhibited significant improvements in all aspects of fitness; however, only MOV exhibited improvements in spine and frontal plane knee motion control when performing each transfer task (effect sizes [ESs] of 0.2-1.5). FIT exhibited less controlled spine and frontal plane knee motions while squatting, lunging, pushing, and pulling (ES: 0.2-0.7). More MOV participants (43%) exhibited only positive posttraining changes (i.e., improved control), in comparison with FIT (30%) and CON (23%). Fewer negative posttraining changes were also noted (19, 25, and 36% for MOV, FIT, and CON). These findings suggest that placing an emphasis on how participants move while exercising may be an effective training strategy to elicit behavioral changes beyond the gym environment. For occupational athletes such as firefighters, soldiers, and police officers, this implies that exercise programs designed with a movement-oriented approach to periodization could have a direct impact on their safety and effectiveness by engraining desirable movement patterns that transfer to occupational tasks.

The Influence of Load and Speed on Individuals' Movement Behavior.

Because individuals' movement patterns have been linked to their risk of future injury, movement evaluations have become a topic of interest. However, if individuals adapt their movement behavior in response to the demands of a task, the utility of evaluations comprising only low-demand activities could have limited application with regard to the prediction of future injury. This investigation examined the impact of load and speed on individuals' movement behavior. Fifty-two firefighters performed 5 low-demand (i.e., light load, low movement speed) whole-body tasks (i.e., lift, squat, lunge, push, and pull). Each task was then modified by increasing the speed, external load, or speed and load. Select measures of motion were used to characterize the performance of each task, and comparisons were made between conditions. The participants adapted their movement behavior in response to the external demands of a task (64 and 70% of all the variables were influenced [p ≤ 0.05] by changing the load and speed, respectively), but in a manner unique to the task and type of demand. The participants exhibited greater spine and frontal plane knee motion in response to an increase in speed when compared with increasing loads. However, there were a large number of movement strategies exhibited by individual firefighters that differed from the group's response. The data obtained here imply that individuals may not be physically prepared to perform safely or effectively when a task's demands are elevated simply because they exhibit the ability to perform a low-demand activity with competence. Therefore, movement screens comprising only low-demand activities may not adequately reflect an individual's capacity, or their risk of injury, and could adversely affect any recommendations that are made for training or job performance.

Analysis of pushing exercises: muscle activity and spine load while contrasting techniques on stable surfaces with a labile suspension strap training system.

Labile surfaces in the form of suspension straps are increasingly being used as a tool in resistance training programs. Pushing is a common functional activity of daily living and inherently part of a well-rounded training program. This study examined pushing exercises performed on stable surfaces and unstable suspension straps, specifically muscle activation levels and spine loads were quantified together with the influence of employing technique coaching. There were several main questions that this study sought to answer: Which exercises challenged particular muscles? What was the magnitude of the resulting spine load? How did stable and unstable surfaces differ? Did coaching influence the results? Fourteen men were recruited as part of a convenience sample (mean age, 21.1 ± 2.0 years; height, 1.77 ± 0.06 m; mean weight, 74.6 ± 7.8 kg). Data were processed and input to a sophisticated and anatomically detailed 3D model that used muscle activity and body segment kinematics to estimate muscle force-in this way, the model was sensitive to the individuals choice of motor control for each task; muscle forces and linked segment joint loads were used to calculate spine loads. Exercises were performed using stable surfaces for hand/feet contact and repeated where possible with labile suspension straps. Speed of movement was standardized across participants with the use of a metronome for each exercise. There were gradations of muscle activity and spine load characteristics to every task. In general, the instability associated with the labile exercises required greater torso muscle activity than when performed on stable surfaces. Throughout the duration of an exercise, there was a range of compression; the TRX push-up ranged from 1,653 to 2,128.14 N, whereas the standard push-up had a range from 1,233.75 to 1,530.06 N. There was no significant effect of exercise on spine compression (F(4,60) = 0.86, p = 0.495). Interestingly, a standard push-up showed significantly greater shear than TRX angle 1 (p = 0.02), angle 2 (p = 0.01), and angle 3 (p = 0.02). As with any training program for the elite or recreational athlete alike, specific exercises and programs should reflect one's injury history, capabilities, limitations, and training goals. Although none of the exercises examined here breached the NIOSH action limit for compression, those exercises that produced higher loads should be used relative to the individual. Thus, the atlas of muscle activation, compression, and shear forces provided can be used to create an appropriate program. Those individuals not able to tolerate certain loads may refer to the atlas and choose exercises that minimize load and still provide sufficient muscle activation. Conversely, an individual with a resilient back that requires an increased muscular challenge may choose exercises with higher muscle activation and spine load. This helps the individual, trainer, or coach in program design respecting individual differences and training goals.

Exercises to activate the deeper abdominal wall muscles: the Lewit: a preliminary study.

The abdominal wall is a prime target for therapeutic exercises aimed to prevent and rehabilitate low back pain and to enhance performance training. This study examined the "Lewit," a corrective exercise prescribed for several purposes, which is performed lying supine in a crook-lying position and involves forceful breathing. Muscle activation and lumbar posture were compared with bracing the abdominal wall (stiffening) with robust effort and "hollowing" (attempting to draw in the wall toward the naval) with robust effort. Eight healthy male volunteers with 6 channels of electromyography were collected by means of surface electrode pairs of the rectus abdominis, external oblique, and internal oblique (IO) together with lumbar motion. The Lewit exercise caused higher muscle activity in the deeper abdominal wall muscles, in particular the IO and by default the transverse abdominis were activated at 54% maximum voluntary contractions (MVCs) on average and 84% MVC peak with no change in spine posture to maintain the elastic equilibrium of the lumbar spine. The Lewit is a deep oblique muscle activation exercise, and the activation levels are of a sufficient magnitude for training muscle engrams. This information will assist strength and conditioning coaches with program design decisions where this corrective abdominal exercise may be considered for clients who elevate the ribcage during strength exertions, or for clients targeting the deep obliques.

Physical fitness improvements and occupational low-back loading - an exercise intervention study with firefighters.

The impact of exercise on firefighter job performance and cardiorespiratory fitness has been studied extensively, but its effect on musculoskeletal loading remains unknown. The aim of this study was to contrast the physical fitness and low-back loading outcomes of two groups of firefighters who completed different exercise programmes. Before and after 12 weeks of exercise, subjects performed a physical fitness test battery, the Functional Movement Screen™ (FMS) and simulated job tasks during which peak L4/L5 joint compression and reaction shear forces were quantified using a dynamic biomechanical model. Subjects who exercised exhibited statistically significant improvements (p < 0.05) in body composition, cardiorespiratory fitness, muscular strength, power, endurance and flexibility, but FMS scores and occupational low-back loading measures were not consistently affected. Firefighters who are physically fit are better able to perform essential job duties and avoid cardiac events, but short-term improvements in physical fitness may not necessarily translate into reduced low-back injury risk.

The use of a novel injectable hydrogel nucleus pulposus replacement in restoring the mechanical properties of cyclically fatigued porcine intervertebral discs.

Repeated flexion and extension of an intervertebral disc has been shown to affect the angular stiffness of spinal motion segments and is a barometer of the mechanical integrity of the disc. A degenerated disc that loses height causes higher levels of stress on the annulus and facet joints which may increase its level of degeneration; restoring disc height may therefore help to slow this degenerative cascade. Previous research has indicated that nucleus implants have the potential to improve the mechanical characteristics of a disc and an implant that is custom-fit to the intervertebral disc yields the best results with respect to decreasing annular degeneration. Two groups of porcine spinal motion segments were exposed to repeated flexion and extension. One group was then injected with a novel hydrogel while the other group was used as a control. Both groups were then exposed to another round of cyclic flexion and extension to examine the effect that the hydrogel had on restoring the original mechanics to the motion segments. Angular stiffness was restored to the group which received the hydrogel injection in addition to a significant improvement in specimen height. No significant changes were seen in the group which did not receive an injection. It would appear that use of the novel injectable hydrogel is able to restore angular stiffness to cyclically fatigued spinal motion segments. It is also important to note that continued repetition of the event causing specimen fatigue after performing hydrogel injection will result in an eventual return to the same fatigued state.

Improvements in hip flexibility do not transfer to mobility in functional movement patterns.

The purpose of this study was to analyze the transference of increased passive hip range of motion (ROM) and core endurance to functional movement. Twenty-four healthy young men with limited hip mobility were randomly assigned to 4 intervention groups: group 1, stretching; group 2, stretching plus hip/spine disassociation exercises; group 3, core endurance; and group 4, control. Previous work has documented the large increase in passive ROM and core endurance that was attained over the 6-week interventions, but whether these changes transferred to functional activities was unclear. Four dynamic activities were analyzed before and after the 6-week interventions: active standing hip extension, lunge, a standing twist/reach maneuver, and exercising on an elliptical trainer. A Vicon motion capture system collected body segment kinematics, with hip and lumbar spine angles subsequently calculated in Visual 3D. Repeated measures analyses of variance determined group effects on various hip and spine angles, with paired t-tests on specific pre/post pairs. Despite the large increases in passive hip ROM, there was no evidence of increased hip ROM used during functional movement testing. Similarly, the only significant change in lumbar motion was a reduction in lumbar rotation during the active hip extension maneuver (p < 0.05). These results indicate that changes in passive ROM or core endurance do not automatically transfer to changes in functional movement patterns. This implies that training and rehabilitation programs may benefit from an additional focus on 'grooving' new motor patterns if newfound movement range is to be used.

Low back loads while walking and carrying: comparing the load carried in one hand or in both hands.

This study investigates the consequences of carrying load in one hand versus both hands. Six participants walked carrying buckets containing various weights. The weight was either carried in one hand or distributed evenly between both hands. Electromyography, force plate and body kinematic data were input to a three-dimensional anatomically detailed model of the spine to calculate spine loading. Carrying loads in one hand resulted in more load on the low back than when the load was split between both hands. When carrying 30 kg in one hand, the low back compression exceeded 2800 N; however, splitting the load between hands reduced low back compression to 1570 N (reduction of 44%). Doubling the total load by carrying 30 kg in each hand actually produced lower spine compression than when carrying 30 kg in one hand. Balancing the load between both hands when carrying material has merit and should be considered when designing work. PRACTITIONER SUMMARY: Carrying a load in one hand (30 kg) resulted in more spine load than splitting the same load between both hands (15 kg). When carrying double the load in both hands (30 kg in each hand vs. 30 kg in one hand), spine load decreased, suggesting merit in balancing load when designing work.

Changes in torso muscle endurance profiles in children aged 7 to 14 years: reference values.

OBJECTIVE: To establish torso muscle endurance values in children aged 7 to 14 years, as well as ratios between torso extensors, flexors, and lateral torso flexors, with applications in clinical assessment, rehabilitation, physical education targets, and athletic training program designs. It was hypothesized that boys and girls mature differently in terms of torso muscle endurance. DESIGN: Measurements of torso muscle endurance were performed by using 4 tests in healthy children. SETTING: Elementary school in Novi Sad, Province of Vojvodina, Republic of Serbia. PARTICIPANTS: Children from 1 elementary school (N=753, n=394 boys and n=359 girls) were grouped into 8 age strata. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Four tests established isometric physical endurance: Biering-Sørensen test for extensor endurance, flexor endurance test, and right- and left-side bridge tests. The mean, ratio, standard deviation, and 25th, 50th, and 75th percentile scores were determined for each sex/age stratum. RESULTS: A 2-way analysis of variance indicated that girls had higher mean endurance times for torso extension and torso flexion than did boys. For example, times measured by using Biering-Sørensen and right-side bridge tests were significantly greater for girls than for boys across all age groups (P<.023). Boys can sustain the side torso test longer than can girls. Furthermore, 3-dimensional torso muscle endurance is under significant impact of age. Tukey Honestly Significant Difference post hoc tests confirmed that within and between sex exist significant differences in mean endurance times in all age strata at the significance level P=.05. CONCLUSION: Both age and sex influence differences in torso endurance in children aged 7 to 14 years. These data of endurance times, their ratios, and percentiles in healthy subjects form a database that may be useful for providing training and rehabilitation targets.

Hip joint range of motion improvements using three different interventions.

The purpose of this study was to analyze the effect of 3 different exercise interventions plus a control group on passive hip range of motion (ROM). Previous research studies into the methods of improving passive hip mobility have focused on stretching protocols aimed specifically at the hip joint. The effect of core stabilization, motor training, and myofascial stretching techniques on hip mobility in a selected asymptomatic group with limited hip mobility is unclear. In this study, 24 young men with limited hip mobility (<50th percentile) were randomly assigned to 4 groups: stretching, stretching with motor control exercises for the hip and trunk, core endurance with motor control exercises, and the control group. Six-week home exercise programs were individually prescribed based on the assigned group, hip ROM, movement patterns, and timed core endurance. Two-way analyses of variances were conducted to analyze the effect of group assignment on hip ROM improvements. Both stretching groups demonstrated significant improvements in hip ROM (p < 0.05), attaining hip mobility levels at or above the 75th percentile, with rotation improving as much as 56%. The group receiving core endurance and motor control exercises with no stretching also demonstrated a moderate increase in ROM but only significantly so in rotation. Average core endurance holding times improved 38-53%. These results indicate that stretches aimed at the myofascial components of the upper body, in addition to the hip joint, resulted in dramatic increases in hip ROM in a group of young men with limited hip mobility. Hip ROM also improved in the group that did no active stretching, highlighting the potential role of including stabilization or "proximal stiffening training" when rehabilitating the extremities.

Predicting performance and injury resilience from movement quality and fitness scores in a basketball team over 2 years.

The purpose of this study was to see if specific tests of fitness and movement quality could predict injury resilience and performance in a team of basketball players over 2 years (2 playing seasons). It was hypothesized that, in a basketball population, movement and fitness scores would predict performance scores and that movement and fitness scores would predict injury resilience. A basketball team from a major American university (N = 14) served as the test population in this longitudinal trial. Variables linked to fitness, movement ability, speed, strength, and agility were measured together with some National Basketball Association (NBA) combine tests. Dependent variables of performance indicators (such as games and minutes played, points scored, assists, rebounds, steal, and blocks) and injury reports were tracked for the subsequent 2 years. Results showed that better performance was linked with having a stiffer torso, more mobile hips, weaker left grip strength, and a longer standing long jump, to name a few. Of the 3 NBA combine tests administered here, only a faster lane agility time had significant links with performance. Some movement qualities and torso endurance were not linked. No patterns with injury emerged. These observations have implications for preseason testing and subsequent training programs in an attempt to reduce future injury and enhance playing performance.

Kettlebell swing, snatch, and bottoms-up carry: back and hip muscle activation, motion, and low back loads.

The intent of this study was to quantify spine loading during different kettlebell swings and carries. No previously published studies of tissue loads during kettlebell exercises could be found. Given the popularity of kettlebells, this study was designed to provide an insight into the resulting joint loads. Seven male subjects participated in this investigation. In addition, a single case study of the kettlebell swing was performed on an accomplished kettlebell master. Electromyography, ground reaction forces (GRFs), and 3D kinematic data were recorded during exercises using a 16-kg kettlebell. These variables were input into an anatomically detailed biomechanical model that used normalized muscle activation; GRF; and spine, hip, and knee motion to calculate spine compression and shear loads. It was found that kettlebell swings create a hip-hinge squat pattern characterized by rapid muscle activation-relaxation cycles of substantial magnitudes (∼50% of a maximal voluntary contraction [MVC] for the low back extensors and 80% MVC for the gluteal muscles with a 16-kg kettlebell) resulting in about 3,200 N of low back compression. Abdominal muscular pulses together with the muscle bracing associated with carries create kettlebell-specific training opportunities. Some unique loading patterns discovered during the kettlebell swing included the posterior shear of the L4 vertebra on L5, which is opposite in polarity to a traditional lift. Thus, quantitative analysis provides an insight into why many individuals credit kettlebell swings with restoring and enhancing back health and function, although a few find that they irritate tissues.