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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. [ABSTRACT FROM AUTHOR]

The main issue addressed here is the paradox of muscle contraction to optimize speed and strike force. When muscle contracts, it increases in both force and stiffness. Force creates faster movement, but the corresponding stiffness slows the change of muscle shape and joint velocity. The purpose of this study was to investigate how this speed strength is accomplished. Five elite mixed martial arts athletes were recruited given that they must create high strike force very quickly. Muscle activation using electromyography and 3-dimensional spine motion was measured. A variety of strikes were performed. Many of the strikes intend to create fast motion and finish with a very large striking force, demonstrating a 'double peak' of muscle activity. An initial peak was timed with the initiation of motion presumably to enhance stiffness and stability through the body before motion. This appeared to create an inertial mass in the large 'core' for limb muscles to 'pry' against to initiate limb motion. Then, some muscles underwent a relaxation phase as speed of limb motion increased. A second peak was observed upon contact with the opponent (heavy bag). It was postulated that this would increase stiffness through the body linkage, resulting in a higher effective mass behind the strike and likely a higher strike force. Observation of the contract-relax-contract pulsing cycle during forceful and quick strikes suggests that it may be fruitful to consider pulse training that involves not only the rate of muscle contraction but also the rate of muscle relaxation. KEY WORDS striking, electromyography, muscle stiffness, muscle relaxation

The objective of this study was to investigate 3 different rowing exercises and quantify the muscle activation of the torso and the hip musculature, together with the corresponding spinal loading and stiffness. Seven healthy male subjects from a university population were instrumented to obtain surface electromyography of selected trunk and hip muscles and to obtain spine position using an electromagnetic spine position sensor, together with video analysis to calculate joint moments. The 3 rowing exercises investigated are the inverted row, standing bent-over row, and the standing 1-armed cable row. The inverted row elicited the highest activation of the latissimus dorsi muscles, upper back, and hip extensor muscles. The lower activation of the lumbar erector spinae muscles during the inverted row corresponded to the lower-spine load measured. The standing bent-over row produced large activation symmetrically across the back but produced the largest lumbar spine load. The 1-armed cable row challenged the torsional capabilities of the trunk musculature. Some 'core' exercises may be better for rehabilitation (e.g., having the training goals of modest muscle activation with low spine load), while other exercises may be better for athletic training (e.g., resulting in higher muscle activation and larger spine load). When prescribing 'core' exercises, those wishing to spare the low back may choose the inverted row given the lowest spine load exercise. The standing bent-over row elicited large muscle activation symmetrically from the upper to lower back, however induced larger spine loads, but not surprisingly the highest spine stiffness. If torsional endurance or strength is the training goal, the 1-armed cable row might be considered. KEY WORDS stability, core training, technique, performance

Strongman events are attracting more interest as training exercises because of their unique demands. Further, strongman competitors sustain specific injuries, particularly to the back. Muscle electromyographic data from various torso and hip muscles, together with kinematic measures, were input to an anatomically detailed model of the torso to estimate back load, low-back stiffness, and hip torque. Events included the farmer's walk, super yoke, Atlas stone lift, suitcase carry, keg walk, tire flip, and log lift. The results document the unique demands of these whole-body events and, in particular, the demands on the back and torso. For example, the very large moments required at the hip for abduction when performing a yoke walk exceed the strength capability of the hip. Here, muscles such as quadratus lumborum made up for the strength deficit by generating frontal plane torque to support the torso/ pelvis. In this way, the stiffened torso acts as a source of strength to allow joints with insufficient strength to be buttressed, resulting in successful performance. Timing of muscle activation patterns in events such as the Atlas stone lift demonstrated the need to integrate the hip extensors before the back extensors. Even so, because of the awkward shape of the stone, the protective neutral spine posture was impossible to achieve, resulting in substantial loading on the back that is placed in a weakened posture. Unexpectedly, the super yoke carry resulted in the highest loads on the spine. This was attributed to the weight of the yoke coupled with the massive torso muscle cocontraction, which produced torso stiffness to ensure spine stability together with buttressing the abduction strength insufficiency of the hips. Strongman events clearly challenge the strength of the body linkage, together with the stabilizing system, in a different way than traditional approaches. The carrying events challenged different abilities than the lifting events, suggesting that loaded carrying would enhance traditional lifting-based strength programs. This analysis also documented the technique components of successful, joint-sparing, strongman event strategies. KEY WORDS core exercises, lumbar Spine, peak activation, strongman events, strength, stability

The purpose of this study was to document the muscle activity and spine motion during several tasks requiring rapid abdominal contraction. Eight healthy men from a university population were instrumented to obtain surface electromyography of selected trunk and hip muscles, together with video analysis to calculate joint moments and electromagnetic lumbar spine position sensor to track spine posture. Exercises included a punch, throw, and a ballistic torso-stiffening maneuver. This study found that no muscle turned on significantly before any other muscle during both the 1-in. punch and ballistic torso-stiffening maneuver. Conversely, there was a significant order or muscle onset during the baseball throw. Muscles reached peak activation significantly before any other muscle during the baseball throw and 1-in. punch, but there were no significant differences for the torso-stiffening maneuver. The exercises quantified in this study demonstrated how muscle contraction dynamics change to meet differing demands for stiffening, for force/moment production, and for rapid movements. Specifically, it seems that there is an order of contraction when movement is the goal but not when just spine stability is required. Thus, a different intensity of abdominal bracing is required to achieve the different objectives of sports tasks and exercises. KEY WORDS clinical technique, corrective exercise, lumbar

The purpose of this study was to document the muscle activity, spine motion, spine load, and stiffness during several movement-based or 'functional' exercises and to assess the effect of technique change. Eight subjects, all healthy men from a university population, were instrumented to obtain surface electromyography of selected trunk and hip muscles, together with video analysis and electromagnetic lumbar spine position sensor to track spine posture. Exercises included a walkout in the sagittal plane that compared an upright form against a wall with those performed on the floor, overhead cable pushes, lateral cable walkouts, the good morning exercise, and the bowler's squat. Generally, muscle activation levels were quite modest even though the tasks were quite strenuous in many cases. Even though similar joint moments were required in different exercises, the pattern of activity between muscles was different. Abdominal bracing increased spine stiffness at the expense of more spine load. Thus, muscle activity seems to be constrained in 'functional' exercises. There are several possible reasons for this. Single muscles cannot be activated to 100% of the maximum voluntary contraction in functional exercises because this would upset the balance of moments about the 3 orthopedic axes of the spine, or it would upset the balance of stiffening muscles around the spine required to ensure stability of the spinal column. The one exception was the floor walkout, which resulted in full activation of the rectus abdominis; however, this was a sagittal plane task without the joint moment constraints of multiplanar exercise. Therefore, maximal muscle activity is observed during single-plane tasks, but muscle activation levels were constrained during functional tasks. Thus, strength training muscles may not help in 'functional multiplanar' tasks. These data can be used to assist decisions regarding the selection of exercises, specifically choices regarding the starting challenge, progression, exercise form, and possibly corrective technique for those who have spine concerns, or those simply looking for performance enhancement. KEY WORDS stability, lumbar, corrective, exercise, clinical technique

Ergonomics interventions into pushing and pulling heavy objects are replacing lifting and carrying heavy objects, as manual material handling has become a major risk factor for injury. Pushing and pulling of heavy objects in a wheeled container would enable transportation of heavier weights and create a more efficient work setting but it is important to know the proper pushing and pulling techniques as they have a large influence on back loading.

Back muscle oxygenation during prolonged isometric contractions is reduced, even at contraction intensity as low as 2 percent of maximum voluntary contraction. The finding has implications for occupational conditions.

A proposed polynomial equation can predict low-back compression forces during 3-D loading tasks by using a 90-muscle anatomical model. The model takes into account the way a muscle force vector contributes simultaneously to generation of all three moments namely, axial twist, flexion and lateral bend. The equation is based on model output, which considers muscle co-contractions and also biological muscle coupling which occurs in 3-D spine loading. The method can reasonably examine the risk of compression injury for 3-D tasks in the industry.

Several types of analyses in biomechanics require estimates of both muscle force and stiffness. Simulations were performed using the two-state cross-bridge Bond Distribution-Moment muscle model of Zahalak (1981), together with other parameters for passive elasticity and tendon compliance, to estimate instantaneous stiffness and to compare these estimates with the wide range of values reported in the literature. While the relatively simple cross-bridge theory appears to approximate the stiffness of skinned muscle fibers, the stiffness of a complete muscle-tendon unit become complex and non-linear due to relative changes in muscle-tendon length and interaction with activation and length dependent passive elastic components. It would appear that the variability in muscle stiffness values reported in the literature can be explained with the D-M approach.