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This study examined the effect of water immersion on trunk and lower limb kinematics during squat exercises in older participants. A total of 24 active older adults (71.4 ± 5.4 years) performed squats and split squats on land and while partially submerged in water. Inertial sensors (100 Hz) were used to record trunk and lower body kinematics. Water immersion increased the squat depth (squat: p = .028, d = 0.63 and split squat: p = .005, d = 0.83) and reduced the trunk flexion range (squat: p = .006, d = 0.76 and split squat: p

The aim of this article was to examine changes in elite youth volleyball players’ performance, proximal-to-distal sequencing, and coordination variability of the spike motion between the start and after 1 year of a talent development program. Eight boys and eight girls in late puberty/early adolescence were measured with 3D motion capturing for 2 consecutive years. Performance and performance variability increased and decreased, respectively, but both changes were not significantly correlated with growth. Gender differences were identified for proximal-to-distal sequencing, but a very strong similarity between both years was observed for all seven degrees of freedom (pelvis and trunk rotation, trunk flexion, shoulder horizontal adduction, shoulder internal rotation, elbow extension, and wrist flexion). The fact that this sequence was kept stable, despite marked growth effects, likely indicates that this sequence is biomechanically efficient and the motor control systems try to preserve it. Coordination variability was analyzed by coordination profiling with self-organizing maps. The decrease in coordination variability correlated strongly and significantly with increase in body height. Participants with stronger growth rates were observed to show smaller decreases in coordination variability, which possibly represents a mechanism to explore various coordination patterns to adapt to the more rapidly changing organismic constraints.

Virtual environments with real-time feedback can simulate extrinsic goals that mimic real life conditions. The purpose was to compare jump performance and biomechanics with a physical overhead goal (POG) and with a virtual overhead goal (VOG). Fourteen female subjects participated (age: 18.8 ± 1.1 years, height: 163.2 ± 8.1 cm, weight 63.0 ± 7.9 kg). Sagittal plane trunk, hip, and knee biomechanics were calculated during the landing and take-off phases of drop vertical jump with different goal conditions. Repeated-measures ANOVAs determined differences between goal conditions. Vertical jump height displacement was not different during VOG compared with POG. Greater hip extensor moment (P < .001*) and hip angular impulse (P < .004*) were found during VOG compared with POG. Subjects landed more erect with less magnitude of trunk flexion (P = .002*) during POG compared with VOG. A virtual target can optimize jump height and promote increased hip moments and trunk flexion. This may be a useful alternative to physical targets to improve performance during certain biomechanical testing, screening, and training conditions.

Two-dimensional methods have been used to compute trunk kinematic variables (flexion/extension, lateral bend, axial rotation) and X-factor (difference in axial rotation between trunk and pelvis) during the golf swing. Recent X-factor studies advocated three-dimensional (3D) analysis due to the errors associated with two-dimensional (2D) methods, but this has not been investigated for all trunk kinematic variables. The purpose of this study was to compare trunk kinematic variables and X-factor calculated by 2D and 3D methods to examine how different approaches influenced their profiles during the swing. Trunk kinematic variables and X-factor were calculated for golfers from vectors projected onto the global laboratory planes and from 3D segment angles. Trunk kinematic variable profiles were similar in shape; however, there were statistically significant differences in trunk flexion (–6.5 ± 3.6°) at top of backswing and trunk right-side lateral bend (8.7 ± 2.9°) at impact. Differences between 2D and 3D X-factor (approximately 16°) could largely be explained by projection errors introduced to the 2D analysis through flexion and lateral bend of the trunk and pelvis segments. The results support the need to use a 3D method for kinematic data calculation to accurately analyze the golf swing.

Background:The purpose of this study was to evaluate a college’s exercise leadership program, which was developed to help students, faculty and staff implement behavior changes necessary to begin and maintain a comprehensive exercise program.Methods:From 2006–2011, a total 66 subjects were recruited and each was assigned to a student exercise leader. Based on comprehensive baseline assessments, each student designed an individualized exercise program for his/her subject. At program completion, the subjects were reassessed.Results:Paired t tests were used to find significant statistical changes (P < .05) among the fitness components. Significant changes as a function of the 6-week exercise program were observed in body weight, body fat percentage, waist circumference, 1-mile walk time, sit-ups, push-ups, and trunk flexion.Conclusions:Getting started is the most difficult step, but beginning an exercise program has immediate benefits. Institutions of higher education are addressing issues of wellness as a means for increasing graduation, retention, and productivity rates among their campus constituents. These efforts are part of a collaborative effort initiated by the American College Health Association known as Healthy Campus 2020. The findings from this study have a direct impact on programmatic efforts.

This paper introduces the concept of dynamic isometrics in training athletes to improve core/postural-related movements while potentially decreasing the occurrence of injury manifested as lower back pain (LBP). Moreover, suggested resistance-training exercises are provided to guide the sport coach. Lower back pain is a common musculoskeletal injury that can be caused by imbalances between anterior and posterior muscle groups. Traditional exercises such as sit-ups and crunches are insufficient as preventatives because very few athletic movements are performed with weighted trunk flexion. Alternatively, sport coaches could implement dynamic isometric training, which closely reflects athletic activities, supports the principle of training specificity, improves balance and strength, and might decrease the occurrence of LBP (Hamlyn, Behm, & Young, 2007).

Mild trunk flexion held during working tasks throughout the day is considered a risk factor for low back pain. Exactly how the duration of these postures impacts the low back musculature during work tasks is not well understood. The objective of this study was to evaluate the effects of the temporal variation of mild trunk flexion and erect standing postures on low back discomfort and muscular fatigue, defined as a decrease in torso extension strength, during a realistic light assembly task. Study participants performed light assembly tasks for 20 minutes while in mild trunk flexion for periods of either 30 or 60 seconds, followed by recovery periods in which they stood erect, for periods of either 15, 30, 60, or 120 sec. Localized muscle discomfort, decreases in torso extension strength, and muscle activity of erector spinae were recorded. Duration of recovery period had a statistically significant effect on localized muscle discomfort of the lower back, upper back, and shoulders. Duration of trunk flexion and recovery time had an interactive effect on decreases in torso extension strength, for which strength decreased with decreasing recovery time and was more pronounced for trunk flexion periods of 60 sec rather than 30 sec. The mean RMS erector spinae muscle activity during mild trunk flexion was approximately 25% of the measured maximum voluntary RMS muscle activity across all conditions. The results suggest that it is the temporal pattern of muscular trunk flexion, and not the total time spent in trunk flexion, that affects localized discomfort and muscular fatigue of the low back.

Context:Trunk flexion and extension in normal participants using the Biodex and a LIDO-Back isokinetic trunk dynamometer.Objective:Assessment of interreproducibility of the isokinetic LIDO-Back system.Design and Setting:Intertester reproducibility study in a tertiary-care center (outpatient rehabilitation).Participants:10 healthy individuals (4 women and 6 men) with a mean age of 29 years.Main Outcome Measures:Intertester reproducibility correlations of the isokinetic LIDO-Back. Measurements of 2 therapists were calculated using intraclass correlation coefficient (ICC1,1).Results:For the flexion parameters the ICCs were between .86 and .98, and for extension, between .63 and .78.Conclusions:A high intertester reproducibility relating to measurements of the LIDO-Back isokinetic trunk dynamometer was demonstrated. Intertester-reproducibility studies should become a routine method in the rehabilitation process.

Low back problems account for the largest proportion of injuries among amateur and professional golfers. However, there is little data on how the trunk or spine moves during a golf swing. Also, it may be that different golf clubs produce different trunk motion characteristics. The purpose of this study was to compare trunk range of motion (ROM) and velocity in three movement planes during the execution of a full golf swing using a driver and a 7-iron. Forty-four members of the Alberta Professional Golf Association volunteered to participate in this study. Trunk ROM and velocities in the sagittal, frontal, and transverse planes were measured using a triaxial electrogoniometer. Results showed that significantly more trunk flexion was required when setting up to hit the ball with the 7-iron compared to the driver,p< 0.05. During the swing, significantly greater maximum flexion and left-side-bend ROM occurred when using the 7-iron,p< 0.05. Maximum right-side-bending velocity during the golf swing was also significantly greater with a 7-iron. These findings suggest that differences in shaft length and ball positioning associated with the different clubs affects swing mechanics and trunk/spinal motion. In particular, the shorter club (7-iron) tended to place more emphasis on lateral trunk motion than did the driver. The results from this study may help clinicians better understand how the golf swing creates stress on the back as well as how club fitting may affect trunk motion characteristics.

When rising from a chair, older adults have been reported to use a strategy in which the trunk is flexed to a greater extent than young adults, a strategy attributed by some to concerns with the postural stability demands of the task. This study determined the extent to which maximum trunk flexion angle during a self-paced sit-to-stand from a standardized initial position was influenced by the maximum isometric strength of the knee and trunk/hip extensor muscles in older adults. The hypothesis was that the larger maximum trunk flexion angle attained by older adults when rising from a chair is related to the maximum isometric strength of the knee and trunk-hip extensor muscles. To test this hypothesis, maximum voluntary isometric strength of the trunk extensor and knee extensor muscles of 28 older men and women were measured. Trunk motion during the sit-to-stand by these adults was men assessed using motion analysis. Multiple regression was used to characterize the relationship between the maximum trunk flexion angle and maximum isometric knee extensor and trunk extensor muscle strength. The derived relationship was neither statistically significant nor biomechanically meaningful. This result suggests that the trunk flexion angle attained by healthy older adults when rising from a chair from a standardized initial position is not influenced by knee extension and trunk-hip extension strength as measured in the present study.

Olympic skiers in the women's 30-km race were analyzed as they double poled on a moderate downhill slope. Movement patterns of 20 skiers were analyzed 10 from a top finishing group and 10 from slower finishers in the bottom third of the field. Skiers in the faster group not only were faster overall in the race but were faster as they double poled through the site (6.75 vs. 6.43 m/s). Cycle length was significantly correlated with cycle velocity (r = .81). Trunk flexion and shoulder extension during poling were similar between groups; however, considerable variability of shoulder positioning was noted for both groups of skiers. Distinct shoulder-elbow-pole positioning differences were noted among skiers. Disadvantageous positionin» of the shoulder at the beginning of poling was related to poorer pole inclination during elbow extension. While many skiers in both fast and slow groups double poled with good positioning, others would benefit from greater shoulder flexion to maximize double poling performance.

Context: Lateral trunk-flexion strength is an important determinant of overall trunk stability and function, but the reliability in measuring this outcome clinically in athletic individuals is not known. Objective: To determine the interrater and intrarater reliability of lateral trunk-flexion strength measurement in athletic individuals using handheld dynamometry. Design: Reliability study. Setting: Research laboratory. Participants: 12 healthy, athletic individuals. Intervention: Lateral trunk-flexion strength was measured using handheld dynamometry across 2 different trunk placements (lateral aspect of the axilla and laterally at the level of the midtrunk) and 2 testing occasions by 2 therapists. Three maximum-effort trials during a "make test" at each placement were completed for each therapist on both occasions. Main Outcome Measures: Maximum force output was identified and converted to a torque. Intraclass correlation coefficients (ICC2,1) were calculated for each dynamometer placement, therapist, and test occasion to determine intrarater and interrater reliability. Results: Intrarater reliability was moderate to good (ICC2,1 = .53-.77), while interrater reliability was good to very good (ICC2,1 = .79-81) at the axilla position. For the midtrunk position, intrarater reliability was good to very good (ICC2,1 = .80-.86), while interrater reliability was good on both days (ICC2,1 = .87-.88). Finally, the standard errors of measurement were low for the axilla position (0.20 Nm/kg; 95% CI .15, .28) and midtrunk position (0.09 Nm/kg; 95% CI .07, .12). Conclusions: Maximum lateral trunk-flexion strength can be reliably measured in athletic individuals with greater overall strength. Based on the 2 positions used in this study, measurement with a dynamometer placement at the midtrunk may be more reliable than that obtained at the axilla.

The women's 30-km freestyle cross-country race at the 1992 Winter Olympic Games was selected to determine the kinematic differences between more and less successful skiers. Three-dimensional filming techniques were used to capture the movement patterns on level terrain of 8 skiers who placed in the top 50% (Group 1) and 8 skiers who placed in the bottom 50% (Group 2) of the field. The mean cycle velocity for Group 1 was significantly faster (p < .005) than the velocity for Group 2. Significant correlations (p < .05) were found between race velocity and cycle velocity (r = .89) and between cycle length and cycle rate (r = -.82). Group 1 had significantly greater (p < .03) weak-side elbow flexion at pole plant, as well as less (p < .01) weak-side elbow extension and more (p < .05) trunk flexion during poling. The mean cycle velocity differences between Groups 1 and 2 may have been the result of smaller resistive and/or larger propulsive forces.

This study analyzes the associations of socioeconomic status (SES), health, and physical activity with maximal isometric strength in 75-year-old men (n = 104) and women (n = 191). Maximal isometric strength was measured with dynamometers; the forces were adjusted using body weight. The maximal forces for women varied from 66% (trunk flexion) to 73% (knee extension) of those of the men. SES was not associated with muscle force. For men the trunk forces and elbow flexion force correlated negatively with the number of chronic diseases, index of musculoskeletal pain, and self-rated health. For women all the strength test results correlated with self-rated health; the other health indicators showed significant correlation with trunk extension force only. For both sexes the physically more active exhibited greater strength. The index of musculoskeletal symptoms explained the variance on trunk force factor in both sexes. It was concluded that a higher level of everyday physical activity and good values in the state-of-health indicators were the most important variables explaining greater strength among the elderly.

This study examined the mechanics of translation and rotation during the conventional and handspring soccer throw-ins. Thirteen male collegiate soccer players were filmed at 100 fps while performing a conventional soccer throw-in for distance. Additionally, two male collegiate and two male youth league soccer players were filmed at 200 fps while performing a handspring throw-in. Analysis of the conventional throw-in revealed that rapid trunk flexion, and shoulder and elbow extension just prior to release appear to make important contributions to the performance variables (initial ball velocity, angle of release, range, angular momentum). Results of the handspring throw-in analysis suggest that the angular momentum generated during the preparatory and ball support phases was transferred to the arms, forearms, and ball during the latter stages of the movement. Although generalization to a larger population is limited, the results of this study suggest that the handspring throw-in technique has the potential to generate greater release velocities and longer throws, thereby enhancing scoring opportunities during throw-in situations.