Acute effect of dry needling on trunk kinematics and balance of patients with non-specific low back pain.

BACKGROUND: Limited knowledge exists about the effectiveness of dry needling (DN) concerning the torso kinematics in patients with non-specific low back pain (NS-LBP). Acute effects of DN in NS-LBP patients from a functional perspective were investigated. METHODS: Sixteen NS-LBP patients and 11 healthy individuals (HG) were examined. NS-LBP patients received a single session of DN at the lumbar region. Baseline and immediate post-treatment measurements during flexion-extension and lateral bending of the trunk were conducted for the NS-LBP patients. HG were measured only at baseline to be used as a reference of NS-LBP patients' initial condition. Algometry was applied in NS-LBP patients. Centre of pressure, range of motion of the trunk and its' derivatives were obtained. FINDINGS: HG performed significantly faster, smoother and with greater mobility in the performed tasks compared to the pre intervention measurements of the NS-LBP patients. For the NS-LBP patients, significant greater angular velocity in frontal plane and significant lower jerk in the sagittal plane were demonstrated post intervention. DN alleviated pain tolerance significantly at the L5 level. Regarding the effectiveness of the DN upon spine kinematics, their derivatives were more sensitive. INTERPRETATION: It appeared that the pathological type of torso movement was acutely affected by DN. NS-LBP patients showcased smoother movement immediately after the intervention and better control as imprinted in the higher derivative of motion although range of motion did not improve. This quantitative variable may not be subjected to acute effects of DN but rather need additional time and training to be improved.

Subject-specific sensitivity of several biomechanical features to fatigue during an exhaustive treadmill run.

The aim of the present study was to examine the sensitivity of several movement features during running to exhaustion in a subject-specific setup adopting a cross-sectional design and a machine learning approach. Thirteen recreational runners, that systematically trained and competed, performed an exhaustive running protocol on an instrumented treadmill. Respiratory data were collected to establish the second ventilatory threshold (VT2) in order to obtain a reference point regarding the gradual accumulation of fatigue. A machine learning approach was adopted to analyze kinetic and kinematic data recorded for each participant, using a random forest classifier for the region pre and post the second ventilatory threshold. SHapley Additive exPlanations (SHAP) analysis was used to explain the models' predictions and to provide insight about the most important variables. The classification accuracy value of the models adopted ranged from 0.853 to 0.962. The most important feature in six out of thirteen participants was the angular range in AP axis of upper trunk C7 (RTAPu) followed by maximum loading rate (RFDmaxD) and the angular range in the LT axis of the C7. SHAP dependence plots also showed an increased dispersion of predictions in stages around the second ventilatory threshold which is consistent with feature interactions. These results showed that each runner used the examined features differently to cope with the increase in fatigue and mitigate its effects in order to maintain a proper motor pattern.

Validation of a Portable Wireless Force Platform System To Measure Ground Reaction Forces During Various Tasks.

Background: Force platforms are widely used in biomechanics to measure ground reaction forces (GRF) during various human movements. However, traditional force plates are not easily used outside a research lab. To overcome this issue, researchers and manufacturers are developing low-cost portable force platforms that can be used in a variety of settings, including outdoors. Purpose: To validate the kinetic data obtained from a pair of portable K-Deltas force platforms compared to gold standard platforms fixed in the lab and to examine the measurement reliability between this pair of portable force platforms. Methods: Force-time curves from known masses, countermovement vertical jumps, and balance tests were used to assess validity of K-Deltas using a pair of Bertec force plates as a gold standard and between the K-Deltas pair of plates. Bland-Altman plots were used to evaluate the differences between K-Deltas and Bertec force plates. For the assessment of countermovement vertical jumps, impulse, peak rate of force development and peak force were calculated for both instruments and checked for agreement between instruments. Three young adults (2 male, 1 female, 25.4±0.83 years) participated in the study. Results: The percentage of Bland-Altman plot point within the limits of agreement was 94.59 % for the comparison between K-Deltas and Bertec and 94.83% between the pair of K-Deltas. Conclusion: The results show that the portable force platforms could be utilized successfully for assessing pertinent parameters in clinical and sports biomechanics. The findings suggest that portable force platforms can be used as an alternative to traditional laboratory equipment for field assessment, providing significant improvements compared to the past. Level of Evidence: Level 3.

Analysis of upper limb propulsion in young swimmers in front-crawl through Statistical Parametric Mapping.

This study aimed to: (i) verify the within-subject effect of the dominant and non-dominant upper limb propulsion during consecutive arm-pulls through discrete (average) and continuous analysis (SPM), and; (ii) compare young swimmers' propulsion between both upper limbs through discrete (average) and continuous analysis (Statistical Parametric Mapping - SPM). The sample consisted of 17 young male swimmers (age = 16.02 ± 0.61-years) who regularly participate in national and international level competitions. A set of kinematic and propulsion variables were measured during a 25-m maximal trial in front-crawl. Statistical analysis of propulsion was performed using discrete variables and through SPM. Swimming velocity showed a significant decrease over time. A significant interaction between the "time" (consecutive arm-pulls) and "side" (dominant vs. non-dominant) effects was observed in both statistical analyzes. Only the dominant upper limb demonstrated a significant "time" effect with a significant difference (p < 0.05) between the first and third arm-pulls. SPM indicated that the "time" effect was observed between the âˆ¼ 34% and âˆ¼ 42% of the arm-pull. The differences between the first and third arm-pull were verified between the âˆ¼ 32% and âˆ¼ 43% of the arm-pull. A non-significant "side" effect was verified in both analyzes. Therefore, SPM analysis provided more sensitive and accurate outputs than discrete analysis. This will allow coaches to design specific training drills focused on specific moments of the arm-pull.

Time of Day Influence on Postural Balance of Young and Older Men.

BACKGROUND: Many physiologic parameters fluctuate on a diurnal basis following the circadian rhythm function. The purpose of the study was to investigate if postural performance is interdependent of time of day and age. METHODS: 19 young (22.63 ± 3.43 y.o.) and 19 older male adults (60.21 ± 3.67 y.o.) performed three balance tests (quiet stance with open and closed eyes and bipedal balance on a Togu ball) at 12:00 AM and at 12:00 PM. Time and frequency domain variables of the center of pressure were analyzed. RESULTS: At eyes closed test, the younger had significant less distance traveled by the Center of Pressure (CoP) at night compared to day. At open eyes test, the younger had significant less CoP sway in the anterior-posterior (AP) axis at night compared to day. At Togu ball test the older showed increased peak-to-peak amplitude of CoP in both axes compared to younger. They also had lower frequency in the medial-lateral (ML) axis but higher in the AP axis compared to the younger. CONCLUSION: Younger seem to function better at night. There is also an indication that the older are better at day. The results on unstable surface indicate different control strategies between the two groups.

Kinetic time-curves can classify individuals in distinct levels of drop jump performance.

This study examined whether analysing kinetic features of drop jumps (DJ) as one-dimensional biomechanical curves can reveal specific patterns that are consistent and can cluster DJ performance. Hierarchical clustering analysis on DJ from 40 cm data performed by 128 physically active male participants (23.0 ± 4.5 yrs, 1.84 ± 0.07 m, 79.1 ± 10.8 kg) was performed on the derived time-normalised force, power and vertical stiffness curves to unmask the underlying patterns and to explore the dissimilarities identified from the subgroup (cluster) analysis. Results revealed poor, average and top DJ performers. Top performers exhibited larger peak force, power and vertical stiffness compared to the other two groups, and the poor performers had lower values compared to the average performers (p < .05). The time curves of force, power and vertical stiffness exhibited between cluster dissimilarities from ~25% to ~70%, and ~20% to 40% plus ~55% to 70% from the beginning of the ground contact, respectively. The force and power time-curves distinguished DJ ability similarly since they shared 69% of the cases in the top performers' cluster. The content of cases (membership) for vertical stiffness was different from the membership for the force and power time-curve clusters. In conclusion, stiffness should be considered during plyometric training, but does not distinctly define DJ performance.

Comparison of the arm-stroke kinematics between maximal and sub-maximal breaststroke swimming using discrete data and time series analysis.

The aim of the current study was to compare the arm-stroke kinematics during maximal and sub-maximal breaststroke swimming using both discrete and continuous data analysis. Nine male breaststrokers swam 2 × 25 m with maximal and sub-maximal intensity and their full body 3-D kinematics were obtained using eight video cameras. The arm-stroke was divided into five phases: recovery, glide, out-sweep, in & down-sweep and in & up-sweep. The statistical treatment of selected discrete variables was conducted using t-test, while the analysis of their equivalent time series, when applicable, was conducted using Statistical Parametric Mapping. Sub-maximal trial, compared to maximal, presented lower swimming velocity, greater stroke length and less stroke rate. Moreover, the absolute and relative duration of the glide phase was longer, while the relative duration of all the other phases was shorter. The resultant hand velocity during the arm recovery was slower, as well as the hand velocity time series in the transverse and longitudinal axis which were slower from âˆ¼ 45 % to âˆ¼ 60 % and from âˆ¼ 5 % to âˆ¼ 15 % of the stroke cycle, respectively. Both discrete and continuous data analysis revealed that the main discriminating factor between the two conditions concerns to the adjustment of the glide and the recovery phase and consequently the continuation of the propulsive movements.

Sensitivity of movement features to fatigue during an exhaustive treadmill run.

HIGHLIGHTS: Trunk frontal plane kinematics is the most sensitive parameter to fatigue. Practitioners should consider this finding during endurance training.Kinetics exhibit a stable linear increase in mean values but a non-linear increase in variance during an exhaustive incremental treadmill run. This may affect training at a submaximal fatigued state.Specific areas in the joint distributions of kinetics and kinematics during treadmill running exhibit increased sensitivity in predicting fatigue state.

The effects of dry needling on pain relief and functional balance in patients with sub-chronic low back pain.

BACKGROUND: Pain relief is important both for the movement of patients suffering from low back pain and the quality of life. Dry needling is effective on myofascial trigger points but its effect on the area of pain and the functional balance is not fully known. OBJECTIVE: To examine the immediate effect of dry needling on pain and functional balance of patients suffering from low back pain. METHODS: Twenty five patients with sub-chronic low back pain were randomly divided into two groups: the intervention or control group. Needles were used for the participants of the intervention group, bilaterally at the spinus level, one and a half finger breath from the midline in levels L2-L5 of the lumbar spine. A third line of needles was inserted in the interspinosus spaces, except L5-S1 level. Bipedal stance, lateral loading and mediolateral body sway were assessed using a pair of force plates. Pain tolerance was assessed using an algometer. RESULTS: The pain tolerance significantly increased in the intervention group from (M = 4.87, SE 0.663) to (M = 6.52, SE 0.547) (F(1,23) = 7.8, p< 0.05) after intervention. During mediolateral body sway the force signal in the dominant frequency significantly increased in the intervention group from (M = 43.2, SE 4.6) to (M = 54,9, SE 3.6) (F(1,23) = 4.63, p< 0.05) after intervention, exhibiting more controlled rhythmic behavior. CONCLUSIONS: Dry needling in painful areas and penetrating all the muscle groups seems to improve pain and functional balance, yet its effect on specific muscles needs to be studied further.

Classification of Soccer and Basketball Players' Jumping Performance Characteristics: A Logistic Regression Approach.

This study aimed to examine countermovement jump (CMJ) kinetic data using logistic regression, in order to distinguish sports-related mechanical profiles. Eighty-one professional basketball and soccer athletes participated, each performing three CMJs on a force platform. Inferential parametric and nonparametric statistics were performed to explore group differences. Binary logistic regression was used to model the response variable (soccer or not soccer). Statistical significance (p < 0.05) was reached for differences between groups in maximum braking rate of force development (RFDDmax, U79 = 1035), mean braking rate of force development (RFDDavg, U79 = 1038), propulsive impulse (IMPU, t79 = 2.375), minimum value of vertical displacement for center of mass (SBCMmin, t79 = 3.135), and time difference (% of impulse time; ΔΤ) between the peak value of maximum force value (FUmax) and SBCMmin (U79 = 1188). Logistic regression showed that RFDDavg, impulse during the downward phase (IMPD), IMPU, and ΔΤ were all significant predictors. The model showed that soccer group membership could be strongly related to IMPU, with the odds ratio being 6.48 times higher from the basketball group, whereas RFDDavg, IMPD, and ΔΤ were related to basketball group. The results imply that soccer players execute CMJ differently compared to basketball players, exhibiting increased countermovement depth and impulse generation during the propulsive phase.

Classification methods can identify external constrains in swimming.

The purpose of the present study is to examine whether the use of fins is identifiable based on swimmers' technique and to find out technique-related features that depict fins' influence. First, a number of features were extracted from kinematic data given by movement sensors attached to swimmers' bodies during butterfly swimming technique. Then, dimensionality reduction, feature selection and classification methods were applied to the extracted features. Two classification tasks were defined, one for the three classes of long, short and no fins, attaining accuracy up to 70, 62 and 70%, respectively, and the two-class simplified version (long fins, no fins) with accuracy up to 78%. These high accuracy levels were also found statistically significant and suggest that the use of fins influences swimming technique in a recognizable way and that the selected features that depict those differences are swimming type depended.

Rotational kinematics of pelvis and upper trunk at butterfly stroke: Can fins affect the dynamics of the system?

The purpose of the present study was to investigate the rotational kinematics pattern of the upper trunk and the pelvis and the complexity-variability of their movement, during the sprint butterfly stroke between male and female swimmers with long fins (18-26 cm) and without fins. Two pairs of 3D accelerometers and gyroscopes were used to measure segments' flexion-extension angles. There were no gender differences apart from the record. The amplitude values at the pelvis were significantly larger when swimming without fins while at the C7 they were significantly larger when swimming with them. Autocorrelation coefficients of angles' time histories were higher when swimming with fins for both segments. The power spectrums revealed a dominant frequency representing the stroke period which grew significantly stronger for the fin condition. Correlation Dimension verified a lower dimensionality for the fin condition for the C7 segment movement pattern. Overall fin use seems to offer "strength" to the swimmer's movement pattern. This does not imply better movement coordination, but rather a trend toward a more stable attractor.

Commercial video frame rates can produce reliable results for both normal and CP spastic gait's spatiotemporal, angular, and linear displacement variables.

To investigate what sampling frequency is adequate for gait, the correlation of spatiotemporal parameters and the kinematic differences, between normal and CP spastic gait, for three sampling frequencies (100 Hz, 50 Hz, 25 Hz) were assessed. Spatiotemporal, angular, and linear displacement variables in the sagittal plane along with their 1st and 2nd derivatives were analyzed. Spatiotemporal stride parameters were highly correlated among the three sampling frequencies. The statistical model (2 × 3 ANOVA) gave no interactions between the factors group and frequency, indicating that group differences were invariant of sampling frequency. Lower frequencies led to smoother curves for all the variables, with a loss of information though, especially for the 2nd derivatives, having a homologous effect as the one of oversmoothing. It is proposed that in the circumstance that only spatiotemporal stride parameters, as well as angular and linear displacements are to be used, in gait reports, then commercial video camera speeds (25/30 Hz, 50/60 Hz when deinterlaced) can be considered as a low-cost solution to produce acceptable results.

Changes in the limits of stability induced by weight-shifting training in elderly women.

This study examined the impact of visually guided weight-shifting training on elderly women's limits of stability during static leaning and dynamic swaying in different directions. Sixty-three elderly women were assigned into a group that practiced weight shifting (30-min sessions, 3 sessions/week, 4 weeks) either in the anterior/posterior or medio/lateral direction and a control group. Training resulted in a reduction of upper body rotation and an increase of shank rotation and center of pressure displacement. It is concluded that weight-shifting practice increases the limits of stability and enhances the inverted pendulum pivoting of the human body during leaning and dynamic swaying balance tasks.

Direction-induced effects of visually guided weight-shifting training on standing balance in the elderly.

BACKGROUND: Controversial findings exist in the literature with respect to the efficacy of visually guided weight-shifting (WS) training as a means of improving balance in healthy older adults. OBJECTIVE: The purpose of this study was to investigate the impact of two direction-specific, visually guided WS training protocols on standing balance of healthy elderly women. METHODS: Forty-eight community-dwelling elderly women, all free of any neurological or musculoskeletal impairment, were randomly assigned into: a group that practiced WS in the anterior/posterior direction (A/P group, n=19), a group that practiced WS in the medio/lateral direction (M/L group, n=15) and a control group (n=14). Participants performed 12 training sessions of visually guided WS (3 sessions a week for 25 minutes per session). Static balance was measured before and after training in normal (bipedal) quiet stance (NQS) and sharpened-Romberg stance (SRS) by recording center of pressure (CoP) variations and angular segment kinematics. RESULTS: In NQS, neither of the two training protocols had a significant impact on postural sway measures, although a significant decrease in interlimb asymmetry of CoP displacement was noted for the A/P group. In SRS, A/P training induced a significant reduction of CoP displacement, lower limb pitch and upper trunk roll rotation. CONCLUSION: The results of the study stress the importance of using direction-specific WS tasks in balance training, particularly in the A/P direction, in order to improve control of static balance in elderly women.

Bilateral inter-arm coordination in freestyle swimming: effect of skill level and swimming speed.

The aim of this study was to examine the influence of level of skill and swimming speed on inter-limb coordination of freestyle swimming movements. Five elite (2 males, 3 females; age 18.9+/-1.0 years, height 1.71+/-0.04 m, body mass 62.1+/-7.0 kg) and seven novice (age 22.0+/-2.0 years, height 1.77+/-0.04 m, body mass 74.8+/-9.0 kg) swimmers swam a sprint and a self-paced 25 m freestyle trial. The swimming trials were recorded by four digital cameras operating at 50 Hz. The digitized frames underwent a three-dimensional direct linear transformation to yield the three-dimensional endpoint kinematic trajectories. The spatio-temporal relationship between the upper limbs was quantified by means of the peak amplitude and time lag of the cross-correlation function between the right and left arm's endpoint trajectories. A strong anti-phase coupling between the two arms, as confirmed by peak amplitudes greater than 0.8, was noted for both groups and swimming speeds. Significantly higher (P<0.05) peak amplitudes were observed for the sprint compared with self-paced swimming. No significant differences in the strength of inter-limb coupling were noted between the elite and novice swimmers (P>0.05). Time lags were very close to 0 ms and did not differ between groups or swimming speeds. We conclude that in freestyle swimming, the intrinsic anti-phase (180 degrees phase difference) inter-limb relationship is strongly preserved despite the physically powerful environmental influence of the water and this "preferred" pattern is not affected by level of skill. In contrast, increasing movement speed results in stronger inter-limb coupling that is closer to the anti-phase inter-limb relationship.