Employing body-fixed sensors and machine learning to predict physical activity in military personnel.

INTRODUCTION: This was a feasibility pilot study aiming to develop and validate an activity recognition system based on a custom-made body-fixed sensor and driven by an algorithm for recognising basic kinetic movements in military personnel. The findings of this study are deemed essential in informing our development process and contributing to our ultimate aim which is to develop a low-cost and easy-to-use body-fixed sensor for military applications. METHODS: Fifty military participants performed a series of trials involving walking, running and jumping under laboratory conditions in order to determine the optimal, among five machine learning (ML), classifiers. Thereafter, the accuracy of the classifier was tested towards the prediction of these movements (15 183 measurements) and in relation to participants' gender and fitness level. RESULTS: Random forest classifier showed the highest training and validation accuracy (98.5% and 92.9%, respectively) and classified participants with differences in type of activity, gender and fitness level with an accuracy level of 83.6%, 70.0% and 62.2%, respectively. CONCLUSIONS: The study showed that accurate prediction of various dynamic activities can be achieved with high sensitivity using a low-cost easy-to-use sensor and a specific ML model. While this technique is in a development stage, our findings demonstrate that our body-fixed sensor prototype alongside a fully trained validated algorithm can strategically support military operations and offer valuable information to commanders controlling operations remotely. Further stages of our developments include the validation of our refined technique on a larger range of military activities and groups by combining activity data with physiological variables to predict phenomena relating to the onset of fatigue and performance decline.

The biomechanics of maintaining effective force application across cycling positions.

Cyclists are known to change their cycling position to reduce aerodynamic drag. Research has shown that this compromises their physical capacity to perform, but there is considerable inter-individual variability present. Proposed training specificity effects by cycling position do not explain all of the observations in the literature, so a search for other influencing parameters is warranted and might help practitioners to further optimise cycling position. This study captured full-body kinematics and 2D crank forces in 19 Time-Trial (TT) and 36 Road trained cyclists. Data in preferred and standardised cycling positions were systematically evaluated and showed that, amongst other kinematic differences, TT cyclists prefer a more forwardly positioned hip joint over Road cyclists. Despite their different setup, no effects in mechanical effectiveness were seen between the groups when tested in their preferred position. Across the standardised positions, the full cohort showed lower mechanical effectiveness when lowering trunk angle. However, significant group by position interactions showed this effect to be less extreme for the TT group. Kinematic data revealed that an increased pelvic tilt resulted in increased hip flexion and induced a more dorsiflexed ankle angle. In addition, linear hip position acutely responded to positional changes by moving forwards when the trunk angle was lowered. A more forwards hip position is thus associated with maintaining a better mechanical effectiveness in aerodynamic cycling positions. This suggests that there is potential to mitigate the effect of negative crank forces in aerodynamic positions by acutely adjusting the saddle placement to facilitate linear hip movement.

The impact of repetition mechanics on the adaptations resulting from strength-, hypertrophy- and cluster-type resistance training.

PURPOSE: The purpose of this study was to examine the acute and chronic training responses to strength-, hypertrophy- and cluster-type resistance training. METHODS: Thirty-four trained males were assigned to a strength [STR: 4 × 6 repetitions, 85 % of one repetition maximum, (1RM), 900 s total rest], hypertrophy (HYP: 5 × 10 repetitions, 70 % 1RM, 360 s total rest), cluster 1 (CL-1: 4 × 6/1 repetitions, 85 % 1RM, 1400 s total rest), and cluster 2 (CL-2: 4 × 6/1 repetitions, 90 % 1RM, 1400 s total rest) regimens which were performed twice weekly for a 6-week period. Measurements were taken before, during and following the four workouts to investigate the acute training stimulus, whilst similar measurements were employed to examine the training effects before and after the intervention. RESULTS: The improvements in 1RM strength were significantly greater for the STR (12.09 ± 2.75 %; p < 0.05, d = 1.106) and CL-2 (13.20 ± 2.18 %; p < 0.001, d = 0.816) regimens than the HYP regimen (8.13 ± 2.54 %, d = 0.453). In terms of the acute responses, the STR and CL-2 workouts resulted in greater time under tension (TUT) and impulse generation in individual repetitions than the HYP workout (p < 0.05). Furthermore, the STR (+3.65 ± 2.54 mmol/L(-1)) and HYP (+6.02 ± 2.97 mmol/L(-1)) workouts resulted in significantly greater elevations in blood lactate concentration (p < 0.001) than the CL-1 and CL-2 workouts. CONCLUSION: CL regimens produced similar strength improvements to STR regimens even when volume load was elevated (CL-2). The effectiveness of the STR and CL-2 regimens underlines the importance of high loads and impulse generation for strength development.

Technical characteristics of elite junior men and women race walkers.

AIM: Successful coaching in race walking requires a thorough understanding of the biomechanical principles underlying this unique form of gait. The purpose of this study was to analyze elite male and female junior race walkers and identify key kinematic variables. METHODS: Twenty junior men and 20 junior women were videoed as they competed over 10 km in the 8th European Cup Race Walking. Three-dimensional kinematic data were obtained using motion analysis software (SIMI, Munich). RESULTS: Step length and cadence were correlated with speed in both sexes, and greater step lengths were the kinematic reason for junior men's faster walking speeds. While cadence did not differ between junior men and junior women, there was a difference in proportion of step time spent in contact. There were some differences between genders for upper body joint angles (e.g., elbow) but there were few differences within lower limb joint angles. CONCLUSION: Although some technical aspects (e.g., pelvic and shoulder girdle rotation) appeared undeveloped, it was noteworthy that most athletes achieved full knee extension at initial contact in accordance with the rules. However, in many athletes flight times were evident that might present problems during the transition to the higher standards of senior competition. There was a large range of ability among both sexes and coaches are advised to ensure that technical development continues during the transition to senior competition.

The use of various strength-power tests as predictors of sprint running performance.

AIM: The aim of the present study was to assess the relationship between various strength-power tests and maximal running velocity parameters. METHODS: Nine trained males were tested on four separate occasions. On the first occasion the maximum running velocity (MRV), stride rate (SR) and stride length (SL) were measured over 35 m. On the second occasion maximal vertical jumps (squat jump [SJ], standing broad jump [SBJ], counter movement jump [CMJ] and drop jumps [DJ] from heights of 30, 50 and 80 cm) were performed on a force platform. On the third occasion the maximal bilateral isometric force (MBIF) of leg extensors and the force time characteristics (f-t 10-30%, f-t 10-60% and f-t 10-90%) were determined using a leg extension machine connected to a force plate. On the final fourth occasion peak anaerobic power was measured via repeated 6 sec maximum cycle sprints. Pearson product-moment correlation coefficients were calculated for all the aformentioned parameters. RESULTS: The correlation coefficients showed that MRV correlated significantly with f-t 10-60% and DJ 30 (r=-0.73 and r=0.73, P<0.05 respectively). In addition, SR and SL showed significant relationships with f-t 10-60% (r=-0.82, P<0.01 and r=0.75, P<0.05 respectively). CONCLUSION: The present findings suggest that the ability to produce force quickly, as measured by the time to achieve 60% of maximum voluntary contraction is related to sprinting performance, with the coefficient of determination accounting for 53% of the variance in the data. These data also show that sprinting ability is linked with DJ performance, especially the drop jump from a height of 30 cm. It is suggested that the above tests may prove useful in preparing and testing the sprinting ability and sprint specific strength levels.

Percutaneous nephrolithotomy to remove a cartridge detonating cap mimicking a renal pelvic stone 12 years after renal trauma.

Complications of gunshot injuries of the kidney usually present in the early postoperative period. We describe a case of a cartridge's plastic detonating cap retained in the renal pelvis of a young male patient for 12 years. Renal colic was the cause of admission. This missile's part was mimicking a renal stone on both an intravenous urogram and a CT scan. The nature of the "stone" was identified during a percutaneous nephrolithotomy procedure during which the foreign body was removed.

Biliary peritonitis complicating percutaneous nephrostomy.

Biliary peritonitis is a rare but serious complication of percutaneous renal access and surgery. We present such a case and review the literature.

Flow cytometric analysis of cellular DNA in human prostate cancer: relationship to 5 alpha-reductase activity of the tissue.

Flow cytometry of 20 prostate cancer specimens was carried out and the percentage DNA content in each phase of the cell cycle was correlated to the 5 alpha-reductase activity of the tumour. A group of 20 hyperplastic specimens was also entered into this study as control. Tumours were divided into 3 groups on the basis of their 5 alpha-reductase activity. This classification made it possible to identify a group of tumours of which none formed metastases (diploid tumours with 5 alpha-reductase activity greater than 20 pmol/mg protein/30 min and with less than 10% of the cells undergoing mitosis) and a second group of which 78% had metastasised at the time of presentation (diploid tumours with 5 alpha-reductase activity less than 10 pmol/mg protein/30 min and with more than 15% of the cells undergoing mitosis). DNA content within each of the 5 alpha-reductase groups appeared also to correlate with the histological grade of the cancer but no relationship was established with the stage of the disease. Our results suggest that a multi factorial discriminant combining DNA ploidy and 5 alpha-reductase measurements offers a good prognostic index for the assessment of disease progression in prostate cancer and that this might form the basis of a new approach to the treatment of this disease.