The mechanical loading of the spine in physical activities.

PURPOSE: To summarize the mechanical loading of the spine in different activities of daily living and sports. METHODS: Since the direct measurement is not feasible in sports activities, a mathematical model was applied to quantify spinal loading of more than 600 physical tasks in more than 200 athletes from several sports disciplines. The outcome is compression and torque (normalized to body weight/mass) at L4/L5. RESULTS: The data demonstrate high compressive forces on the lumbar spine in sport-related activities, which are much higher than forces reported in normal daily activities and work tasks. Especially ballistic jumping and landing skills yield high estimated compression at L4/L5 of more than ten times body weight. Jumping, landing, heavy lifting and weight training in sports demonstrate compression forces significantly higher than guideline recommendations for working tasks. CONCLUSION: These results may help to identify acute and long-term risks of low back pain and, thus, may guide the development of preventive interventions for low back pain or injury in athletes.

Metabolic power in the men's European handball championship 2020.

PURPOSE: To ascertain the typical metabolic power characteristics of elite handball players of different positions, and whether changes occur within matches. METHODS: 414 elite male handball players were included. During all 65 matches of the EURO 2020, local positioning system data were collected, yielding 1853 datasets. Field players were categorised into six positional groups: centre backs (CB), left/right wings (LW/RW), left/right backs (LB/RB) and pivots (P). Metabolic power, total energy expenditure, high-power energy, and the equivalent distance index were calculated. We used linear mixed models with players as random and positions as fixed effects models. Intensity models adjusted for time-dependency by incorporating the duration of play. RESULTS: LW/RW spent most time on the court, expanded most total energy, and most relative energy per kg body weight in the high-intensity categories. CB played at the highest mean metabolic power (7.85 W/kg; CI95% [7.67, 8.03]). Playing intensity decreased by 2.5% (0.2 kJ/kg/s; CI95% [0.17, 0.23]) per 10 min played. CONCLUSION: Positional differences in metabolic power parameters exist. In general, wing players had the highest volume and CB the highest intensity of match-play. Analysis of metabolic intensity in handball should take position and players' time on the court into account.

Effects of oral contraceptive use on muscle strength, muscle thickness, and fiber size and composition in young women undergoing 12 weeks of strength training: a cohort study.

BACKGROUND: It is suspected that hormonal fluctuations during menstruation may cause different responses to strength training in women who use oral contraceptives (OC) versus those who do not. However, previous studies that investigated the existence of such differences produced conflicting results. In this study, we hypothesized that OC use has no effect on muscle strength and hypertrophy among women undergoing strength training. Thus, we compared the differences in muscle strength and thickness among women who used OCs and those who did not. METHODS: We investigated the influence of OC use on muscle strength (Fmax), muscle thickness (Mtk), type 1-to-type 2 muscle fiber (NO) ratio, muscle fiber thickness (MFT), and nuclear-to-fiber (N/F) ratio. Seventy-four healthy young women (including 34 who used OCs and 40 who did not) underwent 12 weeks of submaximal strength training, after which Fmax was evaluated using a leg-press machine with a combined force and load cell, while Mtk was measured using real-time ultrasonography. Moreover, the NO ratio, MFT, and N/F ratio were evaluated using muscle needle biopsies. RESULTS: Participants in the non-OC and OC groups experienced increases in Fmax (+ 23.30 ± 10.82 kg and + 28.02 ± 11.50 kg respectively, p = 0.073), Mtk (+ 0.48 ± 0.47 cm2 and + 0.50 ± 0.44 cm2 respectively, p = 0.888), Fmax/Mtk (+ 2.78 ± 1.93 kg/cm2 and + 3.32 ± 2.37 kg/cm2 respectively, p = 0.285), NO ratio (type 2 fibers: + 1.86 ± 6.49% and - 4.17 ± 9.48% respectively, p = 0.169), MFT (type 2 fibers: + 7.15 ± 7.50 µm and + 4.07 ± 9.30 µm respectively, p = 0.435), and N/F ratio (+ 0.61 ± 1.02 and + 0.15 ± 0.97 respectively, p = 0.866) after training. There were no significant differences between the non-OC and OC groups in any of these parameters (p > 0.05). CONCLUSIONS: The effects of 12 weeks of strength training on Fmax, muscle thickness, muscle fiber size, and composition were similar in young women irrespective of their OC use.

Spinal and Pelvic Kinematics During Prolonged Rowing on an Ergometer vs. Indoor Tank Rowing.

ABSTRACT: Trompeter, K, Weerts, J, Fett, D, Firouzabadi, A, Heinrich, K, Schmidt, H, Brüggemann, GP, and Platen, P. Spinal and pelvic kinematics during prolonged rowing on an ergometer vs. indoor tank rowing. J Strength Cond Res 35(9): 2622-2628, 2021-This investigation aimed to compare spinopelvic kinematics during rowing on an ergometer vs. in a rowing tank and to evaluate changes with progressing fatigue. Spinal and pelvic kinematics of 8 competitive scull rowers (19.0 ± 2.1 years, 179.9 ± 7.6 cm, and 74.8 ± 8.1 kg) were collected during 1 hour of rowing on an ergometer and in a rowing tank using a routine training protocol. Kinematics of the upper thoracic spine, lower thoracic spine, lumbar spine, and pelvis were determined using an infrared camera system (Vicon, Oxford, United Kingdom). There was a greater lumbar range of motion (ROM) and less posterior pelvic tilt at the catch during rowing on the ergometer compared with in the rowing tank (p = 0.001-0.048), but no differences in pelvic ROM. In the rowing tank, the pelvic ROM increased over time (p = 0.002) and the ROM of the lower thoracic spine decreased (p = 0.002). In addition, there was an extended drive phase (when the rower applies pressure to the oar levering the boat forward) and an abbreviated recovery phase (setting up the rower's body for the next stroke) in the rowing tank (p = 0.032). Different rowing training methods lead to differences in spinopelvic kinematics, which may lead to substantially different spinal loading situations. Greater pelvic rotation and lesser lumbar ROM are considered ideal; therefore, the present results indicate that rowing in the rowing tank might facilitate the maintenance of this targeted spinopelvic posture, which might help protect the lower back. Rowers, coaches, and researchers should consider the differences between rowing training methods, especially when giving training recommendations.

Nine typical injury patterns in German professional male football (soccer): a systematic visual video analysis of 345 match injuries.

AIM: We aimed to systematically analyse the videos of acute injuries in professional men's football and describe typical injury patterns. METHODS: Injuries were registered with the German statutory accident insurance for professional athletes as part of occupational accident reporting. Following each season (2014-2017), video footage of the two highest divisions in German male football was searched for moderate and severe acute match injuries. Two raters then independently assessed the injuries for: game situation, player and opponent behaviour, referee decision, and injury mechanisms. RESULTS: The total data set included 7493 acute injuries. Of these, 857 (11%) were moderate or severe match injuries. The video search yielded 345 (40%) clearly identifiable injuries and of those 170 (49%) were contact injuries. We describe nine typical injury patterns: one each for head and shoulder injuries, two for thigh and ankle, and three for knee injuries. The nine patterns are called: (1) Head-to-head injury. (2) Collision-and-fall shoulder injury. (3) Sprinter's thigh injury. (4) Perturbation-and-strain thigh injury. (5) Tackle knee injury. (6) Tackle-and-twist knee injury. (7) Non-contact knee injury. (8) Attacked ankle injury. (9) Collision-and-twist ankle injury. Thigh injuries occurred primarily in non-contact situations (44/81), mostly while the player was sprinting (23/44). Knee injuries were often caused by direct external impact (49/84)-mainly suffered by the tackler during a tackle (17/49). CONCLUSION: The nine common injury patterns in football differed substantially in their mechanisms and causes.

Contact - but not foul play - dominates injury mechanisms in men's professional handball: a video match analysis of 580 injuries.

AIM: We aimed to identify patterns and mechanisms of injury situations in men's professional handball by means of video match analysis. METHODS: Moderate and severe injuries (absence of >7 days) sustained in competition in one of six seasons (2010 to 2013 and 2014 to 2017) in men's professional handball were prospectively analysed with a newly developed standardised observation form. Season 2013 to 2014 was excluded because of missing video material. RESULTS: 580 injuries were identified: 298 (51.4%) contact injuries, 151 (26.0%) indirect contact injuries and 131 (22.6%) non-contact injuries. Head (87.5%), hand (83.8%), shoulder (70.2%) and ankle (62.9%) injuries were mainly sustained during direct contact. Typical contact injuries included collision with an opponent's upper extremity or torso, and ankle injuries mainly consisted of foot-to-foot collisions. A large proportion (41.7%) of knee injuries were caused by indirect contact, whereas thigh injuries mainly occurred (56.4%) through non-contact mechanism. Wing (56.9%) and pivot (58.4%) players had the highest proportion of contact injuries, whereas backcourt players had a high proportion of indirect contact injuries (31.5%) and goalkeepers of non-contact injuries (48.9%). The injury proportion of foul play was 28.4%. Most injuries occurred in the central zone between the 6-metre and 9-metre lines (26.1%) and during the last 10 min of each match half (OR 1.71, p=0.016). CONCLUSIONS: In men's professional handball in a league setting, contact - but not foul play - was the most common mechanism associated with moderate and severe injuries. Head, hand, shoulder and ankle injury were mainly sustained during direct contact.

Injury burden differs considerably between single teams from German professional male football (soccer): surveillance of three consecutive seasons.

PURPOSE: The purpose of this study was to analyse unique injury data of the national statutory accident insurance for the two highest divisions in German male football (Bundesliga and 2. Bundesliga) over three consecutive seasons regarding inter-season, inter-division and inter-team differences. METHODS: This was a prospective observational open cohort study over the seasons 2014/2015, 2015/2016 and 2016/2017. Every acute injury that was registered by clubs or physicians with the German statutory accident insurance for professional athletes (VBG) as part of occupational accident reporting and that led to time loss and/or to medical attention, was included. RESULTS: The complete sample consisted of 1449 players. The study covered 2663.5 player seasons with an observed match exposure of 69,058 h and a projected training exposure of 529,136 h. In total, 7493 injuries were included. The overall incidence rate was 12.5 (± 0.28) injuries per 1000 exposure hours, which translated into match and training rates of 47.0 (± 1.62) and 8.02 (± 0.24) injuries per 1000 h, respectively. CONCLUSION: Findings of 2.7 injuries per player and season underline the need of effective preventive approaches. Higher injury incidences in seasons after international tournaments suggest an increasing risk of injury with increasing number of matches. However, large differences between the single teams from the same division indicate that a reduction in the injury burden is generally possible. Continuing the presented injury surveillance might be helpful to identify injury trends in the future and to evaluate the effectiveness of preventive approaches under real-life conditions. LEVEL OF EVIDENCE: Level  II.

Reliability and Validity of a New Portable Tethered Sprint Running Test as a Measure of Maximal Anaerobic Performance.

Limmer, M, Berkholz, A, de Marées, M, and Platen, P. Reliability and validity of a new portable tethered sprint running test as a measure of maximal anaerobic performance. J Strength Cond Res 34(8): 2197-2204, 2020-The purposes of this study were to develop a new portable tethered sprint running (PTSR) test for field-based anaerobic performance testing with restricted spatial conditions and the logistical challenge of carrying test equipment, and to determine reliability of the PTSR test. For validity, performance measures were compared with the cycle ergometer Wingate Anaerobic Test (WAnT) power outputs. Twelve recreationally active men and women (24.3 ± 1.6 years; 1.77 ± 0.07 m; 73.3 ± 12.5 kg) performed one familiarization trial followed by 3 randomly assigned experimental 60-second all-out effort trials consisting of one WAnT and 2 PTSR tests. All trials were performed in a randomized order on different days separated by at least 48 hours. Heart rate (HR) and maximum blood lactate concentration were recorded for each experimental trial to determine the physiological responses to the maximal efforts. Correlation coefficients indicated significant relationships between mean force (MF) and peak force (PF) in the PTSR test and mean power (MP) (r = 0.651, p = 0.022) and peak power (PP) (r = 0.877, p = 0.002) in the WAnT, but not for the fatigue index (r = 0.280, p = 0.379). In addition, both PTSR trials showed no significant differences (p > 0.05) between trials and a high reliability for the performance variables MF (intraclass correlation coefficient [ICC] = 0.98, coefficient of variation [%CV] = 7.7), PF (ICC = 0.98, %CV = 8.4), and HR (ICC = 0.92, %CV = 3.1). In conclusion, our results suggest that despite insufficient stimulation of anaerobic metabolism in some subjects resulting from poor implementation of test instructions, the PTSR is a reliable and valid test for an easy and practical assessment of maximal anaerobic performance under different field conditions.

Increased injury rates after the restructure of Germany's national second league of team handball.

PURPOSE: Scientific injury data in men's professional team handball injuries are rare and even less scientific information exists on injury prevention. In 2011, Germany's national second team handball league was restructured by merging the existing two regional leagues into one league. This study evaluates the injury patterns in professional team handball and compares the injury rates between the first and second league before and after the restructure. METHODS: All players of Germany's national first and second men's team handball leagues have mandatory trauma insurance with the same insurance company. This retrospective cohort study analysed the injury data of three consecutive seasons 2010-2013 using standardized injury definitions. RESULTS: 1194 professional team handball players were included in this study. The majority of severe injuries affected the lower extremities, shoulders, and hands. The average injury incidence significantly differed between the first (4.9 injuries per 1000 h) and the second league (3.9 per 1000 h, p < 0.01). The injury incidence in the restructured second league had increased from 3.7 to 4.1 per 1000 h (p < 0.01) and prevalence from 67.1 to 79.3% (p < 0.001), thus almost to the same levels of the first league. The second league showed more time-loss injuries at all severity levels. CONCLUSION: This study yielded a high injury incidence after the restructure of the national second team handball league and presents details on prevalence, incidence, and patterns of injury in professional men's team handball. This study is an important basis for developing injury prevention strategies that should focus on the shoulders, hands, and lower extremities and on reducing the number of matches and travel burden. LEVEL OF EVIDENCE: III.

Eating disorders and their putative risk factors among female German professional athletes.

This study examines putative non-sport-specific and sport-specific risk factors for eating disorders (ED) among groups of professional female athletes versus non-athletes. In detail, societal pressure to be thin, its internalisation, body dissatisfaction, sports pressure and early specialisation were investigated. The cross-sectional study included 46 aesthetic and 62 ball game sports athletes, and 108 age-matched non-athletes. Study methods comprised a clinical interview to detect ED and questionnaires. More athletes from aesthetic (17%) than from ball game sports (3%) and non-athletes (2%) suffered from ED. Aesthetic sports athletes did not differ from non-athletes in non-sport-specific factors but obtained higher levels than ball game sports athletes in sport-specific variables (p < .01). All factors together accounted for 57.3% of variation in disordered eating, with sports pressure and body dissatisfaction as significant predictors. The results confirm ED risk for German aesthetic athletes and indicate the importance of sports pressure and body dissatisfaction in explaining athletes' vulnerability.

Diurnal profiles of pedometer-determined physical activity in chronically ill and mobility-limited older adults: a cross-sectional study.

BACKGROUND: The aim of this study was to analyze diurnal profiles of physical activity for community-dwelling adults aged 70 years and over, and to explore the moderating effect of sex, age, morbidity, mobility limitation, and season on physical activity throughout the day. METHODS: A sample of 149 primary health care patients (mean age 79.5 ± 5.2 years, 74.5% females) was included in the analyses. Participants' physical activity was measured on up to six consecutive days via Omron Walking Style Pro HJ-720IT-E2 pedometer. Step count per day and per hour, and pedometer wear time were descriptively analyzed. A repeated measures ANOVA with physical activity per hour as dependent variable was performed to analyze the moderating effect of sex, age, morbidity, mobility limitation, and season on diurnal profiles of physical activity. The diurnal profile for the total sample and adjusted diurnal profiles for subgroups are presented. RESULTS: Participants' daily step count averaged 3280 ± 1873 steps/day. They wore the pedometer for 14.2 ± 1.7 hours per day and walked on average 234 ± 139 steps per hour. With respect to diurnal profiles, there were two peaks at 10-11 AM (mean [95%-confidence interval]: 382 [329-435] steps) and at 3-4 pm (313 [261-365] steps) interrupted by a period of lower activity with a low point at 1-2 pm (229 [190-268] steps). A mobility limitation, defined by use of a cane or a rollator, had a significant moderating effect (p = 0.0237) on diurnal physical activity. CONCLUSIONS: This is the first study to explore pedometer-determined diurnal profiles of physical activity in chronically ill and mobility-limited older adults. Prolonging periods of elevated physical activity in the afternoon while respecting individual daily routine and commitments could be one option for facilitating the integration of physical activity and for making it a habit in older adults' daily lives. The use of a walking aid seems to be an indicator for a quite low activity plateau during the second half of the day. People who use walking aids should be motivated to increase their physical activity during afternoon; this might help to increase the overall low physical activity level of this vulnerable subgroup of older adults.

Tissue oxygenation during exercise measured with NIRS: reproducibility and influence of wavelengths.

Near-infrared spectroscopy (NIRS) is widely used for the measurement of skeletal muscle oxygenation during exercise as it reflects muscle metabolism, and most studies report a large variability between subjects. Here we assess the data quality of tissue oxygen saturation (SO2) and oxygenated (oxyHb) and deoxygenated (deoxyHb) haemoglobin concentrations recorded during an incremental cycling protocol in nine healthy volunteers. The protocol was repeated three times on the same day and a fourth session on a different day to estimate the reproducibility of the method with a broadband, spatially resolved spectroscopy (SRS) system. We found that the inter-subject variation in SO2 (standard deviation ≈ 6 %) was considerably larger than the reproducibility (≈ 1.5 %) both for the same-day and different-day tests. The reproducibility of changes in SO2 was better than 1 %.

Performance factors in women's team handball: physical and physiological aspects--a review.

Team handball is an Olympic sport played professionally in many European countries. Nevertheless, a scientific knowledge regarding women's elite team handball demands is limited. Thus, the purpose of this article was to review a series of studies (n = 33) on physical characteristics, physiological attributes, physical attributes, throwing velocity, and on-court performances of women's team handball players. Such empirical and practical information is essential to design and implement successful short-term and long-term training programs for women's team handball players. Our review revealed that (a) players that have a higher skill level are taller and have a higher fat-free mass; (b) players who are more aerobically resistant are at an advantage in international level women team handball; (c) strength and power exercises should be emphasized in conditioning programs, because they are associated with both sprint performance and throwing velocity; (d) speed drills should also be implemented in conditioning programs but after a decrease in physical training volume; (e) a time-motion analysis is an effective method of quantifying the demands of team handball and provides a conceptual framework for the specific physical preparation of players. According to our results, there are only few studies on on-court performance and time-motion analysis for women's team handball players, especially concerning acceleration profiles. More studies are needed to examine the effectiveness of different training programs of women's team handball players' physiological and physical attributes.

A novel motorized office chair causes low-amplitude spinal movements and activates trunk muscles: A cross-over trial.

INTRODUCTION: Inactivity and long periods of sitting are common in our society, even though they pose a health risk. Dynamic sitting is recommended to reduce this risk. The purpose of this study was to investigate the effect of continuous passive motion (CPM) conducted by a novel motorized office chair on lumbar lordosis and trunk muscle activation, oxygen uptake and attentional control. STUDY DESIGN: Randomized, single-session, crossover with two periods/conditions. METHODS: Twenty office workers (50% women) sat for one hour on the motorized chair, one half with CPM, the other not. The starting condition (CPM/no CPM) was switched in half of the sample. The participants were equipped with a spirometric cart, surface EMG, the Epionics SPINE system and performed a computer-based test for attentional control (AX-CPT). Outcomes were lumbar sagittal movements and posture, number of trunk muscle activations, attentional control and energy expenditure. RESULTS: The CPM of the chair causes frequent low-amplitude changes in lumbar lordosis angle (moved: 498 ± 133 vs. static: 45 ± 38) and a higher number of muscle activations. A periodic movement pattern of the lumbar spine according to the movement of the chair was observed in every participant, although, sitting behavior varied highly between individuals. Attentional control was not altered in the moved condition (p = .495; d = .16). Further, oxygen uptake did not increase higher than 1.5 MET. CONCLUSION: The effects of the motorized chair can be particularly useful for people with static sitting behavior. Further studies should investigate, whether CPM provides the assumed beneficial effects of dynamic sitting on the spine.

Metabolic power and energy expenditure in the German Bundesliga.

The aims of the study were to analyze metabolic power (MP) and MP derived parameters for different positions in the German Soccer Bundesliga and to evaluate if classification of high-intensity is more suited using the metabolic power approach instead of using traditional speed-based methods. 1,345 video match analysis (25 Hz) datasets from 380 players in 96 matches of the German first Bundesliga were gathered by an automatic player tracking system. Displacement (speed, acceleration, distance) and energetic (MP, energy expenditure) variables were determined. Intensity was classified utilizing conventional thresholds. Metabolic and running profiles were compared among six positional groups and between the halves of the match respectively (one-way ANOVA). Further, time spent, distance covered and energy expended at high speed (>15.5 km h-1) and high acceleration (>2 m s-2) were compared to those at high MP (>20 W kg-1) (one-way ANOVA) for evaluating if metabolic power is more suited to describe intensity in team sports. Main findings are that central-attacking midfielders (CAM) and central midfielders (CM) expended more energy (CAM: 59.8 ± 4.2 kJ kg-1; CM: 59.6 ± 3.6 kJ kg-1) and covered more distance (CAM: 11,494 ± 765 m; CM: 11,445 ± 638 m) than all other positions (p < 0.001). In the whole group of players, less time (t) and less energy were expended (EE) in high speed (t: 302 ± 84 s; EE: 10.1 ± 2.9 kJ kg-1) and at high acceleration zones (t: 147 ± 24 s; EE: 5.5 ± 1.2 kJ kg-1) when compared to high MP zone (t: 617 ± 141 s; EE: 20.0 ± 4.4 kJ kg-1) (p < 0.001). Furthermore, players covered more distance at high MP (2,464 ± 597 m) than at high speed (1,638 ± 458 m) and much less at high acceleration (359 ± 67 m) (p < 0.001). The higher activity profiles of CAM and CM compared to the other positions indicate the need for higher developed physiological performance in players of these positions. High intensity activities should be interpreted differently when using MP and displacement parameters as indicators of high intensity in soccer.

Dose-response relationship and effect modifier of stabilisation exercises in nonspecific low back pain: a project-wide individual patient data re-analysis on 1483 intervention participants.

ABSTRACT: This planned MiSpEx-Network reanalysis was designed to derive a dose-response relationship under consideration of further effect modifiers in exercises on low back pain. One thousand four hundred eighty three intervention participants with low back pain (mean age, 40.9 years [SD 14 years]) performed stabilisation exercises (3 weeks supervised, 9 weeks self-administered). Patients reported pain intensity, disability, and disability days at baseline, 3 weeks, 12 weeks, and 6 months post randomisation. Exercise characteristics and effect modifiers were prospectively monitored. Beyond the comparison to the results of the control group, linear mixed models were calculated to determine a dose-response relationship. The interventions led to small but significantly larger symptom reductions than in the control group at each measurement. Longer durations of the intervention led to larger symptom reductions. Higher exercise frequencies were associated with a decrease in pain intensity: to train once more per week led to a mean decrease of 0.93 points in pain intensity [95% CI = -1.54 to -0.32]. Disability days were also impacted (estimate = -0.07 [-0.14 to 0.00]), but disability was not (-0.09 [-0.67 to 0.48]). Adding perturbation was superior to adding stretching or a behavioural module. The relationships were robust when additional effect modifiers were considered and against the control group' effects. The odds ratio for a clinically important effect with higher exercise frequencies decreased at 3 weeks (OR = 0.71 [0.618-0.813] for >2.5*week -1 ) and increased at 12 weeks (1.13 [1.006-1.270], >1.5*week -1 ). Using longer intervention durations, adding a perturbation component to the stabilisation trainings and using higher frequencies (up to a certain point) may lead to an even more beneficial response on exercise in patients with low back pain. Developing strategies to maintain a training frequency of at least 2 times per week may be relevant in stabilisation exercises to treat low back pain.

Plasticizers excreted in urine: indication of autologous blood transfusion in sports.

BACKGROUND: Misuse of autologous blood transfusions in sports remains undetectable. The metabolites of the plasticizer di-(2-ethylhexyl)phthalate (DEHP) were recently proposed as markers of blood transfusion, based on high urinary concentrations of these compounds observed in patients subjected to blood transfusion. This study evaluates DEHP metabolites in urine for detecting autologous blood transfusion. STUDY DESIGN AND METHODS: One blood bag was drawn from moderately trained subjects and the red blood cells (RBCs) were reinfused after different storage periods. Group 1 (12 subjects) was reinfused after 14 days, and Group 2 (13 subjects), after 28 days of storage. Urine samples were collected before and after reinfusion for determination of the concentrations of three DEHP metabolites, mono-(2-ethylhexyl)phthalate, mono-(2-ethyl-5-hydroxyhexyl)phthalate, and mono-(2-ethyl-5-oxohexyl)phthalate. RESULTS: Concentrations of DEHP metabolites on the days before reinfusion were in agreement with those described after common environmental exposure. A few hours after the reinfusion a significant increase was observed for all metabolites in all volunteers. Concentrations 1 day later were still higher (p < 0.05) than before reinfusion. Variations in urine dilution supported normalization by specific gravity. Concentrations of DEHP metabolites tended to be higher after longer storage times of RBCs. CONCLUSION: Autologous transfusion with RBCs stored in plastic bags provokes an acute increase in the urinary concentrations of DEHP metabolites, allowing the detection of this doping malpractice. The window of detection is approximately 2 days. The method might be applied to urine samples submitted for antidoping testing.

Cycling exercise-induced myofiber transitions in skeletal muscle depend on basal fiber type distribution.

The link between specific changes in myofiber type proportions and modulation of training in human skeletal muscle has yet to be unraveled. We investigated whether a defined increase in training volume induces a corresponding change of myofiber shifting in human skeletal muscle with distinct basal myofiber distribution. Twenty-one male cyclists (Age 26 ± 4 years) with different performance levels were exposed to increased cycling training volume with reduced power output for 3 months. Biopsies were taken from vastus lateralis muscle PRE-POST and the proportions of type I, IIa, IIx and IIc myofibers were determined. Total training time did not correlate to the degree of fiber type shifting of any type. In the entire sample of subjects, the proportion of type I myofibers tended to increase (P = 0.14) while IIa fibers decreased significantly (P < 0.05). Subgroups of subjects possessing higher (HPS) and lower proportions (LPS) of type I myofibers at baseline showed a distinct pattern in changing myofiber distribution. Subjects in HPS offered no change in myofiber proportions of any type. In contrast, subjects in LPS showed marked increases in type I (P = 0.06) and a significant reduction in IIa myofibers (P = 0.01). An inverse correlation between baseline proportion of type I and IIa myofibers and its change was observed. We conclude that individual myofiber composition constitutes a modulating factor for exercise-induced changes in its distribution. This might be influenced by altered demands of myofiber recruitment in relation to the intensity of muscle contraction but also by its relative abundance in contracting muscle.

Optimal Jamar dynamometer handle position to assess maximal isometric hand grip strength in epidemiological studies.

PURPOSE: Hand grip strength is an indicator of general muscle strength that is measured using a hand dynamometer. In some studies, a subject's grip strength is taken to be the maximal grip strength achieved from measurements taken at several different dynamometer handle positions. However, little is known about the influence of these different positions on the measured grip strength. The aim of the study was to identify one standard handle position that could be used to assess the grip strength of all subjects. METHODS: Grip strength was assessed with a hand dynamometer (Jamar Plus+; Sammons Preston, Rolyon, Bolingbrook, IL). Each participant's grip strength was measured 3 times in each of 5 different handle positions with each hand. The best position for each participant was defined as the position at which they achieved maximal grip strength. RESULTS: The mean (± standard deviation) age of the 50 participants was 41 (± 13) years. Maximal grip strength was 43.7 (± 12.4) kg for all participants; 55.0 (± 10.2) kg for men and 35.4 (± 5.2) kg for women. Handle position 2 was the best position for 70% of participants. The mean difference between the grip strength achieved by each participant at handle position 2 and that achieved at each participant's best position was 0.8 (± 1.78) kg. CONCLUSIONS: Our results show that measurements taken at a single standard handle position are sufficiently accurate to assess grip strengths for all subjects. We therefore recommend handle position 2 as the standard position for measuring grip strength with the Jamar Plus+ hand dynamometer. CLINICAL RELEVANCE: The assessment of grip strength with the Jamar Plus+ dynamometer is easier and faster if a single, standard handle position is used rather than multiple different positions. As well as providing accurate results, a single, standard handle position also reduces fatigue and increases the comparability of results between subjects.

Perturbation-based trunk stabilization training in elite rowers: A pilot study.

INTRODUCTION: Low back pain is a major health issue in elite rowers. High training volume, frequent flexion movements of the lower spine and rotational movement in sweep rowing contribute to increased spinal strain and neuropathological patterns. Perturbation-based trunk stabilization training (PTT) may be effective to treat neuromuscular deficits and low back pain. METHODS: All boat classes (8+, 4+/-, 2-) of the male German national sweep rowing team participated in this non-randomized parallel group study. We included 26 athletes (PTT: n = 12, control group: n = 14) in our analysis. Physical and Sports therapists conducted 16 individualized PTT sessions á 30-40 minutes in 10 weeks, while the control group kept the usual routines. We collected data before and after intervention on back pain intensity and disability, maximum isometric trunk extension and flexion, jump height and postural sway of single-leg stance. RESULTS: We found less disability (5.3 points, 95% CI [0.4, 10.1], g = 0.42) for PTT compared to control. Pain intensity decreased similar in both groups (-14.4 and -15.4 points), yielding an inconclusive between-group effect (95% CI [-16.3, 14.3]). Postural sway, strength and jump height tend to have no between- and within-group effects. CONCLUSION: Perturbation-based trunk stabilization training is possibly effective to improve the physical function of the lower back in elite rowers.