ObjectivesThe aim of this study was to examine the concurrent validity of the HUMAC Balance System (HBS) and Balance Trainer BTG4 (BTG) in comparison to a laboratory-grade force platform (FP) for postural control (PC) and vertical jump performance (VJP) assessment. In addition, reliability of the three devices was measured for PC.MethodsOverall 22 participants (age = 37.8 ± 13.3 years; gender = 9 male, 13 female; height = 174.1 ± 10.5 cm; body mass = 75.3 ± 17.6 kg) were recruited to participate. Double and single leg standing balance tests with eyes open or closed and counter movement jumps (CMJ) were performed on two separate occasions. Reliability and concurrent validity for COP parameters and VJP were examined using intraclass correlation coefficients (ICC), Bland-Altman plots (BAP), standard error of measurement (SEM) and minimum detectable change (MDC).ResultsCOP path length test-retest reliability was predominantly good to excellent for all three devices (ICC = 0.80–0.95). SEM and MDC values were high for all plates (SEM% = 8.0–15.2; MDC% = 22.8–44.5), with the HBS MDC values higher than the KIS and BTG in three of the four trials. ICC scores for concurrent validity were good to excellent for the BTG (ICC = 0.76–0.93) and moderate to good for the HBS (0.49–0.83). Band-Altman plots revealed a systematic bias for the HBS towards higher COP path length values under all conditions and for the BTG in two out of four trials towards lower values. Validity of VJP was excellent for the BTG (ICC = 1.0) and poor for the HBS (0.34), with a systematic bias towards lower values.ConclusionThe comparative analysis of PC and VJP revealed reliable and valid results for the BTG in comparison to a laboratory-grade force plate. The HBS showed reliable results for PC assessment with restrictions regarding its validity. Results of VJP showed that the HBS revealed deficits in the assessment of activities that require rapid, high force movements such as jumping and running. Due to the variable results of all three devices, it is recommended not to use them interchangeably.

Supplemental Digital Content is Available in the Text.Longer stabilisation exercise durations and intervention frequencies of 2.5 times per week led to the largest symptom reductions in low back pain.

Introduction:Analyzing metabolic power of horizontal movements may contribute to the understandings of physical and metabolic demands in professional handball. Purpose:To ascertain the typical metabolic power characteristics of elite handball players of different positions, and whether changes occur within matches during the European Championship 2020.Design: Prospective cohort study.Methods: 414 elite male handball players were included. During all 65 matches of the EURO 2020, local positioning system data were collected (16.6 Hz), yielding in 1853 datasets. Field players were categorized in six positional groups: centre backs (CB), left and right wings (LW/RW), left and right backs (LB/RB) and pivots (P). Metabolic power, total energy expenditure, high-power energy and the equivalent distance index was calculated from the position data and further processed as dependent variables. We used linear mixed models with players as random and positions as fixed effects models. Intensity models included time played to account for a time-dependency of the intensity.Results: LW/RW spent most time on the pitch, expended most total energy, and most relative energy per kg body weight in the high intensity categories. CB played at the highest mean intensity (highest mean metabolic power). Playing intensity decreased with longer playing time in a curvilinear manner with a stronger decrease in the short playing time areas. Conclusion:Metabolic power intensity profiles are modulated by playing positions and players' time on the pitch. Analysis of metabolic intensity in handball should take these parameters into account for optimizing training and performance during matches.

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. ResultsThe 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.

Introduction:Analyzing metabolic power of horizontal movements may contribute to the understandings of physical and metabolic demands in professional handball. Purpose:To ascertain the typical metabolic power characteristics of elite handball players of different positions, and whether changes occur within matches during the European Championship 2020.Design: Prospective cohort study.Methods: 414 elite male handball players were included. During all 65 matches of the EURO 2020, local positioning system data were collected (16.6 Hz), yielding in 1853 datasets. Field players were categorized in six positional groups: centre backs (CB), left and right wings (LW/RW), left and right backs (LB/RB) and pivots (P). Metabolic power, total energy expenditure, high-power energy and the equivalent distance index was calculated from the position data and further processed as dependent variables. We used linear mixed models with players as random and positions as fixed effects models. Intensity models included time played to account for a time-dependency of the intensity.Results: LW/RW spent most time on the pitch, expended most total energy, and most relative energy per kg body weight in the high intensity categories. CB played at the highest mean intensity (highest mean metabolic power). Playing intensity decreased with longer playing time in a curvilinear manner with a stronger decrease in the short playing time areas. Conclusion:Metabolic power intensity profiles are modulated by playing positions and players' time on the pitch. Analysis of metabolic intensity in handball should take these parameters into account for optimizing training and performance during matches.