The use of fractal dimension methods in clinical epidemiology: an application for postural assessment

Background: this study considers the analysis of postural sway by comparing the use of a fractal dimension outcome (DBOX) with the usual sway ellipse area (SEA), calculated by the least squares method. Both the response variables come from centre of pressure (COP) dynamics detected by means of a force platform. Methods: recent literature regarding postural stability assessment in subjects with muscularskeletal disorders, or neuromuscular diseases affecting their motor skills, has suggested, both for practical and theoretical reasons, the use of some fractal dimension as a good outcome measurement for overall postural status. A sample group of 24 male subjects was recruited. The postural stabilogram was recorded both with eyes open (EO) and eyes closed (EC) while standing upright. A matched-pair comparison of the sway ellipse area with the COP dynamics box counting dimension was performed. A ROC analysis of the outcome variables was performed. Then, a ROC comparison of the tests, using the area under the curve (AUC) index, was conducted. Results: the comparison of paired groups showed a statistically significant difference between EO and EC status, according to the sway ellipse area and the fractal dimension (p<0.05). The ROC analysis, describing the test performance in terms of AUC difference, was statistically significant (p<0.05). The comparison of the AUCs showed an overall superior performance of the DBOX with respect to SEA (p<0.05). Conclusions: this study showed a statistically significant better overall performance of DBOX with respect to SEA, suggesting possible improvements of clinical practice, as well as theoretical insights into the response patterns

The Influence of Maturity Status on Anthropometric Profile and Body Composition of Youth Goalkeepers

The anthropometric profile assessment is an important aspect to consider during the growth stages of youth sport practitioners due to its usefulness in controlling maturity status and overall health. We performed an anthropometric profile evaluation in a sample of youth goalkeepers (n = 42) during a training camp, dividing them into three categories based on their years from peak height velocity (YPHV). We also checked if the selection of goalkeepers was associated with the birth quartile. The results showed that most of the participants’ anthropometric parameters followed the normal trend according to the maturation stages. However, several subjects showed an overweight/obese condition and/or high waist circumference. Non-optimal values were found, mostly in the group of goalkeepers around the PHV. In addition, no selection based on birth quartile was seen. Therefore, the anthropometric profile and body composition of youth goalkeepers are physiologically affected by maturity status. However, several subjects were found to be overweight/obese and at cardiometabolic risk, suggesting that children and adolescents, although practicing sport, should pay attention to potentially contributing factors such as the attainment of the recommended levels of physical activity, lowering sedentary time, and adopt a healthy lifestyle

Training loads of a microcycle during the competitive season (first year).

<p>Training loads of a microcycle during the competitive season (first year).</p

Flow diagram of the experimental design.

<p>The first and second testing sessions were performed on two different days separated by two days of rest. The measurements were taken at the same time of day for several testing days. SSP15 = Short Sprint Performance (15 m), SSP30 = Short Sprint Performance (30 m), SJ = Squat Jump CMJ = Counter Movement Jump, HT = Hopping Test, CCMJ = Continuous Counter Movement Jump.</p

Training loads of a microcycle during the competitive season (second year).

<p>Training loads of a microcycle during the competitive season (second year).</p

Explosive strength and endurance adaptations in young elite soccer players during two soccer seasons

<div><p>The purpose of the present study was to investigate the explosive strength and endurance adaptations in young elite soccer players who underwent a supervised training program for a period of two years. Nineteen players, with seven years of training experience (age: 13.3 ± 0.1 years; body weight: 57.9 ± 4.9 kg; height: 168.9 ± 4.7 cm; BMI: 20.1 ± 1.1 kg/m²), voluntarily participated in the present study. The testing sessions were performed at the beginning of the preparation period in the first (T1), second (T2), and third year (T3). The following performance variables were measured: explosive strength [squat-jump (SJ) and counter-movement-jump (CMJ)], pre-stretch augmentation (CMJ-SJ), leg stiffness [hopping test (HT)], short sprint performance [15 m (SSP15) and 30 m (SSP30)], aerobic endurance [test of Leger (VO2max)], maximal heart rate [at the last step of Leger (HR)], and speed-strength endurance [continuous counter-movement-jumps (CCMJ)]. A significant main effect on the VO2Max (+5.72%; F_(2.49) = 3.822; <i>p</i> = 0.029; ES = 1.00), HR (-1.70%; F_(2.54) = 3.472; <i>p</i> = 0.038; ES = 0.97), CCMJ (+7.64%; F_(2.54) = 5.438; p = 0.007; ES = 1.15), SJ (+10.26%; F_(2.54) = 15.254; p = 0.0001; ES = 1.53), CMJ (+7.36; F_(2.54) = 8.270; <i>p</i> = 0.001; ES = 1.33), HT (+8.34%; F_(2.48) = 3.297; <i>p</i> = 0.046; ES = 1.01), SSP15 (-3.50%; F_(2.44) = 12.760; <i>p</i> = 0.0001; ES = 1.53), and SSP30 (-4.44%; F_(2.44) = 5.797; <i>p</i> = 0.006; ES = 1.16) was observed in the two soccer seasons. These results highlight that, in long-term training, the monitoring of the adaptive responses in relation to the training load may provide a guideline to optimize the trainability of some performance variables in young elite soccer players (13–15 years). In the present study, we cannot exclude the influence of growth and maturation on some performance variables; therefore, the monitored adaptive responses should be considered as the possible results of an interaction between the applied training load and maturation.</p></div

Reliability of the variables.

<p>Reliability of the variables.</p

Mean values (SE) for SSP15 and SSP30.

<p>T1, T2 and T3 represent the test times. (SSP15) *Significant differences between T1 and T2 (p = 0.019). **Significant differences between T1 and T3 (p = 0.001). †Significant differences between T2 and T3 (p = 0.0001). (SSP30) *Significant differences between T1 and T2 (p = 0.0047). **Significant differences between T1 and T3 (p = 0.0001). †Significant differences between T2 and T3 (p = 0.027).</p

Anthropometric characteristics of the soccer players.

<p>Anthropometric characteristics of the soccer players.</p

Training loads of a microcycle during the preparation period (second soccer year).

<p>Training loads of a microcycle during the preparation period (second soccer year).</p