Gross motor coordination in relation to weight status: a longitudinal study in children and pre-adolescents

Introduction: Gross Motor Coordination (GMC) is crucial for the adequate development of motor competence. Our purpose in this semi-longitudinal study was to evaluate the influence of BMI on GMC in children and pre-adolescents of both sexes, across school years (classes). Methods: We evaluated 117 subjects (aged 8–13 years) belonging to three different cohorts for 4 consecutive years, providing data over 6 years (classes). GMC was assessed through the Körperkoordinationstest für Kinder (KTK) test. Class and weight status effects were then evaluated by dividing the subjects into a normal weight group and an overweight group based on their weight status. Results: A significant increase across classes was found for BMI (p < 0.001) and KTK raw score (p < 0.001) and a decrease was found for KTK normalized score (MQ) (p = 0.043). Significantly lower MQ values were found for girls. Absolute GMC increased across the years and there was no difference between boys and girls. Correlations between GMC scores and BMI were negative and significant in 5 of 6 classes. It was confirmed that overweight subjects had lower MQ and RAW values than normal-weight subjects, with no class-by-weight status interaction. Discussion: The level of competence and its development are strictly dependent on weight status during childhood and pre-adolescence. The present investigation suggests that the adequate development of GMC requires not only targeted physical education programs but also the promotion of healthy habits aimed at maintaining a normal weight status during childhood and pre-adolescence

Talent development in young cross-country skiers: longitudinal analysis of anthropometric and physiological characteristics

Introduction: Very little is known about talent development and selection processes in young cross-country skiers. Aim: (1) to analyze the effect of age on anthropometric and physiological parameters in medium-to-high level cross-country skiers during the late teenage period; (2) to describe parameters' trend in selected talents after the late teenage period; (3) to define which characteristics during the late teenage period could discriminate against further talent selection. Method: We found 14 male (M) and nine (F) athletes in our database, identified as talents by regional teams during the late teenage period, who performed the same diagonal-stride roller-skiing incremental test to exhaustion at 17 and 18 years old. Of these, four M and three F teenagers performed four further evaluations, and were selected by the national team. Age effect during the late teenage period was verified on anthropometric and physiological parameters measured at maximal intensity (MAX), first (VT1), and second (VT2) ventilatory thresholds, and 3\ub0 and 6\ub0 of treadmill incline. An observational analysis allowed to evaluate parameters' trend after the late teenage period in selected athletes, and to determine possible characteristics early discriminating further selection. Results: During the late teenage period, height, weight, and BMI was still raising in M as well as V'O2 at VT2 and 6\ub0 of treadmill incline (all P > 0.05). In F, mass-scaled V'O2 MAX increased while heart rate (HR) at MAX and VT2 decreased (all P > 0.05). Since the late teenage period, all selected males showed maximal ventilation volumes, absolute V'O2 at MAX, VT1, and VT2 that were within or above the 75th percentile of their group; the same was found in selected females for mass-scaled V'O2 MAX, VT1, and VT2 time. After the late teenage period, all selected athletes showed an increasing trend for VT2 time, while a decreasing trend for sub-maximal energetic cost, %V'O2 and HR. Discussion: During the late teenage period, males are still completing their maturation process. Since the late teenage period, some physiological parameters seem good indicators to early discriminate for further talents. A progressive increase in skiing efficiency was demonstrated in developing talents of both sexes after the late teenage period

Neuromuscular Fatigue Does Not Impair the Rate of Force Development in Ballistic Contractions of Submaximal Amplitudes

The effect of muscle fatigue on rate of force development (RFD) is usually assessed during tasks that require participants to reach as quickly as possible maximal or near-maximal force. However, endurance sports require athletes to quickly produce force of submaximal, rather than maximal, amplitudes. Thus, this study investigated the effect of muscle fatigue induced by long-distance running on the capacity to quickly produce submaximal levels of force. Twenty-one male amateur runners were evaluated before and shortly after a half-marathon race. Knee extensors force was recorded under maximal voluntary and electrically evoked contractions. Moreover, a series of ballistic contractions at different submaximal amplitudes (from 20 to 100% of maximal voluntary force) was obtained, by asking the participants to reach submaximal forces as fast as possible. The RFD was calculated for each contraction. After the race, maximal voluntary activation, resting doublet twitch, maximal force, and RFD during maximal contraction decreased (-12, -12, -21, and -19%, respectively, all P-values < 0.0001). Nevertheless, the RFD values measured during ballistic contractions up to 60% of maximal force were unaffected (all P-values > 0.4). Long-distance running impaired the capacity to quickly produce force in ballistic contractions of maximal, but not of submaximal, amplitudes. Overall, these findings suggest that central and peripheral fatigue do not affect the quickness to which muscle contracts across a wide range of submaximal forces. This is a relevant finding for running and other daily life activities that rely on the production of rapid submaximal contractions rather than maximal force levels

Neuromuscular fatigue does not impair the rate of force development in ballistic contractions of submaximal amplitudes

The effect of muscle fatigue on rate of force development (RFD) is usually assessed during tasks that require participants to reach as quickly as possible maximal or nearmaximal force. However, endurance sports require athletes to quickly produce force of submaximal, rather than maximal, amplitudes. Thus, this study investigated the effect of muscle fatigue induced by long-distance running on the capacity to quickly produce submaximal levels of force. Twenty-one male amateur runners were evaluated before and shortly after a half-marathon race. Knee extensors force was recorded under maximal voluntary and electrically evoked contractions. Moreover, a series of ballistic contractions at different submaximal amplitudes (from 20 to 100% of maximal voluntary force) was obtained, by asking the participants to reach submaximal forces as fast as possible. The RFD was calculated for each contraction. After the race, maximal voluntary activation, resting doublet twitch, maximal force, and RFD during maximal contraction decreased (-12, -12, -21, and -19%, respectively, all P-values 0.4). Long-distance running impaired the capacity to quickly produce force in ballistic contractions of maximal, but not of submaximal, amplitudes. Overall, these findings suggest that central and peripheral fatigue do not affect the quickness to which muscle contracts across a wide range of submaximal forces. This is a relevant finding for running and other daily life activities that rely on the production of rapid submaximal contractions rather than maximal force levels

Exploring muscle activation during nordic walking: a comparison between conventional and uphill walking

Nordic Walking (NW) owes much of its popularity to the benefits of greater energy expenditure and upper body engagement than found in conventional walking (W). Muscle activation during NW is still understudied, however. The aim of the present study was to assess differences in muscle activation and physiological responses between NW and W in level and uphill walking conditions. Nine expert Nordic Walkers (mean age 36.8\ub111.9 years; BMI 24.2\ub11.8 kg/m2) performed 5-minute treadmill trials of W and NW at 4 km/h on inclines of 0% and 15%. The electromyographic activity of seven upper body and five leg muscles and oxygen consumption (VO2) were recorded and pole force during NW was measured. VO2 during NW was 22.3% higher at 0% and only 6.9% higher at 15% than during W, while upper body muscle activation was 2- to 15-fold higher under both conditions. Lower body muscle activation was similarly increased during NW and W in the uphill condition, whereas the increase in erector spinae muscle activity was lower during NW than W. The lack of a significant increase in pole force during uphill walking may explain the lower extra energy expenditure of NW, indicating less upper body muscle activation to lift the body against gravity. NW seemed to reduce lower back muscle contraction in the uphill condition, suggesting that walking with poles may reduce effort to control trunk oscillations and could contribute to work production during NW. Although the difference in extra energy expenditure between NW and W was smaller in the uphill walking condition, the increased upper body muscle involvement during exercising with NW may confer additional benefit compared to conventional walking also on uphill terrains. Furthermore, people with low back pain may gain benefit from pole use when walking uphill

Cost of force generation in double poling cross-country skiing

Upper body has a considerable role in cross-country skiing particularly during double poling (DP), in which strong and fast propulsive actions are exerted entirely through the poles. Our hypothesis was that metabolic rate during DP exercises is determined by the cost of force generation. Furthermore, since DP is far from human legged-locomotion, we hypothesized that the cost of force generation coefficient (K [J\u2022N-1]) could be more predictive of performance than energetic cost of locomotion (C [J\u2022m-1\u2022kg-1]), because of the dimensional meaning of the measurements

Effect of training on specific power expression in elite cross country skiers

Cross country skiing is characterized by many techniques which differ in contribution offered by upper and lower limbs to propulsion. In diagonal stride technique upper and lower body are fully involved in the movement. The aim of this study is to analyze upper body contribution in diagonal stride and the effect of training on specific power expression in elite cross country skiers

Double poling kinematic changes during the course of a long-distance race: effect of performance level

We aimed to evaluate the changes in double poling (DP) kinematics due to a long-distance cross-country skiing race in athletes with different performance levels. A total of 100 cross-country skiers, belonging to 10 different performance groups, were filmed on flat terrain 7 and 55 km after the start line, during a 58-km classical race. Cycle velocity, frequency and length decreased from the best to the lower-ranked group, while duty cycle increased (all P <.001). Between track sections, cycle velocity and length decreased, duty cycles increased (all P <.001) while frequency was unaltered (P =.782). Group*section interactions resulted for cycle velocity (P =.005). Considering all the participants together, % change in cycle velocity between sections correlated with % change in length and duty cycle (all P <.001). Thus i) skiers in better groups showed longer and more frequent cycles as well as shorter duty cycles than skiers in slower groups; ii) throughout the race all the groups maintained the same cycle frequency while decreasing cycle velocity and length; iii) better groups showed a lower reduction in cycle velocity. Individually, a low reduction in cycle velocity during the race related to the capacity to maintain long cycles and short duty cycles

From front to back-load ergometer: muscular and biomechanical differences

The relevance of double poling ski technique is already underlined by a lot of authors. Double poling technique involves massively upper body (Holmberg, 2005).To achieve high specificity of indoor double poling force training, different ergometers are developed. The aim of this preliminary study was to compare biomechanical and neuromuscular differences between standard pull-down ergometer and a new idea of back-load ergometer to better emulate double poling technique during maximal force training