Table 1: Body composition of the young soccer players participating in the study

 

Legend: PHV = Peak Height Velocity; APHV: Age Peak Height Velocity; BM: Body Mass; VmaxM: Velocity maximum Match; Tukey post hoc tests; significant differences (p <0.05) between maturational groups in relation to Pre-PHV (*); Mid-PHV (#); Post-PHV (ⱡ).

 

Figure 1: Comparison of the parameters of the explosive strength manifestations: a) neural component (SJ); b) elastic component (CMJ); c) stretch speed component (DJ); d) reflex component (DJ h / t); e) reactive stiffness component (CJ 5s). indicates group differences * (p <0.05) and ** (p <0.01).

 

 

 

Performance of strength manifestation

This study results revealed that the three maturational groups differed in performance of strength manifestations, estimated in SJ vertical jumping techniques (F = 118.069, p < 0.01), CMJ (F = 106.28, p < 0.01), DJ (F = 15.19, p < 0.01), DJ h/t (F = 116.02, p < 0.01), and CJ5s (F = 35.48, p < 0.01).

 

Relation between speed and strength in the Mid-PHV

                                     Significant positive relations were observed between the maximum speed during a soccer match with the vertical jump technique CJ5s (r = 0.640; p <0.05). However, no significant correlations were found with the other strength variables.

The relation between strengths, significant positive correlations were observed between some strength manifestations, as between some of the parameters of strength production; (r = 0.760, p <0.05), DJ x DJ h / t (r = 0.677, p<0.05) = P<0.05), DJh / t (r = 0.911, p <0.05), DJ x CJ5s (r = 0.529, p <0.05). For the strength production parameters, relations between strength production and eccentric strength (r = 0.503, p <0.05), isometric and eccentric strength (r = 0.700, p <0.05), eccentric strength and coupling r = 0.566, p <0.05), and isometric strength x coupling (r = 0.490, p <0.05). There were no other significant correlations (p> 0.05) between the strength variables (Table 4).

Relation between speed and strength in the Post-PHV

Significant positive relations were observed in the Post-PHV group between speed and all strength variables. Significant positive relations were observed between the strength manifestations and between the parameters of strength production, as between both (Table 5). However, significant negative relations were observed between the coupling parameter and the vertical jump technique variables in the strength estimation.

 

 

Table 4: Correlation between variables coefficient in the Mid-PHV group

 

Legend: *p <0.05; VmaxM: Velocity maximum Match; SJ: Squat Jump; CMJ: Countermovement Jump; DJ: Drop Jump; DJ h / t: Drop Jump high / time; CJ5s: continuum Jump five seconds; RSF: rate of strength production; ES: eccentric strength; IS: isometric strength; C: coupling.

 

Table 5: Correlation coefficient between variables in the Post-PHV

 

Legend: *p <0.05; VmaxM: Velocity maximum Match; SJ: Squat Jump; CMJ: Countermovement Jump; DJ: Drop Jump; DJ h / t: Drop Jump high / time; CJ5s: continuum Jump five seconds; RSF: rate of strength production; ES: eccentric strength; IS: isometric strength; C: coupling.

 

 

Discussion

The main discovery of the present study was that the variation in the statistics of the maximum speed performances, obtained during a football match with young players, is detailed by a combination of parameters of the strength production and some strength manifestation’s estimates measured by vertical jump tests inside the protocol of somatic maturation.

In comparing maturational groups, significant differences were perceived, mainly about the maximum speed attained in a soccer match, and the performances of strength, both in the one estimated by manifestations of strength as in the one dimensioned by strength production’s parameters. This revealed that the Post-PHV group exhibit superior performance in comparison to others. Growth of maturation has reflected in substantial rise in strength and speed performance in all groups – this was reported also in some other researches ^{32,34,35,40,42,44}. 

Analysis has shown three different tendencies about how the trend behaves on the determination of strength influence in the maximum speed during a match in distinct maturational groups. In the first course, the strength attributes have a moderate weight in speed performance for the Pre-PHV group. In the second trend, strength had a minor determination on the speed in the group in Mid-PHV, yet it was not significant. Ultimately, in the third trend, there was a distinguished variable with major influence upon the speed by the strength in the Post-PHV group.

 

Influence of strength performance in the speed to Pre-PHV group.

 

Results of multiple regression have indicated significant explanation of 40,48% (Multiple Determination Coeficient, R²=0.4048) of the strength generation performance and its manifestations in vertical jump tests, that predicts influences upon speed in soccer matches on Pre-PHV group. The strength behavior explained some variations from the motion to stabilization of the movement, which was the primary predictor of velocity performance.

This may reflect the more dynamic nature of these tasks, especially in the case of the maximum speed of movement during the game, and causes a greater need for unilateral stabilization skills and mechanisms of equilibrium movement to efficiently perform shifts in agility movements, accelerations and running speed^1,35,44. Interestingly, the stability of the motion contributed to explain the variation in the performance of the maximum velocity during the start in the Pre-PHV group. It appears that these youngsters in the present study may not have the necessary motor coordination and strength to effectively guide, stabilize and apply strength through their lower limbs^16,35.

The results have indicated that somatic maturation still have some relevance, although being small or moderate, in explaining the fluctuation associated both in the strength generation to optimize maximum speed during a match, as well as to increase its power through the manifestations of strength. Therefore, suggesting that the performance in both of them related to the maturational status^4,44.

This notion is also portrays in the high to moderate connexion (r=0,553 a 0,882; p<0,05) between the vertical jump techniques, such as strength output (r=-0,581 a 0,711, p<0,05), which suggests that different neuromuscular qualities for squatting and jumping^{31,32,33,34,35} are required both to potentiate jump heights³¹ and to stabilize movement independently [35].

This study has shown that selected vertical jump tests can explain a part of the variation on the speed performance in young soccer Mid-PHV. Such variation is cognized in low speed and strength performances in boys who approach PHV caused by problems in motor coordination^19,44,51. That is, they require age-related neuromuscular adaptations for the function of cycle stretching and shortening^28,31, specifically, enhanced levels of pre-activation of eccentric strength in the concentric phase of vertical jump³⁸, and musculotendine stiffness²⁸.

 

Influence on strength performance in speed to the group Mid-PVC

 

Analysis upon multiple regression did not revealed substantial influence in strength performance, under the maximum speed in a soccer match for the group Mid-PHV. The results conclude that there is an interesting phenomenon occurring during PVC: there were significant differences in the performance of the maximum speed during a match in this maturational group. However, it has found low influences of determination of the production and manifestation of strength associated with the changes of the maximum speed during a game in young soccer players.

A possible explanation for this phenomenon existence is that there is periods of morphological, neurological, hormonal and muscle adaptations in young players. That can be associated to a time of biological settings, which provides low relevance in strength performance on speed and reflects in a non-linear performance of children and adolescents^36,37.

Some links within the strength manifestations estimated by vertical jump techniques, found by this study, are related to the proximal components, such as: the relation of SJ with CMJ; CMJ with DJ; DJ com DJh/t and CJ5 seg, DJh/t with CJ5seg. On the other hand, in the production of strength, significant relations were found between the rate of strength output with eccentric strength, isometric strength with itself, and isometric strength with stability strength.

This finding is associated with periods of sensivity and specificity²⁰ in some components of production, after this stage changes occur in its development. One of the characteristics presented in this period is the possibility of a temporary interruption in the performance of motor control^3,51,53. This may determine that the phenomenon is associated with the increase of the accelerated body size, the height and the length of lower limbs]. ^31,40,41

Such changes concerning physical growth would be expected, as part of a natural rise and development^36,37. Consequently, that may have been temporarily restricted, as players adjusted to perform motor skills with longer limbs^{21, 45}.

Increases in velocity performance are more likely attributed to changes in tendon muscle characteristics during maturation, especially in this group Pre-PHV (ie at the time of growth spurt). This may include modifications relevant to increase cross-sectional area of muscle^39,46, fascicle lengths^25,26, muscle-tendon junction size²⁹ and stiffness⁴⁷, adjustments in muscle balance in the relationship between contraction of the agonist-antagonist muscles¹⁵, adaptations of the pre-activation of both the eccentric strength in the concentric phase of the vertical jump³⁸ and the increase in recruitment of motor units^21,22,29,38, and speed of contraction³⁰, adaptations in the elastic properties of the tendon^25,26, and age-related increases in tendon muscle rigidity²⁸ are in perios of adaptation due to changes in body dimensions. 

Analysis in multiple regression revealed that CJ5seg was the main predictor of the variance in maximum speed performance during a football match. The results suggested that the manifestation of strength presents a certain degree dependent on maturity; these changes are attributable to development and learning, and modifications as a consequence of growth and development processes¹⁹, as well as in the great stability adjustments in vertical jumping movements¹³, in which jumps⁵² are more representative in the fast elongation and shortening cycle activities due to their need for pre-activation, use of stored elastic energy, neuromuscular potentiation²⁹, and stretch reflex mechanism^26,50.

 

Influence in strength performance on speed to Post-PHV group.

 

Specifically, it can be considered that maturation was the strongest predictor of maximum speed performance during a match, while strength performance explained the greater amount of Post-PHV variation in both strength production and performance demonstration of the estimated strength in vertical jumps tests.

It may be suggested that maturation was found to explain the greater variation in strength performance in the performance of velocity, may simply reflect the hormonal changes^44,46,55, and consequent adaptations in muscle size and function influenced by maturity^44,46,55, as adaptations of other neural components^14,29, elastic^25,47, elastic/reflex^31,32,33, of the complex muscle tendon and stiffness^28,31, but they also influenced by the strength production that stabilize the coupling, to generate a higher rate produced with a certain power (rate of strength production) with certain safety in the explosive actions³⁵, both to increase the eccentric potentiated strength of the muscles and the isometric one that support the muscle tendon complex.

This suggests that the period immediately following the peak velocity of height seems to be a naturally occurring accelerated development phase and may be an opportune time to improve physical performance³³.

Results show an excellent determination of the performance of the strength parameters and the indicators of the strength manifestations estimated by the jumping techniques on the speed, suggesting the influence of the strength in the improvement of the velocity related to the maturity observed in the Post-PHV period [14], that may facilitate improved technical efficiency and strength application during commuting, resulting in greater speed in young soccer players after PHV.

Limitations

A limitation of this study was the procedure used to delineate the division of maturational groups, with a 1-year interval, before and after the largest growth spurt (± 1 year). Another limitation was the impossibility of controlling the factors that interfered in soccer matches. In addition, the generalization was restricted, for all the participants were male and pro soccer players.

Future studies will be necessary for a methodological outline that can make use of maturational groups with a shorter time of peak height velocity, using feminine sex in sample participation, as well as soccer players with qualification of different competitive levels: amateur and recreationist. Further research would be essential in order to evaluate the influence of body composition, bone mass on maximal velocity performance during a match in young soccer players throughout maturation, which could provide further evidence on how best to improve these capabilities.

As this study has demonstrated, there is evidence that the maximum speed performance during a football match is directly influenced by the status of maturity, whose impacts may be considered as a determinant factor in the strength performances’ capacities in Pre-PHV and Post-PHV, however not in the Mid-PHV group.

The results indicate that the productions parameters and strength manifestations are decisive in the maturity status in young soccer players during periods of Pre-PHV and Post-PHV, yet they may not discern in during-PVC period. Notably, Pre-PHV groups had moderate relations in the strength performance, although isolated between strength production and its manifestations; Mid-PHV group had a low link, with some sparse relations between variables of strength in seclusion; also Post-PHV group was associated with considerable high relation for strength performance.

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Conflict of interest: The authors state that they do not present any conflict of interest for this paper.

Financing: Self-financed