Contextualizing Evaluation of Performance in Volleyball: Introducing Contextual Individual Contribution Coefficients to Assess Technical Actions.

In this study, we proposed novel metrics for evaluating volleyball technical performance in relation to the action context. To assess each player's relative participation, we also introduced relative contextual coefficients. We analyzed 20 games played by the world's top eight teams during the 2019 FIVB Women's Club World Championship, using Data Volley software and Python programming. We evaluated inter- and intra-observer reliability and used binomial logistic regression models to estimate each variable's probability of having contributed to the team's set win. We calculated estimated confidence intervals, standard errors, and Wald values; and we employed Akaike's and Bayesian criteria to evaluate the model's goodness of fit. We identified optimal cut-off points using receiver operating characteristic curves, and we found that the proposed contextual evaluation coefficients prevented overestimation of a player's technical performance in uneven situations. We addressed the issue in which the winning team may be the one that scored the fewest points, and we were able to predict a team's victory with confidence. The proposed coefficients made multiple technical and contextual aspects of the game easily accessible and comprehensible, offering significant beneficial implications for coaches and players.

Low Back Pain in Cycling. Are There Differences between Road and Mountain Biking?

Low back pain (LBP) is known to affect cyclists. This study aimed to describe perceived lumbar dysfunction and compare the pain sensation in recreational cyclists who practice road and mountain biking. Forty males were randomly assigned to carry out a 3-h road cycling (RC) and mountain biking (MTB) time trial (TT) at submaximal intensity. LBP and pain pressure threshold (PPT) were measured before and after the TT. A significant increment at the LBP was found after RC TT (p < 0.001; d = 2.61), similar to MTB TT (p < 0.001; d = 2.65). However, PPT decreased after completing the RC TT (p < 0.001; d = 1.73) and after MTB TT (p = 0.024; d = 0.77). There were no differences in the LBP evolution between both interventions (p > 0.01). Low back pain perception increases with cycling in recreational cyclists. Nevertheless, this increase appears to be more related to the traits of the cyclist than the modality practiced.

In the Opinion of Elite Volleyball Coaches, How Do Contextual Variables Influence Individual Volleyball Performance in Competitions?

The main objective was to know the elite coaches' opinions regarding the relevance, definition, and importance of volleyball contextual variables to measure individual performance in competition. After performing a literature review, an instrument to gather the opinion of the world's elite volleyball coaches was elaborated by four volleyball specialists. The sample of experts consisted in 20 world's elite volleyball coaches who met at least three experience years in first division or national teams. The instrument collected experts' information on the contextual variables in relation to relevance, definition, and importance. Cronbach's α and Aiken's V coefficient were used to test the reliability and content validity of the contextual variables, respectively. To compare the importance of the contextual variables U de Mann-Whitney and Kruskal-Wallis tests were used. Results showed that opposition level, set period, score difference, results of the previous set, competitive load variables, high level, final periods ≥20, and high load categories were relevant (Aikens V > 0.70). In addition, high level, final period ≥20 and ≥+10, and high load categories were significantly more important (p < 0.05). We conclude that, according to the elite coaches, the contextual variables should not be analyzed separately. Future studies should consider contextual variables dynamically.

Relationship of the skin and subcutaneous tissue thickness in the tensiomyography response: a novel ultrasound observational study.

BACKGROUND: The aim of the study was to describe and correlate the skin, subcutaneous tissue, and superficial fascia thickness assessed by ultrasonography (US) with the lumbar erector spinae muscles contractile properties evaluated by tensiomyography (TMG). METHODS: A cross-sectional descriptive study with 50 healthy participants was performed. The point of maximum lordosis in the lumbar region of the right erector spinae was evaluated by US and TMG. First, the skin, subcutaneous tissue, and superficial fascia thicknesses (cm) were assessed by US. Second, the five contractile TMG parameters were analyzed from the right erector spinae muscles belly displacement-time curves: maximal radial displacement (Dm), contraction time (Tc), sustain time (Ts), delay time (Td), and half-relaxation time (Tr). Finally, correlation analyses using Pearson (r for parametric data) and Spearman (rs for non-parametric data) coefficients were performed. RESULTS: A strong negative correlation was shown between Dm and subcutaneous tissue thickness (rs=-0.668; P<.001). Furthermore, moderate negative correlations were observed between Dm and skin thickness (r=-0.329; P=0.020) as well as Tr and subcutaneous tissue thickness (rs=-0.369; P=0.008). The rest of the parameters did not show statistically significant correlations (P >.05). CONCLUSION: Therefore, the lumbar erector spinae contractile properties during TMG assessments, especially Dm and Tr, may be widely correlated by the skin and subcutaneous tissue thickness.

Relationship of the skin and subcutaneous tissue thickness in the tensiomyography response: a novel ultrasound observational study

SUMMARY BACKGROUND: The aim of the study was to describe and correlate the skin, subcutaneous tissue, and superficial fascia thickness assessed by ultrasonography (US) with the lumbar erector spinae muscles contractile properties evaluated by tensiomyography (TMG). METHODS: A cross-sectional descriptive study with 50 healthy participants was performed. The point of maximum lordosis in the lumbar region of the right erector spinae was evaluated by US and TMG. First, the skin, subcutaneous tissue, and superficial fascia thicknesses (cm) were assessed by US. Second, the five contractile TMG parameters were analyzed from the right erector spinae muscles belly displacement-time curves: maximal radial displacement (Dm), contraction time (Tc), sustain time (Ts), delay time (Td), and half-relaxation time (Tr). Finally, correlation analyses using Pearson (r for parametric data) and Spearman (rs for non-parametric data) coefficients were performed. RESULTS: A strong negative correlation was shown between Dm and subcutaneous tissue thickness (rs=-0.668; P<.001). Furthermore, moderate negative correlations were observed between Dm and skin thickness (r=-0.329; P=0.020) as well as Tr and subcutaneous tissue thickness (rs=-0.369; P=0.008). The rest of the parameters did not show statistically significant correlations (P >.05). CONCLUSION: Therefore, the lumbar erector spinae contractile properties during TMG assessments, especially Dm and Tr, may be widely correlated by the skin and subcutaneous tissue thickness.

RESUMO CONTEXTO: O estudo foi elaborado para descrever e correlacionar a pele, o tecido subcutâneo e a espessura da fascia superficial avaliados pelo ultrassom (EUA) com as propriedades contráteis do músculo eretor da coluna lombar avaliadas por tensiomiografia (TMG). MÉTODOS: Foi realizado um estudo descritivo transversal com 50 participantes saudáveis. O ponto de lordose máxima na região lombar da coluna ereta direita foi avaliado pelos EUA e TMG. Primeiro, a pele, o tecido subcutâneo e as espessuras da fáscia superficial (cm) foram avaliadas pelos EUA. Em segundo lugar, os cinco parâmetros TMG contráteis foram analisados a partir das curvas de deslocamento-tempo da barriga do músculo eretor da espinha direita: deslocamento radial máximo (Dm), tempo de contração (Tc), tempo de sustentação (Ts), tempo de atraso (Td) e meio tempo de relaxamento (Tr). Finalmente, foram realizadas análises de correlação usando os coeficientes Pearson (r para dados paramétricos) e Spearman (rs para dados não paramétricos). RESULTADOS: Uma correlação forte negativa foi mostrada entre Dm e espessura subcutânea do tecido (rs = −0,668; P < 0,001). Além disso, foram observadas correlações moderadas negativas entre Dm e espessura da pele (r = −0,329; P = 0,020), bem como a espessura subcutânea do tecido (rs = −0,369; P = 0,008). O restante dos parâmetros não mostrou correlações estatisticamente significativas (P > 0,05). CONCLUSÃO: Portanto, as propriedades contráteis do eretor da espinha lombar durante as avaliações TMG, especialmente Dm e Tr, podem ser amplamente correlacionadas com a pele e a espessura subcutânea do tecido.