Influence of 2D:4D ratio on fitness parameters and accumulated training load in elite youth soccer players

The Relationship Between Digit Ratio (2D:4D) and Aspects of Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis

INTRODUCTION

Digit ratio (2D:4D), a proxy of prenatal testosterone exposure, is a putative marker of physical fitness. No study has comprehensively synthesized studies examining associations between 2D:4D and cardiorespiratory fitness (CRF). We aimed to systematically review and meta-analyze studies reporting associations between 2D:4D and aspects of CRF.

METHODS

We systematically searched the literature for full text, refereed, cross-sectional studies reporting Pearson's correlation coefficients between objectively measured 2D:4D and at least one aspect of CRF. CRF was objectively assessed using field-based measures (maximal long-duration exercise performance) or laboratory-based measures (maximal oxygen uptake [VO2max], ventilatory threshold [VT], or mechanical efficiency [ME]). We used random-effects meta-analysis to estimate the pooled correlation and 95% confidence interval (95% CI) for aspects of CRF, and moderator analyses to estimate the influence of sex and age.

RESULTS

Data from 22 studies, representing 5293 individuals (54% male; mean age range = 10.1-40.2 years) from 12 countries were included. We found a significant strong negative correlation for VT (r = -0.61, 95% CI = -0.78, -0.37) and a significant weak negative correlation for exercise performance (r = -0.18, 95% CI = -0.25, -0.10), indicating that individuals with lower 2D:4Ds had higher VT and better exercise performance. No significant correlations were found for VO2max or ME. Neither sex nor age were significant moderators, except for age which moderated the correlation for exercise performance.

CONCLUSIONS

2D:4D is a proxy for some aspects of CRF like exercise tolerance (i.e., VT) and performance, but not other aspects like aerobic capacity and efficiency.

Correlation Between Propulsive Velocity, Maximum Velocity, and Power and the 2D:4D Ratio in Paralympic Powerlifting Athletes

Background: Among the strength sports we have Paralympic powerlifting, and the factors that influence strength have been investigated; among them is the relationship between strength and the ratio of the size of the second and fourth fingers of the hand (2D:4D). Objectives: The study is aimed at evaluating the relationship between the 2D:4D finger length ratio and the dynamic strength indicators, mean propulsive velocity (MPV), maximum velocity (Vmax), and power, with loads of 45% and 80% of one repetition maximum (1RM), in Paralympic powerlifting. Methodology: Sixteen elite Paralympic powerlifting athletes were evaluated for dynamic strength indicators, MPV, Vmax, and power, with loads of 45% and 80% 1RM. The 2D:4D proportions and correlations between the indicators were evaluated of 2D:2D ratios and dynamic strength indicators. Results: Moderate correlations were found between MPV 45% and 4D (r = 0.551, p = 0.027), between MPV 45% and R-L 2D:4D diff. (r = -0.595, p = 0.015), between power 80% and L2 (r = 0.542, p = 0.030), and between MPV 45% and R-L 2D:4D (r = -0.585, p = 0.017). There was also a moderate correlation between power 80% left 2D (r = -0.542, p = 0.030). However, no correlation was found between the 2D:4D ratios and dynamic strength indicators in Paralympic powerlifting. Conclusion: The 2D:4D ratio presents a moderate correlation with dynamic strength indicators in Paralympic powerlifting athletes, where the ratios with the velocity of 45 of 1RM can be used as a predictor but with caution.

Understanding Covid-19: Digit ratios and duration of oxygen therapy in hospitalized Covid-19 patients

BACKGROUND

Covid-19 severity shows a sex difference (males>females) and progressive hypoxia among the most seriously affected. Digit ratios are sexually dimorphic and may be negatively-related to prenatal (2nd-to-4th digits' ratio; 2D:4D) and pubertal (3rd-to-5th digits' ratio; 3D:5D) testosterone. Oxygen therapy is important in Covid-19 treatment and low 2D:4D is linked to efficient oxygen metabolism. We consider relationships between digit ratios and duration of oxygen treatment in hospitalized Covid-19 patients.

METHODS

Digit lengths were measured from photographs of the patient's hands. Age, Sex, BMI, vaccination status and number of days of O2 treatment, were recorded.

RESULTS

There were 100 (58 women) patients. Sex differences (males

CONCLUSION

We have found that high (feminized) 2D:4D of males and females is positively related to duration of oxygen therapy. This adds to the evidence for links between severity of Covid-19 and national and individual level variation in foetal androgen (as measured by 2D:4D). We discuss our finding in the light of the "low-androgen-driven COVID-19 pandemic theory".

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Key Words

• COVID-19
• Digit ratio
• Oxygen therapy

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MESH Headings

• Humans
• Male
• Female
• Androgens
• Fingers/anatomy & histology
• Digit Ratios
• COVID-19/therapy
• Pandemics
• COVID-19 Drug Treatment
• Sex Characteristics
• Oxygen/therapeutic use

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Affiliation(s)

Anna Kasielska-Trojan Plastic, Reconstructive and Aesthetic Surgery Clinic, Institute of Surgery, Medical University of Lodz, Lodz, Poland.
Maciej Jabłkowski Department of Infectious and Liver Diseases, Medical University of Lodz, Lodz, Poland
Jolanta Białkowska-Warzecha Department of Infectious and Liver Diseases, Medical University of Lodz, Lodz, Poland
Oliwia Kwaśniewska Medical University of Lodz, Lodz, Poland
Bogusław Antoszewski Plastic, Reconstructive and Aesthetic Surgery Clinic, Institute of Surgery, Medical University of Lodz, Lodz, Poland

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Prenatal androgenization (2D:4D) predictions of tennis match-play success in junior players: A search for physiological explanations

AIM

This study aims to investigate the possible association between digit ratio (2D:4D) and match-play success (MPS) in junior tennis players. In addition, we consider the possible explanatory pathways of these associations in relation to psychological, strength, power, and hormonal parameters.

METHODS

We performed a cross-sectional study, with a sample comprised of 64 male junior tennis players (11-18 years old). Digit ratio was calculated from direct finger measurements. In addition, we measured the ratio of wins by number of matches played in 5 years of official competition (MPS), handgrip strength (HGS), standing long jump (SLJ), training (in weekly hours), and expertise (number of years in official competition). Salivary testosterone and cortisol levels were measured before and after physical "challenge" tests.

RESULTS

The 2D:4D correlated negatively with HGS and SLJ. MPS was also negatively associated with 2D:4D, but was positively correlated to HGS, expertise, training, and self-confidence (SC). Multiple linear regression showed 2D:4D and expertise were associated with MPS (43%-54%). None of the physical, or hormonal variables tested explained the links between 2D:4D and MPS.

CONCLUSION

Therefore, the specific fitness components influenced by prenatal androgenization that moderate sports success remain unknown. Future studies should explore the interaction of 2D:4D, with tennis exercises as a challenge to induce hormonal change, the effect of pubertal stage, and the influence of aerobic endurance in determining MPS.

Association between 2D:4D ratios and sprinting, change of direction ability, aerobic fitness, and cumulative workloads in elite youth soccer players

BACKGROUND

The aim of this study was two-fold: (i) to determine the correlation between 2D:4D, maximal oxygen uptake (VO_2max), body fat percentage (BF%), maximum heart rate (HRmax), change of direction (COD), and accumulated acute and chronic workload variables; (ii) to verify if the length of the second digit divided by fourth digit (2D:4D) can explain fitness variables and accumulated training load.

METHODS

Twenty elite young football players (age: 13.26 ± 0.19 years; height: 165.8 ± 11.67 cm; body mass: 50.70 ± 7.56 kg; VO_2max, 48.22 ± 2.29 ml.kg^- 1.min^- 1) participated in the present study. Anthropometric and body composition variables (e.g., height, body mass, sitting height, age, BF%, body mass index, right and left finger 2D:4D ratios) were measured. The following fitness tests were also conducted: 30 - 15 Intermittent Fitness Test (VO_2max and HRmax), COD (5-0-5 agility test), and speed (10-30msprint test. HRmax and the training load were also measured and monitored using the Rate of Perceived Exertion during the 26 weeks.

RESULTS

There were associations between HRmax and VO_2max, between 2D and 4D lengths and Left and Right hand ratios. Also, in AW with Right and Left 4D. The CW and de ACWR with the Right 4D. There were other associations between physical test variables and workload variables.

CONCLUSIONS

Under-14 soccer players with low right and left-hand 2D:4D ratios did not perform better in the selected fitness tests to assess VO_2max, COD, or sprint ability. However, it cannot be ruled out that the absence of statistically significant results may be related to the small sample size and the maturational heterogeneity of the participants.

Variations in cumulative workload and anaerobic power in adolescent elite male football players: associations with biological maturation

BACKGROUND

It is considered that the maturity condition of young football players is related to their physical performance during short high-intensity efforts dependent on anaerobic power ability. Hence, the aim was to determine possible relationships between maturity status and training intensity by measuring the footballer´s peak height velocity (PHV), maturity offset and anaerobic power.

METHODS

Seventeen youth male players of different playing positions participated in the study and performed tests at three different stages of the season (early-, mid- and end-season) All the anthropometric parameters and biomarkers related to maturation were controlled during the season. The training intensity and load was monitored and the anaerobic power of the players was assessed by a running-based anaerobic sprint test (RAST).

RESULTS

The analysis of all the recorded data revealed a positive relationship between PHV and anaerobic power in the early- and end-season stages (p < 0.05). Maturity offset and anaerobic power (mean RAST) showed an absolute correlation in early- and end -season stages (r: - 0.39 to 0.91). The multiple linear regression analysis revealed that min RAST was the best predictor for both PHV and maturity offset. The analysis of the training intensity and workloads showed a positive effect on the performance in the fitness test (p < 0.05). Additionally, players experienced less fatigue at the end-season stage than at the early-season.

CONCLUSIONS

The results show that coaches might benefit from monitoring training loads and the maturity status of the players in order to enhance their physical performance during the season.

INFLUENCE OF EXPLOSIVE STRENGTH TRAINING ON LOWER LIMBS OF BADMINTON ATHLETES

ABSTRACT Introduction In sports, most athletes are required to have great explosive power, that is, the maximum power that athletes can show in a short period. Explosive power is often an important index to evaluate the physical capacity of athletes. Objective To analyze the influence of explosive training in lower limbs on the performance of badminton players. Methods Taking the 17 existing players of the Middle School B girls’ badminton team as the experimental object, the explosive power of the lower limbs of the 17 players were tested and compared before and after the experiment. Results The 30m run results showed that the fastest athletes completed in 4.39s, with most of them completing in 5S. The overall test results were higher than before the experiment. Conclusion After adopting the improved training method, the lower limbs of the team members improved in technical and tactical performance, raising the athletes’ fitness. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

INFLUENCE OF STRENGTH TRAINING ON THE EXPLOSIVE POWER OF LOWER LIMBS OF SOCCER PLAYERS

ABSTRACT Introduction The explosive power of the lower limbs is an indispensable index in soccer. Having a good level of explosive power establishes a solid foundation for the performance and the competitive level of soccer players. Objective Promote the conditions to improve the explosive level of soccer players and improve their performance and competitive level. Methods This paper presents the influence of compound strength training on the explosive power of the lower limbs of soccer athletes. Based on 27 young 9-year-old soccer players from Zai Ming Football Club of a sports college as experimental material, the composite training was carried out. Results The growth rates of these rates in the experimental group were 3.3%, 2.3%, 5.0%, 3.6%, 9.2%, 12.1%, 20.5%, 5.7%, 11.9%, 16.9% and 19.5% respectively, while those in the control group were 1.2%, 0.7%, 4.2%, 3.1%, 6.8%, 7.8%, 5.1%, 4.2%, 4.8%, 12.5% and 19.2% respectively. The growth rate of the experimental group was higher than that of the control group and the blank control group. Conclusion Compared with the control group and the neutral control group, the experimental group with compound training has a better training effect on improving the lower limb explosiveness of youth soccer players. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Does maturity estimation, 2D:4D and training load measures explain physical fitness changes of youth football players?

OBJECTIVES

The purpose of the present study was two-fold: (1) To analyse physical fitness changes of youth football players after a full-season; and (2) to examine whether physical fitness changes are explainable by estimated maturity status, 2digit:4digit ratio (2D:4D) from each hand and training load (TL) measures.

METHODS

Twenty-seven youth elite Under-15 football players were daily monitored for training load measures during 38 weeks. At the beginning and at the end of the season, all players were assessed for physical fitness. Also, the maturity status estimation and the length of the second and fourth digits of both hands were collected at the beginning of the season.

RESULTS

Significant differences were found for all physical fitness measures after the season. The second and fourth digits of left and right hands had negative moderate correlations with change of direction (COD) changes (r=-.39 to - 0.45 | p = .05 to 0.02). Also, the maturity offset measure had negative moderate correlations with COD changes (r=-.40 | p = .04). From the reported significant correlations, the maturity offset, Left 4D, Right 2D and Right 4D significantly predicted the Mod.505 COD test changes (β = 0.41, p = .04; β = -0.41, p = .04; β = -0.45, p = .02; and β = -0.44, p = .03, respectively).

CONCLUSION

The maturity offset and the 2D:4D measures have the potential to predict COD performance changes over-time in youth football players. Given the lack of associations between the maturity estimation, 2D:4D and training load measures, with the overall physical fitness measures, coaches should rely only at COD changes.

The digit ratio (2D:4D) and testosterone co-predict vertical jump performance in athletic boys: Evidence of organizational and activational effects of testosterone on physical fitness

The digit ratio (2D:4D) is a negative correlate of boy's physical fitness, and thought to arise from organizational effects of prenatal testosterone on different bodily systems. During human ontogeny, activational effects of testosterone on body size and strength offers another pathway to physical fitness. We tested these hypotheses by examining the organizational and activational effects of testosterone on vertical jump performance in athletic boys. Using a cross-sectional design, 173 boys (aged 9 to 18 years) were tested for standing height, body mass, body fat, fat-free mass, weekly training activity, training history, salivary testosterone and cortisol, R2D:4D, L2D:4D, and right-left 2D:4D (Dr-1), and vertical height in 3 different countermovement jump (CMJ) tests. A generalized additive model was employed to delineate age-related trajectories and predict CMJ performance. Our models yielded significant non-linear increases (or changes) in body size, current hormone concentration, training outcomes, and CMJ performance with chronological age. All 2D:4D measures were age invariant. The R2D:4D and testosterone were significant non-linear predictors of CMJ height with (R² = 66.2%) or without (R² = 54.3%) covariates, whereby a higher current testosterone concentration (up to a certain level) and a lower or higher R2D:4D were linked to better performance. The L2D:4D and Dr-1 had no predictive value. In conclusion, the R2D:4D and testosterone were co-predictors of CMJ height among athletic boys, with non-linear performance effects that differed in timing, tempo, and direction. Our findings confirm that testosterone can regulate a simple measure of boy's physical fitness through both an activational and organizational pathway.

Gender Differences and Relationship of 2D:4D-Ratio, Mental Toughness and Dark Triad Traits among Active Young Adults

Simple Summary

There is evidence that the exposure to more testosterone and less estrogen hormones before birth, that is, in utero, has a physiological impact on the relation between the index finger (2D) and the ring finger (4D). This relation is called the 2D:4D-ratio. A lower 2D:4D-ratio mirrors a longer ring finger (4D), relative to the index finger (2D); a higher 2D:4D-ratio mirrors a shorter ring finger (4D), relative to the index finger (2D). A higher exposure to testosterone and a lower exposure to estrogen hormones are associated with a lower 2D:4D-ratio. Further, a higher exposure to androgen hormones is associated with higher masculine traits. In the present study, we assessed 460 physically active young male and female adults. We showed that (1) males had lower 2D:4D ratios than females. Next, (2) active females and males had similar personality and mental toughness traits. (3) Females with more “dark” personality traits had a higher ability to perform consistently under stress and pressure; such females were mentally tougher. (4) Males with lower 2D:4D-ratios were mentally tougher. Overall, there is evidence that prenatal exposure to androgen hormones and personality traits in adulthood appear to be related, though, in a different fashion between male and female adults.

Abstract

There is consistent evidence that prenatal exposures to higher testosterone and lower estrogen concentrations during the first trimester of embryonal and fetal development are associated with a lower 2D:4D-ratio, which is to say: The index finger (2D) is shorter, compared to the ring finger (4D). Compared to non-active, athletes show lower 2D:4D ratios. However, athletes also report specific personality traits such as mental toughness, assertiveness, and competitive behavior. Here, we tested if 2D:4D-ratios were related to specific personality traits. We further investigated possible gender differences. A total of 460 active young adults (mean age: 24.81 years; 67% females) completed a series of self-rating questionnaires covering sociodemographic information and traits of the dark triad and mental toughness. Participants also provided a scan of their right palm hand to measure and calculate 2D:4D-ratios. t-tests, Pearson’s correlations, and multiple regression analysis were performed to analyze data. Compared to male participants, female participants had a higher 2D:4D-ratio. Female and male participants did not differ as regards dark triad traits and mental toughness traits. Irrespective of gender, and based on correlational computations, 2D:4D-ratios were unrelated to the dark triad (DT) and mental toughness (MT) scores. Higher DT scores were modestly associated with higher MT scores among females, but not among males. Lower 2D:4D-ratios were associated with higher constancy scores and the male gender. The constancy and male gender appeared to be associated with lower 2D:4D-ratios.

The influence of maturation, fitness, and hormonal indices on minutes played in elite youth soccer players: a cross-sectional study

Background

The main purpose of this study was to investigate the relationships between minutes played (MP) with maturity status, fitness, and hormonal levels, and to quantify their influence on minutes played.

Methods

Twenty-four elite youth soccer players under-16 years participated in this study, over a full-season period. Anthropometric measures, maturity status, hormonal and physical fitness levels were collected. Participants were monitored during the season. After the end-season, players were assessed in 6 different tests over a four-day period.

Results

The maximum oxygen consumption (V̇O_2max) was strongly correlated with MP (r = 0.75), maturity offset (r = 0.52), and countermovement jump (r = 0.53). Multiple linear regression explained 76% of MP (F (8, 15) = 6.05, p = 0.001), with an R2 of 0.76. Moreover, Growth hormone (GH) and V̇O_2max. were the most influential factors in MP (F (2, 21) = 17.92, p ≤ 0.001), with an R2 of 0.63.

Conclusion

High levels of GH and V̇O_2max have a preponderant role in MP by elite youth soccer players, it appears to be more pragmatic to consider other contextual dimensions, as they can impact selection for competition and minutes of participation in a match.