'Nordic' Hamstrings Exercise - Engagement Characteristics and Training Responses

The present study examined the neuromuscular activation characteristics of the hamstrings during the 'Nordic' hamstrings exercise (NHE) and changes in the eccentric strength of the knee flexors with NHE training. Initially, the normalised root mean square electromyographic (EMG) activity of the hamstrings of both limbs during various phases (90-61 degrees, 60-31 degrees and 30-0 degrees of knee extension) of the NHE were determined in 18 soccer players. Subsequently participants were randomly allocated to either a training (n = 10) or control group. The isokinetic eccentric peak torques of the dominant and non-dominant limbs were recorded at 60, 120 and 240 degrees/s pre- and post-training. The EMG values of both limbs were comparable (P = 0.184) and greater EMG activity was recorded at more extended knee positions of the NHE (P = 0.001). 4 weeks of NHE training significantly improved peak torque by up to 21% in all assessment conditions. Data indicate the hamstrings of both limbs are engaged identically during the NHE and training results in gains in the eccentric peak torque of the hamstrings of both limbs; these gains may augment the force that the hamstrings can withstand when forcefully stretched, attenuating injury risk

A preliminary investigation into concurrent aerobic and resistance training in youth runners

BACKGROUND: Studies in adults have shown benefits in endurance performance by combining aerobic and resistance training. However, whether concurrent strength and aerobic training is beneficial in children remains to be identified. OBJECTIVE: The purpose of this study was to examine the effect of a 10 week aerobic training programme compared to a concurrent aerobic and resistance training programme on leg strength, fat free mass (%FFM), forced vital capacity (FVC) and 3 km-running performance in youth athletes. METHODS: Twelve trained youth competitive runners were pair matched into either an aerobic (AT) or concurrent (CT) training group based on maturational status and initial 3 km-running performance. The aerobic training consisted of continuous and interval training twice weekly for all participants. The CT group additionally performed resistance training twice weekly. RESULTS: There were no statistically significant differences between groups for any parameters pre-training. Significant correlations were found between 3 km-running performance and leg strength, FVC and %FFM. No significant interaction or main effects for any of the key outcome variables were found. There was however, a 38 s group difference in 3 km-running time post intervention indicating some interference of the resistance training on ERP. CONCLUSIONS: These findings suggest that concurrent endurance and resistance training should be avoided in trained youth athletes

Grass-root coaches' knowledge, understanding, attitude and confidence to deliver injury prevention training in youth soccer: a comparison of coaches in three EU countries

Purpose: It is well recognised that injury prevention training can reduce injury incidence, however current coach education pathways do not provide grass-root coaches with the knowledge and confidence to deliver such training to youth players. The aim of this study was to explore differences in knowledge, understanding, attitude and confidence to deliver such injury prevention training in three European countries. Methods: A total of 269 grass-root soccer coaches from 3 European countries (UK, Spain, Czech Republic) were recruited for this study. A validated questionnaire exploring knowledge, understanding, attitude towards and confidence to deliver youth injury prevention training was completed prior to a 2hr workshop on injury prevention training. Differences between countries was examined using Bayesian factors to quantify the evidence for and against the hypothesis of independence (H0) by assuming a Poisson sampling scheme (as there was no a priori restriction on any cell count, nor on the grand total) (BF10 Poisson). Results: Current knowledge, attitude and confidence to deliver injury prevention training to youth players was poor across all three European countries. Relatively few coaches were currently using injury prevention training in their coaching sessions (23%). There were some country specific differences for attitude towards injury prevention training and confidence to deliver injury training, with Spanish coaches reporting a more positive attitude and confidence to deliver such training. Significantly fewer coaches in the UK were using injury prevention training compared to coaches in Spain and the Czech Republic. Conclusion: As coaches identified a need for coach education and few were delivering injury prevention training, there is a clear need to embed and implement this programme into the grassroots coaching framework of sports governing bodies to improve adoption, implementation and maintenance

Age-related differences in functional hamstring/quadriceps ratio following soccer exercise in female youth players: An injury risk factor

Purpose: Fatigue negatively alters dynamic knee control and the functional hamstring/quadriceps ratio (H/QFUNC) plays an important role in stabilising the joint. The aim of this study was to investigate the influence of soccer specific exercise on H/QFUNC in U13, U15 and U17 year-old female soccer players. Methods: 36 female players performed concentric and eccentric actions of the hamstrings at 60, 120 and 180°/s before and after an age group specific field based soccer protocol. H/QFUNC was determined in the first 30° of knee flexion. Results: Significant angle x velocity (p = 0.001) and time x angle (p = 0.033) interaction effects were found indicating a lower H/QFUNC with increased movement velocity at 0-10° as opposed to greater knee flexion angles. Fatigue related effects were only evident near full knee extension. Probabilistic inferences indicated that changes in H/QFUNC were generally unclear in U13s, likely detrimental in U15s and very likely beneficial in U17s. Conclusions: Altered muscular control following soccer specific exercise is age dependent with players 1-year post peak height velocity at greatest risk of injury. Injury prevention and screening need to be age and maturation appropriate, should take into account the effects of fatigue, and include movements near full extension

Relationships Between Field-Based Measures of Strength and Power and Golf Club Head Speed

Increased golf club head speed (CHS) has been shown to result in greater driving distances and is also correlated with golf handicap. The purpose of this study was to investigate the relationships between field-based measures of strength and power and golf CHS with a secondary aim to determine the reliability of the selected tests. A correlation design was used to assess the following variables: anthropometrics, squat jump (SJ) height and squat jump peak power (SJPP), unilateral countermovement jump (CMJ) heights (right leg countermovement jump and left leg countermovement jump [LLCMJ]), bilateral CMJ heights, countermovement jump peak power (CMJPP), and medicine ball seated throw (MBST) and medicine ball rotational throw (MBRT). Fouty-eight male subjects participated in the study (age: 20.1 +/- 3.2 years, height: 1.76 +/- 0.07 m, mass: 72.8 +/- 7.8 kg, handicap: 5.8 +/- 2.2). Moderate significant correlations were reported between CHS and MBRT (r = 0.67; p < 0.01), MBST (r = 0.63; p < 0.01), CMJPP (r = 0.54; p < 0.01), and SJPP (r = 0.53; p < 0.01). Weak significant correlations (r = 0.3-0.5) were identified between CHS and the other remaining variables excluding LLCMJ. Stepwise multiple regression analysis identified that the MBST and SJ were the greatest predictors of CHS, explaining 49% of the variance. Additionally the intraclass correlation coefficients reported for tests of CHS and all performance variables were deemed acceptable (r = 0.7-0.9). The results of this study suggest that the strength and conditioning coach can accurately assess and monitor the physical abilities of golf athletes using the proposed battery of field tests. Additionally, movements that are more concentrically dominant in nature may display stronger relationships with CHS due to MBST and SJ displaying the highest explained variance after a stepwise linear regression

Solid stress facilitates spheroid formation: potential involvement of hyaluronan

When neoplastic cells grow in confined spaces in vivo, they exert a finite force on the surrounding tissue resulting in the generation of solid stress. By growing multicellular spheroids in agarose gels of defined mechanical properties, we have recently shown that solid stress inhibits the growth of spheroids and that this growth-inhibiting stress ranges from 45 to 120 mmHg. Here we show that solid stress facilitates the formation of spheroids in the highly metastatic Dunning R3327 rat prostate carcinoma AT3.1 cells, which predominantly do not grow as spheroids in free suspension. The maximum size and the growth rate of the resulting spheroids decreased with increasing stress. Relieving solid stress by enzymatic digestion of gels resulted in gradual loss of spheroidal morphology in 8 days. In contrast, the low metastatic variant AT2.1 cells, which grow as spheroids in free suspension as well as in the gels, maintained their spheroidal morphology even after stress removal. Histological examination revealed that most cells in AT2.1 spheroids are in close apposition whereas a regular matrix separates the cells in the AT3.1 gel spheroids. Staining with the hyaluronan binding protein revealed that the matrix between AT3.1 cells in agarose contained hyaluronan, while AT3.1 cells had negligible or no hyaluronan when grown in free suspension. Hyaluronan was found to be present in both free suspensions and agarose gel spheroids of AT2.1. We suggest that cell–cell adhesion may be adequate for spheroid formation, whereas solid stress may be required to form spheroids when cell–matrix adhesion is predominant. These findings have significant implications for tumour growth, invasion and metastasis

The impact of soccer match play on the muscle damage response in youth female soccer athletes

Post-match assessment of creatine kinase (CK) activity and delayed onset muscle soreness (DOMS) are common markers of exercise-induced muscle damage and recovery status in soccer players. These responses have not been examined in youth female players. This study examined the effect of competitive match play on CK activity and DOMS in elite youth players. Thirty-four elite female players, divided into three chronological age groups (U13, n = 11; U15, n = 10; U17 n = 12). Players completed baseline testing for CK and DOMS that was repeated immediately (for DOMS), 80, 128 and 168h post competitive match play for CK. Significant time effects were reported for CK (P = 0.006) and DOMS (P < 0.01). Significant differences between baseline and 168h post-match were reported for CK (P < 0.01), with significant group differences between U13 and U17’s for CK (P < 0.01). All parameters returned to baseline in U17’s at 168h but increased CK was evident for U13 and U15’s at 168h. In conclusion seven days may be insufficient for biochemical recovery in youth female athletes. Therefore, monitoring strategies to assess muscle damage between training and match play should be considered to track recovery and potentially reduce muscular injury risk

The scientific foundations and associated injury risks of early soccer specialisation

Early specialisation is characterised by formal participation in a single sport at the exclusion of others. Limited data are available to support this approach in the development of soccer players who attain elite status later in life. Of growing concern is the associated increased risk of injury and suggestions that single sport specialisation is a risk factor independent of age, growth, biological maturation and training volumes In the United Kingdom, elite soccer organisations have recently adopted an early sport specialisation approach following the introduction of the Elite Player Performance Plan. A key tenet of this programme is increased opportunities for training through a marked rise in the specified on-pitch hours per week. The accumulation of high training hours may be less of a relevant marker for success, and the impact of such a significant increase in training volume for young athletes who are experiencing a range of growth and maturational processes is currently unknown. This critical commentary includes an evidence based discussion of the effectiveness of early sport specialisation and the potential injury risks associated with such programmes placing a specific focus on elite male youth soccer players. Available data indicate that modifications to the existing EPPP framework could enhance player development and reduce injury risk. Proposed alterations include reduced volume of soccer specific training at key stages of growth and maturation and guidelines for the provision of a greater variety of physical activities that are integrated within other programme components