Timing of Nordic Hamstring Exercise in Youth Soccer Players to Reduce Injury

The Nordic hamstring exercise (NHE) has been demonstrated to be an effective strength exercise to help mitigate the risk of hamstring injury in soccer players. It is a component of the FIFA 11+ grassroots injury prevention program, which is a series of warm-up exercises designed to be administered in large groups and at minimal cost. Recent evidence in adults suggests that the acute fatigue associated with the NHE may increase the risk of injury during training, causing some to suggest moving the NHE until the end of training. PURPOSE: To determine whether this same level of fatigue persists in young soccer players, where training intensities and volumes are often much lower than in adults. METHODS: We designed a field-based crossover experimental study where youth soccer players completed two experimental sessions in a randomized manner. Participants included 18 youth players (mean ± SD: males, n=18; age 15.5 ± 0.7 years, height 1.77 ± 0.13 m, weight 66.4 ± 10.8 kg) participating in the Major League Soccer (MLS) Next player development pathway in Phoenix, USA. One session included the NHE as part of a standardized warm-up prior to a 75-minute standardized training session, and the alternative session incorporated the NHE at the end of the training session. Maximal hamstring force was measured at baseline, post-warm-up, and after completion of training. RESULTS: There was no interaction, condition, or main effect of NHE timing as indicated by maximal force output in the left (p \u3e 0.69) and right leg (p \u3e 0.65). CONCLUSION: Our findings add to the growing body of literature with regard to lower-limb fatigue profiles and adolescent soccer players, as well as suggest youth soccer coaches should not be concerned with the timing of these interventions, allowing them to focus instead on adherence and player buy-in

The effects of Energised Greens™ upon blood acid-base balance during resting conditions

<p>Abstract</p> <p>Background</p> <p>The consumption of fresh fruit & vegetable in concentrate form (FVC) have recently become an alternative approach to combating excessive renal acid loads often associated with <it>Western Diets</it>. Additionally, these FVC's have been purported to induce metabolic alkalosis, which perhaps may enhance the blood buffering capacity of an individual. Therefore, the aim of this preliminary study was to profile the acid-base response after ingestion of an acute dose of fruit and vegetable extract (Energised Greens™ (EG), Nottingham, UK) and compare it to a standard, low dose (0.1 g·kg^-1) of sodium bicarbonate (NaHCO₃).</p> <p>Findings</p> <p>As part of a randomized, cross over design participants consumed 750 mL of water with either 9 g of EG (manufacturer recommendations), 0.1 g·kg^-1of NaHCO₃or a placebo (plain flour) in opaque encapsulated pills following an overnight fast. Capillary samples were obtained and analyzed every 15 min for a period of 120 min following ingestion. Significant interactions (p < 0.01), main effects for condition (p < 0.001) and time (p < 0.001) were evident for all acid-base variables (pH, HCO_3^-, BE). Interactions indicated significant elevation in blood alkalosis for only the NaHCO₃condition when compared to both placebo and EG from 15 to 120 minutes.</p> <p>Conclusions</p> <p>Despite previous findings of elevated blood pH following acute mineral supplementation, manufacturer recommended doses of EG do not induce any significant changes in acid-base regulation in resting males.</p

Aspartame in conjunction with carbohydrate reduces insulin levels during endurance exercise

Gold OAAs most sport drinks contain some form of non-nutritive sweetener (e.g. aspartame), and with the variation in blood glucose regulation and insulin secretion reportedly associated with aspartame, a further understanding of the effects on insulin and blood glucose regulation during exercise is warranted. Therefore, the aim of this preliminary study was to profile the insulin and blood glucose responses in healthy individuals after aspartame and carbohydrate ingestion during rest and exercise. Each participant completed four trials under the same conditions (45 min rest + 60 min self-paced intense exercise) differing only in their fluid intake: 1) carbohydrate (2% maltodextrin and 5% sucrose (C)); 2) 0.04% aspartame with 2% maltodextrin and 5% sucrose (CA)); 3) water (W); and 4) aspartame (0.04% aspartame with 2% maltodextrin (A)). Insulin levels dropped significantly for CA versus C alone (43%) between pre-exercise and 30 min, while W and A insulin levels did not differ between these time points. Aspartame with carbohydrate significantly lowered insulin levels during exercise versus carbohydrate alone.Peer Reviewe

Hamstring Injury Prevention in Soccer:Before or After Training?

We examined the effects of a 12-week program of Nordic hamstring exercises (NHE), administered before or after football training, upon eccentric hamstring strength, muscle activity, and architectural adaptations. Amateur soccer players were randomized into three groups. The control group (CON; n=11) undertook core stability exercises, whereas a periodized NHE program was delivered either before (NHEBEF; n=10) or after (NHEAFT; n=14) biweekly training sessions. Outcome measures included peak torque and concomitant normalized peak surface electromyography signals (sEMG) of the biceps femoris (BF) and medial hamstring (MH) muscles during knee flexor maximal eccentric contractions, performed at 30°.s-1. Ultrasonography was used to determine BF muscle thickness, muscle fiber pennation angle, and fascicle length. Performing the NHE derived likely moderate peak torque increases in both NHEBEF (+11.9%; 90% confidence interval: 3.6%-20.9%) and NHEAFT (+11.6%; 2.6%-21.5%) vs CON. Maximum sEMG increases were moderately greater in the BF of both NHE training groups vs CON. There were likely moderate increases in BF muscle thickness (+0.17 cm; 0.05-0.29 cm) and likely small pennation angle increases (+1.03°; -0.08° to 2.14°) in NHEAFT vs CON and NHEBEF. BF fascicle length increases were likely greater in NHEBEF (+1.58 cm; 0.48-2.68 cm; small effect) vs CON and NHEAFT. A 12-week eccentric hamstring strengthening program increased strength and sEMG to a similar magnitude irrespective of its scheduling relative to the football training session. However, architectural adaptations to support the strength gains differed according to the timing of the injury prevention program

Reproducibility of measurement techniques used for creatine kinase, interleukin-6 and high-sensitivity C-reactive protein determination over a 48 h period in males and females

To examine the reproducibility of three measurement techniques used to determine creatine kinase, interleukin-6 and high-sensitivity C-reactive protein, 50 participants had blood samples taken on two occasions. Fingertip plasma samples were analysed using the Reflotron for CK determination. Venous blood samples collected into serum separator tubes were used for IL-6 and hs-CRP analyses. IL-6 was measured using an enzyme linked immune assay development kit. The hs-CRP was measured by an in-house ELISA method. Dependent t-tests showed no systematic bias between samples. The interdian CV was 20.0% for CK, 15.3% for IL-6 and 44.2% for hs-CRP. The intraclass correlation coefficient was 0.90 for CK, 0.98 for IL-6 and 0.70 for hs-CRP. The 95% limits of agreement were ?69.7 to 63.5 IU/L for CK, ?1.48 to 1.80?pg/ml for IL-6 and ?1.10 to 0.91??g/L for hs-CRP. The results demonstrate low absolute reproducibility, which may obscure a true experimental effect. ? 2018, ? 2018 Taylor & Francis.Association of Anaesthetists of Great Britain and Ireland, University of Western Sydney, Aspetar Orthopaedic and Sports Medicine Hospital, Central Manchester University Hospitals NHS Foundation Trust, Loughborough University, College of Arts and Sciences, Boston University, University of Hul

Scheduling of eccentric lower limb injury prevention exercises during the soccer micro-cycle: Which day of the week?

Scheduling eccentric-based injury prevention programs (IPP) during the common 6-day micro-cycle in soccer is challenged by recovery and tapering phases. This study profiled muscle damage, neuromuscular performance, and perceptual responses to a lower limb eccentric-based IPP administered 1 (MD+1) vs 3 days (MD+3) postmatch. A total of 18 semi-professional players were monitored daily during 3 in-season 6-day micro-cycles, including weekly competitive fixtures. Capillary creatine kinase concentration (CK), posterior lower limb isometric peak force (PF), counter-movement jump (CMJ) performance, and muscle soreness were assessed 24 hours prior to match-day (baseline), and every 24 hours up to 120 hours postmatch. The IPP consisted of lunges, single stiff leg dead-lifts, single leg-squats, and Nordic hamstring exercises. Performing the IPP on MD+1 attenuated the decline in CK normally observed following match play (CON: 142%; MD+3: 166%; small differences). When IPP was delivered on MD+3, CK was higher vs CON and MD+1 trials on both MD+4 (MD+3: 260%; CON: 146%; MD+1: 151%; moderate differences) and MD+5 (MD+3: 209%; CON: 125%; MD+1: 127%; small differences). Soreness ratings were not exacerbated when the IPP was delivered on MD+1, but when prescribed on MD+3, hamstring soreness ratings remained higher on MD+4 and MD+5 (small differences). No between-trial differences were observed for PF and CMJ. Administering the IPP in the middle of the micro-cycle (MD+3) increased measures of muscle damage and soreness, which remained elevated on the day prior to the next match (MD+5). Accordingly, IPP should be scheduled early in the micro-cycle, to avoid compromising preparation for the following match

Whole body cryotherapy and recovery from exercise induced muscle damage: A systematic review

Introduction Cold therapies are used regularly in medicine for their analgesic and anti-inflammatory effects. Whole-body cryotherapy (WBC) involves exposure to air maintained between -110 and -160oC, and is hypothesised to reduce pain, local and systemic inflammation. WBC has recently become popular in an exercise and sporting context as a recovery method after skeletal muscle damage, however, research examining the efficacy of WBC in an athletic context is minimal. This review seeks to summarise the evidence for the effects of WBC on exercise recovery measures. Methods Electronic database searches were conducted from March to April 2013. Six large online databases were used; MEDLINE, SPORTDiscus, Scopus, Web of Science, PubMed and AMED. The search targeted human studies with an exercise task, and WBC intervention. Results included randomised controlled trials (RCT’s), uncontrolled trials and crossover designs. Results A total of 8 studies were included in the review. Two RCT’s, four crossover trials and two uncontrolled trials were identified. Five studies showed WBC had no effect on markers of muscle damage or inflammation post exercise, while 3 studies show a positive effect. Three out of the eight studies measured maximal muscle force production and subjective pain levels following exercise and WBC, with two showing WBC had a positive effect on muscle force recovery and pain. A meta-analysis was not conducted due to the heterogeneity of the studies. Conclusion The current evidence for the efficacy of WBC on exercise recovery is unclear. Published studies report mixed findings, and the study designs make these results difficult to interpret. As WBC is proposed as an aid to recovery in an athletic population, repeated measures of performance, muscle force production and pain are of importance to the athlete, however, are minimally reported in the literature. Cold water immersion (CWI) is widely used in an athletic setting for recovery, and has much literature supporting its use for the reduction of pain post-exercise. Well-designed RCT’s with controlled exercise interventions targeting performance measures are needed, in particular comparison of WBC with CWI data is needed for evaluation

The physiological stress response to anaerobic exercise is altered following sodium bicarbonate supplementation

Sodium bicarbonate (NaHCO3) is a nutritional aid that is proposed to enhance performance by reducing the state of exercise induced acidosis, however research is currently equivocal. Despite this, most research still focuses on its effects upon performance, and not whether the reduced acidosis impacts upon any other factors related to exercise. There is some research to suggest that such a reduction in [H+] can attenuate a number of physiological stress pathways such as stress hormones (1, 4), heat shock protein 72 (HSP72) and oxidative stress (3), suggesting a potential role in exercise recovery. However there are some limitations with this previous research as work intensities were not controlled for, hence making comparisons between treatments difficult. Also limited markers of stress were measured despite the physiological stress response being multi-faceted. The aim of this study was to examine whether the ingestion of NaHCO3 would influence the expression of several markers of stress measured simultaneously, following a work controlled anaerobic exercise