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Tuesday, September 27, 2011

Physiology of small-sided games: what's new?


Koklu et al. Comparison of the physiological responses to different small-sided games in elite young soccer players. J Strength Cond Res. 2011 25(6):1522-8.


 The purpose of this study was to compare the blood lactate (La), heart rate (HR) and percentage of maximum HR (%HRmax) responses among the small-sided games (SSGs) in elite young soccer players. Sixteen players (average age 15.7 6 0.4 years; VO2max 53.1 6 5.9 ml /kg/min) volunteered to perform the Yo-Yo intermittent recovery test and 6 bouts of soccer drills including 1-a-side, 2-a-side, 3-a-side, and 4-a-side games without a goalkeeper in random order at 2-day intervals. Significant differences were found on La, HR, and %HRmax among the bouts. The 3-a-side and 4-a-side games were significantly higher than 1-a-side and 2-a-side games on HR and %HRmax, whereas the 1-a-side game significantly resulted in higher La responses compared to other SSGs. This study demonstrated that physiological responses during the 1-a-side and 2-a-side games were different compared to 3-a-side and 4-a-side games. Therefore, it can be concluded that a decreased number of players results in increased intensity during SSGs including 6 bouts. These results suggest that coaches should pay attention on choosing the SSG type and the number of bouts to improve desired physical conditioning of elite young soccer players in soccer training.


Da Silva et al. Exercise intensity and technical demands of small-sided games in young Brazilian soccer players: effect of number of players, maturation, and reliability. J Strength Cond Res. 2011 Sep 8. [Epub ahead of print]

The aims of this study were to examine in young soccer players (a) the effect of varying the number of players on exercise intensity (EI) and technical actions during small-sided games (SSGs), (b) the reliability of EI and technical actions, and (c) the influence of the players' maturation on EI and involvements with the ball (IWBs). Sixteen male soccer players (mean ± SD; age 13.5 ± 0.7 years) completed 2 bouts of 3 vs. 3 (SSG3), 4 vs. 4 (SSG4), and 5 vs. 5 (SSG5) training. Exercise intensity was measured using heart rate and expressed as a percentage of maximal heart rate (%MHR). Technical actions were quantified from video recordings. Maturation stage was determined with the Tanner scale. Exercise intensity in SSG3 (89.8 ± 2%MHR) was higher than that in SSG5 (86.9 ± 3%MHR). The EI in the first set (86.8 ± 4%MHR) was lower than that in the second (89.1 ± 3%MHR) and in the third set (89.4 ± 3%MRH). No effects of number of players were found in IWB, passes, target passes, tackles, and headers. Significantly more crosses, dribbling, and shots on goal were observed during SSG3 compared to during SSG4 or SSG5. The level of maturation was not correlated with either EI or IWB. These results extend previous findings with adult players suggesting that SSGs can provide an adequate training stimulus for young players and are feasible for groups with heterogeneous maturation levels.


Dellal et al. Effect of the number of ball contacts within bouts of 4 vs. 4 small-sided soccer games. Int J Sports Physiol Perform. 2011, 6(3):322-33.

 

The aim of this study was to examine the influence of the number of ball touches authorized per possession on the physical demands, technical performances and physiological responses throughout the bouts within 4 vs. 4 soccer small-sided games (SSGs). Twenty international soccer players (27.4 ± 1.5 y) performed three different 4 vs. 4 SSGs (4 × 4 min) in which the number of ball touches authorized per possession was manipulated (1 touch = 1T; 2 touches = 2T; Free Play = FP). The SSGs were divided in 4 bouts (B1, B2, B3 and B4) separated by 3 min of passive recovery. The physical performances, technical activities, heart rate responses, blood lactate and RPE were analyzed.
The FP rule presented greater number of duels, induced the lowest decreases of the sprint and high-intensity performances, and affected less the technical actions (successful passes and number of ball losses) from B1 to B4 as compared with 1T and 2T forms. Moreover, the SSG played in 1T form led to reach higher solicitation of the high-intensity actions while players presented more difficulty to perform a correct technical action.
In conclusion, the modification of the number of ball touches authorized per possession affects the soccer player activity from the first to the last bout of SSG, indicating that the determination of this rule has to be precisely planned by the coach according to the objectives of the training.

Saturday, September 24, 2011

Tear fluid analysis: a new assessment technique in sports science?

Human tears are a complex solution consisting mainly of water and electrolytes. Tear fluid has been reported to be isotonic with plasma. Accordingly, measurement of tear osmolarity has been used as a tool to evaluate hydration status in clinical studies. Its reliability however was relatively low due mainly to a) large sample variability, b) evaporation of tear fluids in the time elapsed between tear collection and analysis (3-5min).

Recently, a portable, noninvasive tear collection and analysis device has been produced. Its advantages are a) small tear volume required (50 nanoliter), b) very short time for tear collection (<5sec) and analysis (10 sec). The validity of the new device to track hydration level in athletes was tested in a study published in Medicine and Science in Sports and Exercise August 2011 by Fortes et al.



Figure. The new tear collection and analysis device (TearLab).

The aim of this study was to compare changes in Tear osmolarity (Tosm) and another widely used noninvasive marker, urine specific gravity (USG), with changes in Plasma osmolarity (Posm) during hypertonic-hypovolemia. In a randomized order, 14 healthy volunteers exercised in the heat on one occasion with fluid restriction (FR) until 1%, 2%, and 3% body mass loss (BML) and with overnight fluid restriction until 08:00 h the following day, and on another occasion with fluid intake (FI).

Posm and USG increased with progressive dehydration on FR. Tosm increased significantly on FR from 293 ± 9 to 305 ± 13 mOsm·L(-1) at 3% BML and remained elevated overnight (304 ± 14 mOsm·L(-1); P < 0.001). P(osm) and T(osm) decreased during exercise on FI and returned to preexercise values the following morning. The mean correlation between Tosm and Posm was r = 0.93 and that between USG and Posm was r = 0.72.
The conclusions of this study were that
·         Tear osmolarity increased with dehydration and tracked alterations in plasma osmolality
·         It seems that this new tear collection and analysis device offers a practical and rapid hydration assessment technique.

Wednesday, September 21, 2011

COMBINING STRENGTH AND ENDURANCE TRAINING: WHAT'S NEW?

Today, I would like to share with you my thoughts on the benefits and disadvantages of combining strength and endurance at the same training session. My thoughts are based on two recent studies published in well respected, high quality scientific journals last month. 


As you all know, combining endurance and strength training (concurrent training) may change the adaptations compared with single mode training. The mechanism behind this hypothesis is still unclear. 

In the first of these studies, 10 healthy subjects performed either only endurance exercise (E: 1h cycling at ~65% of VO2max) or endurance exercise followed by resistance exercise (ER: 1h cycling + 6 sets of leg press at 70-80% of 1 repetition maximum) in a randomized cross-over design (Wang et al., 2011). Muscle biopsies were obtained before and after exercise. The results showed that resistance exercise, performed after endurance exercise, amplifies the adaptive signaling response of mitochondrial biogenesis compared with single-mode endurance exercise. The mechanism may relate to a crosstalk between signaling pathways mediated by mTOR. Simply, resistance training performed after endurance exercise may amplify aerobic adaptations. Thus, we can speculate, although not directly examined in this study, that this type of training will improve aerobic performance more than endurance training alone.

In the second study, Ronnestad et al (2011) compared the effect of 12 weeks of strength training combined with a large volume of endurance training (S+E) with the effect of strength training alone (S) on the strength training adaptations. Well-trained cyclists with no strength training experience performed heavy strength training twice a week in addition to a high volume of endurance training during a 12-week period. A group of non-strength trained individuals performed the same strength training as S + E, but without added endurance training. Thigh muscle cross-sectional area, 1 repetition maximum (1RM) in leg exercises, squat jump performance, and peak rate of force development (RFD) were measured. Following the intervention period, both S + E and S increased 1RM strength, thigh muscle cross-sectional area, and squat jump performance (p < 0.05), and the relative improvements in S were greater than in S + E (p < 0.05). S increased peak RFD while S + E did not, and this improvement was greater than in S + E (p < 0.05). These results suggest that the strength training response on muscle hypertrophy, 1RMstrength, squat jump performance, and peak RFD is attenuated in well-trained endurance athletes during a period of concurrent endurance training.

Taking this evidence together it seems that:

  • Resistance training performed after endurance exercise may amplify aerobic adaptations 
  • Endurance exercise performed with resistance exercise at the same session may result in lower level of hypertrophy and lower improvement in power than performing resistance training only. 

For more reading
Ronnestad et al. High volume of endurance training impairs adaptations to 12 weeks of strength training in well-trained endurance athletes. Eur J Appl Physiol, 2011 [Epub ahead of print]
Wang et al. Resistance exercise enhances the molecular signaling of mitochondrial biogenesis induced by endurance exercise in human skeletal muscle. J Appl Physiol, 2011 [Epub ahead of print]

Tuesday, September 20, 2011

Does abdominal exercise training reduce abdominal fat?


Male players usually accumulate fat in the torso and in particular around the abdominals. This excess fat is associated with lower performance and if it becomes of large amount may also negatively affect vessels health. So, the question that often arises by athletes and others is “Can I lose abdominal fat with exercises for the abdominals?

There are not many studies on this issue in the literature. In a recent study by Vispute et al (2011), 24 volunteers were randomly assigned to 1 of the following 2 groups: control group (CG) or abdominal exercise group (AG). The AG performed 7 abdominal exercises, for 2 sets of 10 repetitions, on 5 d·wk−1 for 6 weeks. The CG received no intervention, and all participants maintained an isocaloric diet throughout the study. The results showed no significant effect of abdominal exercises on body weight, body fat percentage, abdominal fat and abdominal circumference.

It was concluded that 6 weeks of abdominal exercise training alone was not sufficient to reduce abdominal subcutaneous fat and other measures of body composition.


Vispute et al. The effect of abdominal exercise on abdominal fat. J Strength Cond Res 25(9): 2559-2564, 2011

Sunday, September 18, 2011

ΑΝ INJURY PREVENTION PROGRAM FOR YOUNG AND ADULT FOOTBALL PLAYERS


There is a number of studies in the literature on exercises that protect from muscle injuries in athletic population. Today, I would like to share with you one of the most realistic and integrated program for football players.

This is the “11+” FIFA program for injury prevention. The “11+” is an injury prevention program targeting on strengthening the body core, legs, improve stability and agility, among others. Few key points about the program:
  • Exercises can be performed prior to every training session or at least twice a week.
  • Players should perform all exercises in the correct way.
  • Players should be at least 14 years of age to start with it


To learn more on the program and view exercises and exercise description please visit FIFA’s web site at

Tuesday, September 13, 2011

Recent studies with practical applications to football-Part 2


Nassis et al. (2010). Relationship between the 20-m multistage shuttle run test and 2 soccer-specific field tests for the assessment of aerobic fitness in adult semi-professional soccer players. J Strength Cond Res., 24(10):2693-7.


The aim of this study was to examine the relationship of 2 different field tests for the assessment of aerobic fitness in soccer players with the multistage 20-m test used for the evaluation of maximum oxygen uptake. Nineteen semi-professional male soccer players (age: 22.8 ± 2.5 mean ± SD) performed, under similar conditions, 3 field tests in a counterbalanced order 7 days apart. These tests were the multistage 20-m shuttle run test (MSRT), the Bangsbo test, and the Hoff test. There was a significant correlation between the Hoff test and performance in the MSRT (r = 0.49, p < 0.05). The Bangsbo test was not associated with the MSRT score (r = 0.26, p > 0.05). In conclusion, the Hoff test can be used for the assessment of endurance in adult semi-professional soccer players. Coaches and teams could benefit from using the Hoff test that resembles soccer actions for the assessment of players' aerobic fitness.

Amiri-Khorasani et al.  (2010). Acute effect of different stretching methods on Illinois Agility Test in soccer players J. Strength & Condit. Res., 24 (10), 2698-2704. 

The purpose of this study was to examine the effects of static, dynamic, and the combination of static and dynamic stretching within a pre-exercise warm-up on the Illinois agility test (IAT) in soccer players. Nineteen professional soccer players (age = 22.5 ± 2.5 years) were tested for agility performance using the IAT after different warm-up protocols consisting of static, dynamic, combined stretching, and no stretching. The players were subgrouped into less and more experienced players (5.12 ± 0.83 and 8.18 ± 1.16 years, respectively). There were significant decreases in agility time after no stretching, among no stretching vs. static stretching; after dynamic stretching, among static vs. dynamic stretching; and after dynamic stretching, among dynamic vs. combined stretching during warm-ups for the agility: mean ± SD data were 14.18 ± 0.66 seconds (no stretch), 14.90 ± 0.38 seconds (static), 13.95 ± 0.32 seconds (dynamic), and 14.50 ± 0.35 seconds (combined). There was significant difference between less and more experienced players after no stretching and dynamic stretching. There was significant decrease in agility time following dynamic stretching vs. static stretching in both less and more experienced players. Static stretching does not appear to be detrimental to agility performance when combined with dynamic warm-up for professional soccer players. However, dynamic stretching during the warm-up was most effective as preparation for agility performance. The data from this study suggest that more experienced players demonstrate better agility skills due to years of training and playing soccer.


Bowtell et al. (2011). Montmorency cherry juice reduces muscle damage caused by intensive strength exercise. Med Sci Sports Exerc. 43(8):1544-51.

Montmorency cherries contain high levels of polyphenolic compounds including flavonoids and anthocyanins possessing antioxidant and anti-inflammatory effects. This study investigated whether the effects of intensive unilateral leg exercise on oxidative damage and muscle function were attenuated by consumption of a Montmorency cherry juice concentrate using a crossover experimental design.
Ten well-trained male overnight-fasted athletes completed two trials of 10 sets of 10 single-leg knee extensions at 80% one-repetition maximum. Trials were separated by 2 wk, and alternate legs were used in each trial. Participants consumed each supplement (CherryActive® (CA) or isoenergetic fruit concentrate (FC)) for 7 d before and 48 h after exercise. Knee extension maximum voluntary contractions (MVC) were performed before, immediately after, and 24 and 48 h after the damaging exercise. Venous blood samples were collected at each time point, and serum was analyzed for creatine kinase activity, nitrotyrosine, high-sensitivity C-reactive protein, total antioxidant capacity, and protein carbonyls.
The results showed that montmorency cherry juice consumption improved the recovery of isometric muscle strength after intensive exercise perhaps owing to the attenuation of the oxidative damage induced by the damaging exercise.

Matos et al. (2011). Prevalence of nonfunctional overreaching/overtraining in young English athletes. Med Sci Sports Exerc., 43(7):1287-94.

Three hundred seventy-six athletes (131 girls and 245 boys, age=15.1±2.0 yr) completed a 92-item survey about Nonfunctional overreaching and overtraining (NFOR/OT). The sample included athletes competing at club to international standards across 19 different sports. Athletes were classified as NFOR/OT if they reported persistent daily fatigue and a significant decrement in performance that lasted for long periods of time (i.e., weeks to months).
Approximately one-third of young athletes have experienced NFOR/OT, making this an issue for parents and coaches to recognize. OT is not solely a training load-related problem with both physical and psychosocial factors identified as important contributors.

López-Segovia et al. (2010). Effect of 4 months of training on aerobic power, strength, and acceleration in two under-19 soccer teams. J. Strength & Condit. Res., 24 (10), 2705-2714. 
The purpose of this study was to assess the effect of the training executed by 2 under-19 teams from the first Spanish division on aerobic power, strength, and acceleration capacity. Two under-19 soccer teams that competed in the same league were evaluated on 2 occasions. The first evaluation (E1) was done at the beginning of the competitive period, and the second evaluation (E2) was done 16 weeks later, coinciding with the end of the first half of the regular season. The following were evaluated: lower-body strength through jump height with countermovement with and without load (CMJ/CMJ20), speed of the Smith machine bar movement in a progressive load test of full squats (FSL), acceleration capacity in 10, 20, and 30 m (T10, T20, T30, T10-20, T10-30, T20-30), and maximal aerobic speed (MAS). Team A executed complementary strength training, and training loads were determined with regard to the speed with which each player moved the bar in FSL. Between the evaluations, the training sessions of each team were recorded to assess their influence on the changes in E2. Team A significantly improved its MAS (p < 0.01) and its application of strength in the CMJ20 (p < 0.05) and FS20-30-40 (p < 0.01), while significantly worsening their acceleration capacity in all the splits (p < 0.01). Team B slightly worsened its MAS and significantly improved its application of strength in the CMJ20 (p < 0.01) and FS50-60 (p < 0.05). Its acceleration capacity improved insignificantly except for in the 20- to 30-m interval/T20-30 (p < 0.05). The present study demonstrates that the use of loads as a function of the speed of movement, without the need to determine maximum repetitions is a methodology that is adequate for the improvement of the application of strength in under-19 soccer players. 

Wednesday, September 7, 2011

SCIENCE MAKES TRAINING MORE EFFECTIVE!

Source: Loughborough University, UK
What separates a top performer from the rest of athletes? Talent, of course, plays an important role but it is also deliberate, focused practice. To achieve your potential, mapped by the genes, you must train EFFECTIVELY.  This is what science makes!

SCIENCE MAKES TRAINING MORE EFFECTIVE!
 


 
Here are 4 tips for effective training:
  • Clearly identify sports-related and position-related needs. In terms of fitness, football requires certain abilities. Set the priorities and try to combine them with technical and tactical aspects. 
  • Evaluate current fitness level with reliable tests. It is important to know where you are. This should be done using reliable tools otherwise you might get confused.
  • Design a training program based on each player characteristics and needs. The same training program is not effective for all players. Training programs should be based on individual needs and be as flexible as possible.
  • Evaluate physical fitness and thus the effectiveness of the training program with testing at regular intervals. Be as objective and open-minded as possible. Change performance strategy if needed, otherwise YOU OR YOUR PLAYER MIGHT NEVER REACH THE TOP.



Monday, September 5, 2011

FUTURE CONGRESSES



Here are the links for some very interesting congresses on football in the next months. 

Leaders in Football
Leaders in Performance
5-6 October 2011, Stamford Bridge Stadium, Chelsea F.C., London

ASPIRE4SPORT International Sports Congress & Exhibition
11-14 November 2011, Doha, Qatar

Football Medicine Strategies for Knee Injuries Conference 2012
21-22 April 2012
Stamford Bridge Stadium, Chelsea FC, London
3rd World Conference on Science and Soccer
15-16 May 2012, Ghent, Belgium

Recent studies with practical applications to football-Part 1

Hamilton (2010). Vitamin D and human skeletal muscle. Scand J Med Sci Sports. 20(2):182-90.

 

Vitamin D deficiency is an increasingly described phenomenon worldwide, with well-known impacts on calcium metabolism and bone health. Vitamin D has also been associated with chronic health problems such as bowel and colonic cancer, arthritis, diabetes and cardiovascular disease. In the early 20th century, athletes and coaches felt that ultraviolet rays had a positive impact on athletic performance, and increasingly, evidence is accumulating to support this view. Both cross-sectional and longitudinal studies allude to a functional role for vitamin D in muscle and more recently the discovery of the vitamin D receptor in muscle tissue provides a mechanistic understanding of the function of vitamin D within muscle. The identification of broad genomic and non-genomic roles for vitamin D within skeletal muscle has highlighted the potential impact vitamin D deficiency may have on both under-performance and the risk of injury in athletes. This review describes the current understanding of the role vitamin D plays within skeletal muscle tissue.

Papacosta and Nassis  (2011). Saliva as a tool for monitoring steroid, peptide and immune markers in sport and exercise science. J Sci Med Sport. 14(5):424-34.

This paper discusses the use of saliva analysis as a tool for monitoring steroid, peptide, and immune markers of sports training. Salivary gland physiology, regarding the regulation and stimulation of saliva secretion, as well as methodological issues including saliva collection, storage and analysis are addressed in the paper. The effects of exercise on saliva composition are then considered. It is concluded that the measurement of physiological biomarkers in whole saliva can provide an important tool for assessing the immunological and endocrinological status associated with exercise and training.

Chelly et al. (2010). Effects of in-season short-term plyometric training program on leg power, jump- and sprint performance of soccer players J. Strength & Condit. Res., 24 (10), 2670-2676. 
The subjects (23 men, age 19 ± 0.7 years) were randomly assigned to a control (normal training) group (n = 11) and an experimental group (n = 12) that also performed biweekly plyometric training. The results showed that biweekly plyometric training of junior soccer players (including adapted hurdle and depth jumps) improved important components of athletic performance (squat and countermovement jump and sprinting).


Buchheit, et al. (2010). Improving repeated sprint ability in young elite soccer players: repeated shuttle sprints vs. explosive strength training J. Strength & Condit. Res., 24 (10), 2715-2722. 

To compare the effects of explosive strength (ExpS) vs. repeated shuttle sprint (RS) training on repeated sprint ability (RSA) in young elite soccer players, 15 elite male adolescents (14.5 ± 0.5 years) performed, in addition to their soccer training program, RS (n = 7) or ExpS (n = 8) training once a week for a total of 10 weeks. RS training consisted of 2-3 sets of 5-6 × 15- to 20-m repeated shuttle sprints interspersed with 14 seconds of passive or 23 seconds of active recovery (˜2 m/s); ExpS training consisted of 4-6 series of 4-6 exercises (e.g., maximal unilateral countermovement jumps (CMJs), calf and squat plyometric jumps, and short sprints). Before and after training, performance was assessed by 10 and 30 m (10 and 30 m) sprint times, best (RSAbest) and mean (RSAmean) times on a repeated shuttle sprint ability test, a CMJ, and a hopping (Hop) test. After training, except for 10 m (p = 0.22), all performances were significantly improved in both groups (all p's < 0.05). Relative changes in 30 m (-2.1 ± 2.0%) were similar for both groups (p = 0.45). RS training induced greater improvement in RSAbest (-2.90 ± 2.1 vs. -0.08 ± 3.3%, p = 0.04) and tended to enhance RSAmean more (-2.61 ± 2.8 vs. -0.75 ± 2.5%, p = 0.10, effect size [ES] = 0.70) than ExpS. In contrast, ExpS tended to induce greater improvements in CMJ (14.8 ± 7.7 vs. 6.8 ± 3.7%, p = 0.02) and Hop height (27.5 ± 19.2 vs. 13.5 ± 13.2%, p = 0.08, ES = 0.9) compared with RS. Improvements in the repeated shuttle sprint test were only observed after RS training, whereas CMJ height was only increased after ExpS. Because RS and ExpS were equally efficient at enhancing maximal sprinting speed, RS training-induced improvements in RSA were likely more related to progresses in the ability to change direction.


Arnoczky et al. (2011). What Is Platelet-Rich Plasma? Operative Techniques in Sports Medicine 19(3), 142-148

Platelet-rich plasma (PRP) has been advocated as a way to introduce increased concentrations of growth factors and other bioactive molecules to injured tissues in an attempt to optimize the local healing environment. PRP has been used extensively in dental and cosmetic surgery for almost 30 years, and the safety and efficacy of this autologous product in these areas have been well established. Recently, PRP has been increasingly used in the treatment of a variety of sports-related injuries in the hopes that the increased levels of autologous growth factors and secretory proteins provided by the concentrated platelets could enhance the biological processes associated with tissue repair and regeneration. However, all PRP preparations are not the same. Variations in the volume of whole blood taken, the platelet recovery efficacy, the final volume of plasma in which the platelets are suspended, the presence or absence of red and/or white blood cells, the addition of thrombin or calcium chloride to induce fibrin formation, and the addition of pH-altering compounds can all affect the character and potential efficacy of the final PRP product. This article reviews the basic principles involved in creating PRP and examines the potential basic science significance of the individual blood components contained in the various forms of PRP currently used in sports medicine.


Mejia et al. (2011). The Effects of Platelet-Rich Plasma on Muscle: Basic Science and Clinical Application. Operative Techniques in Sports Medicine 19(3), 149-153

Muscle injuries are the most common type of injuries in sports. The natural course in this repair process is often slow, incomplete, and unpredictable. For competitive or professional athletes, this delay or unpredictability in complete healing may be costly or career ending. With the introduction of the potential benefits of platelet-rich plasma (PRP) preparations, our treatment algorithm is changing. Our understanding of growth factors and their roles in the modulation and activation in soft-tissue healing is expanding at a rapid pace. This has led to its clinical use far outpacing clinical trials. Basic science has documented a potential for PRP to regenerate and modulate skeletal muscle and, thus, provides a foundation for clinical treatment and improved patient outcomes. Despite widespread anecdotal use in a variety of musculoskeletal injuries, research investigating its clinical efficacy is still in its infancy. This article addresses the biological effects of PRP on skeletal muscle myogenesis and its potential clinical applications.