"Evaluate the physiological adaptations of small-sided games in professional soccer players and effects on aerobic performance"

Small-sided games (SSGs) provide an adequate physiological response to the aerobic endurance of professional soccer players. Small-sided games (SSGs) are soccer games played on smaller pitches with different rules and fewer players than traditional soccer games. Although less structured than traditional fitness training methods, these games are very popular training drills for players of all ages and levels. There is currently little information on how SSGs can best be used to improve soccer players' physical capacities and technical or tactical skills. During SSGs, however, several prescriptive variables controlled by the coach can have an impact on the exercise intensity, SSGs are commonly used by coaches to develop the technical attributes of soccer players and are now increasingly being used for aerobic fitness development. Coaches usually try to change the training stimulus in SSGs by changing the pitch area, player rotation, and so on. (Hill-Haas, Dawson, et al., 2009; Hill-Haas et al., 2011). Soccer is classified as a high-intensity intermittent team sport. Previous research has found that elite players cover a distance ranging from 10 to 12 km, with 3–7 percent of their time spent in high-intensity activities, an average of 80–90% of maximum heart rate (HRmax) or 75–80% of Vo2max (Dellal, Varliette, et al., 2012). There has been substantial growth in the research related to specific training methods in particular the effects of small-sided games due to the popularity obtained by specific soccer conditioning and reduced time available for fitness training in soccer, therefore an understanding of the physiological adaptations of SSGs is important (Aguiar et al., 2012). This essay begins by discussing the use of SSGs as a conditioning alternative. It then evaluates the physiological adaptations in professional soccer players and their effects on the aerobic system. Subsequently, it explores the wide-ranging effects of small-sided games and their use in driving specific aerobic performance.

Before proceeding to evaluate the physiological effects of SSGs, multiple constraints need to be considered and can be added to small-sided games which can affect the physiological adaptation of players. (Hill-Haas et al., 2011) found that 4 vs 4 SSGs produced greater time above 90% heart rate max and found that players had less time between efforts exceeding 18km/h. In contrast (Brandes et al., 2012)?highlight within their research that the use of 2 v 2 SSGs elicits demands on the anaerobic energy system when comparing the HR and lactate concentration levels compared with 3 and 4 player formats and state that these remain as aerobic dominant SSGs. This suggests that player numbers influence physiological adaptation to players, with more players increasing intensity due to increased HR and decreased recovery between efforts, whereas 2 v 2 increases the volume of work completed by each player due to the lower player count and more area per player to cover, increasing lactate concentration levels. This then can contradict the physiological adaptation required and coaches need to be aware of how player numbers affect the adaptation they are chasing. Furthermore, different pitch dimensions produce a different physiological responses. (Casamichana & Castellano, 2010) Players spent 50% of their time in >90% HRmax in a 5 v 5 format using a 275m area, indicating that an increase in playing area leads to an increase in physical and physiological workloads. (Rampinini et al., 2007) The use of 3 vs 3 formats elicited a greater response in maximum heart rate 89.4 percent of the time. The manipulation of pitch dimensions also produced an additional response, with medium (15 x 25m) and large (18 x 30m) pitches allowing players to work at 90% of their HRmax. (Hill-Haas et al., 2011) The researchers compared two SSG formats, 4 v 4 and 8 v 8, with intervals running 4 x 1000m repeats separated by 150 seconds of recovery and discovered that the SSG produced a higher percent heart rate max response, 91 percent versus 85 percent. This adds to the complexity that can be seen when planning and implementing SSGs, as well as a clear understanding of the effects of these constraints and how this can affect the physiological response of the players. Moreover, SSGs can be used in two different exercise formats continuous and interval. (Fanchini et al., 2011) compared SSG bouts of 2,4 and 6 minutes in duration and found that 4 minutes bouts produced higher % HR max than the 2 and 6-minute bouts. (Hill-Haas, Rowsell, et al., 2009) found there was no significant difference in total distance traveled or distance traveled while walking, jogging, or running at a moderate pace when SSG continuous and SSG interval were compared. However, when comparing the SSG interval to the SSG continuous, players covered a significantly greater distance at 13.0-17.9km/h, indicating that the intensity of the SSG interval was higher, but would induce a similar physiological response in terms of aerobic performance. (K?klü, 2012) found in a comparison of small-sided games interval and continuous that the physiological responses are similar except for the 2 v 2 formats which elicited greater lactate concentration-response. It would seem intuitive to mention that soccer is played in both the anaerobic and aerobic systems, as players play at or above 75% of their maximum heart rate. Improving the aerobic system would, in turn, improve player performance and reduce recovery time between bouts of high-intensity exercise (Clemente, 2014). After defining what restrictions are and demonstrating the many rules that coaches might use, we'll look at the important traits emphasized in the research and their effects on player physiology.

?Subsequently, players spend a lot of time in a higher % HR zone which provides evidence that players would see an increase in Vo2 max, the upper limit of the aerobic pathway. (Helgerud et al., n.d.; Hoff, 2002) established that an HR max between 90-95% would provide an increase in Vo2 max capacity using an interval method, increasing Vo2 max from 55.4 to 64.3. This would imply that SSGs would increase Vo2 max capacity when players are above 90% HR max and would indicate that 2 v 2 to 4 v 4 games would provide this stimulus due to their potential to increase players' %HR to the adequate level to induce this adaptation. (McMillan, 2005) Highlight aerobic metabolism is estimated to contribute 90% of the energy cost of soccer match play. The number of sprints attempted during a match was likewise influenced by Vo2max, 70%–80% of maximum oxygen uptake. It is vital to offer additional energy in anaerobic form for athletes who perform high-intensity loads since they burn 80 – 90 percent of their energy from their aerobic energetic system during a match. After then, a player can work at a high-intensity level for a longer amount of time. Glycogen stores are consequently preserved, allowing players to work at a high level of intensity towards the finish of the game. It is estimated that energy expenditure during match play accounts for 70 – 75 percent of maximum oxygen intake (Reilly, 2005; Teplan et al., n.d.). It was recently demonstrated that by increasing the mean Vo2max of professional soccer players by 11% over 8 weeks, a 20% increase in total distance covered during competitive match play was manifested, as well as a 23% increase in involvement with the ball and a 100% increase in the number of sprints performed by each player. (K?klü, 2012) found that interval SSGs provoke a higher % heart rate with 3 and 4 players small-sided games providing a 90%+ HR max using an interval exercise type. (Bosquet., Léger, & Legros, P, 2002) found in multiple studies that the time to exhaustion when using an intensity of maximal oxygen uptake was a mean of 5.92 minutes. It might be predicted that SSGs lasting 4-6 minutes employing an interval method, working at 90 percent + HR max, and player numbers ranging from 2 to 4 would increase the intensity even higher, assuring a favorable Vo2 max response in players. Before using these theories of SSGs training for players above a specific percent HRmax in the hopes of a beneficial physiological effect, it is vital to assess the further impact on the players' physiology.

Additionally, blood lactate concentration levels seem to be a regular marker within research and seem to have a relationship with Vo2 max. Blood lactate concentration levels appear to be strongly linked to training-induced performance, and they represent the accumulation of lactate production during soccer-specific workouts, also known as blood lactate accumulation (OBLA). (Brandes et al., 2012; Shrier, 2007) found increases in blood lactate concentration levels using SSGs, although different players' numbers induced different lactate responses. For instance (Brandes et al., 2012) found a greater blood lactate concentration level (5.5 mmol) in 2 vs 2 whereas 3 vs 3 and 4 vs 4 showed similar blood lactate concentration 4.3 mmol and 4.4 mmol. Interestingly (K?klü, 2012) found higher blood lactate concentration in 2 v 2 compared to 3 and 4 a side but produced a lower % higher rate max. This suggests that there isn't necessarily a relationship between percent HR max and blood lactate concentration levels. (Dellal, Owen, et al., 2012) Blood lactate concentration was lower during SSGs than during match-play, and SSGs had a higher number of high-intensity running bouts per minute of play. In contrast, during continuous exercise, blood lactate concentrations are lower but accurately reflect muscle lactate concentrations. These differences between intermittent and continuous exercise are most likely due to differences in muscle and blood lactate turnover rates during the two types of exercise. In general, muscle lactate concentration is a result of lactate production and removal, either as turnover within the muscle or release into the bloodstream, both of which are restricted during intense exercise (Shrier, 2007). Anaerobic energy turnover is expected to contribute more to muscle metabolism in SSGs than in match-play due to the increased high-intensity running during SSGs. The lower blood lactates in the SSGs, on the other hand, could be explained by the fact that the SSGs' high-intensity running bouts were shorter in duration, resulting in a greater dependence on ATP and CP breakdown, rather than anaerobic glycolysis. SSGs' effects on blood lactate concentration levels may not produce adequate adaptation due to the lower levels seen in SSGs as opposed to match-play; on the other hand, smaller player numbers appear to produce higher lactate concentration levels; therefore, using smaller player numbers to improve lactate concentration levels would make sense. Furthermore, due to the nature of the game, blood lactate concentration tolerance would provide adequate performance benefits to players, guaranteeing that they do not fatigue as quickly and can perform at higher levels of high intensity. After defining what is meant by blood lactate concentration levels and the impact on players when using SSGs, the following section will go into greater detail about the additional adaptations that occur when utilizing SSGs.

As the intensity of an SSG drill increases, hemoglobin levels appear to decrease. Indeed, higher hemoglobin levels are associated with improved aerobic performance due to increased oxygen transport capacity (Otto et al., 2013). Several studies have found that hemoglobin levels in professional soccer players drop after high-intensity activity. Given this, monitoring hemoglobin levels can be useful for determining the intensity of SSGs and aerobic training during the preparation period, which helps players improve and maintain their hematological values throughout the season. Normally, endurance training decreases red blood cells, hemoglobin, and the ratio of the volume of red blood cells. The plasma volume expansion resulting from an increase in aldosterone (corticosteroid hormone) production accompanied by osmotically active plasma proteins, a decrease in urodilatin activity, and sensitivity of central baroreceptors located in the medulla oblongata are responsible for these adaptations. The growth of specific physical capacities; (endurance, strength, power, sprinting, and jumping) is primarily responsible for changes in erythrocytes, hemoglobin, hematocrit, and plasma volume. (Bekris et al., 2015; Silva et al., 2008). A decrease in hemoglobin due to a decrease in the total circulating mass of hemoglobin may impair exercise capacity in a variety of ways. To begin, a decrease in arterial oxygen content reduces muscular O2 availability for the same muscle blood flow. Second, when hemoglobin is lowered, muscle O2-diffusing capacity decreases, which may be due to changes in erythrocyte intracapillary spacing or slower dissociation of O2 from hemoglobin. Third, when hemoglobin is reduced, pulmonary diffusion is reduced (Otto et al., 2013).?SSGs' effects on increasing Vo2 max capacity, and hence the efficiency of hemoglobin levels and effective O2 delivery to muscles, would, admittedly, improve the players' aerobic capacity and performance.

Exercise causes alterations in ION, pH, and metabolites inside and outside contracting muscle cells, which may contribute to tiredness development. It is believed that a rise in extracellular K+ and a concurrent decrease in sarcolemmal excitability play a crucial role in fatigue processes during brief bouts of high-intensity exercise (Thomassen et al., 2010). When speed endurance training and small-sided games were compared, it was discovered that Beta-hydrox-CoA-dehydrogenase activity increased by 24 percent in both groups. Na+–K+ ATPase 1 subunit protein expression rose by 37% in SSGs, while MCT4 protein expression increased by 67% in SSGs. SOD2 protein expression increased by 37% in SSGs, while GLUT-4 protein expression increased by 40% in SSGs, exclusively (Fransson et al., 2018). When compared to speed endurance training, producing higher concentration levels in all markers. (Bangsbo et al., 2009) discovered that if speed endurance training is performed, performance can be improved with a reduction in training volume and that the Na+–K+ pump plays a role in controlling the homeostasis of K+ in the development of fatigue. Muscle transport proteins that exchange H+, Na+, K+, Cl-, and lactate across the sarcolemma appear to be important in delaying fatigue during intense exercise. The Na+ K+ pump appears to be critical in maintaining muscle potential. There appears to be a net synthesis of proteins, which may lower muscle membrane potential while preserving cell excitability, resulting in a decrease in fatigue levels. This also highlights the positive effects of high-intensity training as opposed to the long duration and volume type work used to improve aerobic capacity levels, which could support the notion that the effects of interval-based high-intensity work have similar, if not identical, physiological effects to those produced by long continuous aerobic work. Interestingly, bout intensity, volume, and type appear to influence the effectiveness and alterations, but a clear physiological effect is a benefit of affecting fatigue in players. Incorporating these theories into soccer training for players proves SSGs not only work on the tactical and technical aspects. However, it also has a positive impact on players' physiological profiles and can produce a very respectable alternative to traditional conditioning formats.

?In summary, this then supports the notion that SSGs do appear to have physiological consequences on players, particularly in terms of aerobic performance capability. They can be a helpful tool for eliciting physiological demands. In addition, the evidence presented supports the notion that aerobic endurance does not have to be of a long continuous nature, but can be induced through interval-based SSGs. There appears to be a relationship between the player numbers, pitch dimensions, and the exercise format (continuous vs interval). There also appears to be both anaerobic and aerobic responses to small-sided games, which was indicated in blood lactate concentration levels, which would be a key consideration when planning SSGs. It is also clear that SSGs have an impact on players' percent HRmax and, in turn, Vo2 max, which has been indicated. Furthermore, this then affects the hemoglobin capacity of the players to efficiently provide O2 to working muscles. The effects of high-intensity aerobic endurance exercise within muscle cells have a positive effect on managing fatigue levels in players which could be an effective training stimulus, especially in the latter stages of match play. The limitations of the current evaluation are that some studies analyzed a small cohort of players, over a relevantly short period varying from 6-12weeks, this could have potentially affected the results and is something to consider. Conclusively, SSGs can be quite difficult to replicate due to different conditions, environments, intensity, touches of the ball, coaches' commands. Some studies examine heart rate readings, which may be influenced by external factors such as weather, coach input, and player influences away from soccer. As a result of the evidence presented, it would seem logical that exercise prescription focused on fewer players (2v2 to 4v4) and medium to larger playing areas (15 x 25m +) would induce maximal physiological and perceptual responses, such as; an increase in Vo2 max capacity, improved hemoglobin efficiency, and reduced fatigue levels during high-intensity bouts, allowing the players to maintain higher levels of performance for longer.

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