Authors - Stanislav Kasampalis

Aerobic capacity is crucial for the performance in football players, and its assessment is one of the most important ergometric tests in the early stages of pre-season (2,6). In the modern football the distance covered during a match in elite football players range between 10 – 13Km (2,4) and with mean values for VO2max between 55- 75 mL · kg–1 · min (6,2,4), it has been proposed that a VO2max of > 60 mL · kg–1 · min should be the minimum threshold in order to perform in top class contemporary football (6,2,4). However, there many other biochemical factors that should be taken into consideration in football players which their importance and usefulness are crucial to make final conclusions about the fitness levels and the design of a particular training program based on the results. One of the most well know parameters in the athletic world is the anaerobic threshold or lactate threshold. Why this parameter is such of an importance? Because its concentration in the blood is being used as an indicator of aerobic and anaerobic energy production (4,13), it helps to examine the rate of production and its removal from the blood (12), the tolerance to lactate (9), evaluate physical fitness as well as identify any adaptations might occur after following a specific training plan are some of the information can be collected from the test.

The assessment can be carried out in the laboratory (treadmill) or outdoor (football court). In a laboratory environment the test protocol consists of several incremental stages (4-7, depends on the sport and the athlete) with a small break between the stages in order to collect capillary blood either from the finger (Picture 1) or the ear lobe. Then, the treadmill speed increasing gradually until volitional exhaustion of the athlete where VO2max and vVO2max can be determined as well. After the completion of the test, the anaerobic threshold can be detected with various methods. The diagram bellow shows the determination of 2 thresholds, the LT1 (around 2 mmol L −1) and LT2 (between 3.5 and 4 mmol L −1 ).

L1 represents the velocity (vLT1) / intensity where the main energy source derived from the aerobic system. L2 shows the velocity (vLT2) / intensity and the transition from aerobic to the anaerobic system and also indicating the upper limit of the steady state between lactate production and removal. Based on these results the sport scientist can develop a training program, monitor the intensity of the players based on the blood lactate results and most importantly work at the right intensities as well as at the right amount of time.

Based on the literature, a football player with high anaerobic threshold would be able to cover more distance in high intensity without accumulating much lactic acid in the blood (6). At the table below, various of velocities at the anaerobic threshold can be seen in professional football players from different leagues and countries.

Table 1. Mean ± SD values of velocity at LT2 in various studies in football players.

Lactate threshold has shown to strongly correlated to endurance performance, and more emphasis has been placed in comparison to VO2max the recent years. Also, measurement of LT should implemented as a tool during in competitive period for the investigation of aerobic fitness (4,5,1,13). The main reason for this is because LT is associated with peripheral adaptations such as an increase in capillary density and in the ability to transport hydrogen ions and it is more sensitive to changes in training regimens, whereas VO2max is basically limited to central factors (Cardiac Output), where it makes it harder to improve (6). Lastly, LT assessment is one of the gold standard methods to evaluate the aerobic and anaerobic fitness and is a valid as well as reliable tool in monitoring changes in aerobic capacity in football players. However, it should not be a primarily criterion for a player selection as there are other important determinants that should be taken into consideration to define overall a player’s fitness.

REFERENCES:

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In football it is well known that the ability to have explosiveness and power at the lower extremities in a football player are very important factors in performance, as the nature of the sport requires many explosive actions during a match (1,3). Also, the jumping ability, as an expression of power, is a basic factor for a good performance in the specific sport (2,7,9). The reason for this is that the football player requires to perform fast and jump high for a successful header and in order to achieve that, it also requires high and explosive jumping ability. One way to evaluate jumping ability, lower body power and neuromuscular coordination, is the use of vertical jump test. It’s a simple, practical, valid and very reliable measure which can provide us with very useful information and work on any weakness might present. The test has been measured using force platforms or led bar systems connected to a laptop. The most widely used techniques by researchers are Squat Jump (SJ) and Counter – Movement Jump (CMJ). Both are useful for assessing athletic performance and each of the test provides us with different information due to their different techniques. The SJ (Picture 1) is used as a measure of lower body concentric strength / power and is performed in a semi squat position while CMJ (Picture 2) is used as a measure of lower body reactive strength / power (performed with counter movement), the ability of the neuromuscular coordination and the coordination among muscles (stretch and shortening cycle, (SCS) (1,5,7).

Why is this test useful and what is the conclusion? Research has shown that these tests have relationship with sprint performances (3), acceleration in a sprint (4), greater flight time (6), and increased 1RM maximal strength in squat (9). The jumping ability in football players varies between 47.8 – 60.1 cm. Based on the literature the vertical jumping profile of a football player should be at least 45 cm in a competitive level (2).

Taking these information into consideration, the strength and conditioning coach may design or develop a training plan based on the athletes results as well as for the whole team in order to enhance performance. A large proportion of literature has conducted variety of studies in improving jumping ability and also what kind of exercise training is more efficient. The vertical jumps are explosive movements which require fast action and strength in the lower extremities (3,5). For this reason, plyometric exercises have been proposed and have attracted the attention of sport scientists for the reasons mentioned earlier above. Several research studies have shown that plyometric exercise develop the power and explosiveness in athletes (7,8,9). The table below illustrates various of training methods in enhancement of jumping ability alongside with other parameters. It is clear that plyometric exercise training positively contributing to improved performance after conducting numerous of tests.

Table 1. Values for each exercise training program and its effect on different parameters

Lastly, the vertical jump assessment can provide us with useful information regarding athlete jumping ability as well as other variables, where strengths and weaknesses can be detected and an appropriate training plan can be designed in order to develop sport specific characteristics. Based on the research, it can be concluded that applying plyometric exercise training into a football training program can induce significant improvements in various parameters.

REFERENCES:

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