Pierros Thomakos

This study examined the effects of two different intensities of running between repeated sprints and compared them with passive recovery. Thirteen professional soccer players performed two sets of six 30 m sprints on three randomly assigned occasions. A 5 min passive rest period separated the two sets, while sprints were interspersed with either passive standing, running at 95% of the first lactate threshold (MOD) and running at maximum aerobic speed (HIGH). Performance decrements were greater in HIGH than MOD at the last sprint in both sets (set 1: 5.8 ± 4.2% vs. 2.6 ± 3.2%, p = 0.07; set 2: 9.1 ± 4.5% vs. 4.0 ± 6.1%, p = 0.016). Acceleration (0–15 m) was more affected than maximal-speed running (15–30 m) (condition × sprint interaction: p < 0.001). Mean and peak heart rate were higher in both running conditions than passive (p < 0.05), with no difference between MOD and HIGH. Blood lactate showed a significant set × condition interaction (p < 0.001), peaking at 13.6 ± 2.7 mmol·L⁻¹ in HIGH, while blood lactate responses to passive and MOD were similar and peaked after the second set of sprints (10.7 ± 2.1 and 11.5 ± 2.8 mmol·L⁻¹, respectively). Between-sprint running intensity markedly influenced fatigue development during repeated-sprint exercise. The HIGH condition elicited greater metabolic strain and performance decrements than MOD or passive conditions. Within the present protocol, passive standing was associated with smaller decrements in repeated-sprint performance despite high heart rate and blood lactate responses.

Background: We examined changes in hematological, biochemical, and hormonal biomarkers, along with endurance and explosive performance indices, in amateur soccer players over a 4-week preseason period. Methods: Thirteen players (age: 19.7 ± 2.0 years; body mass: 73.0 ± 6.8 kg; height: 180 ± 0.1 cm; body fat: 8.6 ± 3.5%) were monitored during a 4-week preseason program, which included 21 training days, three friendly matches, and four days of rest. Before and after this period, endurance capacity was evaluated using the Yo-Yo IR1 test, and leg power was assessed using the CMJ. Blood samples were collected for three consecutive days in week 1 and after week 4 to assess hematological and biochemical parameters. Internal load during all weeks was assessed with session RPE (sRPE). Results: There was a 25.5% increase in Yo-Yo IR1 distance (2123 ± 413 vs. 1560 ± 356 m, p = 0.002), with the estimated VO₂max and the speed associated with VO₂max (vVO₂max) improving by 8.7% (49.5 ± 3.0 to 54.2 ± 3.5 mL/kg/min, p = 0.002) and 5.3% (16.0 ± 0.7 to 16.9 ± 0.6 km/h, p = 0.002), respectively. In contrast, CMJ performance in weeks 2–4 declined by 13.4–21.0% relative to baseline, while sRPE peaked during week 3 (4011 ± 440 AU). Hematological variables were mostly stable except for small increases in MCV and MCH (1.5–1.8%, p < 0.001), while there were significant reductions in urea (12%), uric acid (6.2%), and erythropoietin (33%). Conclusions: A 4-week preseason program substantially improved aerobic capacity yet compromised leg power. Changes in biomarker profiles suggest that the training load maintained an appropriate balance between overload and recovery. These findings provide valuable guidance for coaches seeking to optimize training protocols while minimizing the risk of overtraining and preventing injuries during the competitive season.

Supplementary high-intensity interval training (HIIT) programs, focusing on different aspects of fitness, are commonly used in soccer practice. This study examined the impact of two different HIIT formats applied during the competitive season on aerobic and neuromuscular performance. Twenty-six young players from two youth amateur soccer teams (aged 18.1 ± 0.7 and 18.7 ± 1.1 years) participated. In a randomized design, Team A served as an experimental group, performing either a 10s/10s linear running HIIT or a 15s/15s HIIT with changes of direction, both at 100% of maximum aerobic speed, twice per week for six weeks. In that period, team B acted as a control group, maintaining their usual training soccer regimen. Following two weeks of lower volume and frequency training, team B added the two HIIT formats in their training for six weeks, while team A acted as control. Before and after each 6-weeks period, aerobic fitness and neuromuscular performance was evaluated by the countermovement jump (CMJ). The 3-way ANOVA showed that both HIIT formats significantly enhanced Yo-Yo Intermittent Recovery Test Level 1 (Yo-YO IR1) performance compared to the respective control periods. However, the main finding was that the 10s/10s compared with the 15s/15s HIIT format induced 45-50% greater improvements in Yo-YO IR1 (total distance: 18.5 ± 11.7% vs. 9.0 ± 8.5%, V̇O2max: 5.6 ± 3.2% vs. 3.0 ± 2.7%, and vV̇O2max: (3.3 ± 1.9% vs. 1.8 ± 1.7%, all p = 0.39, d = 0.85). Countermovement jump performance remained unchanged across both groups (p > 0.68). During HIIT rating of perceived exertion was higher in the 15s/15s vs. the 10s/10s format (6.4 ± 0.5 vs. 4.7 ± 1.2 a.u., p < 0.001). These findings suggest that while both HIIT formats effectively enhance aerobic performance during the season, the 10s/10s format offers superior benefits with less perceived exertion, while the 15s/15s format induces higher internal load.

The aim of the present study was to investigate the effect of weighted vest on-field small-sided games (SSG) soccer training, during the in-season period, on body composition and soccer-specific performances, in young, trained soccer players. A counterbalance study design was adopted, in which the fourteen well-trained players (age: 19.1 ± 0.5 yrs, body mass: 70.3 ± 5.3 kg, body height: 180.3 ± 3.0 cm, body fat: 9.2 ± 4.1%) performed both the Interventional (Vest) and Control (Con) training routines (6 weeks/season; 5 training sessions/week; 1 match/week), in different occasions (winter/spring period). Con group followed a regular weekly training plan. When the Con group performed their intense training sessions, Vest group performed only the on-field SSGs training wearing a vest (12.5% of athletes' body mass). All the evaluations were performed one week before and after each training period. Statistical analyses include repeated ANOVA and T-test (p < 0.05). Significant increases in sprinting, jumping, change of direction (COD), aerobic and anaerobic performances were observed only after Vest intervention (-4.7 ± 2.2% to 11.2 ± 4.2%; p < 0.05). Significant changes were observed only after Vest training, compared to Cont (p < 0.05). These results suggest that using a weighted vest, during the in-season, onfield SSG training two times/week induces greater increases in young soccer players' sprinting, jumping, COD, aerobic and anaerobic performances.

This study compared the effects of adding a weekly session of either strength training followed by high-intensity interval training (HIIT) or high load plyometric training followed by small-sided games (SSG) on aerobic fitness, goals scored and conceded, and match results. Twenty-nine players from two youth elite teams competing in an under 19 (U19) first division league took part in the study. Of those, 16 players from one team followed the HIIT program (age: 17.8 ± 0.6 years) and 13 players from the other team trained once a week, following the SSG program (age: 18.0 ± 0.6 years). The training intervention lasted for 11 weeks and was applied once per week. For the HIIT team it included high-load strength training (80–95% of 1 RM) followed by high-intensity intermittent running, whereas for the SSG team (n = 13) it included plyometric exercises followed by SSG. Aerobic fitness was assessed before and after the intervention, while goals scored and conceded, as well as match results during the intervention period, were compared with the 11-week period preceding it. Only the HIIT team improved Yo-Yo IR2 performance (running distance: from 902.5 ± 147.5 to 1092.5 ± 155.8 m, p < 0.001) while there was no change for the SSG group. Moreover, during the 11-week intervention, the HIIT team improved the number of goals scored in the last 30 min of the game compared with the pre-intervention period (0.36 ± 0.50 to 1.27 ± 0.90 per match, p < 0.05) and the scored vs. conceded goals were higher in the second half (1.36 ± 1.03 vs. 0.27 ± 0.47, p < 0.05). No significant differences were found for these parameters in the SSG team. Regarding match result, the HIIT team increased the proportion of wins from 5 wins in 11 matches (or 45%) in the pre-intervention period to 9 wins in 11 matches (or 82%) during the intervention period, while this profile remained unchanged for the SSG team. In conclusion, the present study demonstrated that the HIIT program performed once per week was superior to SSG as it improves aerobic fitness, scored and conceded goals, and match result during the in-season period.

The aim of the present study was to evaluate two different intervention programs applied during a 4-week pre-season period. Twenty-nine players participated in this study and were divided into two groups. One group (Ball_Train, n = 12, age: 17.8 ± 0.4 years, body mass: 73.9 ± 7.6 kg, height: 178 ± 0.1 cm, body fat: 9.6 ± 5.3%) performed a higher percentage of aerobic training with ball and strength training using plyometrics and exercises with body weight. The other group (HIIT_Train, n = 17, age: 17.8 ± 0.7 years, body mass: 73.3 ± 5.0 kg, height: 179 ± 0.1 cm, body fat: 8.0 ± 2.3%) trained with high-intensity interval training (HIIT) without the ball and performed resistance training with weights in the same session. Both groups trained for strength (two times/week) and performed aerobic–anaerobic fitness without the ball, passing games, and tactical and small-sided games. Lower limb power (CMJ) and aerobic fitness (Yo-Yo intermittent recovery test level 1-IR1) were evaluated before and after the four-week training program. Yo-Yo IR1 performance was improved in both groups, but the improvement was greater for the HIIT_Train than Ball_Train group (468 ± 180 vs. 183 ± 177 m, p = 0.07). CMJ showed a non-significant improvement in the Ball_Train group (5.8 ± 8.8%, p = 0.16), but it decreased by 8.1 ± 9% (p = 0.001), in the HIIT_Train group. In conclusion, we have shown that a short pre-season period of training results in improvements in aerobic fitness in both groups, with high-intensity interval training showing superior adaptations than training with the ball. However, CMJ performance was reduced in this group, possibly suggesting higher fatigue levels and overload, and/or showing the effects of concurrent HIIT_Train and strength training in soccer.

The purpose of this study was to explore the respiratory response of acute interval and continuous exercise (CE) of low and high intensity. Fourteen recreational athletes (7 men and 7 women; VO₂max = 35.7 ± 6.1 mlkg^–1min^–1) performed a bout of continuous and a bout of interval exercise (IE) both consisted of 5-min cycling at low intensity [80% of the power output (W) of the predetermined gas exchange threshold (GET) (80%W_GET)] and 5-min cycling at high intensity {W_GET plus the work rate corresponding to 50% of the difference between peak power output (PPO) at oxygen uptake (VO₂max) test and the W_GET [W_GET + 0.50 Δ(PPO – W_GET)]}. CE compared to IE induced significant higher heart rate and ventilation as well as significant higher levels of mouth occlusion pressure for 0.1 s (P_0.1) (P < 0.05) during low and high intensities. Our results indicate that CE stimulates respiration more than IE when the exercise is performed at the same relative intensity.