Background: Small-Sided and Conditioned Games are characterised by modifications of field dimensions, number of players, rules of the game, manipulations used to shape the key task constraints that performers need to satisfy in practice. Evidence has already demonstrated the importance of designing practice to enhance understanding of tactical behaviours in football, but there is a lack of information about how coaches can manipulate task constraints to support tactical learning. Objective: To investigate which task constraints have been most often manipulated in studies of SSCGs; and what impact each manipulation had on emerging tactical behaviours, technical–tactical actions, and positional relationships between players. Methods: PubMed, Web of Science, Scielo, and Academic Google databases were searched for relevant reports without time limits. The criteria adopted for inclusion were: a) studies performed with football players; b) studies that included SSCGs as an evaluation method; c) studies that investigated tactical behaviours in SSCGs; and d), articles in English and Portuguese. Results: The electronic database search included 24 articles in the review. Of these, five manipulated field dimensions, six manipulated number of players involved, five manipulated field dimensions and number of players, five used different scoring targets, two altered the number of players and scoring target, and one manipulated the number of players, field dimension, and scoring target. Conclusion: Among the task constraints analyzed in this systematic review, manipulation of number of players and playing field dimensions concomitantly occurred most frequently.

The effects of a recreational soccer program (RSP) upon body composition, heart rate variability (HRV), biochemical markers, cardio-respiratory fitness, and endothelial function in obese adolescents were investigated. A randomised controlled clinical trial was conducted with 30 adolescents aged 12–17 years and body mass index (BMI) >2 standard deviations of WHO reference values, which were assigned to RSP (n = 10, 2 girls) and obese control (n = 10, 4 girls) groups. The 12-week RSP included 60-min sessions performed 3 times/week. BMI, waist circumference, blood pressure, blood glucose, lipid profile, insulin, C-reactive protein, HRV, and maximal oxygen consumption (VO₂peak) were evaluated following standardised procedures. Body composition was determined by dual-energy X-ray absorptiometry and endothelial function by venous occlusion plethysmography. After intervention, RSP exhibited significant reductions in BMI (−0.7 ± 0.2 kg · m^–2), waist circumference (−8.2 ± 1.4 cm), %body fat (−2.2 ± 0.4%), systolic blood pressure (−5.0 ± 2.3 mmHg), total cholesterol (−16.2 ± 5.8 mg · dL⁻¹), triglycerides (−20.5 ± 12.9 mg · dL⁻¹), C-reactive protein (−0.06 ± 0.01 mg · dL⁻¹), insulin resistance (HOMA-IR, −1.4 ± 0.6), and sympathetic activity (LF, −13.9 ± 6.6 un) vs. controls (P < 0.05). Significant increase was observed in parasympathetic activity (HF, 13.9 ± 6.6 un), VO₂peak (7.9 ± 2.8 ml · kg⁻¹ · min⁻¹), and high-density lipoprotein cholesterol (11.0 ± 6.3 mg · dL⁻¹) (P < 0.05). Vascular conductance (19.5 ± 8.1 ml · min⁻¹ · 100 ml, P = 0.005) increased and vascular resistance (−5.9 ± 2.4 ml · min⁻¹ · 100 ml, P = 0.041) decreased in RSP, but not in controls. A 12-week recreational soccer intervention was effective to improve biochemical, cardiovascular, and fitness health markers in obese adolescents.

The findings of previous studies investigating the strength of the relationships between the percentages of maximal heart rate (%HR_max), heart rate reserve (%HRR), maximal oxygen uptake (%VO_2max), and oxygen uptake reserve (%VO₂R) have been equivocal. This inconsistency between studies could largely be due to differences in methodology. The purpose of this study was therefore to determine whether different VO_2max test protocols and resting VO₂ assessment influence the relationships between the %HR_max, %HRR, %VO_2max, and %VO₂R. Thirty-three young men performed maximal treadmill protocols (ramp, Bruce) to assess HR_max and VO_2max. Resting VO₂ was assessed as follows: a) resting VO_2standard, using strict criteria (24 h exercise abstention, alcohol, soft drinks, or caffeine; 8 h fasting; 30 min assessment); b) resting VO_2sitting and; c) resting VO_2standing (both 5 min before exercise testing). The %HRR was closer to %VO_2max than to %VO₂R, especially in the ramp protocol (p<0.001). In the Bruce protocol, relationships were closer to the identity line, and there was no significant difference between %HRR and %VO_2max, or %VO₂R. The VO_2max was significantly higher in the ramp protocol compared to the Bruce protocol (p<0.001). In both protocols resting VO₂ assessment produced no significant difference in the intercepts and slopes of the %HRR-%VO₂R relationships obtained from individual regression models. The %VO₂R calculated using resting VO_2standard was closer to %HRR compared to VO_2sitting and VO_2standing. The premise that %HRR is more strongly related to %VO₂R than to %VO_2max was not confirmed. Methodological differences should be considered when interpreting previous studies investigating %HR_max, %HRR, %VO_2max, and %VO₂R relationships.