This study explores how different small-sided football games affect players' heart and technical skills. We will compare two ways of playing: "Free Play," where players act freely, and "Controlled Pass," where passing rules are used. Elite football players will participate in both types of games on small fields (3 vs 3 and 4 vs 4). We will measure heart responses (like heart rate) and how often players touch the ball. The goal is to help coaches choose the best game format to improve fitness and technical ability in training.

Small-sided games (SSGs) are widely used in football training because they combine technical, tactical, and physical demands in a single activity. However, the way rules are modified during these games can change how players respond both physiologically and technically. Despite the popularity of SSGs in elite football, limited evidence exists regarding how specific rule modifications influence cardiovascular strain and technical involvement in real training settings.

This study was designed to examine the effects of two rule conditions, Free Play and Controlled Pass, in both 3v3 and 4v4 SSG formats. The Free Play condition allows players to participate without additional restrictions, whereas the Controlled Pass condition requires a minimum number of passes before attempting to score. These modifications are expected to alter both the cardiovascular responses and technical actions of players.

A total of 24 elite male football players, aged 18 to 30 years, with at least five years of professional experience, were recruited to participate. All participants underwent baseline assessments and were then assigned to play both conditions in a randomized sequence. Each SSG session lasted eight weeks and was closely monitored by the research team. Heart rate responses were measured continuously using Polar heart rate monitors, and technical performance was evaluated through video-based notational analysis.

The primary outcomes of interest were maximum heart rate (HRmax) and percentage of HRmax, which provide indicators of cardiovascular load. The secondary outcomes were the number of ball touches, reflecting the degree of technical involvement during play. Statistical analysis included paired-samples t-tests and Wilcoxon signed-rank tests, with significance set at p < 0.05.

Preliminary evidence suggests that Free Play conditions elicit greater cardiovascular load, especially in the initial sets of training, while Controlled Pass conditions promote higher technical engagement by increasing ball touches. The findings are expected to help coaches and practitioners make evidence-based decisions when designing training tasks for elite football players. Specifically, coaches may select Free Play conditions when the aim is to maximize physical conditioning and Controlled Pass rules when the aim is to enhance technical and tactical involvement.

This study was approved by the Ethics Committee of Bilecik Şeyh Edebali University (approval date: June 29, 2020; decision no: 8/26). All participants provided written informed consent prior to enrollment, and the study was conducted in accordance with the Declaration of Helsinki.

By addressing the gap in evidence on rule modifications in SSGs, this trial provides new insights into optimizing training design for elite football. Its findings may inform practical applications for strength and conditioning coaches, sport scientists, and football practitioners worldwide.

Inclusion Criteria:

• Male elite football players
• Aged 18-30 years
• At least 5 years of professional football experience
• Currently training and competing at the professional level

Exclusion Criteria:

• Presence of cardiovascular, respiratory, or musculoskeletal disease or injury that could interfere with participation
• Use of medication affecting cardiovascular function
• Inability to complete training sessions or follow study protocol
• Refusal to provide informed consent

De-identified individual participant data (e.g., age, heart rate responses, ball touches) that underlie the results of the study will be shared. Supporting documents, including the study protocol and statistical analysis plan, will also be available.

Data will be available beginning 6 months after publication of the main results and ending 3 years after publication.

Researchers who provide a methodologically sound proposal for use in achieving the aims of their research will be granted access. Proposals should be directed to [your institutional email]. Data will be shared via secure data repository.