Effects of Different Sled Loads on Sprint and Neuromuscular Performance in Young Male Football Players: An 8-Week Periodized Field Study

Condition(s) studied

Investigational drug(s) / intervention(s)

Resisted Sled Sprint Training: An 8-week periodized resisted sprint training protocol using weighted sleds. Sessions are performed twice weekly over a 15-meter sprint distance, immediately following a standardized warm-up. Participants are assigned to sled towing loads equivalent to 10%, 15%, or 20% of their individual body weight (BW). Training volume progresses systematically from 2 sets of 3 repetitions (Weeks 1-2) to 3 sets of 4 repetitions (Weeks 7-8) with 2 minutes of inter-repetition rest and 3 minutes of inter-set rest.

Study summary

The purpose of this 8-week periodized field study is to investigate and compare the acute and chronic effects of three different sled towing loads (10%, 15%, and 20% of body weight \[BW\]) on sprint performance (5m, 10m, 15m) and neuromuscular characteristics (Squat Jump \[SJ\], Countermovement Jump \[CMJ\], Drop Jump \[DJ\], and Reactive Strength Index \[RSI\]) in trained male youth football players aged 13-14 years. While all other training variables (distance, frequency, volume, and rest intervals) are standardized, this study aims to identify the optimal sled load that enhances acceleration and horizontal force production without compromising running mechanics during a critical pediatric athletic development window.

Eligibility

Primary outcome measure(s)

• Linear Sprint Performance (5m, 10m, and 15m Sprint Times) — Baseline (Pre-test) and 8 weeks (Post-test)
  Linear sprint performance measured over 5 meters (acceleration), 10 meters, and 15 meters using a high-precision wireless photocell timing system. Times are measured in seconds (s), where lower values indicate better sprint performance.
• Squat Jump (SJ) Height — Baseline (Pre-test) and 8 weeks (Post-test)
  Lower-limb concentric explosive power output measured via Squat Jump test on a digital contact mat/force platform. Surcharge from arm swing is isolated by keeping hands on hips. Jump height is measured in centimeters (cm), where higher values indicate greater explosive power output.
• Countermovement Jump (CMJ) Height — Baseline (Pre-test) and 8 weeks (Post-test)
  Stretch-shortening cycle (SSC) performance and lower-limb reactive power measured via Countermovement Jump test on a digital contact mat/force platform. Jump height is recorded in centimeters (cm), where higher values represent superior vertical jump capacity.
• Reactive Strength Index (RSI) — Baseline (Pre-test) and 8 weeks (Post-test)
  Reactive strength capacity and neuromuscular stiffness assessed via Drop Jump (DJ) test from a 30 cm box. Calculated as jump height (meters) divided by ground contact time (seconds) \[RSI = Jump Height (m) / Contact Time (s)\]. Higher index scores reflect better reactive strength and shorter contact time.

Trial sites (1)

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