뎁스 점프 플라이오메트릭 훈련: 기술, 프로그래밍 & 반응 근력

The depth jump (also called the drop jump) is one of the most potent and most commonly misunderstood exercises in plyometric training. When executed correctly, it develops reactive strength — the ability to rapidly absorb and redirect forces through the stretch-shortening cycle (SSC) — to a degree unmatched by other plyometric exercises. Elite sprinters, jumpers, and team-sport athletes use the depth jump as a cornerstone of their power development programs.

However, the depth jump is also one of the most technically demanding and mechanically stressful plyometric exercises. Poor technique, inappropriate drop heights, or premature introduction in a training program can result in excessive eccentric loading without the intended reactive training effect — and increased injury risk. This guide provides a comprehensive framework for implementing depth jumps safely and effectively.

Definition and Mechanics

A depth jump involves stepping off an elevated platform (the "drop box"), landing on both feet, and immediately jumping as high (or as far) as possible. The critical distinction: the athlete does not jump off the box — they step off and fall. The drop creates a controlled eccentric loading that pre-stretches the muscle-tendon units, storing elastic energy that is then released explosively in the subsequent concentric push.

This sequence — eccentric loading → amortization (brief coupling phase) → concentric push — is the stretch-shortening cycle (SSC). The depth jump maximally stresses the SSC by increasing the rate and magnitude of the eccentric loading phase via the gravitational drop.

Depth Jump vs. Box Jump

These exercises are often confused. Key differences:

• Box jump: Jump up onto a box — primarily tests and develops concentric (pushing) power from a standing position. The SSC is less emphasized.
• Depth jump: Drop off a box and immediately jump — maximally stresses the SSC and reactive strength. The drop height and ground contact time determine the magnitude of elastic energy storage.
• Drop jump: Synonymous with depth jump; the same exercise described by different naming conventions in different research traditions.

Reactive Strength Index (RSI)

The depth jump is the primary method for measuring Reactive Strength Index (RSI = jump height ÷ ground contact time). RSI provides a more complete picture of plyometric quality than jump height alone — a high RSI means the athlete can produce significant height while maintaining a very short ground contact time. This quality is directly related to sprint performance, as each ground contact in sprinting requires rapid force generation within a very brief contact window.

Setup

• Box height: Start at 30–40 cm for beginners; advance to 45–60 cm for intermediate; 60–75 cm for advanced (see optimal height section)
• Landing zone: Flat, firm surface. Avoid overly cushioned surfaces that extend ground contact time and reduce the reactive stimulus.
• Starting position: Stand at the edge of the box, toes at or just over the edge

Step-by-Step Execution

1. Step off (do not jump off): Simply step forward off the box — jumping off adds forward momentum that changes the exercise mechanics. Both feet should leave the box simultaneously or in a short sequence that allows a two-foot landing.
2. Fall phase: During the drop, maintain a tall, neutral spine. Arms are in front of the body, ready to drive upward on take-off. Slight forward lean is acceptable.
3. Initial contact: Land on the balls of both feet simultaneously (mid-foot to forefoot), with hips directly above or slightly ahead of the ankles. Do not land with feet excessively forward — this increases braking forces.
4. Amortization phase: The brief ground contact. The goal is to minimize amortization time while absorbing landing forces. Think "quick ground — immediate launch." Excessive knee/hip flexion during amortization dissipates elastic energy as heat rather than returning it in the jump.
5. Take-off: Drive arms aggressively upward as the legs extend rapidly. Full hip-knee-ankle extension at take-off.
6. Landing (from jump): Land softly with both feet, absorbing force through ankle-knee-hip flexion. Do not immediately perform another rep — reset and recover (typically 60–90 seconds).

Technical Cues

• "Land and go" — think of the ground as hot — minimize time on the ground
• "Quiet feet" on the initial landing — soft, controlled landing prevents excessive loading
• "Drive the arms" — arm swing contributes 10–15% to jump height
• Maintain stiff ankles and knees during amortization — avoid excessive collapse

The Drop Height Paradox

Higher drop heights create greater eccentric loading — but only up to a point. Above the optimal height, athletes shift from a reactive SSC response to a more controlled, "catch and push" pattern. The eccentric load exceeds the athlete's capacity to rapidly transition, ground contact time increases dramatically, and the reactive stimulus is lost. The optimal drop height maximizes RSI, not just jump height.

Finding Optimal Drop Height

Research suggests a practical method: incrementally test drop heights (30, 40, 50, 60, 70 cm) and measure RSI at each. The height producing the highest RSI is the individual's optimal drop height. This varies considerably (30–75 cm across trained populations) depending on strength levels, training history, and neurological factors.

General guidelines by training level:

• Beginner (< 1 year plyometric training): 30–40 cm — mastery of landing mechanics before reactive stimulus
• Intermediate: 40–60 cm — developing reactive capacity
• Advanced: 50–75 cm — maximizing RSI at individually optimal height
• Elite (sprinters, jumpers): Individual optimal, often 50–70 cm

Signs the Drop Height Is Too High

• Ground contact time increases significantly (> 250–300 ms for advanced athletes)
• Excessive knee flexion during amortization (knees collapse deep into a squat position)
• Jump height does not increase despite higher drop
• Athlete reports feeling "stuck" on the ground
• RSI decreases compared to lower drop height

RSI Formula

RSI = Jump Height (m) ÷ Ground Contact Time (s)

Example: 0.35m jump height ÷ 0.22s contact time = RSI of 1.59

RSI Benchmarks by Level

• Recreational / untrained: RSI < 1.0 — focus on mechanics and strength foundation before depth jump training
• Trained amateur: RSI 1.0–1.5
• Competitive athlete: RSI 1.5–2.0
• Elite team sport: RSI 2.0–2.5
• Elite sprinters / jumpers: RSI 2.5–3.5+

Using RSI to Guide Training

• If RSI < 1.0: Prioritize countermovement jumps, box jumps, and strength development before depth jumps
• If RSI 1.0–1.5: Begin depth jump training at 30–40 cm; emphasize ground contact time reduction
• If RSI 1.5–2.0: Progress drop height; challenge ground contact time at higher drop heights
• If RSI > 2.0: Advanced depth jump variations, approach jumps, and sport-specific plyometric combinations

Prerequisites Before Depth Jumps

Athletes should demonstrate before beginning depth jump training:

• Squat ≥ 1.5x bodyweight (minimum strength base to absorb landing forces)
• Stable two-leg landing mechanics (no knee valgus collapse, controlled deceleration)
• CMJ height of ≥ 35 cm (males) or ≥ 25 cm (females)
• Competence with box jumps and drop landings

Beginner Phase (Weeks 1–4)

• Drop height: 30–40 cm
• Volume: 3 sets × 5 reps
• Rest: 2–3 minutes between sets
• Focus: Landing mechanics and consistent technique before maximizing RSI

Intermediate Phase (Weeks 5–10)

• Drop height: 40–55 cm (test optimal height)
• Volume: 4 sets × 5–6 reps
• Rest: 3 minutes between sets
• Focus: Minimizing ground contact time — "land and go" mindset
• Add RSI measurement: target RSI progression over the block

Advanced Phase (Weeks 11+)

• Drop height: Individual optimal (typically 50–70 cm)
• Volume: 4–5 sets × 4–5 reps
• Rest: 3–4 minutes between sets
• Combine with other plyometrics in a contrast or complex training protocol
• Monitor RSI weekly — reduce volume if RSI declines more than 10% from baseline

Weekly Integration

Depth jumps are neurologically demanding. 1–2 sessions per week is optimal during intensive training phases. Place depth jump sessions early in a training session (after warm-up, before strength work) when the nervous system is fresh. Avoid pairing with very high-volume lower body strength work in the same session.

Sprinters

Sprint performance is closely correlated with RSI — sprinting requires producing large forces in brief ground contact windows (80–120 ms at maximum velocity). Depth jump training directly develops this quality. Protocol: 4x5 at individual optimal height, emphasize minimal ground contact. Measure RSI with PoinT GO to track sprint-specific power development.

Basketball / Volleyball

These sports require repeated vertical jumps with short recovery times. The depth jump develops the SSC qualities that translate to repeated jump performance and the ability to jump off one foot or off a deceleration. Combine depth jumps (two-foot) with lateral approach jump variants for complete plyometric preparation.

Soccer / Football

Cutting, acceleration, and jumping tasks in field sports demand reactive strength. Lateral depth jumps (step off box, land on outside foot, immediately cut laterally) provide more sport-specific training for these athletes than standard vertical depth jumps.

Weightlifters / Power Lifters

While seemingly incongruous, depth jumps improve rate of force development and SSC utilization that transfer to the explosive phases of the clean, snatch, and even the squat. Begin at lower heights and lower volumes — these athletes are strong but may have less SSC training background than track athletes.