Impact: Complete Guide

What is Impact?

Impact is mechanical stress on bones (and surrounding tissues) created by rapid loading, most commonly during activities like jumping, hopping, landing, running, and quick direction changes. In practical terms, impact is the moment your body meets the ground (or an external object), and the skeleton must absorb and transmit force.

Impact is not automatically “high impact.” It exists on a spectrum, from very low impact (brisk walking, step-downs) to moderate impact (skipping, small hops) to high impact (drop jumps, sprinting, plyometrics, hard landings in sport). What matters is not only how hard you hit the ground, but also:

• How fast the force is applied (rate of loading)
• How often it is repeated (volume)
• Where it is distributed (foot, ankle, knee, hip, spine)
• How well your muscles and tendons can buffer it (strength and technique)

Because bone is living tissue that adapts to stress, impact can be a tool. It can also be a problem if the dose exceeds your current capacity.

> Key idea: Impact is a stimulus. Like sun exposure or strength training, it can be beneficial at the right dose and harmful at the wrong dose.

How Does Impact Work?

Impact affects the body through biomechanics and biology. The most important concept is that bone responds to strain and the signals created when strain is high enough, fast enough, and novel enough.

The biomechanics: ground reaction force and loading rate

When you land from a hop or jump, the ground pushes back with an equal and opposite force called ground reaction force. Your body manages this force by distributing it across:

• Foot and ankle (arch stiffness, calf and Achilles tendon)
• Knee (quadriceps and patellar tendon)
• Hip (glutes, hip stabilizers)
• Spine and pelvis (trunk stiffness and alignment)

Two people can experience very different tissue stress from the same exercise. A “quiet,” well-controlled landing spreads force over time and joints. A stiff, noisy landing spikes force quickly, increasing peak stress.

Bone biology: mechanotransduction

Bone adapts through a process often described as mechanotransduction, where mechanical strain is converted into cellular signals.

• Osteocytes (bone’s “sensor” cells) detect strain and fluid flow within bone.
• They signal osteoblasts (bone-building cells) and osteoclasts (bone-resorbing cells).
• Over time, the balance of formation vs. resorption can shift toward stronger, denser, better-structured bone.

Impact is especially potent because it creates high strain rates, which appear to be an efficient trigger for adaptation compared with slow, steady loads.

Why variety and “novelty” matter

Bone seems to respond best to:

• Unusual directions of force (multi-directional hops, cutting, lateral steps)
• Brief bouts rather than endless repetition
• Progressive overload (gradually increasing intensity)

This is one reason why simply doing more and more steady-state running does not always produce proportional bone gains, while short sessions of jumping or hopping can.

Tendons, muscles, and the “spring” system

Impact is not only about bone density. The body’s elastic tissues matter:

• Tendons (Achilles, patellar) can become stiffer and more efficient, improving power transfer.
• Muscles pre-activate before landing, acting like shock absorbers.
• Neuromuscular control improves timing, balance, and joint alignment.

When strength and coordination are lacking, the same impact dose shifts stress toward passive structures (bone, cartilage, joint surfaces), raising injury risk.

Benefits of Impact

Impact training is best viewed as a targeted stimulus for the musculoskeletal system. Benefits are most consistent when impact is progressive, brief, and paired with strength training.

Improved bone density and bone strength

The most discussed benefit is supporting bone mineral density (BMD) and bone strength, particularly at common fracture sites like the hip and spine.

Impact can be useful because it provides:

• Higher strain rates than walking
• A strong stimulus in relatively little time
• A complementary signal to heavy resistance training

This is especially relevant for people at risk of age-related bone loss, including postmenopausal women and older adults.

Better balance and fall resilience

Many impact drills require single-leg control, quick stabilization, and coordination. Over time, this can improve:

• Proprioception (joint position sense)
• Reactive balance (catching yourself after a perturbation)
• Confidence moving quickly

Because falls are a major driver of fractures, improving the ability to recover from a trip or misstep can be as important as improving BMD.

Increased tendon capacity and stiffness

Appropriately dosed jumping and hopping can support tendon properties that matter for daily life and sport, including stiffness and energy storage. This may translate to:

• Easier stair climbing
• Better running economy
• Higher jump or sprint performance

Tendons adapt more slowly than muscles, which is one reason impact progressions should be conservative.

Athletic performance and power

Impact training overlaps with plyometrics. Benefits may include:

• Improved rate of force development
• Better landing mechanics
• Faster changes of direction

For athletes, impact is often non-negotiable. The key is managing dose so it builds capacity rather than accumulating injury.

Potential metabolic and functional benefits

Although impact is not primarily a cardio tool, short bouts of jumps, hops, or stair work can increase heart rate and contribute to overall activity. More importantly, impact can improve functional capacity: carrying groceries, moving quickly, getting off the floor, and navigating uneven surfaces.

> Practical framing: For many adults, the “why” of impact is not jumping higher. It is maintaining bone and movement capacity so normal life stays normal.

Potential Risks and Side Effects

Impact is powerful because it is stressful. The risks rise when intensity increases faster than tissue adaptation.

Common side effects when dose is too high

• Foot soreness, heel pain, plantar fascia irritation
• Achilles or patellar tendon flare-ups
• Shin pain (medial tibial stress syndrome)
• Knee pain (especially with poor landing mechanics)
• Low back discomfort if trunk control is limited

Mild soreness that resolves in 24 to 48 hours can be normal, especially early. Pain that escalates, changes your gait, or persists is a sign to reduce dose.

Stress reactions and stress fractures

The most important serious risk is bone stress injury, which occurs when micro-damage accumulates faster than bone can remodel. Risk increases with:

• Rapid volume increases (too much, too soon)
• Low energy availability (under-fueling, eating disorders)
• Menstrual dysfunction or low testosterone
• Low vitamin D or calcium intake
• History of stress fractures
• Hard surfaces and poor footwear choices

Joint degeneration concerns

Many people worry that impact “wears out” joints. In reality, moderate impact with good mechanics and adequate strength is not automatically harmful. However, impact can aggravate symptoms in people with:

• Symptomatic osteoarthritis
• Significant joint malalignment
• Unresolved meniscus or cartilage injuries

The safer approach is to treat impact like a medication: find the minimum effective dose and adjust based on symptoms.

Contraindications and “pause and assess” situations

Impact should be avoided or medically supervised in cases such as:

• Recent fracture or orthopedic surgery without clearance
• Severe osteoporosis with high fracture risk
• Uncontrolled vestibular disorders or high fall risk
• Acute tendon rupture or severe tendinopathy
• New, unexplained bone pain (especially focal and persistent)

> Red flag: Focal pain on one bone that worsens with impact and improves with rest, especially in the shin, foot, or hip, should raise concern for a stress injury.

How to Implement Impact Safely (Dosage, Progressions, Best Practices)

The best impact plan is the one you can repeat consistently without flare-ups. For most people, that means starting easier than you think, progressing gradually, and pairing impact with strength.

Step 1: Choose your starting level

Level 0 (foundation, 2 to 4 weeks)

• Brisk walking, incline walking
• Calf raises, step-ups, controlled step-downs
• Balance drills (single-leg stands)

Level 1 (low impact)

• Marching with strong foot strike
• Heel drops and quick calf “pops” (small amplitude)
• Low pogo hops (two feet) on a soft surface

Level 2 (moderate impact)

• Skipping, small hops forward/back
• Single-leg hops in place (very low volume)
• Low box step-off to stick landing

Level 3 (higher impact)

• Drop jumps from higher boxes
• Bounding, sprinting, sport cutting
• Multi-directional plyometrics

Many adults do well living in Levels 1 to 2 for bone and function.

Step 2: Use a simple dosing framework

A practical “bone-focused” approach is short sessions, a few times per week. Research and coaching practice often converge on something like:

• Frequency: 2 to 4 days per week
• Volume: 20 to 60 total ground contacts per session for beginners (a “contact” is one landing)
• Intensity: start low, progress by height, stiffness, or single-leg work
• Rest: full recovery between sets (30 to 90 seconds), because quality matters

If you are older, deconditioned, or returning from injury, start at the lower end.

Step 3: Progress one variable at a time

Progression options include:

• Increase contacts (example: 20 to 30 per session)
• Increase intensity (example: higher hop, faster pogo)
• Increase complexity (example: two-leg to single-leg)
• Increase direction changes (example: forward to lateral)

Avoid increasing all of them in the same week.

Step 4: Prioritize landing mechanics

Good impact mechanics reduce joint stress and improve training effect.

Cues that often help:

• “Land quietly” (reduces peak loading)
• “Knees track over toes” (avoid knee collapse inward)
• “Hips back slightly” (share load with hips)
• “Stiff but not rigid” (use ankles, knees, hips together)

If you cannot land quietly, reduce height or switch to a simpler drill.

Step 5: Pair impact with strength training

Impact and strength are not competitors. They are complementary.

• Strength training builds the muscular “brakes” that control landings.
• Heavy resistance provides bone strain through muscle pull.
• Impact adds high strain rate and movement skill.

A common weekly structure:

• 2 to 3 strength sessions (lower body emphasis)
• 2 to 3 short impact sessions (often before strength or on separate days)

Step 6: Pick surfaces and footwear strategically

• Start on slightly forgiving surfaces (rubber floor, track, turf).
• Avoid very hard surfaces early (concrete) and very soft unstable surfaces that distort mechanics.
• Use stable shoes that fit your foot. Highly worn shoes can increase stress.

Sample beginner plan (4 weeks)

Week 1 to 2 (2x/week):

• Warm-up: 5 minutes brisk walk + ankle/calf mobility
• Drill A: 3 sets of 10 low pogo hops (two feet)
• Drill B: 2 sets of 6 step-off from a low step, stick landing

Week 3 to 4 (3x/week):

• Drill A: 4 sets of 10 low pogo hops
• Drill B: 3 sets of 6 step-off to stick
• Optional: 2 sets of 6 lateral line hops (two feet)

Stop each set while quality is high.

Monitoring: the 24-hour rule

A simple way to self-check dose:

• If discomfort is mild during training and returns to baseline within 24 hours, you are likely within capacity.
• If pain increases that night or the next day, reduce contacts or intensity.

What the Research Says

The evidence base for impact and bone health is substantial, but nuanced. Findings vary by age, sex, baseline bone status, and how impact is delivered.

What we know with good confidence

1) Bone responds to mechanical loading, especially dynamic and higher strain-rate loading.

Across decades of exercise physiology and orthopedic research, dynamic loading (jumping, hopping, resistance training) consistently outperforms low-load activity for stimulating bone adaptation.

2) Short bouts can work.

Bone appears to respond to relatively small numbers of high-quality impacts, particularly when they are novel and progressive. This supports programming that is time-efficient.

3) Combining impact with resistance training is often superior to either alone.

Many interventions showing meaningful improvements in bone outcomes include both strength and impact components, especially in older adults.

Where evidence is mixed or population-specific

Hip and spine outcomes vary.

Some trials show clearer improvements at the hip than the spine, or vice versa, depending on the exact drills and participant characteristics. Spinal outcomes can be influenced by posture, loading direction, and concurrent strength work.

Older adults and high-risk populations require careful dosing.

In people with osteopenia or osteoporosis, supervised, progressive programs can be beneficial, but the margin for error is smaller. Many successful protocols use moderate impact or “impact-like” loading (step-downs, stomps, weighted carries, heavy strength) rather than maximal plyometrics.

Running is not a guaranteed bone-builder.

Recreational running can support bone health for many, but high-volume endurance training, low energy availability, and menstrual dysfunction can negate benefits or increase stress fracture risk.

Evidence quality considerations

• Exercise trials vary widely in duration, adherence, and measurement methods.
• Bone changes take time. Studies shorter than 6 months may miss meaningful remodeling.
• “Impact” is not standardized. A small hop and a drop jump are both impact but not equivalent.

Practical conclusion from the literature

The most defensible, current takeaway is:

> Progressive impact, performed a few times per week in low to moderate volumes, is a credible tool for supporting bone strength and function, especially when paired with resistance training and adequate nutrition.

Who Should Consider Impact?

Impact is not only for athletes. Many non-athletes benefit because bone and balance are everyday health issues.

People likely to benefit most

Adults over 40, especially over 50

Age-related declines in power, tendon capacity, and bone density make targeted impact increasingly relevant, provided it is introduced safely.

Postmenopausal women

The years around menopause are associated with accelerated bone loss. Impact plus strength training can be a practical countermeasure when individualized to risk.

People with osteopenia (with clinician clearance)

Many with osteopenia can tolerate and benefit from low to moderate impact progressions, particularly when combined with strength training.

Athletes returning to sport

Impact exposure is part of preparing tissues for sprinting, cutting, and jumping. Structured progressions can reduce re-injury risk.

People who should be more cautious

• Anyone with a history of stress fractures
• People with significant foot biomechanics issues or severe plantar heel pain
• Those with active tendinopathy flares
• Individuals with poor balance or high fall risk

In these cases, it may be smarter to start with strength, balance, and low-impact loading before adding jumps.

Common Mistakes, Smart Alternatives, and How Impact Fits into Whole-Body Health

Impact is often discussed as a bone topic, but outcomes depend on the whole system: recovery, nutrition, coordination, and risk management.

Common mistakes

Doing impact without strength

Weak hips and calves often show up as knee collapse, loud landings, and tendon irritation. Strength first (or at least alongside) is protective.

Copying athlete plyometrics

High box jumps and depth drops look impressive but are not necessary for most health goals. Many people get the bone stimulus they need from small hops and step-offs.

Chasing fatigue

Impact is not a “burn” workout. When you are fatigued, mechanics degrade and injury risk rises.

Ignoring recovery and nutrition

Bone and tendon adaptation require adequate sleep, protein, and micronutrients (notably calcium and vitamin D). Under-fueling is a major hidden risk factor for bone stress injuries.

Smart alternatives when jumping is not appropriate

If you cannot jump comfortably right now, you can still load bone and connective tissue:

• Heavy resistance training (squats, deadlifts, leg press, split squats)
• Loaded carries (farmer carries, suitcase carries)
• Step-downs and fast step-ups (higher rate of loading without leaving the ground)
• Stair climbing or incline walking
• Low-amplitude “stomps” or heel drops (as tolerated)

These options can build capacity so you can later add true impact.

How impact connects to other health topics you cover

Impact is one lever in a broader health system:

• Training over 50 and bone density: Impact is often recommended as a time-efficient bone stimulus, but it is safest when paired with heavy strength work and individualized progression.
• Pain and recovery: Pain is not always equal to damage, but persistent focal bone pain deserves attention. Using graded exposure can help rebuild tolerance without fear-based avoidance.
• Head hits and second impacts: In sports, impact is not only on bones. If your impact exposure involves contact or fall risk, concussion prevention and avoiding repeat head impacts becomes part of responsible programming.

Frequently Asked Questions

1) How much impact do I need for bone benefits? Many people respond to 2 to 4 short sessions per week with 20 to 60 quality landings per session, progressed over time. The minimum effective dose varies, but more is not always better.

2) Is walking enough impact for bone density? Walking is excellent for health, but for many adults it is not a strong enough bone stimulus on its own, especially at the hip. It is a great foundation, and adding targeted impact or heavy strength often provides a stronger signal.

3) Can I do impact training if I have knee pain? Sometimes yes, sometimes no. Knee pain depends on cause and mechanics. Start with strength (quads, hips, calves), reduce impact intensity, and prioritize quiet landings. If pain persists or worsens, get assessed.

4) Is running considered impact training? Yes, running is repetitive impact. However, it is also high volume for many people, which can raise stress injury risk if progressed too fast. Bone benefits depend on dosing, recovery, and nutrition.

5) Should impact be done before or after strength training? If you are doing both in one session, impact is often best early, after a warm-up, when you are fresh and coordination is highest. Keep it brief.

6) What are early signs I am doing too much? Rising soreness that lasts more than 48 hours, worsening pain during sessions, limping, focal bone tenderness, or performance drop-offs are common warning signs. Reduce volume or intensity and reassess.

Key Takeaways

• Impact is mechanical stress on bones from landings and rapid loading, and it is a potent stimulus for adaptation.
• Benefits can include better bone strength, balance, tendon capacity, and functional resilience, especially when paired with strength training.
• The biggest risks are tendon flare-ups and bone stress injuries, usually from progressing too fast or under-recovering.
• Effective impact training is typically short, progressive, and technique-focused, not fatigue-focused.
• Start with low-level drills, progress one variable at a time, and use the 24-hour response to adjust dosage.
• If jumping is not appropriate, heavy strength training and step-based loading can provide bone-friendly alternatives while you build capacity.