Muscle injuries represent over 30% of athletic injuries. Warming up, stretching, and strengthening are widely accepted ways to prevent muscular injuries. Research offers differing views on the effectiveness of warm-up and stretching protocols. Dynamic warm-ups involving moderate intensity exercise are most beneficial for preventing injuries in high-intensity sports like football and basketball. Static stretching held for 20-30 seconds can increase flexibility for up to 24 hours. Sports-specific strengthening at least twice per week with progressive overload best supports athletic performance goals.

1. The Science of Warm-up, Stretching and Strengthening: Injury Prevention in Athletics
Lindsay Morgan, PT, DPT, ATC
Anne Arundel Medical Center
Comprehensive Outpatient Rehabilitation Center
Athletic Injuries
• Muscle injuries represent >30% of injuries seen in sports medicine.
• Widely accepted ways for athletes to prevent muscular injuries:
▫ Warm up
▫ Stretching
▫ Strengthening
Are we stretching the truth?
• Various research studies offer different viewpoints regarding the effectiveness of warm-up and stretching
protocols in reducing injuries.
Warm-up
• Prior to all athletic activity
• Designed to improve muscle dynamics, and increase core temperature without fatiguing the individual.
• Warm up can be active or passive
• Physiological Effects of Warm-up
• Increase in speed and force of muscle contractions.
• Increase in temperature leads to the increase of oxygen uptake, providing more oxygen to
working muscles.
• Speed of nerve transmission increases contraction speed and reduction of reaction time.
• Vasodilation
• Should be tailored to needs of the athlete
• Intensity
• 40-60% of VO2 max should be utilized to increase muscle temperature, while also limiting high-
energy phosphate depletion.
• >60% VO2 max has shown to have an inverse relationship between warm up and short term
performance
Stretching
• Therapeutic intervention to increase mobility of soft tissue with the goal of increasing range of motion
(ROM).
• Stretching is SPORTS SPECIFIC!
• High intensity sports
• Football, soccer, basketball
• High intensity stretch-shortening cycles (SSC) require a muscle-tendon unit which is compliant
enough to store and release the high amount of elastic energy.
• Insufficient compliant muscle-tendon units = demands in energy absorption and release may
exceed the capacity of the muscle-tendon unit = injury.
• Stretching is important for injury prevention.
• Low intensity sports
• Jogging, cycling, and swimming
• No need for a very compliant muscle-tendon unit
• Most of power generation is a consequence of active contractile muscle work that needs to be
directly transferred (by the tendon) to the articular system to generate motion.
• Stretching exercises to improve the compliance of the tendon may have no beneficial effect on
injury prevention.
Types of Stretching
• Static

2. • Slow, passive and deliberate movement. Stretch maintained for 20 seconds will facilitate
elongation.
• Dynamic
• Whole body movements and involves actively and rhythmically contracting a muscle through
part of its functional ROM.
• Proprioceptive Neuromuscular Facilitation (PNF)
• Static stretch, an isometric contraction, and relaxation, followed by a static stretch
Effects of Warm-up, and Stretching on Injury Prevention
Stretch or Not to Stretch?
• Evidence suggests pre-exercise muscle stretching protocols do not produce meaningful reduction in risk of
exercise-related injuries.
• HOWEVER, basic science supports the notion that an active warm up might protect against muscle strain
injury.
▫ Theoretically, warm up activities that enhance neural activation will better prepare muscles to
absorb loads.
▫ Muscles under active contraction absorb significantly more energy than muscles at rest.
Effects of Warm-up on Injury
• Study by Bixler and Jones
▫ Examined # of injuries occurring during the 3rd quarter of HS football games
▫ Intervention and control group (warm-up and stretching program conducted at half-time)
▫ No significant difference in total number of 3rd quarter injuries between groups
▫ HOWEVER, intervention group experience fewer 3rd quarter sprains/strains per game over
season.
Effects of Static Stretching on Injury
• Study by Hartig and Henderson
▫ Examined effect of increased flexibility on decreasing lower extremity overuse injuries in military
basic trainees.
▫ Hamstring flexibility was measured before and after the 13-week basic training program
 5 x 30 sec stretches, 3 times a day for 13 weeks
▫ Intervention group flexibility increased from 41.7-34.7 while control group increased slightly
(45.9 to 42.9)
▫ Intervention group experienced significantly fewer (25 vs. 43) LE overuse injuries
▫ Results demonstrate the ability of an increase in flexibility to reduce LE overuse injuries.
Effects of Dynamic Stretching on Injury
• Study by Olsen et al.
▫ Dynamic warm-up vs. No warm-up
 1,886 club soccer players (16 y/o)
▫ Dynamic warm-up and stretching
 Running, agility, plyometric, balance activities
▫ Over course of season:
▫ 103 injuries in dynamic stretching group vs. 195 injuries in the no warm-up group.
▫ Acute knee or ankle injuries can be reduced by 50% with use of dynamic warm-up.
Effects of Dynamic Stretching on Performance
• Study by McMillian et al.
▫ Dynamic vs. Static vs. No warm-up
▫ Statistically significant increase in performance for all tests (agility and power via T drill, 5-step
jump, and medicine ball throw for distance) after completing dynamic stretching warm-up
▫ For tasks requiring power and agility, the results suggest that a dynamic warm-up might offer
performance benefits not found with static stretching or no warm up.

3. Which Stretching Protocol Is Best?
• Static stretches held for 20-30 sec x 3-5 sets reported to increase muscle length that was maintained for
24 hours
▫ GREATEST increase being maintained in first 15 minutes post stretching.
• Dynamic warm-up of 5-10 minutes performed at 40-60% of VO2 max, followed by 5 minutes of recovery
Strengthening
• To improve muscle strength, stress must be progressive and gradually challenged
▫ SAID principle (Specific Adaptation to Imposed Demands)
 Body is placed under stress of varying intensities and durations, it attempts to overcome
the stress by adapting specifically to the imposed demands.
Principles of Strengthening
• Working toward goals
▫ Strength, power, hypertrophy, or endurance
• Varying program with periodization
▫ Changing the intensity, velocity, and volume as needed.
• Type of muscle action focused in athletes sport
▫ Eccentric, concentric, and isometric
Strength Training
• Strength
▫ Ability of the muscle to exert a maximum force at a specified velocity.
• Power
▫ Force exerted x the velocity of movement
▫ Max power is achieved at 30-40% of 1RM
• Endurance
▫ Ability to sustain an activity for extended periods of time
• Isometric
▫ Force generated by muscle and the external force are equal and there is no lengthening of the
muscle.
▫ Most beneficial to increase endurance in spinal stabilizers.
• Concentric
▫ Force produced by the muscle exceeds the external force or load.
• Eccentric
▫ Whenever opposing force acting on a muscle exceeds the force produced by that muscle.
▫ Together with concentric contraction= stretch-shortening cycle (low-amplitude, mod-high
velocity contraction)
▫ Eccentric contractions ease mechanical forces and maximize performance.
Recommended Variables for Strength Training
• Repetitions
▫ Strength: 8-12
▫ Power: 4-6
▫ Endurance: 12-15
• Sets
▫ Multiple sets for all types of strengthening
• Rest periods
▫ 1-2 minutes for smaller muscle groups
▫ 2-3 minutes for larger muscle groups
• Intensity
▫ Strength: Start with 8 reps max
▫ Hypertrophy: Start with 10 reps max

4. ▫ Power: Start with 6 reps max
▫ Endurance: Start with 15 reps max
• Velocity
▫ Slow, moderate, fast depending on specific goals.
• Muscle contraction
▫ Eccentric strengthening focused on with deceleration muscles
▫ Eccentric with concentric need to be focused on for acceleration muscles
• Length of time
▫ AT LEAST 2 days a week
▫ Any training over 4 weeks, the program needs periodization
Clinical Bottom Line
• Stretching is sports specific
▫ Dynamic warm-up/stretching more beneficial prior to high intensity (football, basketball) sports
rather than lower intensity (bicycling, running).
• Static stretching 15 minutes before athletic competition.
• Dynamic stretching has been proven to be more effective in decreasing injuries and improving
performance in sports requiring power and agility.
• Strengthening is goal specific
▫ Strength training is dependent on what the athlete needs for athletic performance.
References
• Olsen et al. Exercise to prevent lower limb injuries in youth sports: cluster randomized controlled trial. BMJ.
2005;330:449.
• McMillian DJ, Moore JH, Hatler BS, Taylor DC. Dynamic vs. static-stretching warm up: the effect of power and agility
performance. Journal of Stretch and Conditioning Research. 2006; 20(3):492-499.
• Curry et al. Acute effects of dynamic stretching, static stretching, and light aerobic activity on muscular performance
in women. Journal of Strength and Conditioning Research. 2009; 23(6):1811-1819.
• Mann DP, Jones MT. Guidelines to the implementation of a dynamic stretching program. Strength and Conditioning
Journal. 1999;21(6):53-55.
• Young WB, Behm DG. Should static stretching be used during a warm-up for strength and power activities? National
Strength and Conditioning Association. 2002; 24(6): 33-37.
• Donatelli R. Strength training concepts in Athletics. Sports –Specific Rehabilitation. St. Louis, Missouri :Elsevier; 2007.
• Woods K, Bishop P, Jones E. Warm-up and stretching in the prevention of muscular injury. Sports Medicine Journal.
2007; 37(12):1089-1099.