Download Flexibility Exercise (Stretching)

FLEXIBILITY EXERCISE (Nieman for ACSM Position Stand)
Exercises to develop flexibility have long been a vital component of several types
of sports and physical activity programs including martial arts, gymnastics, ballet, and
yoga (29). In 1998, ACSM included recommendations on flexibility exercise for the first
time in its position stand on exercise “based on growing evidence of its multiple benefits”
(1). Guidelines in this report emphasized that flexibility exercises should be conducted a
minimum of 2-3 days per week, with static stretches held for 10 to 30 seconds and then
repeated at least four times per major muscle/tendon group.
Similar recommendations have been supported in subsequent reports. A 2007
joint statement by ACSM and AHA on physical activity and public health in older adults
emphasized the importance of flexibility exercise to maintain the range of motion
necessary for daily activities and physical activity and help manage several common
diseases (33). This report recommended that older adults engage in at least 10 minutes of
flexibility activities involving major muscle and tendon groups with 10 to 30 seconds and
3 to 4 repetitions for each static stretch. Other organizations have included flexibility
exercise in their physical activity recommendations, especially for older adults (2,51).
However, because specific health benefits of flexibility exercise programs are not as
strongly evidence-based as for aerobic and muscle strengthening activities, no
recommendations for flexibility exercise were provided in the ACSM/AHA physical
activity and public health report for adults (21).
A plethora of research during the past decade has added much to our
understanding of the role of flexibility exercises on performance, health, and physical
fitness (22,23,43,46,47). Flexibility is defined as the capacity of the joints to move
through a full range of movement. A flexibility program is defined as a planned,
deliberate, and regular program of exercises that can progressively increase the range of
motion of a joint or set of joints over a period of time. There are three basic types of
flexibility: 1) Static flexibility, or the ability to hold a stretched position; 2) Dynamic
flexibility, or the ability to engage in slow, rhythmic movements throughout the full
range of joint motion; and 3) Ballistic flexibility or the ability to engage in bobbing,
bouncing, rebounding, and rhythmic motions.
Joint flexibility is influenced by multiple factors. Each joint is surrounded by
ligaments, tendons, and muscles, and these connective tissues determine whether the joint
is tight or loose. Stretching exercises help to lengthen the muscles and tendons, decrease
tonic reflex activity and passive stiffness, and improve tendon compliance and stretch
tolerance, increasing the joint range of motion (17-20,26,31,34). Joint range of motion is
improved for a short time following acute flexibility exercise, but is chronically enhanced
after approximately 3-4 weeks of regular stretching at a frequency of at least 2-3 times a
week (9,10,15,19,40). Intensive stretching can result in improved joint range of motion
after just 10 sessions (19). Cessation of stretching results in a reversal of flexibility gains
within 4-8 weeks depending on the joint (12,52). As a person ages, flexibility decreases
due to muscle atrophy and physical inactivity, loss of elasticity in soft tissues, and
increased fibrous connective tissue (12). Studies have shown that joint flexibility can be
improved across all age groups (2,10,12,17,18,33,48).
Many claims have been made for the performance-, fitness-, and health-related
benefits of regular flexibility exercise. Some sports and physical activities require unique
types of flexibility that enhance performance including Olympic weight lifting, ballet
dancing, gymnastics, swimming, baseball pitching, and wrestling (29,30,44). Growing
evidence indicates that flexibility exercise has both acute and chronic relationships to
exercise performance. Vertical jump, muscle strength and endurance, sprint
performance, and the ability to generate force and torque may be reduced when
individuals stretch intensely just before exercise (6,8,14,28,35,43,47,57). Intensive
stretching can be scheduled following exercise or as a stand-alone session for individuals
involved in sports where jumping and muscular strength, power, and endurance are
important for performance. Short duration static stretching of moderate intensity or slow
movement stretching just prior to strength exercise does not have a negative effect on
muscle force production (35,43). In contrast to the acute effects of intensive stretching, a
program of regular flexibility exercise over a period of several weeks results in small but
significant improvements in muscle strength and endurance, especially when agonist and
antagonist muscle contraction accompanies the stretching exercises (13,24,25,32,37,47).
No consistent link has been shown between regular flexibility exercise and
prevention of low back pain, injury, or delayed onset of muscle soreness (DOMS)
(22,23,36,38,46,49,50,54,55). The relationship between injury and flexibility exercise
may vary between sports, and pre-event stretching may have less benefit than when a
separate program of flexibility exercise is engaged in. Flexibility exercise is a valuable
component of rehabilitation programs from injury (24,39). Of all age groups, the elderly
have the most to gain through regular flexibility exercise with several studies showing
improved range of motion and capacity for daily activities of living (2,18,33,48).
Flexibility can be developed through several different types of stretching
techniques. Ballistic methods or bouncing stretches use the momentum of the moving
body segment to produce the stretch (26,27,55,56). Dynamic or slow movement
stretching involves the gradual movement from one body position to another, with a
smooth return to the starting point and a progressive increase in reach and range of
motion as the movement is repeated several times (3,28). Static stretching involves
slowly applying a stretch to the muscle and tendon group and then holding the stretched
position for a period of time, often 10-30 seconds (10,19,25,35,42). Static stretching can
be active or passive (25,42,53). Active static stretching is defined as holding the
stretched position with no assistance other than using the strength of the agonist muscle
as common in many forms of yoga. Passive static stretching involves assuming the
stretched position while holding some part of the body or with the assistance of a partner
or piece of apparatus. Proprioceptive neuromuscular facilitation (PNF) methods take
several forms but typically involve an isometric contraction of the muscle/tendon group
to be stretched followed by a static stretching of the same group (i.e., contract-relax)
(7,11,24,41,45). PNF is often conducted with a partner to assist to providing resistance
during muscle contraction and pressure to aid in a slow, static stretch of the muscle
group. The isometric contraction of the target muscle group should be held for
approximately 3-6 seconds at 20-75% of maximum voluntary contraction followed by
10-30 seconds of passive static stretching (7,11,15,45).
PNF may produce slightly larger gains in flexibility of some joints compared to
the other techniques but is less practical than static, ballistic, and dynamic stretching (45).
The enhanced efficiency of PNF has been related to a larger reduction of motor neuron
excitation during stretching due to the submaximal isometric contractions (19,20,45).
However, one comparative review concluded that range of motion gains after 3 to 10
weeks of hamstring stretching are typically 5-20 degrees depending on the outcome
measure with little difference between static and PNF techniques (10). Ballistic
stretching when properly performed increases flexibility similar to static stretching and
may be considered for individuals whose sports activities involve ballistic movements
such as basketball (26,27,55,56). PNF and static stretching produce greater gains in joint
range of motion than dynamic or slow movement stretching (3,10).
The goal of a flexibility program is to develop range of motion in the major
muscle/tendon groups in accordance with individualized goals. Certain minimum
standards include the following for static stretching and PNF:
► Duration of stretched position: Holding the stretch for 10 to 30 seconds at the point
of discomfort enhances flexibility without significantly greater benefit from longer
durations (4,10). Limited evidence suggests that 60 second compared to 15-30 second
static stretches confer greater range of motion gains for the elderly (12). A 3-6 second
contraction at 20-75% maximum contraction followed by a 10 to 30 second assisted
stretch is recommended for PNF techniques (7,11,45).
► Repetitions: Repeat the flexibility exercise for 2-4 repetitions. Most studies showing
gains in joint range of motion over 3-12 weeks have used 2-4 repetitions per flexibility
exercise (4,9,10,16,25,42,52). Aim for 60 seconds of total stretching time per flexibility
exercise by adjusting duration and repetitions according to individual desires. For
example, 60 seconds of stretch time can be met by two 30-second stretches or four 15second stretches (10).
► Frequency: Engage in stretching exercises at least 2-3 days per week (10,25).
Greater gains in joint range of motion can be measured with near-daily flexibility
exercise (12,19,20,39,42,52). Improvements in joint range of motion can be measured
within the first month of flexibility exercise but just as quickly be reversed upon
cessation of stretching (12,19,20,24,52). Thus flexibility exercise needs to be engaged in
regularly to experience and maintain increased joint range of motion.
► Types of flexibility exercises: Use at least eight different exercises for the major
muscle-tendon units, including the shoulder girdle, front of chest, and neck (two different
exercises), lower back, hips, posterior thighs, and trunk (three exercises), anterior thigh
(one exercise), and posterior legs and ankles (two exercises). For most individuals, this
routine can be completed within 10 minutes.
► When to stretch: Flexibility exercise is most effective when the muscle is warmed
through light-to-moderate aerobic activity or passively through external methods such as
moist heat packs or hot baths, although this benefit may vary across muscle-tendon units
(5,16,28,46). A pre-event warm-up that includes both aerobic activity and flexibility
exercise has benefits for specific athletes such as gymnasts and ballet dancers. However,
for most adults, a dynamic warm-up is superior to flexibility exercise for aerobic or
resistive exercise performance (28). Flexibility exercise, especially an intensive regimen
with high duration and repetitions, is generally recommended after aerobic or resistive
exercise, or as a stand alone program (5,46).
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