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Types of exercises
Isotonic and plyometric exercises
These terms combine the prefix "iso" (meaning "same") with "tonic" (strength)
and "plio" (more) with "metric" (distance). In "isotonic" exercises the force
applied to the muscle does not change (while the length of the muscle decreases
or increases) while in "plyometric" exercises the length of the muscle stretches
and contracts rapidly to increases the power output of a muscle.
Weight training is primarily an isotonic form of exercise, as the force produced
by the muscle to push or pull weighted objects should not change (though in
practice the force produced does decrease as muscles fatigue). Any object can be
used for weight training, but dumbbells, barbells and other specialised
equipment are normally used because they can be adjusted to specific weights and
are easily gripped. Many exercises are not strictly isotonic because the force
on the muscle varies as the joint moves through its range of motion. Movements
can become easier or harder depending on the angle of muscular force relative to
gravity - in example, a standard biceps curl becomes easier as the hand
approaches the shoulder as more of the load is taken by the structure of the
elbow. Certain machines such as the Nautilus involve special adaptations to keep
resistance constant irrespective of the joint angle.
Plyometric exercises exploits the stretch-shortening cycle of muscles to enhance
the myotatic (stretch) reflex. This involves rapid alternation of lengthening
and shortening of muscle fibers against a resistance. The resistance involved is
often a weighted object such as a medicine ball, but can also be the body itself
as in jumping exercises. Plyometrics is used to develop explosive speed, and
focuses on maximal power instead of maximal strength by compressing the force of
muscular contraction into as short a period as possible, and may be used to
improve the effectiveness of a boxer's punch, or to increase the vertical
jumping ability of a basketball player.
Isolation exercises versus compound exercises
The leg extension is an isolation exercise.An isolation exercise is one where
the movement is restricted to one joint and one muscle group. For example, the
leg extension is an isolation exercise for the quadriceps. Specialized types of
equipment are used to ensure that other muscle groups are only minimally
involved—they just help the individual maintain a stable posture—and movement
occurs only around the knee joint. Most isolation exercises involve machines
rather than dumbbells and barbells (free weights), though free weights can be
used when combined with special positions and joint bracing.
Compound exercises work several muscle groups at once, and include movement
around two or more joints. For example, in the leg press movement occurs around
the hip, knee and ankle joints. This exercise is primarily used to develop the
quadriceps, but it also involves the hamstrings, glutes and calves. Compound
exercises are generally similar to the ways that people naturally push, pull and
lift objects, whereas isolation exercises often feel a little unnatural.
Compound exercises generally involve dumbbells and barbells (free weights),
involving more muscles to stabilize the body and joints as well as move the
weight.
The leg press is a compound exercise.Each type of exercise has its uses.
Compound exercises build the basic strength that is needed to perform everyday
pushing, pulling and lifting activities. Isolation exercises are useful for
"rounding out" a routine, by directly exercising muscle groups that cannot be
fully exercised in the compound exercises.
The type of exercise performed also depends on the individual's goals. Those who
seek to increase their performance in sports would focus mostly on compound
exercises, with isolation exercises being used to strengthen just those muscles
that are holding the athlete back. Similarly, a powerlifter would focus on the
specific compound exercises that are performed at powerlifting competitions.
However, those who seek to improve the look of their body without necessarily
maximising their strength gains (including bodybuilders) would put more of an
emphasis on isolation exercises. Both types of athletes, however, generally make
use of both compound and isolation exercises.
Free weights versus weight machines
Swiss balls allow a wider range of free weight exercises to be performed. They
are also known as exercise balls, fitness balls, gym balls, sports balls,
therapy balls or body balls. They are sometimes confused with medicine ballsFree
weights are dumbbells, barbells, and kettlebells. Unlike weight machines, they
do not constrain users to specific, fixed movements, and therefore require more
effort from the individual's stabilizer muscles. It is often argued that free
weight exercises are superior for precisely this reason. As weight machines can
go some way toward preventing poor form, they are somewhat safer than free
weights for novice trainees. Moreover, since users need not concentrate so much
on maintaining good form, they can focus more on the effort they are putting
into the exercise. However, most athletes, bodybuilders and serious fitness
enthusiasts prefer to use compound free weight exercises to gain functional
strength.
The weight stack from a Cable machine.Some free weight exercises can be
performed while sitting or lying on a Swiss ball. This makes it more difficult
to maintain good form, which helps to exercise the deep torso muscles that are
important for maintaining posture.
There are a number of weight machines that are commonly found in neighborhood
gyms. The Smith machine is a barbell that is constrained to move only vertically
upwards and downwards. The cable machine consists of two weight stacks separated
by 2.5 metres, with cables running through adjustable pulleys (that can be fixed
at any height) to various types of handles. There are also exercise-specific
weight machines such as the leg press. A multigym includes a variety of
exercise-specific mechanisms in one apparatus.
One limitation of many free weight exercises and exercise machines is that the
muscle is working maximally against gravity during only a small portion of the
lift. Some exercise-specific machines feature an oval cam (first introduced by
Nautilus) which varies the resistance so that the resistance, and the muscle
force required, remains constant throughout the full range of motion of the
exercise.
Exercises for specific muscle groups
Weight training exercises
The back extension should be left to the end of the workout, because in other
exercises the lower back muscles are used to keep the back straight. This is not
possible if the muscles have already been exercised and exhausted.Weight
trainers commonly divide the body's individual muscles into ten major muscle
groups. These do not include the hip, neck and forearm muscles, which are rarely
trained in isolation. The most common exercises for these muscle groups are
listed below. (Videos of these and other exercises are available at exrx.net and
from the University of Wisconsin.) The sequence shown below is one possible way
to order the exercises. The large muscles of the lower body are normally trained
before the smaller muscles of the upper body, because these first exercises
require more mental and physical energy. The core muscles of the torso are
trained before the shoulder and arm muscles that assist them. Exercises often
alternate between "pushing" and "pulling" movements to allow their specific
supporting muscles time to recover. The stabilising muscles in the waist should
be trained last.
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