Resistance training increases muscular strength and muscular endurance, reduces the risk of injury and improves overall quality of life. Everyday tasks and chores can be performed without fatigue and strain. Strength gains are based on the overload principle stating that in order for gains to be achieved, muscles must contract to overcome resistance beyond a normal workload. Muscle contractions, as well as exercises, can be classified as isotonic or isometric. Exercises using free weights are examples of isotonic exercises. Isometric exercises use body weight and gravity as resistance.
Isometric Contractions
Isometric contractions are performed against an immovable object. Muscles contract in a static, or stationary position, exerting force without joint movement. Some sports and activities, such as wall climbing and wrestling, require your muscles to exert force to hold your body in a stationary position in repeated efforts or for long periods of time requiring strength and endurance. Isometric exercises place less strain on your joints and are recommended for some rehabilitation training programs.
Isometric Lower Body Exercises
Wall squats are isometric exercises that strengthen your thighs and are performed with a wall. Stand with your feet 1 to 2 feet ahead of you, shoulder-width apart, placing your back against a wall. Bend your knees, lowering your body down until your thighs are parallel to the floor. Keep your back straight and contract your thighs to hold this position for up to 30 seconds.
Lunges can be performed as an isometric exercise by holding your body in the lunge position for extended periods of time. Many standing yoga exercises are performed by placing your body in a lunge position. Step forward with one leg, bending your front knee and lowering your body until your front thigh is parallel to the floor. Hold the pose for up to five breaths and repeat on the other leg.
Isotonic Contractions
With isotonic weight-training exercises, your muscles tighten and shorten to contract and relax to lengthen and stretch. The contraction phase is known as a concentric contraction while the lengthening phase is the eccentric contraction. Isotonic exercises work your muscles through a full range of motion. Training is functional, mimicking most everyday activities and sport skills.
Isotonic Weight Training Lower Leg Exercises
Lower leg, weight-training exercises can be grouped as compound and isolation exercises. Squats and lunges are examples of compound exercises working more than one muscle group. Your thighs, buttocks and hamstrings work to bend and extend your hips and knees. Lunges work one leg at a time and can be performed by stepping forward, lowering and lifting your body using alternating legs. Squats and lunges can be performed using barbells, dumbbells or your own body weight as resistance.
Leg curls and leg extensions are examples of isolation exercises using weight machines. Your quadriceps, the front of your thighs, contract to straighten your knee to perform leg extensions. Your hamstrings, the back of your thighs, work to bend your knees to perform leg curls.
References
- American College of Sports Medicine: Successful Resistance Training for Arthritis
- Mayo Clinic: Fitness: What Are Isometric Exercises and Are They a Good Way to Build Strength?
- Isometric Training.com: Leg Exercise: Isometrics
- Sports Injury Clinic: Muscle Contractions
- Bodybuilding.com: 5 Intense Exercises for Strong, Shapely Legs & Glutes
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