Exercise to increase strength
Course objectives, Control of Human Movement 2
Reading for Control of Human Movement 2: sections on "exercise prescription for muscular strength" from:
American College of Sports Medicine. (1998). American College of Sports Medicine Position Stand. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults. Medicine & Science in Sports & Exercise, 30, 975-91.Full text versions of this article are available through the University's Medline account on OVID (unique identifier 98287757) or by accessing the list of position stands listed at the ACSM web site.
Prescription parameters (American College of Sports Medicine, 1998).
- Frequency of training: 2 to 3 days a week.
- Intensity of training: Therapists use the concept of a "repetition maximum" (RM) to prescribe the weight or load that one lifts. "... most experts recommend 8-12 repetitions per set; however, a lower repetition
range, with a heavier weight, e.g., 6-8, repetitions may better optimize strength and power. Because orthopaedic injury may occur in ... participants [who are] approximately 50-60 yr of age and above ... when performing efforts to volitional fatigue using a high-intensity, low-to-moderate repetition maximum (RM), the completion of 10-15 repetitions or RM is recommended" (ACSM, 1998).
The ACSM's prescription guidelines differ from older
Delorme and Oxford strengthening protocols.
- Duration of training: "One set of 8-10 exercises that conditions the major muscle groups is recommended. Multiple-set regimens may provide greater benefits if time allows."
- Mode of training The ACSM recommends no specific mode of exercise. Resistance to produce training stimulus can come from the weight of the body
or any of its segments, from free weights, elastic tubing, equipment.
The ACSM's prescription guidelines differ from older Delorme and Oxford strengthening protocols.
The prescription parameters contribute to a total stimulus called training volume
progressive overload Once muscles have adapted to overload, the overload stimulus must be increased to produce further training effects
Exercise prescriptions produce changes that are specific to:
- muscle group (Sale, 1988)
- joint angle or range of motion (Graves, Pollock, Jones, Colvin, & Leggett, 1989)
- type of muscle action
- speed of muscle action
- muscle fiber type
- metabolic energy system
Modes of Exercise
- Isotonic: alternating concentric and eccentric muscle activation that moves a body part through an arc of motion against resistance
- Isokinetic: exercise that involves specialized equipment that provides "accomodating resistance" so that the joint moves at a constant angular velocity
- Isometric: muscle action that is performed against resistance at any point in a joint's range of motion, for
periods of 5-10 seconds, and that produces no joint movement
- Plyometric: exercise that requires eccentric activation of muscles against a resistance, followed by a brief amortization period, followed by concentric activation
Measuring exercise intensity
The ACSM recommends exercising at an intensity of 8 to 12 RM. Two classic strengthening protocols (Arnheim & Prentice, 1993) require a person to determine the 10RM for a given exercise, and then to perform several sets of the exercise:
- Delorme Method of Strengthening:
- 10 reps @ 50% of 10RM
- 10 reps @ 75% of 10RM
- 10 reps @ 100% of 10RM
- Oxford Technique of Strengthening:
- 10 reps @ 100% of 10RM
- 10 reps @ 75% of 10RM
- 10 reps @ 50% of 10RM
Estimating 1RM from a "n-RM"
To estimate a person's 1RM after you've determined a "n RM" (where n=10, for example), you can use a regression equation attributed to Brzycki (1993).
1 RM = weight lifted during n RM / (1.0278 - .0278(n))
Alternatively,
1 RM = weight lifted during n RM * (1 + ( 0.033(n) )
The formula permits one to "assess muscular strength in a safe, efficient manner ... [without requiring] clients to attempt maximum lifts " (Brzycki, 2000). Brzycki's equation predicts the 1 RM in a bench press more accurately than competing formulas, as long as its estimate is based on ten or fewer repetitions (Mayhew, Prinster, Ware, Zimmer, Arabas, & Bemben, 1995).
Brzycki's equation also estimates loads for a "nRM" as a percentage of the 1RM:
An online calculator programmed for Brzycki's equation
Responses to strength training
Muscle strength and flexibility:
Stretch-shorten cycle (SSC): activities in which eccentric muscle action precedes and amplifies force production during concentric muscle activity. During the walking cycle, the stretch shorten cycle occurs in the ankle plantar flexors, the knee extensors, and the hip flexors.
More flexible muscles may develop greater force during the SSC because:
- flexibility permits potentiation of the muscle's stretch reflex
- flexibility permits greater energy storage (Wilson, Elliott, & Wood, 1992; Benn, Forman, Mathewson, Tapply, Tiskus, Whang, & Blanpied, 1998)
Arnheim, D. D., & Prentice, W. E. (1993). Principles of athletic training. St. Louis: Mosby.
Benn, C., Forman, K., Mathewson, D., Tapply, M., Tiskus, S., Whang, K., & Blanpied, P. (1998). The effects of serial stretch loading on stretch work and stretch-shorten cycle performance in the knee musculature. Journal of Orthopedic and Sports Physical Therapy, 27, 412-22.
Brzycki, M. (1993). Strength testing - Predicting a one-rep max from a reps-to-fatigue. Journal of Physical Education, Recreation and Dance 64 (1), 88-90.
Brzycki, M. (June, 2000). Assessing strength. Fitness Management. Retrieved April 13, 2001, from the World Wide Web: //www.fitnessworld.com/info/info_pages/library/strength/assess0600.html
Feigenbaum, M. S., & Pollock, M.L. (1997). Strength training: Rationale for current guidelines for adult fitness programs. Physician and Sportsmedicine, 25, 44-64.
Graves, J. E., Pollock, M. L., Jones, A. E., Colvin, A. B., & Leggett, S. H. (1989). Specificity of limited range of motion variable resistance training. Medicine and Science in Sports Medicine, 21, 84-89.
Graves, J.E., Pollock, M.L., Foster, D., Leggett, S.H., Carpenter, D.M.,Vuoso, R., & Jones, A. (1990). Effect of training frequency and specificity on isometric lumbar extension strength. Spine, 15, 504-509.
Mayhew, J.L., Prinster, J.L., Ware, J.S., Zimmer, D.L., Arabas, J.R., & Bemben, M.G. (1995). Muscular endurance repetitions to predict bench press strength in men of different training levels. Journal of Sports Medicine & Physical Fitness. 35(2), 108-13.
Sale, D.G. (1988). Neural adaptation to resistance training. Medicine & Science in Sports & Exercise, 20, S135-45.
Wilson, G.J., Elliott, B.C., & Wood, G.A. (1992). Stretch shorten cycle performance enhancement through flexibility training. Medicine & Science in Sports & Exercise, 24, 116-123.