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Vol. 83, Issue 5, 1581-1587, 1997
1 Department of Kinesiology, ABSTRACT Lindle, R. S., E. J. Metter, N. A. Lynch, J. L. Fleg, J. L. Fozard, J. Tobin, T. A. Roy, and B. F. Hurley. Age and gender
comparisons of muscle strength in 654 women and men aged 20-93 yr.
J. Appl. Physiol. 83(5): 1581-1587, 1997.
eccentric strength; gender differences
INTRODUCTION IT HAS BEEN WELL DOCUMENTED that both muscle mass and
strength decline with age (17, 20). This decline is associated with an
increased risk of falls (6), hip fractures (4), and adverse physiological changes, such as glucose intolerance (5) and a loss of
bone mineral density (29). Consequently, these changes may predispose
elderly individuals to osteoporosis, atherosclerosis, and diabetes as
well as to functional limitations in activities of daily living (16).
Although many previous studies have assessed age-related declines in
absolute strength by using measurements of isometric (Iso)
and/or concentric (Con) force production (9, 12, 17), few
studies have examined changes in eccentric (Ecc) strength with age.
Information regarding the relationship between Ecc strength and age may
have important functional implications for the elderly, because Ecc
muscle actions play a vital role in normal ambulatory activities by
providing stabilization and deceleration forces (14, 30). The studies
available suggest that Ecc strength in humans may be less affected by
age than is Con strength (15, 27, 27a, 28, 32), particularly at higher
velocities (15, 28). Additionally, in a preliminary study (22), we
observed a gender difference in the age-associated change in Ecc
strength. However, the results of gender difference with age are
conflicting (15, 27, 27a, 28, 32), and these studies have used
relatively small sample sizes and limited age ranges (15, 27, 27a, 28, 32). Furthermore, no data were presented in any of these studies that
would provide evidence explaining gender differences in Ecc strength.
Thus there is a need to further examine this issue by using a larger
sample size of men and women representing a wide age range.
Age-associated changes in the mechanical and elastic properties of the
passive component (connective tissue) have been postulated as one
factor that could preserve Ecc strength (14). These changes could
increase the resistance to stretch during an Ecc action without
affecting the Con or Iso force production (15). Indeed, age-related
increases in connective tissue (21) and collagen cross-linking (1) have
been reported that might enhance the elastic potential and increase Ecc
force production. One method of assessing the mechanical and elastic
properties of the muscle in vivo is to measure the stretch-shortening
cycle (SSC). The SSC reflects the ability of the muscle to store and
recover elastic energy from an Ecc action. Gender differences in the
SSC have been reported in young subjects (18), suggesting that men and women may differ in their ability to store elastic energy. Whether such
gender differences persist into later life is unknown.
Muscle quality (strength per unit of muscle) is an important indicator
of muscle performance and is thought to decline with age in men (9, 17,
26, 34) but not in women (33). However, gender differences have not
been assessed in the same study throughout a wide age range.
Furthermore, only one study has addressed the effects of age on muscle
quality when using Ecc peak torque (15).
Therefore, the main purpose of this study was to compare age and gender
differences in Iso, Con, and Ecc peak torque in the knee extensors. To
help explain age and gender relationships to Ecc strength levels, the
ability to store and utilize elastic energy was examined by using the
SSC in a representative subset of subjects. The effects of age, gender,
and type of muscle action (Con vs. Ecc) on muscle quality was also
examined.
METHODS
To assess age
and gender differences in muscle strength, isometric, concentric (Con),
and eccentric (Ecc) peak torque was measured in the knee extensors at a
slow (0.52 rad/s) and fast (3.14 rad/s) velocity in 654 subjects (346 men and 308 women, aged 20-93 yr) from the Baltimore Longitudinal
Study of Aging. Regression analysis revealed significant
(P < 0.001) age-related reductions in Con and Ecc peak
torque for men and women at both velocities, but no differences were
observed between the gender groups or velocities. Age explained losses
in Con better than Ecc peak torque, accounting for 30% (Con) vs. 19%
(Ecc) of the variance in men and 28% (Con) vs. 11% (Ecc) in women. To
assess age and gender differences in the ability to store and utilize
elastic energy, the stretch-shortening cycle was determined in a subset
of subjects (n = 47). The older women (mean age = 70 yr)
showed a significantly greater enhancement in the stretch-shortening
cycle, compared with men of similar age (P < 0.01) and
compared with younger men and women (each P < 0.05). Both
men and women showed significant declines in muscle quality for Con
peak torque (P < 0.01), but no gender differences were observed. Only the men showed a significant decline in muscle quality
(P < 0.001) for Ecc peak torque. Thus both men and women experience age-related losses in isometric, Con, and Ecc knee extensor
peak torque; however, age accounted for less of the variance in Ecc
peak torque in women, and women tend to better preserve muscle quality
with age for Ecc peak torque. In addition, older women have an enhanced
capacity to store and utilize elastic energy compared with similarly
aged men as well as with younger women and men.
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Con)/EccSCC. The numerator yields
the absolute enhancement of Con peak torque via SSC, and the
denominator relates this enhancement to the Ecc force output, i.e.,
percentage of Ecc peak torque recovered and utilized in the subsequent
Con action.
Statistical analyses.
For the purpose of comparing specific age groups with regard to
physical characteristics and body composition, subjects were divided
into four distinct age categories (Table
2). Analysis of variance was used to
compare age group and gender differences in physical characteristics
(height and body mass), body composition [body mass index (BMI) %body
fat (%Fat) total body and thigh nonosseous FFM, and thigh fat], and
SSC. When a difference was found, a Scheffé's post hoc test was
used to determine the specific comparisons that were significant.
Regression analysis was used to assess age- and gender-related
differences in Con, Ecc, and Iso peak torque. Significance level was
set at P < 0.05 for analyses of physical characteristics,
body composition, and SSC. However, the significance level was set at
P < 0.01 for analysis of peak torque values to compensate for
the effects of an inflated alpha level due to multiple comparisons
[Bonferroni correction for multiple comparisons (
0.5/5)]. All
analyses were performed with the SPSS for Windows (version 6.1)
statistical package.
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RESULTS
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Age-associated losses in Con and Ecc peak torque expressed as a percentage of the mean of the youngest group are shown in Fig. 2, A and B. In contrast to absolute peak torque values (Fig. 1, A and B), the percent decline was similar for both men and women for Con and Ecc peak torque at the slow velocity. Age accounted for ~30% of the variance for Con and 19% for Ecc peak torque.
Muscle quality. Regression analysis of Con and Ecc peak torque (0.52 rad/s) of the knee extensors relative to thigh nonosseous FFM (muscle quality) as a function of age for men and women is presented in Fig. 3. The gender difference diminished from 37 to 9% when Con peak torque was expressed relative to muscle quality for all groups combined. However, age-related differences in muscle quality remained highly significant (P < 0.001) for both men and women. When Ecc peak torque was related to muscle quality, men showed a significant age-related decline (P < 0.001), whereas women showed no significant decline with age.
SSC. The SSC results from the subgroup are presented in Fig. 4. The SSC significantly (P < 0.01) enhanced Con peak torque of the knee extensors in all subject groups tested. Similar enhancement of Con peak torque via the SSC was found in young men (20%), young women (20%), and older men (15%). However, the older women showed a significantly greater (P < 0.01) enhancement than the other three groups. These results suggests that the older women had a greater ability to store and utilize elastic energy via the SSC.
Con)/Ecc] in young (20-35 yr) compared with older
(65-80 yr) men and women. *Significantly different from young men
(P < 0.05), young women (P < 0.05), and the
older men (P < 0.01).
Velocity. To assess the age- and gender-related differences in slow vs. fast Con and Ecc peak torque in the knee extensors, regression analysis was performed on the slow (0.52 rad/s) divided by the fast (3.14 rad/s) peak torque values (Fig. 5). There was no significant age effect or age-by-gender interaction in either Con or Ecc ratios and no significant gender effect in the Ecc ratio. However, there was a significant (P < 0.001) gender difference in Con slow-to-fast ratio, but the difference was quite small.
DISCUSSION
The results of this study do not support the hypothesis that Ecc strength is more preserved with age than Con strength in men or women. However, age does appear to explain losses in Con strength better than losses in Ecc strength. Both men and women experience age-related losses in muscle quality when using Con strength, but only men experience these losses when using Ecc strength. Based on our SSC results from a small representative subgroup, older women have a greater capacity to store and utilize elastic energy compared with similarly aged men and younger women and men.
Investigators have concluded in previous studies that Con strength tends to peak in the 20s and 30s, then plateaus until ~50 yr of age in men and then declines at a rate of ~12-15% per decade (9, 17, 20, 34). The results of the present study show that both men and women exhibit age-related declines in knee extensor Iso and Con strength starting in the fourth decade at a rate of ~8-10% per decade in both men and women. The age-related decline for Ecc strength is about the same for men and women, but women appear to start their decline at least a decade later.
Our results differ from those of Vandervoort et al. (32), who concluded that in women Ecc strength was less affected by age than was Con. The researchers reported a difference of 53% for Con and 34% for Ecc in knee extensor peak torque between the young and the old women. Their 53% difference in Con peak torque of the knee extensors between the ages of 23 and 72 yr is considerably greater than the results of the present study (Con ~34%) and some studies previously reported (20, 25, 29). The results of the present study also slightly differ from those of Poulin et al. (28), who reported a 32% Con vs. 19% Ecc difference in peak torque of the knee extensors between young and old age groups of men at 1.57 rad/s (90°/s) and a 31% Con vs. 2% Ecc age-related difference at the faster velocity (3.14 rad/s). The men in the present study showed almost identical declines in Con (33%) compared with Ecc (31%) strength, whereas women showed more of a difference between Con (35%) and Ecc losses (22%) with age, but this difference was not significant.
Hortobagyi et al. (15) reported a gender difference in the relationship of Ecc strength and age. However, they reported nonsignificant declines in Ecc knee extensor strength with age in both men and women. The older men (70 ± 1.5 yr) generated 20% less Ecc strength than the young men (29.5 ± 1.5 yr), whereas the older women (69 ± 1.8 yr) actually exceeded the young women (29.3 ± 1.8 yr) by ~10% in Ecc strength. This is in contrast to the results in the present study, which found an age-related decline in Ecc knee extensor strength of ~31% in men and ~22% in women. Hortobagyi et al. (15) reported angle-specific (2.36 rad) peak force, whereas in the present study peak force was corrected for the length of the lever arm and reported as peak torque. More recently, Porter et al. (27a) reported Ecc torques of the plantar flexors and dorsiflexors in 16 older women to be 97 and 100%, respectively, of the values obtained from 16 younger women. Thus, these conflicting results may be due to differences in sample sizes, methodological differences, or other factors.
It has been postulated that changes in neural, muscular, and mechanical and/or elastic properties of muscle might contribute to a maintenance of Ecc strength with age (7, 8, 15, 28, 32). We studied the mechanical and elastic properties in the present investigation because these factors have been previously connected to a possible gender difference in Ecc strength decline with age (18), which was indicated from our preliminary findings (22). It is well established in young populations that Con peak torque is enhanced when preceded by an Ecc exertion, i.e., the SSC (10, 13, 18, 30). Prior studies have reported SSC-induced increases in Con peak torque ranging from 5 to 100%, depending on the muscle group, velocity of testing, and methodology (13, 18, 30). Additionally, gender differences in the SSC capacity of young subjects have been reported, but these differences were relatively small (18, 31). In the present study, the older women showed a significantly greater SSC enhancement than the older men, the younger men, and younger women. These results differ from those of Svantesson and Grimby (31), who did not find any age or gender-related differences in the SSC of the plantar flexors. The discrepancy between the studies may be due to differences in the populations and/or to muscle groups tested. The increased ability of the older women to store and utilize elastic energy observed in the present study suggests differences in the mechanical and elastic properties of the muscle and would appear to support our original hypothesis of a greater preservation of Ecc strength with age in women. However, Ecc strength declined similarly with age in both sexes in our overall sample.
The results of this study suggest a decline in muscle quality (strength per kilogram of regional FFM) with age in both men and women when Con strength values are used but only in men when Ecc strength is used. This finding has not been reported elsewhere. Young et al. (33) found no difference in muscle quality when comparing women in their eighth decade with those in their third decade using Con strength, whereas losses have been reported for men (9, 17, 26, 34). More recently, Hortabagyi et al. (15) found no age-related alterations in muscle quality in either men or women when using Ecc strength values. One factor that may explain the discrepancies in the various investigations is that almost every study has used a different technique to estimate muscle mass or FFM. Creatinine excretion, hydrodensitometry, anthropometry, and bioelectrical impedance have all been used in previous studies. To the best of our knowledge, the present study is the first to examine age-related changes in muscle quality by using DEXA to assess regional nonosseous FFM.
Because of the preferential loss of type II fibers associated with aging (20), it has been postulated that older individuals might exhibit a greater loss of maximal Con peak torque at fast compared with slow velocities. However, relatively few studies have examined this relationship in a young compared to an older population, and the results are conflicting (3, 11). Additionally, some studies have reported a greater maintenance of Ecc force with age at the faster velocities (15, 28). We did not observe any differences in losses of strength with age between slow and fast velocities; however, there was a small velocity-related difference between men and women when assessing Con peak torque. Women had a greater age-related decrease in fast velocity peak torque than men.
In conclusion, the results of this study indicate that Con strength levels begin to decline in the fourth rather than in the fifth decade, as was previously reported. Contrary to previous reports, there is no preservation of Ecc compared with Con strength in men or women with advancing age. Nevertheless, the decline in Ecc strength with age appears to start later in women than in men and later than Con strength did in both sexes. In a small subgroup of subjects, there appears to be a greater ability to store and utilize elastic energy in older women. This finding needs to be confirmed by using a larger sample size. Muscle quality declines with age in both men and women when Con peak torque is used, but declines only in men when Ecc peak torque is used.
ACKNOWLEDGEMENTS
This study was supported in part by an National Institutes of Health Intramural Research Training Award fellowship to R. Lindle and was conducted as part of the Baltimore Longitudinal Study of Aging, a component of the National Institute on Aging intramural research program. The authors thank Bernice Swann for analysis of DEXA body composition scans and J. Ryan Lindle for technical assistance. Special thanks to the research volunteers in the Baltimore Longitudinal Study of Aging, who participated in this study.
FOOTNOTES
Address for reprint requests: B. Hurley, Dept. of Kinesiology, Univ. of Maryland, College Park, MD 20742.
Received 12 December 1996; accepted in final form 11 July 1997.
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R. Moreno Lima, B. S. de Abreu, P. Gentil, T. C. de Lima Lins, D. Grattapaglia, R. W. Pereira, and R. J. de Oliveira Lack of Association Between Vitamin D Receptor Genotypes and Haplotypes With Fat-Free Mass in Postmenopausal Brazilian Women J. Gerontol. A Biol. Sci. Med. Sci., September 1, 2007; 62(9): 966 - 972. [Abstract] [Full Text] [PDF]
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M. D. de Boer, C. I. Morse, J. M. Thom, A. de Haan, and M. V. Narici Changes in Antagonist Muscles' Coactivation in Response to Strength Training in Older Women J. Gerontol. A Biol. Sci. Med. Sci., September 1, 2007; 62(9): 1022 - 1027. [Abstract] [Full Text] [PDF]
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S. Walsh, E. J. Metter, L. Ferrucci, and S. M. Roth Activin-type II receptor B (ACVR2B) and follistatin haplotype associations with muscle mass and strength in humans J Appl Physiol, June 1, 2007; 102(6): 2142 - 2148. [Abstract] [Full Text] [PDF]
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C. Suetta, P. Aagaard, S. P. Magnusson, L. L. Andersen, S. Sipila, A. Rosted, A. K. Jakobsen, B. Duus, and M. Kjaer Muscle size, neuromuscular activation, and rapid force characteristics in elderly men and women: effects of unilateral long-term disuse due to hip-osteoarthritis J Appl Physiol, March 1, 2007; 102(3): 942 - 948. [Abstract] [Full Text] [PDF]
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 C. R Gale, C. N Martyn, C. Cooper, and A. A. Sayer Grip strength, body composition, and mortality Int. J. Epidemiol., February 1, 2007; 36(1): 228 - 235. [Abstract] [Full Text] [PDF]
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A. P. Marsh, M. E. Miller, A. M. Saikin, W. J. Rejeski, N. Hu, F. Lauretani, S. Bandinelli, J. M. Guralnik, and L. Ferrucci Lower Extremity Strength and Power Are Associated With 400-Meter Walk Time in Older Adults: The InCHIANTI Study J. Gerontol. A Biol. Sci. Med. Sci., November 1, 2006; 61(11): 1186 - 1193. [Abstract] [Full Text] [PDF]
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B. H. Goodpaster, S. W. Park, T. B. Harris, S. B. Kritchevsky, M. Nevitt, A. V. Schwartz, E. M. Simonsick, F. A. Tylavsky, M. Visser, A. B. Newman, et al. The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study. J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2006; 61(10): 1059 - 1064. [Abstract] [Full Text] [PDF]
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M. G. Giannoulis, P. H. Sonksen, M. Umpleby, L. Breen, C. Pentecost, M. Whyte, C. V. McMillan, C. Bradley, and F. C. Martin The Effects of Growth Hormone and/or Testosterone in Healthy Elderly Men: A Randomized Controlled Trial J. Clin. Endocrinol. Metab., February 1, 2006; 91(2): 477 - 484. [Abstract] [Full Text] [PDF]
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M.-H. Jan, H.-M. Chai, Y.-F. Lin, J. C.-H. Lin, L.-Y. Tsai, Y.-C. Ou, and D.-H. Lin Effects of Age and Sex on the Results of an Ankle Plantar-Flexor Manual Muscle Test Physical Therapy, October 1, 2005; 85(10): 1078 - 1084. [Abstract] [Full Text] [PDF]
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M. Klass, S. Baudry, and J. Duchateau Aging does not affect voluntary activation of the ankle dorsiflexors during isometric, concentric, and eccentric contractions J Appl Physiol, July 1, 2005; 99(1): 31 - 38. [Abstract] [Full Text] [PDF]
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K. R. Short, J. L. Vittone, M. L. Bigelow, D. N. Proctor, J. M. Coenen-Schimke, P. Rys, and K. S. Nair Changes in myosin heavy chain mRNA and protein expression in human skeletal muscle with age and endurance exercise training J Appl Physiol, July 1, 2005; 99(1): 95 - 102. [Abstract] [Full Text] [PDF]
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A. Katsiaras, A. B. Newman, A. Kriska, J. Brach, S. Krishnaswami, E. Feingold, S. B. Kritchevsky, R. Li, T. B. Harris, A. Schwartz, et al. Skeletal muscle fatigue, strength, and quality in the elderly: the Health ABC Study J Appl Physiol, July 1, 2005; 99(1): 210 - 216. [Abstract] [Full Text] [PDF]
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M. C. Kostek, M. J. Delmonico, J. B. Reichel, S. M. Roth, L. Douglass, R. E. Ferrell, and B. F. Hurley Muscle strength response to strength training is influenced by insulin-like growth factor 1 genotype in older adults J Appl Physiol, June 1, 2005; 98(6): 2147 - 2154. [Abstract] [Full Text] [PDF]
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K S. Nair Aging muscle Am. J. Clinical Nutrition, May 1, 2005; 81(5): 953 - 963. [Abstract] [Full Text] [PDF]
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 H. C. Dreyer and E. Volpi Role of Protein and Amino Acids in the Pathophysiology and Treatment of Sarcopenia J. Am. Coll. Nutr., April 1, 2005; 24(2): 140S - 145S. [Abstract] [Full Text] [PDF]
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S. Walsh, J. M. Zmuda, J. A. Cauley, P. R. Shea, E. J. Metter, B. F. Hurley, R. E. Ferrell, and S. M. Roth Androgen receptor CAG repeat polymorphism is associated with fat-free mass in men J Appl Physiol, January 1, 2005; 98(1): 132 - 137. [Abstract] [Full Text] [PDF]
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M. A. Schrager, S. M. Roth, R. E. Ferrell, E. J. Metter, E. Russek-Cohen, N. A. Lynch, R. S. Lindle, and B. F. Hurley Insulin-like growth factor-2 genotype, fat-free mass, and muscle performance across the adult life span J Appl Physiol, December 1, 2004; 97(6): 2176 - 2183. [Abstract] [Full Text] [PDF]
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J. Ochala, D. Valour, M. Pousson, D. Lambertz, and J. Van Hoecke Gender Differences in Human Muscle and Joint Mechanical Properties During Plantar Flexion in Old Age J. Gerontol. A Biol. Sci. Med. Sci., May 1, 2004; 59(5): B441 - B448. [Abstract] [Full Text] [PDF]
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A. M. Holmback, M. M. Porter, D. Downham, J. L. Andersen, and J. Lexell Structure and function of the ankle dorsiflexor muscles in young and moderately active men and women J Appl Physiol, December 1, 2003; 95(6): 2416 - 2424. [Abstract] [Full Text]
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A. M. Payne, S. L. Dodd, and C. Leeuwenburgh Life-long calorie restriction in Fischer 344 rats attenuates age-related loss in skeletal muscle-specific force and reduces extracellular space J Appl Physiol, December 1, 2003; 95(6): 2554 - 2562. [Abstract] [Full Text]
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S. M. Roth, M. A. Schrager, M. R. Lee, E. J. Metter, B. F. Hurley, and R. E. Ferrell Interleukin-6 (IL6) Genotype Is Associated With Fat-Free Mass in Men But Not Women J. Gerontol. A Biol. Sci. Med. Sci., December 1, 2003; 58(12): B1085 - 1088. [Abstract] [Full Text] [PDF]
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S. M. Roth, E. J. Metter, M. R. Lee, B. F. Hurley, and R. E. Ferrell C174T polymorphism in the CNTF receptor gene is associated with fat-free mass in men and women J Appl Physiol, October 1, 2003; 95(4): 1425 - 1430. [Abstract] [Full Text] [PDF]
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 S. N. Hayes Sex Matters Arch Intern Med, November 25, 2002; 162(21): 2490 - 2490. [Full Text] [PDF]
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 M. R. Blackman, J. D. Sorkin, T. Munzer, M. F. Bellantoni, J. Busby-Whitehead, T. E. Stevens, J. Jayme, K. G. O'Connor, C. Christmas, J. D. Tobin, et al. Growth Hormone and Sex Steroid Administration in Healthy Aged Women and Men: A Randomized Controlled Trial JAMA, November 13, 2002; 288(18): 2282 - 2292. [Abstract] [Full Text] [PDF]
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 S. M. Roth, R. E. Ferrell, D. G. Peters, E. J. Metter, B. F. Hurley, and M. A. Rogers Influence of age, sex, and strength training on human muscle gene expression determined by microarray Physiol Genomics, September 3, 2002; 10(3): 181 - 190. [Abstract] [Full Text] [PDF]
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 T. A. Roy, M. R. Blackman, S. M. Harman, J. D. Tobin, M. Schrager, and E. J. Metter Interrelationships of serum testosterone and free testosterone index with FFM and strength in aging men Am J Physiol Endocrinol Metab, August 1, 2002; 283(2): E284 - E294. [Abstract] [Full Text] [PDF]
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A. M. Matsumoto Andropause: Clinical Implications of the Decline in Serum Testosterone Levels With Aging in Men J. Gerontol. A Biol. Sci. Med. Sci., February 1, 2002; 57(2): M76 - 99. [Full Text]
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I. S. Kwon, S. Oldaker, M. Schrager, L. A. Talbot, J. L. Fozard, and E. J. Metter Relationship Between Muscle Strength and the Time Taken to Complete a Standardized Walk-Turn-Walk Test J. Gerontol. A Biol. Sci. Med. Sci., September 1, 2001; 56(9): B398 - 404. [Abstract] [Full Text] [PDF]
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P. J. Snyder Effects of Age on Testicular Function and Consequences of Testosterone Treatment J. Clin. Endocrinol. Metab., June 1, 2001; 86(6): 2369 - 2372. [Full Text] [PDF]
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S. M. Roth, M. A. Schrager, R. E. Ferrell, S. E. Riechman, E. J. Metter, N. A. Lynch, R. S. Lindle, and B. F. Hurley CNTF genotype is associated with muscular strength and quality in humans across the adult age span J Appl Physiol, April 1, 2001; 90(4): 1205 - 1210. [Abstract] [Full Text] [PDF]
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B. C. Schiller, Y. G. Casas, B. L. Tracy, C. A. DeSouza, and D. R. Seals Age-Related Declines in Knee Extensor Strength and Physical Performance in Healthy Hispanic and Caucasian Women J. Gerontol. A Biol. Sci. Med. Sci., December 1, 2000; 55(12): 563B - 569. [Abstract] [Full Text]
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S. K. Hunter, M. W. Thompson, and R. D. Adams Relationships Among Age-Associated Strength Changes and Physical Activity Level, Limb Dominance, and Muscle Group in Women J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2000; 55(6): 264B - 273. [Abstract] [Full Text]
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T. J. Overend, T. H. Versteegh, E. Thompson, T. B. Birmingham, and A. A. Vandervoort Cardiovascular Stress Associated With Concentric and Eccentric Isokinetic Exercise in Young and Older Adults J. Gerontol. A Biol. Sci. Med. Sci., April 1, 2000; 55(4): 177B - 182. [Abstract] [Full Text]
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T. Rantanen, T. Harris, S. G. Leveille, M. Visser, D. Foley, K. Masaki, and J. M. Guralnik Muscle Strength and Body Mass Index as Long-Term Predictors of Mortality in Initially Healthy Men J. Gerontol. A Biol. Sci. Med. Sci., March 1, 2000; 55(3): 168M - 173. [Abstract] [Full Text]
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 D. S. Moran, Y. Shapiro, A. Laor, S. Izraeli, and K. B. Pandolf Can gender differences during exercise-heat stress be assessed by the physiological strain index? Am J Physiol Regulatory Integrative Comp Physiol, June 1, 1999; 276(6): R1798 - R1804. [Abstract] [Full Text] [PDF]
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N. A. Lynch, E. J. Metter, R. S. Lindle, J. L. Fozard, J. D. Tobin, T. A. Roy, J. L. Fleg, and B. F. Hurley Muscle quality. I. Age-associated differences between arm and leg muscle groups J Appl Physiol, January 1, 1999; 86(1): 188 - 194. [Abstract] [Full Text] [PDF]
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B. L. Tracy, F. M. Ivey, D. Hurlbut, G. F. Martel, J. T. Lemmer, E. L. Siegel, E. J. Metter, J. L. Fozard, J. L. Fleg, and B. F. Hurley Muscle quality. II. Effects of strength training in 65- to 75-yr-old men and women J Appl Physiol, January 1, 1999; 86(1): 195 - 201. [Abstract] [Full Text] [PDF]
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T. Rantanen, K. Masaki, D. Foley, G. Izmirlian, L. White, and J. M. Guralnik Grip strength changes over 27 yr in Japanese-American men J Appl Physiol, December 1, 1998; 85(6): 2047 - 2053. [Abstract] [Full Text] [PDF]
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ABSTRACT
