Association of knee pain with a reduction in thigh muscle strength - a cross-sectional analysis including 4553 osteoarthritis initiative participants

OBJECTIVE

To cross-sectionally determine the quantitative relationship of age-adjusted, sex-specific isometric knee extensor and flexor strength to patient-reported knee pain.

METHODS

Difference of thigh muscle strength by age, and that of age-adjusted strength per unit increase on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) knee pain scale, was estimated from linear regression analysis of 4553 Osteoarthritis Initiative (OAI) participants (58% women). Strata encompassing the minimal clinically important difference (MCID) in knee pain were compared to evaluate a potentially non-linear relationship between WOMAC pain levels and muscle strength.

RESULTS

In OAI participants without pain, the age-related difference in isometric knee extensor strength was -9.0%/-8.2% (women/men) per decade, and that of flexor strength was -11%/-6.9%. Differences in age-adjusted strength values for each unit of WOMAC pain (1/20) amounted to -1.9%/-1.6% for extensor and -2.5%/-1.7% for flexor strength. Differences in torque/weight for each unit of WOMAC pain ranged from -3.3 to -2.1%. There was no indication of a non-linear relationship between pain and strength across the range of observed WOMAC values, and similar results were observed in women and men.

CONCLUSION

Each increase by 1/20 units in WOMAC pain was associated with a ∼2% lower age-adjusted isometric extensor and flexor strength in either sex. As a reduction in muscle strength is known to prospectively increase symptoms in knee osteoarthritis (KOA) and as pain appears to reduce thigh muscle strength, adequate therapy of pain and muscle strength is required in KOA patients to avoid a vicious circle of self-sustaining clinical deterioration.

Target intensity and interval walking training in water to enhance physical fitness in middle-aged and older women: a randomised controlled study

PURPOSE

To determine the target intensity for fast walking during interval walking training (IWT) in water for middle-aged and older people to enhance physical fitness.

METHODS

Thirty-one women [59 ± 5 (SD) years old] were randomly divided into two groups: IWT on land (LG, N = 15) and in water (WG, N = 16). All subjects were instructed to perform ≥ 6 sets of fast and slow walking for 3 min each in a day, ≥ 4 days week(-1), for 8 weeks, at an intensity 35% higher than the oxygen consumption rate at the gas exchange threshold (VO2GET), with a subjective feeling of 16-18 points of the Borg scale during fast walking in each condition. Before and after IWT, we measured VO2GET, peak aerobic capacity (VO2peak) by graded walking and cycling tests on land and isometric knee extension (F EXT) and flexion (F FLX) forces.

RESULTS

Before IWT, the VO2GET for walking in water was 14% higher and the heart rate (HR) at a given VO2 was ~10 beats min(-1) lower (P=0.001) than on land. During IWT, subjects in both groups performed IWT for ~4 days week(-1)(P > 0.9) with a 14% higher fast walking intensity in WG than in LG (P < 0.05). After IWT, the VO2peak and VO2GET for cycling, F EXT and F FLX increased more in WG than in LG (all, P < 0.05).

CONCLUSION

Walking in water elevated VO2GET and decreased HR at a given exercise intensity in middle-aged and older women, which enabled them to perform exercise at a higher metabolic rate than on land due to improved subjective feelings, which, for these subjects, resulted in greater gains in physical fitness.

Effects of dried tofu supplementation during interval walking training on the methylation of the NFKB2 gene in the whole blood of older women

Muscle atrophy with aging is closely associated with chronic systemic inflammation and lifestyle-related diseases. Here, we assessed whether dried tofu intake during 5-month interval walking training (IWT) enhanced increases in thigh muscle mass and strength and ameliorated susceptibility to inflammation in older women. Subjects (n = 32, ~ 65 years) who performed IWT for > 6 months participated in this study. They were randomly divided into 2 groups: IWT + placebo intake (PLG, n = 16; 108 kcal, 0.2 g protein, 5.5 g fat, and 14.4 g carbohydrate) and IWT + dried tofu intake (DTG, n = 16; 111 kcal, 9.6 g protein, 6.0 g fat, and 4.6 g carbohydrate). They were instructed to repeat ≥ 5 sets of fast and slow walking for 3 min each at ≥ 70 and 40% peak aerobic capacity for walking, respectively, per day for ≥ 4 days/week. Immediately after daily exercise, subjects were instructed to consume the supplements assigned to each group. In the DTG, after IWT, the methylation increased at 4/6 sites in the promoter region of the NFKB2 gene in the whole blood (all, P < 0.04), with an 18% increase in the average methylation of the 6 sites (P = 0.035). On the other hand, in the PLG, the increase occurred at only 2/6 sites, with no significant increase in the average methylation of the 6 sites. No significant differences were observed in increases in thigh muscle strength or cross-sectional area between the groups (all, P > 0.2). Altogether, dried tofu supplementation during IWT likely enhanced the methylation of the NFKB2 gene more than IWT alone, without detectably enhanced increases in thigh muscle strength or cross-sectional area.

Knee pain in young adult women- associations with muscle strength, body composition and physical activity

BACKGROUND

Knee pain is studied mostly in older age groups, although in young adults it may be an indicator of future impaired musculoskeletal health. Therefore, the aim of this study was to examine the longitudinal association between knee pain and thigh muscle strength in young adult women and to explore the associations between muscle strength, body composition, physical activity and knee pain.

METHODS

The PEAK-25 cohort consists of women aged 25 at baseline (N=1064). At the 10-year follow-up n=728 attended for DXA-measured body composition and muscle strength assessment and n=797 answered the questionnaire on health and lifestyle. Independent samples t-test was used to compare women with and without knee pain, Spearman correlation was used to test the longitudinal association between strength and knee pain.

RESULTS

Knee pain was reported by one third of the women at follow-up (n=260, 33%), although physical activity levels were similar in those with and without pain (high level 50 vs 45 % (p= 0.18). Body composition differed, however. Women with knee pain had higher BMI (25.6 vs 24.1), fat mass index (9.2 vs 8.2) and % total body fat mass (34.7 vs 33.2). Simultaneously, they had lower % lean mass (total body 61.5 vs 62.8; legs 20.6 vs 21.0) and lower thigh muscle strength (extensors 184.9 vs 196.8, flexors 96.6 vs 100.9, p<0.05), but slightly higher hamstrings-to -quadriceps ratio (0.53 vs 0.51, p=0.04). Muscle strength at baseline weakly correlated with knee pain at follow-up (extensor r_s= -0.04; flexor -0.02, p>0.2). Overweight women had higher absolute thigh muscle strength, but lower weight-adjusted strength than normal weight women (p<0.001). Leg lean mass explained 26-34% of the variation in muscle strength and adjustment for physical activity level had little effect.

CONCLUSION

Knee pain is already common among women in their mid-thirties. Lower thigh muscle strength in the mid-twenties was not associated with future knee pain, however women with knee pain tended to have lower thigh muscle strength and a body composition of higher body fat combined with lower lean mass. Maintaining a healthy body composition and adequate thigh muscle strength may be beneficial for knee joint health.