Balance control during stair descent on compliant surface is associated with knee flexor and ankle plantar flexor strength in older adults.

Balance and lower limb strength deficits are associated with a high incidence of falls in older adults. This study investigated the association between balance control during and after stair descent onto a compliant surface and lower limb strength. Thirty-five women and 14 men participated in this study. Stair descent time, mean center of pressure velocity in anteroposterior and mediolateral direction during stair descent (CoP VAP and CoP VML), and CoP velocity in the first 5 s of restabilization phase (CoP V5) were evaluated. Bilateral strength of the knee flexors and extensors, and ankle plantar and dorsal flexors was evaluated. Spearman correlation analysis with Bonferroni correction yielded a significant association between the strength of the knee flexors on the trailing limb and stair descent time in women (r = 0.502, p = 0.002, R2 = 0.246). The same analysis in men revealed a significant association between the strength of the knee flexors on the trailing limb and CoP VAP (r = -0.820, p < 0.001, R2 = 0.280) and CoP VML (r = -0.697, p = 0.006, R2 = 0.359). The strength of the ankle plantar flexors on the trailing limb was significantly associated with stair descent time (r = 0.684, p = 0.007, R2 = 0.429) and CoP VAP (r = -0.723, p = 0.003, R2 = 0.408) in men. Stair descent balance control is associated with knee flexion strength on trailing limb in women, and with ankle plantar flexion and knee flexion strength on the same limb in men.

Effect of aging on the association between ankle muscle strength and the control of bipedal stance.

Previous studies reported a significant association between postural control and lower-limb strength of several muscle groups, however, they were focused especially on knee muscles and ankle plantar and dorsal flexors. The aim of the present study is to examine the correlation between the muscle strength of ankle invertors, evertors, plantar flexors, and dorsal flexors and the control of bipedal stance in young and older adults. Thirty one young (aged 22.8 ± 2.6 years) and thirty one older adults (aged 70.5 ± 7.2 years) voluntarily participated in this study. Ankle muscle strength was evaluated by an isokinetic dynamometer. Normalized peak torque and work were averaged for four repetitions and for both lower limbs. The control of bipedal stance was evaluated by the sample entropy derived from an accelerometer placed on the lumbar spine while the subject stood on a foam pad with eyes open. Results showed significant age-related differences in ankle muscle strength and sample entropy in medial-lateral direction. More interestingly, the correlation between ankle muscle strength and the sample entropy was significantly different between young and older adults. Indeed, no significant correlation was observed in the younger adults. Conversely, in the older adults, the work of the ankle evertors positively correlated with sample entropy in the medial-lateral direction during bipedal stance (r = 0.36), whereas the peak torque and work of the dorsal flexors were significantly correlated with sample entropy in the anterior-posterior direction during bipedal stance (r = 0.44 for both variables). In the young adults, results suggest that, standing on foam with eyes open is a relatively easy postural task that does not require the full ankle muscle strength capacity. Taken together, the present findings suggest that older adults have a different association between ankle muscle strength and the sample entropy during bipedal stance.

Reliability of Ankle⁻Foot Complex Isokinetic Strength Assessment Using the Isomed 2000 Dynamometer.

For quantifying muscle strength in clinical and research practice, establishing the reliability of measurements, specifically to the procedures used, is essential for credible findings. The objective was to establish the reliability of isokinetic measurement of ankle plantar and dorsal flexors (PF/DF) and invertors and evertors (INV/EV) on an IsoMed 2000 dynamometer. Twenty healthy subjects (10 males, 10 females, mean age: 23.1 ± 3.1 years) completed an isokinetic measurement session. The intraclass correlation coefficient (ICC) and standard error of measurement were assessed for peak torque and work of ankle PF/DF (concentric and eccentric) and INV/EV (concentric) for the preferred and nonpreferred limb. Standardized isokinetic measurements of reciprocal PF/DF and INV/EV muscle actions were associated with ICC ranging from 0.77 to 0.98 for the majority of observed parameters. The exception was work in the eccentric mode in the ankle DF and peak torque in the concentric mode in the ankle INV on the preferred limb, where ICC ranged from 0.64 to 0.71. The IsoMed 2000 isokinetic dynamometer can be reliably employed in future studies for reciprocal ankle PF/DF and INV/EV assessment in healthy adult subjects after implementation of a familiarization session.

Muscle Strength Variations of Knee Joint Muscles in Elite Female Handball Players after Pre-Season Conditioning.

Monitoring seasonal variations in strength performance and the relative risk of injury indicators related to strength of hamstring (H) and quadriceps (Q) in female elite athletes is beneficial for the training process. The aim of this study was to examine and compare the level of muscle strength, the conventional ratio (HCONC/QCONC) as well as two functional and strength ratios reflecting the movement of knee extension (HECC/QCONC) and flexion (HCONC/QECC), and the bilateral percentage strength deficit (BSD) in elite female handball players. The concentric and eccentric isokinetic peak torque was measured at an angular velocity of 60°/s on three occasions (in-season cessation, 4 weeks of rest followed by 4 weeks of individual conditioning and 6 weeks of group conditioning) in eleven female handball players (age: 23.1 ± 3.5 years, body height: 1.73 ± 0.6 m). According to ANOVA results, the BSD of H muscles in the concentric mode decreased between the in-season cessation and the end of the pre-season, and HCONC/QCONC increased at the beginning of the pre-season and at the end of the pre-season in comparison with inseason cessation measurement. The effect size analyses showed that the off-season rest followed by 10 weeks of the conditioning programme increased Q and H strength in comparison with the previous season with a large effect. Coaches should include progressive conditioning in the pre-season phase to decrease the bilateral strength deficit and to support further conditioning development.