Explosive-type strength training may alter kinetics and neuromuscular activity during stair ascent in elderly women. This may improve functional ability. Nineteen women (69.7 ± 3.4 yr) were randomly allocated to strength training (TG; twice per wk, 12 wk) or a control group (CG). Stair ascent was assessed at self-chosen (AFV), standardized (ASV), and maximal velocity (AMV) pre- and posttraining. Ground-reaction force (GRF) and EMG quantified kinetics and neuromuscular activity. After training, TG increased AMV and AFV velocity by 8% (p = .02) and 17% (p = .007), respectively (TG vs. CG; p < .05). This was accompanied by elevated rectus femoris EMG (from 21% to 48%, p < .047). At AFV, TG increased GRF first peak force 4% (p = .047), and CG increased second peak force 5% (p = .036). Muscle coactivation remained unaltered in both groups. Explosive-type strength training led to enhanced stair-climbing performance at maximal and self-chosen speed, reflecting an improved functional ability.
Anders Holsgaard-Larsen, Paolo Caserotti, Lis Puggaard and Per Aagaard
Lasse Ishøi, Per Aagaard, Mathias F. Nielsen, Kasper B. Thornton, Kasper K. Krommes, Per Hölmich and Kristian Thorborg
Purpose: To investigate the association between hamstring muscle peak torque and rapid force capacity (rate of torque development, RTD) vs sprint performance in elite youth football players. Methods: Thirty elite academy youth football players (16.75 [1.1] y, 176.9 [6.7] cm, 67.1 [6.9] kg) were included. Isometric peak torque (in Newton meters per kilogram) and early- (0–100 ms) and late- (0–200 ms) phase RTD (RTD100, RTD200) (in Newton meters per second per kilogram) of the hamstring muscles were obtained as independent predictor variables. Sprint performance was assessed during a 30-m-sprint trial. Mechanical sprint variables (maximal horizontal force production [F H0, in Newtons per kilogram], maximal theoretical velocity [V 0, in meters per second], maximal horizontal power output [Pmax, in watts per kilogram]) and sprint split times (0–5, 0–15, 0–30, and 15–30 m, in seconds) were derived as dependent variables. Subsequently, linear-regression analysis was conducted for each pair of dependent and independent variables. Results: Positive associations were observed between hamstring RTD100 and F H0 (r 2 = .241, P = .006) and Pmax (r 2 = .227, P = .008). Furthermore, negative associations were observed between hamstring RTD100 and 0- to 5-m (r 2 = .206, P = .012), 0- to 15-m (r 2 = .217, P = .009), and 0- to 30-m sprint time (r 2 = .169, P = .024). No other associations were observed. Conclusions: The present data indicate that early-phase (0–100 ms) rapid force capacity of the hamstring muscles plays an important role for acceleration capacity in elite youth football players. In contrast, no associations were observed between hamstring muscle function and maximal sprint velocity. This indicates that strength training focusing on improving early-phase hamstring rate of force development may contribute to enhance sprint acceleration performance in this athlete population.
Martin G. Jorgensen, Uffe Laessoe, Carsten Hendriksen, Ole B.F. Nielsen and Per Aagaard
The aims of the current study were to examine the intrarater intersession reproducibility of the Nintendo Wii agility and stillness tests and explore the concurrent validity in relation to gold-standard force-plate analysis. Within-day intersession reproducibility was examined in 30 older adults (age 71.8 ± 5.1 yr). No systematic test–retest differences were found for the Wii stillness test; however, the Wii agility test scores differed systematically between test sessions (p < .05). The Wii stillness test yielded a test–retest ICC of .86 (95% CI 0.74–0.93), CV of 6.4%, LOA of 11.0, and LOA% of 17.9%. Likewise for the Wii agility test ICC was .73 (95% CI 0.50-0.86), CV 5.3%, LOA 1.8, and LOA% of 14.6%. Wii stillness scores correlated to force plate measures (r = .65–.82, p < .01), reflecting moderate to excellent validity. In conclusion, it appears that the Wii stillness test represents a low-cost, objective, reproducible, and valid test of undisturbed postural balance in community-dwelling older adults.
Markus D. Jakobsen, Mikkel Brandt, Emil Sundstrup, Kenneth Jay, Per Aagaard and Lars L. Andersen
This study evaluates the between-day reliability of a newly developed trunk perturbation test and compares mechanical response during known and unknown conditions. Mechanical trunk responses were measured in 17 female subjects during unloading and loading perturbations of the abdomen (A: preloaded abdomen condition) and low back (B: preloaded back condition). The loading perturbation increased the preload from 5.5 kg to a 10.9 kg pull on the trunk whereas the unloading perturbation decreased the pull from 5.5 kg to 0.1 kg. A sequence of loading (known), unloading (known), and randomized loading/unloading (unknown) perturbations were performed for A and B. Between-day reliability of stopping time, trunk displacement, and velocity was quantified using intraclass correlation coefficients (ICCs). ICCs were good to excellent for all loading and unloading measures during the known (0.70–0.98) and unknown (0.64–0.94) perturbations of A and B. In general, larger trunk displacements were seen after the unknown perturbations compared with the known perturbation. The method may be used as a diagnostic tool for screening workers who are in risk of future work-related low back injuries.
Igor Setuain, Mikel Izquierdo, Fernando Idoate, Eder Bikandi, Esteban M. Gorostiaga, Per Aagaard, Eduardo L. Cadore and Jesús Alfaro-Adrián
The muscular function restoration related to the type of physical rehabilitation followed after anterior cruciate ligament reconstruction (ACLR) using autologous hamstring tendon graft in terms of strength and cross-sectional area (CSA) remain controversial.
To analyze the CSA and force output of quadriceps and hamstring muscles in subjects following either an Objective Criteria-Based Rehabilitation (OCBR) algorithm or the usual care (UCR) for ACL rehabilitation in Spain, before and 1 year after undergoing an ACLR.
Longitudinal clinical double-blinded randomized controlled trial.
Sports-medicine research center.
40 recreational athletes (30 male, 10 female [24 ± 6.9 y, 176.55 ± 6.6 cm, 73.58 ± 12.3 kg]).
Both groups conducted differentiated rehabilitation procedures after ACLR. Those belonging to OCBR group were guided in their recovery according to the current evidence-based principles. UCR group followed the national conventional approach for ACL rehabilitation.
Main Outcome Measures:
Concentric isokinetic knee joint flexor-extension torque assessments at 180°/s and Magnetic Resonance Imaging (MRI) evaluations were performed before and 12 months after ACLR. Anatomical muscle CSA (mm2) was assessed, in Quadriceps, Biceps femoris, Semitendinous, Semimembranosus, and Gracilis muscles at 50% and 70% femur length.
Reduced muscle CSA was observed in both treatment groups for Semitendinosus and Gracilis 1 year after ACLR. At 1-year follow-up, subjects allocated to the OCBR demonstrated greater knee flexor and extensor peak torque values in their reconstructed limbs in comparison with patients treated by UCR.
Objective atrophy of Semitendinosus and Gracilis muscles related to surgical ACLR was found to persist in both rehabilitation groups. However, OCBR after ACLR lead to substantial gains on maximal knee flexor strength and ensured more symmetrical anterior-posterior laxity levels at the knee joint.