Background: Lengthening contractions (LC) are commonly prescribed for Physical Rehabilitation (PR) to strengthen muscles, alleviate pain, and for prevention of musculoesketal
injuries; however, unaccustomed LC induces Delayed Onset Muscle Soreness (DOMS). The study of functional impact of DOMS has been limited to describe the decline on maximal isometric contraction, but
Muscular Work (MW) and Time to Peak Torque (TPT) has not been examined yet. The purpose of this study was to describe the changes induced by a session of LC on isometric and isokinetic peak torque
(IPT and KPT, respectively), MW, TPT and DOMS under two conditions (Maximal Dynamic Contraction (MDC) and from standing to sitting position) in healthy and physical active young men.
Methods: 16 men performed 200 LC of the quadriceps at 120º/s (20 sets, 10 reps). DOMS was assessed with Visual Analog Scale (VAS) under the two conditions. IPT, KPT, MW and TPT,
measured during a isometric and isokinetic contraction (60°/s). Muscle damage was confirmed by Creatine Kinase activity (CK). Muscular Perfomance (MP) and DOMS were assessed at baseline (BL), 48h and
96h post-exercise. Comparisons between assessment moments were analyzed by ANCOVA. DOMS and CK activity had to be transformed to normalize its distribution. Data is shown as mean±SEM. The Universidad
Industrial de Santander Ethics Committee approved the study.
Results: Relative to BL measurements, IPT decreased by 1.35±0.1-fold at 48h and 1.18±0.1-fold at 96h, (BL:183.4±10.34Nm; 48h:144.6±11.14Nm; 96h:174±16Nm, p=0.03); similarly, KPT
decreased by 1.56±0.2-fold and 1.33±0.14-fold, at 48h and 96h, respectively (BL:194.3±12.23Nm; 48h:138.3±12.17Nm; 96h:168.1±15.8Nm, p=0.005). MW decreased by 1.49±0.1-fold at 48h and 1.28±0.1-fold at
96h (BL: 229.1±13.41J; 48h:167.1±12.7J; 96h:199.7±17.54J, p=0.005). No change was detected on neither isometric nor isokinetic TTP at any time-point. Relative to BL, DOMS intensity during a MDC
increased by 14.4±10.8-fold at 48h, and 13.7±10.2-fold at 96h (BL:19.3±3.7mm; 48h:44.6±6.5mm; 96h:27.6±5.51mm, p=0.002); DOMS during the functional activity, increased by 25.3±13.1-fold at 48h and
9.5±3.4-fold at 96h (BL:6.6±1.9mm to 35.7±7.4mm at 48h, and to 18.6±5.3mm at 96h, p<0.01). CK activity level increased by 2.0±0.2-fold at 48h, and 3.1±0.7-fold at 96h (BL:244.3±57.5U/L to
429.1±97.3U/L at 48h and to 640.9±161.2U/L at 96h, p=0.04).
Conclusions: Our results show that LC induce significant decline on muscular performance 48h post-exercise, which are maintained at 96h post. The decline in muscular performance is
not only on IPT, but also on the MW which has greater implications on muscle function. These MP alterations are accompanied by DOMS, which might also have a direct impact on muscle force production.
This results should be considered on the design of PR programs and for studies that examine muscle damage and repair.