PurposeForce production frequently remains depressed for several hours or even days after various types of strenuous physical exercise. We hypothesized that the pattern of force changes during the first hour after exercise can be used to reveal muscular mechanisms likely to underlie the decline in muscle performance during exercise as well as factors involved in the triggering the prolonged force depression after exercise.MethodsNine groups of recreationally active male volunteers performed one of the following types of exercise: single prolonged or repeated short maximum voluntary contractions (MVCs); single or repeated all-out cycling bouts; repeated drop jumps. The isometric force of the right quadriceps muscle was measured during stimulation with brief 20 and 100 Hz trains of electrical pulses given before and at regular intervals for 60 min after exercise.ResultsAll exercises resulted in a prolonged force depression, which was more marked at 20 Hz than at 100 Hz. Short-lasting (≤2 min) MVC and all-out cycling exercises showed an initial force recovery (peak after ~ 5 min) followed by a secondary force depression. The repeated drop jumps, which involve eccentric contractions, resulted in a stable force depression with the 20 Hz force being markedly more decreased after 100 than 10 jumps.ConclusionsIn accordance with our hypothesis, the results propose at least three different mechanisms that influence force production after exercise: (1) a transiently recovering process followed by (2) a prolonged force depression after metabolically demanding exercise, and (3) a stable force depression after mechanically demanding contractions.

One hundred drop jumps were performed at maximal intensity every 20 s in 12 untrained subjects (UT), 9 sprinters (S) and 10 long-distance runners (LDR). Muscle contraction force (P20, P50) induced by percutaneous electrical stimulation (20 Hz and 50 Hz, respectively) as well as maximal voluntary contraction force and the height of vertical jumps performed in different ways decreased (P<0.05) and was not restored to the initial value 20 min post exercise. There was a marked increase in low frequency fatigue (LFF) in all the groups studied as substantiated by a significant decrease in the ratio of P20/P50 immediately after exercise as well as 20 min post exercise compared to pre exercise values (P<0.05). However, low frequency fatigue was similar in UT, S and LDR. The jump height of the sprinters during counter-movement jump and drop jump at 90 degrees decreased to a smaller extent compared to jumps performed by LDR and UT. Muscle pain did not differ between UT, S and LDR at 24 h post exercise. The present data indicate that endurance training status as well as prevalence of muscle fibres of the slow type does not decrease muscle resistance to LFF nor accelerate the recovery of muscle contraction force following maximal, intermittent stretch-shortening cycle exercise.

The aim of the study was to investigate the manifestation of potentiation and fatigue as well as the coexistence of these phenomena at different muscle lengths during a 24-hour period after a sprint cycling for 30 s. Material and methods. Twelve healthy untrained men (mean age 23.6±1.7 years) took part in the experiment. The contractility of quadriceps muscle was studied before (Initial) and 2, 5, 30, 60 min and 24 h after exercise via the electrically evoked contractions at 1, 15, 50 Hz and maximal voluntary contractions at short and long muscle length. Results. 1) In early, fast-recovery phase (within the first 5 min), muscle force evoked by electrical stimulation of 1, 15, 50 Hz was restored at short muscle length, conversely at long length (Initial vs. 5 min: 15 Hz and 50 Hz, both P<0.05), whereas maximal voluntary contraction force was still suppressed at both muscle lengths; 2) in the second phase (from 5 min to 30–60 min), muscle force decreased at low- and high-frequency stimulations and was more expressed at low-frequency stimulation and at short muscle length than that at long length, but the maximum voluntary contraction force recovered to initial; 3) in long-lasting phase (within 24 hours), 15 Hz force was still suppressed at both muscle lengths. Conclusion. A bimodal recovery of contractility of the quadriceps following sprint cycling for 30 s is determined by the concomitant complex interaction of mechanisms enhancing (potentiation) and suppressing (fatigue) contractile potential of the muscle.

Cerebral palsy is one of the leading causes of movement and posture disorders. Recently, Vibration, as a treatment method in clinical practice has been used as a complementary approach. The aim of this intervention was to determine the effect of vibration in addition to conventional therapy on spasticity, range of motion and gross motor functions in children with cerebral palsy. A total of 20 children with spastic diplegic cerebral palsy (7-10 years old) were randomly divided into two equal groups (conventional therapy-Control group, and conventional therapy plus Vibration-Vibration group), and participated in a 3-week physiotherapy program. The same exercise program was prescribed for children of both groups; frequency of intervention-five times a week, one session lasted for 45 min. Children in the vibration group apart from conventional therapy also received treatment on a special vibration equipment set at 15 Hz frequency. Ashwort scale was used to assess spasticity, goniometry-range of motion, and Gross Motor Function Measure (GMFM) 88 domain-to assess standing (D) and mobility (E-walking, jumping, and running) functions. Both interventions significantly increased range of motion, decreased spasticity in legs and improved standing and mobility functions (0.05). No statistical differences were found between the two groups after interventions.

Vibroacoustic Therapy (VT) is a very distinct form of treatment. The purpose of this study was to determine the effect of vibroacoustic therapy on low back pain management in adolescents. A total of 40 adolescents (13-18 years old) were randomly divided into two equal groups (exercise-control group, and exercise and vibroacoustic therapy-vibroacoustic group), and participated in a 3-week physiotherapy program for back pain management. The participants in both groups performed the same exercise program five times per week. The participants in the vibroacoustic group apart from exercise also received treatment on a special vibro chair set at 4-8 Hz frequency for relaxation. Music was heard through the headphones. Standard tests (Oswestry disability index and the visual analogue pain scale) to assess low back pain were used before and after the intervention to monitor changes. The intensity of low back pain significantly decreased in both groups after the intervention (< 0.05), but there were no significant differences between the groups in low back pain management in adolescents.