Effects of prolonged running performed at the intensity corresponding to the onset of blood lactate accumulation, on maximum isokinetic strength in active non-athletic individuals

Abstract

Objective: The objective of this study was to analyze the effects of prolonged continuous running performed at the intensity corresponding to the onset of blood lactate accumulation (OBLA), on the peak torque of the knee extensors, analyzed in relation to different types of contraction and movement velocities in active individuals. Method: Eight men (23.4 ± 2.1 years; 75.8 ± 8.7 kg; 171.1 ± 4.5 cm) participated in this study. First, the subjects performed an incremental test until volitional exhaustion to determine the velocity corresponding to OBLA. Then, the subjects returned to the laboratory on two occasions, separated by at least seven days, to perform five maximal isokinetic contractions of the knee extensors at two angular velocities (60 and 180°.s-1) under eccentric and concentric conditions. Eccentric peak torque (EPT) and Concentric peak torque (CPT) were measured at each velocity. One session was performed after a standardized warm-up period (5 min at 50% VO 2 max). The other session was performed after continuous running at OBLA until volitional exhaustion. These sessions were conducted in random order. Results: There was a significant reduction in CPT only at 60°.s-1 (259.0 ± 46.4 and 244.0 ± 41.4 N.m). However, the reduction in EPT was significant at 60°.s-1 (337.3 ± 43.2 and 321.7 ± 60.0 N.m) and 180°.s-1 (346.1 ± 38.0 and 319.7 ± 43.6 N.m). The relative strength losses after the running exercise were significant different between contraction types only at 180°.s-1. Conclusion: We can conclude that, in active individuals, the reduction in peak torque after prolonged continuous running at OBLA may be dependent on the type of contraction and angular velocity.

Can the high intensity interval running in slope affect concurrently explosive strength performance?

“…The results observed by the present study diverge from some evidence in the literature (1)(2)(3) . The loss of isoinertial, isokinetic or power strength after performing an aerobic activity has been reported mainly in long-term running (2,3,6) , but also on protocols of interval exercise (22,23) ,or in submaximal vertical jumps until exhaustion (4) .In these studies, the main mechanisms responsible for the reduction in strength and power immediately after aerobic exercise appear to be related to metabolic production and / or to repeated eccentric loads influencing the SSC mechanisms, or even generating structural damages (4,12) . This phenomenon does not seem to have been reproduced in our study.…”

“…It is possible that a longer aerobic activity, with repeated eccentric loads, could induce the reduction of muscle spindle sensitivity with the concomitant reduction of SSC capacity (1) . It is observed, therefore, that the activity time adopted in the present study ranged from four to five times less than the TTime of exercise reported by authors who showed a significant reduction in strength or power (2,3,6) , (34.6 min and 18.5 min, respectively for C1% and C10%). It is possible that the time of activity administered was insufficient, explaining the absence of competing effects between the activities.…”

“…Physical exercise programs are typically composed of activities directed to the development of different physical abilities, usually stimulated in the same session. When long-term aerobic activities precede isokinetic, isotonic, or explosive strength exercises, deleterious effects on performance seem to be observed (1)(2)(3) .…”

Heavy-intensity aerobic exercise affects the isokinetic torque and functional but not conventional hamstrings:quadriceps ratios

“…N = 16. Decreases in torque after running exercise have been described in the recent literature under isometric (Millet et al, 2003a;Racinais et al, 2007) and isokinetic conditions (Denadai et al, 2007). Several explanations can be associated to these decreases (central and peripheral factors), which probably are influenced by the exercise duration.…”

“…In addition, the velocity of isokinetic contractions may affect the interpretation of the results, considering the differences between slow and fast velocities (Gerodimos et al, 2003;Hewett et al, 2007). Muscular strength can be affected when a prolonged task/exercise is performed, with decreases in strength after short high-intensity running (Skof and Strojnik, 2006;Denadai et al, 2007) or exercises performed with longer durations, such marathon (Millet et al, 2003a). These strength impairments may be related to the muscular fatigue process, which after a running exercise, depending on the intensity and duration can result from decreases in the muscle glycogen content and creatine phosphate concentrations associated with changes in metabolites accumulation (K + , Na + , H + , Pi and lactate).…”