The effect of contrast water therapy on symptoms of delayed onset muscle soreness

This study examined the effect of contrast water therapy (CWT) on the physiological and functional symptoms of delayed onset muscle soreness (DOMS) following DOMS-inducing leg press exercise. Thirteen recreational athletes performed 2 experimental trials separated by 6 weeks in a randomized crossover design. On each occasion, subjects performed a DOMS-inducing leg press protocol consisting of 5 x 10 eccentric contractions (180 seconds recovery between sets) at 140% of 1 repetition maximum (1RM). This was followed by a 15-minute recovery period incorporating either CWT or no intervention, passive recovery (PAS). Creatine kinase concentration (CK), perceived pain, thigh volume, isometric squat strength, and weighted jump squat performance were measured prior to the eccentric exercise, immediately post recovery, and 24, 48, and 72 hours post recovery. Isometric force production was not reduced below baseline measures throughout the 72-hour data collection period following CWT ( approximately 4-10%). However, following PAS, isometric force production (mean +/- SD) was 14.8 +/- 11.4% below baseline immediately post recovery (p < 0.05), 20.8 +/- 15.6% 24 hours post recovery (p < 0.05), and 22.5 +/- 12.3% 48 hours post recovery (p < 0.05). Peak power produced during the jump squat was significantly reduced (p < 0.05) following both PAS (20.9 +/- 13.4%) and CWT (12.8 +/- 8.0%), with the mean reduction in power for PAS being marginally (not significantly) greater than for CWT (effect size = 0.76). Thigh volume measured immediately following CWT was significantly less than PAS. No significant differences in the changes in CK were found; in addition, there were no significant (p > 0.01) differences in perceived pain between treatments. Contrast water therapy was associated with a smaller reduction, and faster restoration, of strength and power measured by isometric force and jump squat production following DOMS-inducing leg press exercise when compared to PAS. Therefore, CWT seems to be effective in reducing and improving the recovery of functional deficiencies that result from DOMS, as opposed to passive recovery.     

Efficacy of lower limb compression and combined treatment of manual massage and lower limb compression on symptoms of exercise-induced muscle damage in women

Strategies to manage the symptoms of exercise-induced muscle damage (EIMD) are widespread, though are often based on anecdotal evidence. The aim of this study was to determine the efficacy of a combination of manual massage and compressive clothing and compressive clothing individually as recovery strategies after muscle damage. Thirty-two female volunteers completed 100 plyometric drop jumps and were randomly assigned to a passive recovery (n = 17), combined treatment (n = 7), or compression treatment group (n = 8). Indices of muscle damage (perceived soreness, creatine kinase activity, isokinetic muscle strength, squat jump, and countermovement jump performance) were assessed immediately before and after 1, 24, 48, 72, and 96 hours of plyometric exercise. The compression treatment group wore compressive tights for 12 hours after damage and the combined treatment group received a 30-minute massage immediately after damaging exercise and wore compression stockings for the following 11.5 hours. Plyometric exercise had a significant effect on all indices of muscle damage (p < 0.05). The treatments significantly reduced decrements in isokinetic muscle strength, squat jump performance, and countermovement jump performance and reduced the level of perceived soreness in comparison with the passive recovery group (p < 0.05). The addition of sports massage to compression after muscle damage did not improve performance recovery, with recovery trends being similar in both treatment groups. The treatment combination of massage and compression significantly moderated perceived soreness at 48 and 72 hours after plyometric exercise (p < 0.05) in comparison with the passive recovery or compression alone treatment. The results indicate that the use of lower limb compression and a combined treatment of manual massage with lower limb compression are effective recovery strategies following EIMD. Minimal performance differences between treatments were observed, although the combination treatment may be beneficial in controlling perceived soreness.     

Time-course of changes in inflammatory response after whole-body cryotherapy multi exposures following severe exercise

The objectives of the present investigation was to analyze the effect of two different recovery modalities on classical markers of exercise-induced muscle damage (EIMD) and inflammation obtained after a simulated trail running race. Endurance trained males (n = 11) completed two experimental trials separated by 1 month in a randomized crossover design; one trial involved passive recovery (PAS), the other a specific whole body cryotherapy (WBC) for 96 h post-exercise (repeated each day). For each trial, subjects performed a 48 min running treadmill exercise followed by PAS or WBC. The Interleukin (IL) -1 (IL-1), IL-6, IL-10, tumor necrosis factor alpha (TNF-α), protein C-reactive (CRP) and white blood cells count were measured at rest, immediately post-exercise, and at 24, 48, 72, 96 h in post-exercise recovery. A significant time effect was observed to characterize an inflammatory state (Pre vs. Post) following the exercise bout in all conditions (p<0.05). Indeed, IL-1β (Post 1 h) and CRP (Post 24 h) levels decreased and IL-1ra (Post 1 h) increased following WBC when compared to PAS. In WBC condition (p<0.05), TNF-α, IL-10 and IL-6 remain unchanged compared to PAS condition. Overall, the results indicated that the WBC was effective in reducing the inflammatory process. These results may be explained by vasoconstriction at muscular level, and both the decrease in cytokines activity pro-inflammatory, and increase in cytokines anti-inflammatory.     

The Effect of Post-Exercise Cryotherapy on Recovery Characteristics: A Systematic Review and Meta-Analysis

The aim of this review and meta-analysis was to critically determine the possible effects of different cooling applications, compared to non-cooling, passive post-exercise strategies, on recovery characteristics after various, exhaustive exercise protocols up to 96 hours (hrs). A total of n = 36 articles were processed in this study. To establish the research question, the PICO-model, according to the PRISMA guidelines was used. The Cochrane’s risk of bias tool, which was used for the quality assessment, demonstrated a high risk of performance bias and detection bias. Meta-analyses of subjective characteristics, such as delayed-onset muscle soreness (DOMS) and ratings of perceived exertion (RPE) and objective characteristics like blood plasma markers and blood plasma cytokines, were performed. Pooled data from 27 articles revealed, that cooling and especially cold water immersions affected the symptoms of DOMS significantly, compared to the control conditions after 24 hrs recovery, with a standardized mean difference (Hedges’ g) of -0.75 with a 95% confidence interval (CI) of -1.20 to -0.30. This effect remained significant after 48 hrs (Hedges’ g: -0.73, 95% CI: -1.20 to -0.26) and 96 hrs (Hedges’ g: -0.71, 95% CI: -1.10 to -0.33). A significant difference in lowering the symptoms of RPE could only be observed after 24 hrs of recovery, favouring cooling compared to the control conditions (Hedges’ g: -0.95, 95% CI: -1.89 to -0.00). There was no evidence, that cooling affects any objective recovery variable in a significant way during a 96 hrs recovery period.     

Effect of aerobic recovery intensity on delayed-onset muscle soreness and strength

ABSTRACT: Tufano, JJ, Brown, LE, Coburn, JW, Tsang, KKW, Cazas, VL, and LaPorta, JW. Effect of aerobic recovery intensity on delayed-onset muscle soreness and strength. J Strength Cond Res 26(10): 2777-2782, 2012-Because of the performance decrements associated with delayed-onset muscle soreness (DOMS), a treatment to alleviate its symptoms is of great interest. The purpose of this study was to investigate the effect of low vs. moderate-intensity aerobic recovery on DOMS and strength. Twenty-six women (22.11 ± 2.49 years; 60.33 ± 8.37 kg; and 163.83 ± 7.29 cm) were split into 3 different groups and performed a DOMS-inducing protocol of 60 eccentric actions of the knee extensors followed by 1 of three 20-minute recovery interventions: moderate-intensity cycling (n = 10), low-intensity cycling (LIC; n = 10), or seated rest (CON; n = 6) after the eccentric protocol. Pain scale (PS), isometric strength (ISO), and dynamic strength (PT) were recorded before (PRE), immediately post (IP), 24- (24h), 48- (48h), 72- (72h), and 96- (96h) hours after exercise. For PT, PRE, 48h, 72h, and 96h were significantly (p < 0.05) greater than IP values but not different from 24h. For PS, IP (4.83 ± 0.36) was greater than that for all other time periods, whereas 24h (2.91 ± 0.42), 48h (2.62 ± 0.53), and 72h (1.97 ± 0.49) were all greater than PRE (0.44 ± 0.19) values. Also, 24h and 48h were not different but were both greater than 72h and 96h (1.13 ± 0.32), whereas 72h was >96h. For ISO, neither CON nor LIC showed any significant difference across time. Moderate-intensity cycling showed no difference between PRE (189.88 ± 40.68), IP (193.75 ± 47.24), 24h (186.52 ± 53.55), or 48h (195.36 ± 55.06), but 72h (210.05 ± 53.57) and 96h (207.78 ± 59.99) were significantly >24h. The 72h was also greater than IP. Therefore, moderate-intensity aerobic recovery may be suggested after eccentric muscle actions.     

Equal volumes of high and low intensity of eccentric exercise in relation to muscle damage and performance

We examined differences in muscle damage and muscle performance perturbations in relation to the same volumes of high (HI) and low intensity (LI) of eccentric exercise. Untrained young healthy men (n = 12) underwent 2 isokinetic quadriceps eccentric exercise sessions, 1 on each randomly selected leg, separated by a 2-week interval. In the first session subjects performed HI exercise (i.e., 12 sets of 10 maximal voluntary efforts). In the second session, volunteers were subjected to continuous exercise of LI (50% of peak torque) until the total work done was approximately equal to that generated during HI. Muscle damage (serum creatine kinase concentration [CK], delayed onset of muscle soreness, and range of motion) and muscle performance (eccentric [EPT] and isometric peak torque [IPT]) indicators were assessed pre-exercise and 24, 48, 72, and 96 hours postexercise. Compared to baseline data, changes in muscle damage indicators were significantly different (p < 0.05) at almost all postexercise time points in both conditions. However, apart from the significant elevation of CK at 24 hours after HI (p < 0.05), no other significant differences were observed between the 2 exercise conditions (p > 0.05). The main finding in relation to muscle performance was that decrements following HI exercise were significantly greater (p < 0.05) compared to LI. Compared with baseline data, the EPT values following HI and LI exercise were as follows: 24 hours, 72.1% vs. 92%; 48 hours, 81.9% vs. 94.8%; 72 hours, 77.7% vs. 100.6%; 96 hours, 86.8% vs. 107.9%. The corresponding data for IPT were as follows: 24 hours, 86.4% vs. 102.8%; 48 hours, 84.2% vs. 107%; 72 hours, 84.8% vs. 109.2%; 96 hours, 86.8% vs. 114.4%. These results indicate that matching volumes of HI and LI eccentric exercise have similar effects on muscle damage, but HI has a more prominent effect on muscle performance.     

Stability of a practical measure of recovery from resistance training

McLester et al. (2003) proposed a practical protocol to determine optimal recovery times between resistance training workouts. For this protocol to be useful, it must be stable. The purpose of this study was to investigate the stability of that protocol. College-aged resistance trained men (n = 10) performed 3 sets to volitional failure using a 10-repetition maximum load for 6 exercises. Recovery was evaluated on 4 occasions by the number of repetitions performed for each individual exercise after recovery periods of 48, 72, 96, and 120 hours in counterbalanced order. To evaluate stability, this procedure was performed twice. The number of repetitions after each recovery interval were compared with initial baseline performances. A priori, adequate stability was defined as 70% of the participants achieving similar recovery duration on both trials. Pooled repetitions over all 6 exercises indicated that 80% of participants returned to baseline strength levels after the same recovery duration for both trials. However, when individual muscle group repetition performance was evaluated, stability varied from 20 to 70%. Variability in rest, nutrition, prior activity, and other factors probably induced instability in individual strength measures, but not sufficiently to influence the aggregate results. Some muscle groups may have greater sensitivity to variations in ecological factors such as these. We believe that the tested protocol may be useful in establishing recovery times for multimuscle group workouts, but not stable enough to be useful in establishing recovery times for individual muscle groups.     

Plyometric exercise increases serum indices of muscle damage and collagen breakdown

The aim of the present study was to examine the effect of acute plyometric exercise on indices of muscle damage and collagen breakdown. Nine untrained men performed an intense bout of plyometric jumping exercises (experimental group) and nine men remained at rest (control group). Seven days before and 24, 48, and 72 hours after plyometric exercise or rest, several physiological and biochemical indices of muscle damage and two biochemical indices of collagen damage were determined. No significant changes in concentric and eccentric peak torque of knee extensors and flexors or flexion and extension range of motion were found after the plyometric exercise. Delayed-onset muscle soreness increased 48 hours after exercise. Creatine kinase increased 48 and 72 hours post exercise, whereas lactate dehydrogenase increased 24, 48, and 72 hours post exercise. Serum hydroxyproline increased 24 hours post exercise, peaked at 48 hours, and remained elevated up to 72 hours post exercise. Hydroxylysine (which was measured only before exercise and at 48 hours) was found increased 48 hours post exercise. No differences were found in any physiological or biochemical index in the control group. Intense plyometric exercise increased muscle damage, delayed-onset muscle soreness, and serum indices of collagen breakdown without a concomitant decrease in the functional capacity of muscles. Hydroxyproline and hydroxylysine levels in serum seem promising measures for describing exercise-induced collagen degradation. Coaches need to keep in mind that by using plyometric activities, despite the increased muscle damage and collagen turnover that follow, it is not necessarily accompanied by decreases in skeletal muscle capacity.     

DIFFERENT RECOVERY METHODS AND MUSCLE PERFORMANCE AFTER EXHAUSTING EXERCISE: COMPARISON OF THE EFFECTS OF ELECTRICAL MUSCLE STIMULATION AND MASSAGE

In this study we assessed the influence of the three different recovery interventions massage (MSG), electrical muscle stimulation (EMS), and passive rest (PR) on lactate disappearance and muscle recovery after exhausting exercise bouts. Twelve healthy male sport students participated in the study. They attended the laboratory on five test days. After measurement of V.O₂max and a baseline Wingate test (WG_b), the three recovery interventions were tested in random counterbalanced order. High intensity exercise, which consisted of six exhausting exercise bouts (interspersed with active recovery), was followed by MSG, EMS or PR application (24 minutes); then the final Wingate test (WG_f) was performed. Lactate, heart rate, peak and mean power, rating of perceived exertion (RPE), and total quality of recovery (TQR) were recorded. In WG_f mean power was significantly higher than in WG_b for all three recovery modalities (MSG 6.29%, EMS 5.33%, PR 4.84% increase, p < 0.05), but no significant differences in mean and peak power were observed between the three recovery modes (p > 0.05). The heart rate response and the changes in blood lactate concentration were identical in all three interventions during the entire protocol (p = 0.817, p = 0.493, respectively). RPE and TQR scores were also not different among the three interventions (p > 0.05). These results provide further evidence that MSG and EMS are not more effective than PR in the process of recovery from high intensity exercise.     

Time course of strength and power recovery after resistance training with different movement velocities

The purpose of this study was to evaluate the time course of strength and power recovery after a single bout of strength training designed with fast and slow contraction velocities. Nineteen male subjects were randomly divided into 2 groups: the slow-velocity contraction (SV) group and the fast velocity contraction (FV) group. Resistance training protocols consisted of 5 sets of 12 repetition maximum (5 × 12RM) with 50 seconds of rest between sets and 2 minutes between exercises. Contraction velocity was controlled by the execution time for each repetition (SV-6 seconds to complete concentric and eccentric phases and for FV-1.5 seconds). Leg Press 45° 1RM (LP 1RM), horizontal countermovement jump (HCMJ), and right thigh circumference (TC) were accessed in 6 distinct moments: base (1 week before exercise), 0 (immediately after exercises), 24, 48, 72, and 96 hours after exercise protocol. The SV and FV presented significant LP 1RM decrements at 0, and these were still evident 24-48 hours postexercise. The magnitude of decline was significantly (p < 0.05) higher for FV. The SV and FV presented significant HCMJ decrements at 0, but only for FV were these still evident 24-72 hours postexercise. The SV and FV presented significant TC increments at 0, and these were still evident 24-48 hours postexercise for SV but for FV it continued up to 96 hours. The magnitude of increase was significantly (p < 0.05) higher for FV. In conclusion, the fast contraction velocity protocol resulted in greater decreases in LP 1RM and HCMJ performance, when compared with slow velocity. The results lead us to interpret that this variable may exert direct influence on acute muscle strength and power generation capacity.     

CHANGES IN MUSCLE DAMAGE MARKERS IN FEMALE BASKETBALL PLAYERS

The aim of the present study was to investigate changes in muscle soreness, blood muscle damage markers, muscle strength and agility following an official basketball match. Eleven elite female professional basketball players (27.4 ± 4.8 years, 179.5 ± 5.5 cm, 72.0 ± 7.8 kg) of a team participated in this study. The official match was the seventh match of the season in the first phase of the Brazilian National Female Basketball Championship. Muscle soreness, plasma creatine kinase activity (CK), and myoglobin concentration (Mb) were determined before and after the match (post-match, 24 and 48 hours after the match). The 1RM strength for bench press and leg press, and the agility T test were assessed before and at 24 and 48 hours after the match. Significant increases in muscle soreness, CK and Mb were observed at 24 and 48 hours post-match (p<0.05). No significant changes in the 1RM strength and T test were detected during recovery (24 and 48 hours after the match). These results suggest that a basketball match induced limited muscle damage with minimal effect on performance during recovery. The small increase in muscle damage markers following a basketball match did not affect strength and agility performance.     

The effect of pomegranate juice supplementation on strength and soreness after eccentric exercise

The purpose of this study was to determine if pomegranate juice supplementation improved the recovery of skeletal muscle strength after eccentric exercise in subjects who routinely performed resistance training. Resistance trained men (n = 17) were randomized into a crossover design with either pomegranate juice or placebo. To produce delayed onset muscle soreness, the subjects performed 3 sets of 20 unilateral eccentric elbow flexion and 6 sets of 10 unilateral eccentric knee extension exercises. Maximal isometric elbow flexion and knee extension strength and muscle soreness measurements were made at baseline and 2, 24, 48, 72, 96, and 168 hours postexercise. Elbow flexion strength was significantly higher during the 2- to 168-hour period postexercise with pomegranate juice compared with that of placebo (main treatment effect; p = 0.031). Elbow flexor muscle soreness was also significantly reduced with pomegranate juice compared with that of placebo (main treatment effect; p = 0.006) and at 48 and 72 hours postexercise (p = 0.003 and p = 0.038, respectively). Isometric strength and muscle soreness in the knee extensors were not significantly different with pomegranate juice compared with those using placebo. Supplementation with pomegranate juice attenuates weakness and reduces soreness of the elbow flexor but not of knee extensor muscles. These results indicate a mild, acute ergogenic effect of pomegranate juice in the elbow flexor muscles of resistance trained individuals after eccentric exercise.     

Effects of whole-body cryotherapy vs. far-infrared vs. passive modalities on recovery from exercise-induced muscle damage in highly-trained runners

Enhanced recovery following physical activity and exercise-induced muscle damage (EIMD) has become a priority for athletes. Consequently, a number of post-exercise recovery strategies are used, often without scientific evidence of their benefits. Within this framework, the purpose of this study was to test the efficacy of whole body cryotherapy (WBC), far infrared (FIR) or passive (PAS) modalities in hastening muscular recovery within the 48 hours after a simulated trail running race. In 3 non-adjoining weeks, 9 well-trained runners performed 3 repetitions of a simulated trail run on a motorized treadmill, designed to induce muscle damage. Immediately (post), post 24 h, and post 48 h after exercise, all participants tested three different recovery modalities (WBC, FIR, PAS) in a random order over the three separate weeks. Markers of muscle damage (maximal isometric muscle strength, plasma creatine kinase [CK] activity and perceived sensations [i.e. pain, tiredness, well-being]) were recorded before, immediately after (post), post 1 h, post 24 h, and post 48 h after exercise. In all testing sessions, the simulated 48 min trail run induced a similar, significant amount of muscle damage. Maximal muscle strength and perceived sensations were recovered after the first WBC session (post 1 h), while recovery took 24 h with FIR, and was not attained through the PAS recovery modality. No differences in plasma CK activity were recorded between conditions. Three WBC sessions performed within the 48 hours after a damaging running exercise accelerate recovery from EIMD to a greater extent than FIR or PAS modalities.     

Time course of strength and echo intensity recovery after resistance exercise in women

The purpose of this study was to evaluate the time course responses of strength, delayed-onset muscle soreness (DOMS), muscle thickness (MT), circumference (CIRC), and ultrasonography echo intensity (EI) after a traditional hypertrophic isoinertial resistance training session in young women. Ten (22.0 ± 3.2 years) healthy, untrained volunteers participated in the study. The resistance exercise session consisted of 4 sets of 10 repetitions at 80% of 1 repetition maximum (1RM) of the dominant arm elbow flexors. Maximum isometric elbow flexion peak torque (PT) at 90°, MT, and EI were recorded for both arms at baseline (PRE), immediately after exercise (0 hours) and at 24, 48, and 72 hours after exercise. Comparisons were made using a 2 × 5 mixed factor analysis of variance. There was a significant (p < 0.05) loss in PT and increase in MT at 0, 24, 48, and 72 hours. In contrast, EI increased only after 24, 48, and 72 hours, not at 0 hours. There were no significant changes in PT, DOMS, MT, and EI in the nondominant (control) arm after the exercise protocol. Our data suggest that after 4 sets of 80% of 1RM of unilateral elbow flexion resistance exercise, nonresistance trained women need >72 hours to fully recover muscle strength, MT, CIRC, and EI. Furthermore, the EI appears to be a sensitive and reliable method to assess MD.     

Mild eccentric exercise increases Hsp72 content in skeletal muscles from adult and late middle-aged rats

The loss of muscle mass with age or sarcopenia contributes to increased morbidity and mortality. Thus, preventing muscle loss with age is important for maintaining health. Hsp72, the inducible member of the Hsp70 family, is known to provide protection to skeletal muscle and can be increased by exercise. However, ability to increase Hsp72 by exercise is intensity-dependent and appears to diminish with advanced age. Thus, other exercise modalities capable of increasing HSP content and potentially preventing the age related loss of muscle need to be explored. The purpose of this study was to determine if the stress from one bout of mild eccentric exercise was sufficient to elicit an increase in Hsp72 content in the vastus intermedius (VI) and white gastrocnemius (WG) muscles, and if the Hsp72 response differed between adult and late middle-aged rats. To do this, 30 adult (6 months) and late middle-aged (24 months) F344BN rats were randomly divided into three groups (n = 6/group): control (C), level exercise (16 m^.min⁻¹) and eccentric exercise (16 m^.min⁻¹, 16 degree decline). Exercised animals were sacrificed immediately post-exercise or after 48 hours. Hematoxylin and Eosin staining was used to assess muscle damage, while Western Blotting was used to measure muscle Hsp72 content. A nested ANOVA with Tukey post hoc analysis was performed to determine significant difference (p < 0.05) between groups. Hsp72 content was increased in the VI for both adult and late middle-aged rats 48 hours after eccentric exercise when compared to level and control groups but no differences between age groups was observed. Hsp72 was not detected in the WG following any type of exercise. In conclusion, mild eccentric exercise can increase Hsp72 content in the rat VI muscle and this response is maintained into late middle-age.     

Muscle Damage following Maximal Eccentric Knee Extensions in Males and Females

Aim

To investigate whether there is a sex difference in exercise induced muscle damage.

Materials and Method

Vastus Lateralis and patella tendon properties were measured in males and females using ultrasonography. During maximal voluntary eccentric knee extensions (12 reps x 6 sets), Vastus Lateralis fascicle lengthening and maximal voluntary eccentric knee extensions torque were recorded every 10° of knee joint angle (20–90°). Isometric torque, Creatine Kinase and muscle soreness were measured pre, post, 48, 96 and 168 hours post damage as markers of exercise induced muscle damage.

Results

Patella tendon stiffness and Vastus Lateralis fascicle lengthening were significantly higher in males compared to females (p<0.05). There was no sex difference in isometric torque loss and muscle soreness post exercise induced muscle damage (p>0.05). Creatine Kinase levels post exercise induced muscle damage were higher in males compared to females (p<0.05), and remained higher when maximal voluntary eccentric knee extension torque, relative to estimated quadriceps anatomical cross sectional area, was taken as a covariate (p<0.05).

Conclusion

Based on isometric torque loss, there is no sex difference in exercise induced muscle damage. The higher Creatine Kinase in males could not be explained by differences in maximal voluntary eccentric knee extension torque, Vastus Lateralis fascicle lengthening and patella tendon stiffness. Further research is required to understand the significant sex differences in Creatine Kinase levels following exercise induced muscle damage.     

Inhibition of Propofol Anesthesia on Functional Connectivity between LFPs in PFC during Rat Working Memory Task

Working memory (WM) refers to the temporary storage and manipulation of information necessary for performance of complex cognitive tasks. There is a growing interest in whether and how propofol anesthesia inhibits WM function. The aim of this study is to investigate the possible inhibition mechanism of propofol anesthesia based on the functional connections of multi-local field potentials (LFPs) and behavior during WM tasks. Adult SD rats were randomly divided into 3 groups: pro group (0.5 mg·kg⁻¹·min⁻¹,2 h), PRO group (0.9 mg·kg⁻¹·min⁻¹, 2 h) and control group. The experimental data were 16-channel LFPs obtained at prefrontal cortex with implanted microelectrode array in SD rats during WM tasks in Y-maze at 24, 48, 72, 96, 120 hours (day 1-day 5) after propofol anesthesia, and the behavior results of WM were recoded at the same time. Directed transfer function (DTF) method was applied to analyze the connections among LFPs directly. Furthermore, the causal networks were identified by DTF. The clustering coefficient (C), network density (D) and global efficiency (E_global) were selected to describe the functional connectivity quantitatively. The results show that: comparing with the control group, the LFPs functional connectivity in pro group were no significantly difference (p>0.05); the connectivity in PRO group were significantly decreased (p<0.05 at 24 hours, p<0.05 at 48 hours), while no significant difference at 72, 96 and 120 hours for rats (p>0.05), which were consistent with the behavior results. These findings could lead to improved understanding the mechanism of inhibition of anesthesia on WM functions from the view of connections among LFPs.     

Parasympathetic nervous activity mirrors recovery status in weightlifting performance after training

Heart rate variability (HRV) and parasympathetic power are closely related to the well-being and health status in humans. The main goal of the study was to determine whether these measures can reflect recovery status after weight training. After a 10-day detraining period, 7 weightlifters were challenged with a 2-hour weight training which elicited approximately fourfold increases in circulating muscle creatine kinase level and protracted pain feeling (p < 0.05). Weightlifting performance was then evaluated 3, 24, 48, and 72 hours after training to determine the degree of recovery from fatigue. Heart rate variability, circulating dehydroepiandrostendione sulfate (DHEA-S), and muscle damage markers were measured before each performance test. An electrocardiogram was recorded for 5 minutes continuously at rest in seated positions. After training, weightlifting performance of the subjects decreased below baseline in paralleled with suppressed parasympathetic power (high-frequency [HF] HRV), whereas sympathetic power (normalized low-frequency HRV) was slightly elevated at 3 hours of recovery (p < 0.05). Both weightlifting performances and parasympathetic power returned to baseline values in 24 hours and further increased above baseline during 48-72 hours of recovery in a similar fashion (p < 0.05). Circulating DHEA-S level dropped at 24 hours (p < 0.05) and returned to normal values by 48 hours. Muscle pain increased at 3 hours after training and remained higher than baseline values for the 72-hour recovery period (p < 0.05). Our data suggest that parasympathetic power, indicated by HF HRV, is able to reflect the recovery status of weightlifters after training.     

Influence of Hypoxic Interval Training and Hyperoxic Recovery on Muscle Activation and Oxygenation in Connection with Double-Poling Exercise

Here, we evaluated the influence of breathing oxygen at different partial pressures during recovery from exercise on performance at sea-level and a simulated altitude of 1800 m, as reflected in activation of different upper body muscles, and oxygenation of the m. triceps brachii. Ten well-trained, male endurance athletes (25.3±4.1 yrs; 179.2±4.5 cm; 74.2±3.4 kg) performed four test trials, each involving three 3-min sessions on a double-poling ergometer with 3-min intervals of recovery. One trial was conducted entirely under normoxic (No) and another under hypoxic conditions (Ho; F_iO₂ = 0.165). In the third and fourth trials, the exercise was performed in normoxia and hypoxia, respectively, with hyperoxic recovery (HOX; F_iO₂ = 1.00) in both cases. Arterial hemoglobin saturation was higher under the two HOX conditions than without HOX (p<0.05). Integrated muscle electrical activity was not influenced by the oxygen content (best d = 0.51). Furthermore, the only difference in tissue saturation index measured via near-infrared spectroscopy observed was between the recovery periods during the NoNo and HoHOX interventions (P<0.05, d = 0.93). In the case of HoHo the athletes’ P_mean declined from the first to the third interval (P < 0.05), whereas P_mean was unaltered under the HoHOX, NoHOX and NoNo conditions. We conclude that the less pronounced decline in P_mean during 3 x 3-min double-poling sprints in normoxia and hypoxia with hyperoxic recovery is not related to changes in muscle activity or oxygenation. Moreover, we conclude that hyperoxia (F_iO₂ = 1.00) used in conjunction with hypoxic or normoxic work intervals may serve as an effective aid when inhaled during the subsequent recovery intervals.