Efficacy of a tart cherry juice blend in preventing the symptoms of muscle damage.

BACKGROUND: Numerous antioxidant and anti-inflammatory agents have been identified in tart cherries. OBJECTIVE: To test the efficacy of a tart cherry juice blend in preventing the symptoms of exercise induced muscle damage. METHODS: This was a randomised, placebo controlled, crossover design. Fourteen male college students drank 12 fl oz of a cherry juice blend or a placebo twice a day for eight consecutive days. A bout of eccentric elbow flexion contractions (2 x 20 maximum contractions) was performed on the fourth day of supplementation. Isometric elbow flexion strength, pain, muscle tenderness, and relaxed elbow angle were recorded before and for four days after the eccentric exercise. The protocol was repeated two weeks later with subjects who took the placebo initially, now taking the cherry juice (and vice versa). The opposite arm performed the eccentric exercise for the second bout to avoid the repeated bout protective effect. RESULTS: Strength loss and pain were significantly less in the cherry juice trial versus placebo (time by treatment: strength p<0.0001, pain p = 0.017). Relaxed elbow angle (time by treatment p = 0.85) and muscle tenderness (time by treatment p = 0.81) were not different between trials. CONCLUSIONS: These data show efficacy for this cherry juice in decreasing some of the symptoms of exercise induced muscle damage. Most notably, strength loss averaged over the four days after eccentric exercise was 22% with the placebo but only 4% with the cherry juice.

Force recovery after eccentric exercise in males and females.

In this study we investigated force loss and recovery after eccentric exercise, and further characterized profound losses in muscle function (n = 192 subjects--98 males, 94 females; population A). Maximal voluntary contractile force (MVC) was assessed before, immediately after, and at 36 and 132 h after eccentric exercise. Two groups were then established (A1 and A2). Group A1 demonstrated a > 70% reduction in MVC immediately after exercise, but were recovering at 132 h after exercise. These subjects performed a follow-up MVC 26 days later (n = 32). Group A2 demonstrated a > 70% reduction in MVC immediately post-exercise, but still exhibited a > 65% reduction in force at 132 h post-exercise; these subjects also performed a follow-up MVC every 7 days until full recovery was established (n = 9). In population A, there was a 57% reduction in MVC immediately post-exercise and a 67% recovery by 132 h post-exercise (P < 0.01), with no significant gender differences (P > 0.05). In group A1, although more females (two-thirds) showed large force losses after exercise, these females demonstrated greater %MVC recovery at 132 h post-exercise (59% vs 44%) and at 26 days post-exercise (93% vs 81%) compared to the males. In group A2, MVC recovery occurred between 33 and 47 days post-exercise. In conclusion, 21% of all subjects showed a delayed recovery in MVC after high-force eccentric exercise. Although there were no significant gender differences in force loss, a disproportionately larger number of females demonstrated force reductions of > 70%. However, their recovery of force was more rapid than that observed for the males who also demonstrated a > 70% force loss.

Effect of ketoprofen on muscle function and sEMG activity after eccentric exercise.

PURPOSE: This study examined whether ketoprofen, a nonsteroidal anti-inflammatory drug, attenuated muscle soreness (SOR), improved maximal isometric force (MIF) recovery, and/or altered myoelectric activity after high-force eccentric exercise. METHODS: 48 subjects were randomly assigned to one of four groups: CON: no exercise/no drug (N = 12); PLA: exercise + placebo (N = 12); TRT-100: exercise + 100 mg oral ketoprofen (N = 12); and TRT-25: exercise + 25 mg oral ketoprofen (N = 12). PLA, TRT-100, and TRT-25 were administered in a double-blind fashion. Baseline measurements of SOR, MIF, and surface electromyographic (EMG) amplitude were taken, and PLA, TRT-100, and TRT-25 performed 50 maximal eccentric contractions of the elbow flexors; 36 h later, subjects reporting moderate soreness were given ketoprofen or placebo and SOR measures were taken hourly for 8 h. EMG amplitude was assessed during MIF before dosing and again 8 h later and during submaximal contractions of 5%, 10%, and 20% of MIF before dosing and hourly for 8 h. RESULTS: Eccentric exercise increased myoelectric activity during submaximal force measurements in PLA, TRT-100, and TRT-25 in all conditions. Ketoprofen had no effect on reducing this increase in EMG activity. Ketoprofen attenuated perceived SOR (P < 0.05) and enhanced MIF recovery (P < 0.05) compared with placebo. TRT-100 and TRT-25 demonstrated 10% and 19% reductions in SOR, respectively, and 16% and 9% increases in MIF, respectively, whereas PLA demonstrated a 1% increase in SOR and 9% decrease in MIF over 8 h. CONCLUSION: Ketoprofen treatment after muscle damaging exercise reduces muscle soreness and improves force recovery.

Activity and immobilization after eccentric exercise: I. Recovery of muscle function.

PURPOSE: The purpose of the present study was to determine whether activity would affect the recovery of muscle function after high-force eccentric exercise of the elbow flexors. METHODS: Twenty-six male volunteers were randomly assigned to one of three groups for a 4-d treatment period: immobilization (N = 9), control (N = 8), and light exercise (N = 9). Relaxed arm angle (RANG), flexed arm angle (FANG), maximal isometric force (MIF), and perceived muscle soreness (SOR) were obtained for 3 consecutive days pre-exercise (baseline), immediately post-exercise, and for 8 consecutive days after the 4-d treatment period (recovery). During the treatment period, the immobilization group had their arm placed in a cast and supported in a sling at 90 degrees. The control group had no restriction of their arm activity. The light exercise group performed a daily exercise regimen of 50 biceps curls with a 5-lb dumbbell. RESULTS: All subjects showed a prolonged decrease in RANG, increase in FANG, loss in MIF, and increase in SOR in the days after eccentric exercise. During recovery, there was no significant interaction observed among groups over time in RANG (P > 0.05) or FANG (P > 0.05), but there was a significant interaction observed among groups over time in both MIF (P < 0.01) and SOR (P < 0.01). Recovery of MIF was facilitated by light exercise and immobilization, whereas recovery from SOR was facilitated by light exercise and delayed by immobilization. CONCLUSIONS: The recovery of MIF in both the light exercise and immobilization groups suggests that more than one mechanism may be involved in the recovery of isometric force after eccentric exercise.

Activity and immobilization after eccentric exercise: II. Serum CK.

PURPOSE: The purpose of the present study was to examine the effect of muscle activity level on serum creatine kinase (CK) activity after high-force eccentric exercise of the elbow flexors. METHODS: Twenty-six male volunteers were randomly assigned to one of three groups for a 4-d treatment period after exercise: immobilization (N = 9), control (N = 8), and light exercise (N = 9). During the treatment period, the immobilization group had their arm casted and supported in a sling at 90 degrees. The control group had no restriction of their arm activity. The light exercise group performed a daily exercise regimen of 50 biceps curls with a 5-lb dumbbell. Serum CK activity was obtained by venipuncture for three consecutive days before eccentric exercise and during the 4-d treatment period. To quantify activity of the arm, CSA (Computer Science and Applications, Inc.) activity-monitoring devices were worn. RESULTS: Serum CK measurements revealed that there was a significant group by time interaction in the analysis of variance (P < 0.05). Peak serum CK activity of the immobilized group (668 IU) was lower than either the control (4230 IU) or light exercise (2740 IU) group. During the treatment period, activity level among the three groups was significantly different from each other (P < 0.001): 529 counts x min(-1) for the immobilization group, 944 counts x min(-1) for the control group, and 1334 counts x min(-1) for the light exercise group. CONCLUSIONS: These results suggest that immobilization of exercised damaged muscle during recovery significantly blunted serum CK activity, which may be due to attenuated removal of CK from the muscle and/or decrease lymphatic transport.

Adverse events associated with eccentric exercise protocols: six case studies.

PURPOSE: Rhabdomyolysis is a condition characterized by muscle damage and degeneration of muscle cells after strenuous, overexertion exercise. Although the incidence of severe rhabdomyolysis is rare, this condition can be dangerous and even fatal. Eccentric exercise protocols are currently being used to induce and study mild forms of muscle damage. However, serious adverse events can occur in these laboratory investigations. The purpose of this report was to expose some of the adverse events resulting from performance of eccentric exercise protocols to study muscle damage in humans. METHODS: The following case studies involved an eccentric exercise protocol where two sets of 25 maximal eccentric actions of the elbow flexors were performed, separated by a 5-min rest period. RESULTS: Case reports are presented that reveal prolonged losses in the ability of the muscle to generate force lasting 43-47 d, extreme swelling of the exercised arm lasting several weeks, and greatly elevated serum creatine kinase levels. CONCLUSIONS: Although adverse events resulting from eccentric exercise are rare, our laboratory has observed a 3% incidence rate during the past year. Investigators should be knowledgeable of the sequelae of events that are associated with muscle damage after high-force eccentric exercise and take appropriate precautions.

Etiology of exercise-induced muscle damage.

Muscle damage is caused by strenuous and unaccustomed exercise, especially exercise involving eccentric muscle contractions, where muscles lengthen as they exert force. Damage can be observed both directly at the cellular level and indirectly from changes in various indices of muscle function. Several mechanisms have been offered to explain the etiology of the damage/repair process, including mechanical factors such as tension and strain, disturbances in calcium homeostasis, the inflammatory response, and the synthesis of stress proteins (heat shock proteins). Changes in muscle function following eccentric exercise have been observed at the cellular level as an impairment in the amount and action of transport proteins for glucose and lactate/H+, and at the systems level as an increase in muscle stiffness and a prolonged loss in the muscle's ability to generate force. This paper will briefly review factors involved in the damage/repair process and alterations in muscle function following eccentric exercise.

Cross-validation of three jump power equations.

UNLABELLED: The vertical jump-and-reach score is used as a component in the estimation of peak mechanical power in two equations put forth by Lewis and Harman et al. PURPOSE: The purpose of the present study was to: 1) cross-validate the two equations using the vertical jump-and-reach test, 2) develop a more accurate equation from a large heterogeneous population, 3) analyze gender differences and jump protocols, and 4) assess Predicted Residual Sum of Squares (PRESS) as a cross-validation procedure. METHODS: One hundred eight college-age male and female athletes and nonathletes were tested on a force platform. They performed three maximal effort vertical jumps each of the squat jump (SJ) and countermovement jump (CMJ) while simultaneously performing the vertical jump-and-reach test. Regression analysis was used to predict peak power from body mass and vertical jump height. RESULTS: SJ data yielded a better power prediction equation than did CMJ data because of the greater variability in CMJ technique. The following equation was derived from SJ data: Peak Power (W) = 60.7x (jump height cm]) +45.3x(body mass [kg])-2055. This equation revealed greater accuracy than either the Lewis or previous Harman et al. equations and underestimated peak power by less than 1%, with a SEE of 355.0 W using SJ protocol. The use of one equation for both males and females resulted in only a slight (5% of power output) difference between genders. Using CMJ data in the SJ-derived equation resulted in only a 2.7% overestimation of peak power. Cross-validation of regression equations using PRESS reveals accurate and reliable R2 and SEE values. CONCLUSIONS: The SJ equation is a slightly more accurate equation than that derived from CMJ data. This equation should be used in the determination of peak power in place of the formulas developed by both Harman et al. and Lewis. Separate equations for males and females are unnecessary.