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Previous studies have shown that sodium bicarbonate ingestion may enhance intense exercise performance, but may also cause severe gastrointestinal distress. The purpose of this study was to determine whether a modified sodium bicarbonate (SB) ingestion protocol would elevate serum bicarbonate concentration more than previous methods without causing gastrointestinal distress. In randomized order, seven (5 men, 2 women) elite middle-distance runners ingested either placebo, Modified SB (600 mg·kg− 1 over 19.5 h), or Acute SB (300 mg·kg− 1) in opaque gelatin capsules. Baseline and post-ingestion blood samples were analyzed for bicarbonate, pH, sodium, hematocrit, and lactate. Repeated measures ANOVA (2 time points × 3 conditions) were analyzed to determine differences in serum bicarbonate, lactate, sodium, blood pH, and hematocrit. Gastrointestinal distress was assessed via self-report on a Likert scale of 1–10. Simple (condition) and repeated (time) within-participant contrasts were used to determine the location of any statistically significant main and interaction effects (p ≤ 0.05). Both Modified SB (7.6 mmol·L− 1, p

Research demonstrates an inverse relationship between the range of motion of selected joint movements (flexibility) and running economy. Since stretching exercises have been shown to increase joint range of motion, stretching exercises may be contraindicated for endurance running performance. Hence, this study investigated the influence of a 10-week program of stretching exercises on the oxygen costs of a 10 min sub-maximal (approx. 70% peak VO(2)) treadmill run. Thirty-two (16 female, 16 male) physically active, treadmill accommodated, college students participated in the study. All participants maintained their current activity level, with half the participants (8 female, 8 male) adding a 40 min, 3 days per week session of thigh and calf muscle stretching exercises. After 10 weeks, the stretching group (STR) exhibited a significant (P0.05) increase (3.1+/-2.2 cm) in the sit-and-reach, while the non-stretching group (CON) experienced no significant (P0.05) change (0.0+/-0.4 cm). However, neither the STR nor the CON exhibited a significant (P0.05) change in the O(2) cost for the submaximal run. It is concluded, therefore, that a chronic stretching program does not necessarily negatively influence running economy.

(1998). Acute Muscle Stretching Inhibits Maximal Strength Performance. Research Quarterly for Exercise and Sport: Vol. 69, No. 4, pp. 411-415.

The purpose of this investigation was to determine, for a planar, multijoint throwing skill, if the relative contributions of the components of the net joint moment (NJM) at the elbow and shoulder change after practice. Each participant (N = 7) performed 200 throwing trials equally distributed across 5 consecutive days. Each participant threw a 0.15-kg ball as far as possible using the nondominant arm while the motion of the throwing arm was restrained to a horizontal plans. From video data and body segment inertial estimations, NJMs and NJM components (i.e., generalized muscle moments and motion-dependent moments) were calculated for selected early and late practice trials. Performance (throwing distance) showed an expected improvement from early to late practice. The dynamics analysis indicated that participants increased average NJMs and NJM components at both joints. However, the relative contribution of NJM components, expressed as ratios of those components to the NJM at each joint, did not change after extended practice. Restraining the throwing arm to a horizontal plane may partly explain why no changes were found in the relative contributions of NJM components. The lack of change in moment ratios support a motor strategy of scaling joint moments for faster movements.

AB Introduction: Consistent, moderate-to-vigorous-intensity exercise has been associated with a lower risk of upper respiratory tract infection (URI). However, the molecular basis for this apparent protection has not yet been fully resolved. Host-derived lipids such as cholesteryl esters (CE) have emerged as important effector molecules of innate defense against infections. Here, we compared antimicrobial CE in nasal fluid before and after moderate-to-vigorous exercise between active and inactive subjects. Methods: Nasal fluid was collected from 14 healthy, recreationally active subjects (32 +/- 11 yr, 7 men and 7 women) and 14 healthy, inactive subjects (25 +/- 3 yr, 7 men and 7 women) before and after treadmill exercise at 70% heart rate reserve. Nasal fluid was analyzed for lysozyme, cholesteryl linoleate (CL), cholesteryl arachidonate (CA), and albumin (Alb) concentrations. Results: Baseline concentrations (mean +/- SEM, inactive vs active) of lysozyme (117.7 +/- 31.1 vs 122.9 +/- 15.5 [mu]g[middle dot]mL-1), CL + CA (15.3 +/- 1.8 vs 26.2 +/- 10.05 [mu]g[middle dot]mL-1), and Alb (156.6 +/- 54.5 vs 126.9 +/- 32.8 [mu]g[middle dot]mL-1) were similar to previously reported levels and did not differ significantly between study groups. However, postexercise, CL + CA concentration was significantly lower in inactive compared with active subjects (7.8 +/- 1.5 vs 20.1 +/- 4.8 [mu]g[middle dot]mL-1, P = 0.036) dropping below the antimicrobial effective range. Once adjusted to Alb concentrations, the changes were no longer significant, suggesting that plasma transudation accounted for the increased CA + CL concentration postexercise in the active group relative to the inactive group. Conclusions: Moderate-to-vigorous aerobic exercise acutely decreases the antimicrobial CE response in inactive subjects but does not modify baseline levels of CE between active and inactive subjects. This suggests that compared with active individuals, inactive individuals may be at greater risk for upper respiratory tract infection immediately postexercise

During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically larger than the sum of forces exerted by the same muscles bilaterally. This phenomenon is known as the bilateral deficit (BLD), and it is suggested that this deficit is due to neural inhibition. It remains unclear, however, whether such inhibition is mediated by supraspinal mechanisms or by reflex pathways at the level of spinal cord. To further study the origin of likely neural influences, we tested for the presence of BLD under the condition of reflexive force generation. Force output and integrated electromyogram (iEMG) (quadriceps femoris) were measured in 17 male participants after initiation of the myotatic patellar reflex under unilateral and bilateral conditions. A significant BLD of 9.26 ± 1.19 ( P = 0.004) and 16.76 ± 4.69% ( P = 0.001) was found for force and iEMG, respectively. However, because similar findings were not evident during maximal isometric knee extensions, it is difficult to predict the contribution of a spinal mechanism to the BLD under the condition of maximal voluntary activation.

Previous research has shown that an acute bout of passive muscle stretching can diminish performance in certain movements where success is a function of maximal force and/or power output. Two possible mechanisms that might account for such findings are a change in active musculotendinous stiffness and a depression of muscle activation. To investigate the likelihood of these two mechanisms contributing to a post-stretch reduction in performance, we examined the acute effects of stretching on the active stiffness and muscle activation of the triceps surae muscle group during maximal single-joint jumps with movement restricted to the ankle joint. Ten males performed both static (SJ) and countermovement (CMJ) jumps before and after passively stretching the triceps surae. Electrical activity of the triceps surae during each jump was determined by integrating electromyographic recordings (IEMG) over the course of the movement. Triceps surae musculotendinous stiffness was calculated before and after stretching using a technique developed by Cavagna (1970). Following stretching, a significant decrease [mean (SD) 7.4 (1.9)%; P0.05] in jump height for the CMJ occurred, but for the SJ, no significant ( P0.05) change in jump height was found. A small but significant decrease [2.8 (1.24)%; P0.05] in stiffness was noted, but the magnitude of this change was probably not sufficient for it to have been a major factor underlying the decline in CMJ performance. Paradoxically, after stretching, the SJ exhibited a significant ( P0.05) decrease in IEMG, but the IEMG for the CMJ remained unchanged ( P0.05). It appears that an acute bout of stretching can impact negatively upon the performance of a single-joint CMJ, but it is unlikely that the mechanism responsible is a depression of muscle activation or a change in musculotendinous stiffness.

Recent research has shown that a regimen of stretching provides an acute inhibition of maximal force production by the stretched muscle group. To further characterize this phenomenon, the effect of an acute stretching regimen on maximal isokinetic knee-extension torque at 5 specific movement velocities (1.05,1.57, 2.62, 3.67, and 4.71 rad·s−1) was examined in 10 men and 5 women (22–28 years). Each person's 5 baseline maximal isokinetic knee-extension torques (dominant leg) were measured on a Cybex NORM dynamometer. Following the baseline torque measurements, the participants stretched the dominant quadriceps for 15 minutes using 1 active and 3 passive stretching exercises. Once the stretching exercises were completed, the maximal torque measurements were repeated. Poststretch maximal torque at 1.05 rad·s−1 was significantly reduced (p 0.05). It appears, therefore, that the deleterious impact of stretching activities on maximal torque production might be limited to movements performed at relatively slow velocities.