RESUMO
This study investigated the effect of caffeinated chewing gum (GUMCAF) on muscle fatigue (isometric vs. dynamic) after severe-intensity cycling bouts. Fifteen trained male cyclists participated in four visits. Each visit involved two severe-intensity cycling bouts (Δ1 and Δ2) lasting 6 min, separated by a 5-min recovery period. Muscle fatigue was assessed by isometric maximal voluntary knee extension contraction (IMVC) with twitch interpolation technique and dynamically by 7 s all-out cycling sprints. Assessments were performed before GUMCAF (Pre-GUM) and after the cycling bouts (Post-Exercise). GUMCAF and placebo gum (GUMPLA) were administered in a randomized double-blind procedure with participants receiving each gum type (GUMCAF and GUMPLA) during two separate visits. The results showed no significant interaction between gum types and time for the isometric and dynamic measurements (p > 0.05). The percentage change in performance from Pre-GUM to Post-Exercise showed no significant difference between GUMCAF and GUMPLA for either the dynamic-derived TMAX (~ -17.8% and -15.1%, respectively; p = 0.551) or isometric IMVC (~ -12.3% and -17.7%, respectively; p = 0.091) measurements. Moderate to large correlations (r = 0.31-0.51) were found between changes in sprint maximal torque and maximal power output measurements and isometric force, for both gum conditions. GUMCAF was not effective in attenuating muscle force decline triggered by severe-intensity cycling exercises, as measured by both isometric and dynamic methods. The correlations between IMVC and cycling maximal torque and power output suggest caution when interpreting isometric force as a direct measure of fatigue during dynamic cycling exercises.
RESUMO
BACKGROUND: Early-life adversity impacts on the offspring's brain development and is associated with a higher risk of developing age-associated diseases. In particular, perinatal protein malnutrition appears to be one of the most critical nutritional deficiencies affecting the individual's health and survival, but little is known about its effects on the persistence of behavioral alterations throughout life. Thus, the aim of the present study was to investigate how perinatal protein malnutrition impacts on age-related changes in the neuromuscular, cognitive and behavioral functions throughout life in a mouse model. METHODS: One group of CF-1 dams received a normal-protein diet (NP: 20% casein) during gestation and lactation, whereas another group received a low-protein diet (LP: 10% casein). The offspring of both groups were analyzed by means of several behavioral tests at four different ages (young: 6-10 weeks old, mature: 22-26 weeks old, middle age: 39-43 weeks old, and old: 55-59 weeks old). RESULTS: Regarding neuromuscular functions, LP mice showed an early deterioration in muscular strength and a reduction in the body weight throughout life. Regarding behavior, while NP mice showed an age-related reduction of exploratory behavior, LP mice showed a constantly low level of this behavior, as well as high anxiety-like behavior, which remained at high levels throughout life. Regarding cognitive functions, LP mice showed deteriorated working memory at middle age. Finally, LP mice died 3.4 times earlier than NP mice. Analysis of the sex-related vulnerability showed that females and males were equally affected by perinatal protein malnutrition throughout life. CONCLUSION: Our results demonstrate that perinatal protein malnutrition induces enduring and age-related impairment behaviors, which culminate in higher death risk, affecting males and females equally.