Gordon G. Sleivert’s research while affiliated with Government of British Columbia, Canada and other places

Demands of the triathlonTriathlon trainingCharacteristics of triathletes and their relationship to performanceConclusions References

Many musculoskeletal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeletal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions. Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender x side x muscle x time) design with significance set at p < 0.05. There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females. The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.

During the 1990s, emphasis on the health and safety of people who exercise in hot, humid conditions increased and many organizations became aware of the need for protection against heat-related disorders. A practical, pre-cooling strategy applicable to several sporting codes, which is low cost, easy to use, light-weight and which enhances cooling of the human body prior to and following exercise, was developed and tested. Eight males and eight females participated in a maximal oxygen consumption (VO2max) test and four trials: a control (without cooling) and wearing each of three different cooling vests (A, B, C). Vests were worn during the rest, stretch, warm-up (50% VO2max) and recovery stages of the protocol, but not during the 30 min run (70% VO2max). Core and skin temperatures during exercise were reduced (by approximately 0.5 degrees C, rectal; 0.1-1.4 degrees C, abdominal skin temperature) and sweat rates were lower (by approximately 10-23%). Endurance times for running at 95% of VO2max were increased by up to 49 s. Perceptions of the thermal state and skin wetness showed changes to greater levels of satisfaction. Physiological and sensory responses were related to design features of the vests.

To investigate the effects of cold acclimation on the thermal response and neuromuscular function of the hand. Ten healthy subjects [three female, seven male, age (mean +/- SD): 27.9 +/- 7.9 years] immersed their right hand in 8 degrees C water for 30 min, 5 days a week for 3 weeks. On the first and the last day, neuromuscular function of the first dorsal interosseus (FDI) muscle was tested. There was no significant change in maximal voluntary contraction strength or evoked contractile characteristics of the FDI after cold acclimation. Minimum finger temperature decreased significantly from 10.6 +/- 1.2 to 9.3 +/- 0.8 degrees C after 3 weeks (P < 0.01), with most of the decrease occurring after a single exposure. Mean finger temperature dropped significantly from 14.2 +/- 1.9 to 11.7 +/- 1.4 degrees C following cold acclimation (P < 0.05), with 90% of this adaptation occurring after 5 days. Onset time of cold-induced vasodilatation increased from 446 +/- 171 to 736 +/- 384 s (P < 0.05) and the amplitude decreased from 5.3 +/- 3.2 to 2.5 +/- 2.1 degrees C (P < 0.05). This was significantly different from the control group, who immersed their right hand on the first and last days only. These data suggest that cold acclimation does not enhance hand temperature or function but may put the hands at a greater risk of cold injury when exposed to the cold.

This study investigated the relationship between sprint start performance (5-m time) and strength and power variables. Thirty male athletes [height: 183.8 (6.8) cm, and mass: 90.6 (9.3) kg; mean (SD)] each completed six 10-m sprints from a standing start. Sprint times were recorded using a tethered running system and the force-time characteristics of the first ground contact were recorded using a recessed force plate. Three to six days later subjects completed three concentric jump squats, using a traditional and split technique, at a range of external loads from 30-70% of one repetition maximum (1RM). Mean (SD) braking impulse during acceleration was negligible [0.009 (0.007) N/s/kg) and showed no relationship with 5 m time; however, propulsive impulse was substantial [0.928 (0.102) N/s/kg] and significantly related to 5-m time ( r=-0.64, P<0.001). Average and peak power were similar during the split squat [7.32 (1.34) and 17.10 (3.15) W/kg] and the traditional squat [7.07 (1.25) and 17.58 (2.85) W/kg], and both were significantly related to 5-m time ( r=-0.64 to -0.68, P<0.001). Average power was maximal at all loads between 30% and 60% of 1RM for both squats. Split squat peak power was also maximal between 30% and 60% of 1RM; however, traditional squat peak power was maximal between 50% and 70% of 1RM. Concentric force development is critical to sprint start performance and accordingly maximal concentric jump power is related to sprint acceleration.

To determine the effects of deer antler velvet on maximal aerobic performance and the trainability of muscular strength and endurance, 38 active males were randomly assigned in a double-blind fashion to either deer antler velvet extract (n = 12), powder (n = 13), or placebo groups (n = 13). Subjects were tested prior to beginning supplementation and a 10-week strength program, and immediately post-training. All subjects were measured for circulating levels of testosterone, insulin-like growth factor, erythropoietin, red cell mass, plasma volume, and total blood volume. Additionally, muscular strength, endurance, and VO2max were determined. All groups improved 6 RM strength equivalently (41 +/- 26%, p < .001), but there was a greater increase in isokinetic knee extensor strength (30 +/- 21% vs. 13 +/- 15%, p = .04) and endurance (21 +/- 19% vs. 7 +/- 12%, p = .02) in the powder compared to placebo group. There were no endocrine, red cell mass or VO2max changes in any group. These findings do not support an erythropoetic or aerobic ergogenic effect of deer antler velvet. Further, the inconsistent findings regarding the effects of deer antler velvet powder supplementation on the development of strength suggests that further work is required to test the robustness of the observation that this supplement enhances the strength training response and to ensure this observation is not a type I error.