1. Normal subjects performed a step test in which the quadriceps of one leg contracted concentrically while the contralateral muscle contracted eccentrically. 2. Maximal voluntary force and the force: frequency relationship were altered bilaterally as a result of the exercise, the changes being greater in the muscle which had contracted eccentrically. Recovery occurred over 24 h. 3. Electromyographic studies using three sites on each muscle showed an increase in electrical activation during the exercise only in the muscle which was contracting eccentrically. Recovery followed a time course similar to that of the contractile properties. 4. Pain and tenderness developed only in the muscle which had contracted eccentrically. Pain was first noted approximately 8 h after exercise and was maximal at approximately 48 h after exercise, at which time force generation and electrical activation had returned to pre-exercise values. 5. Eccentric contractions cause more profound changes in some aspects of muscle function than concentric contractions. These changes cannot be explained in simple metabolic terms, and it is suggested that they are the result of mechanical trauma caused by the high tension generated in relatively few active fibres during eccentric contractions.

The 2010 Deepwater Horizon (DWH) disaster resulted in large-scale oil contamination of the northern Gulf of Mexico. As part of the Natural Resource Damage Assessment designed to investigate the potential impacts of the DWH oil spill, comprehensive health assessments were conducted on bottlenose dolphins Tursiops truncatus living in oiled bays (Barataria Bay [BB], Louisiana, and Mississippi Sound [MS], Mississippi/Alabama) and a reference bay with no evidence of DWH oil contamination (Sarasota Bay [SB], Florida). As previously reported, multiple health issues were detected in BB dolphins during 2011. In the present study, follow-on capturerelease health assessments of BB dolphins were performed (2013, 2014) and indicated an overall improvement in population health, but demonstrated that pulmonary abnormalities and impaired stress response persisted for at least 4 yr after the DWH disaster. Specifically, moderate to severe lung disease remained elevated, and BB dolphins continued to release low levels of cortisol in the face of capture stress. The proportion of guarded or worse prognoses in BB improved over time, but 4 yr post-spill, they were still above the proportion seen in SB. Health assessments performed in MS in 2013 showed similar findings to BB, characterized by an elevated prevalence of low serum cortisol and moderate to severe lung disease. Prognosis scores for dolphins examined in MS in 2013 were similar to BB in 2013. Data from these follow-on studies confirmed that dolphins living in areas affected by the DWH spill were more likely to be ill; however, some improvement in population health has occurred over time.

Field studies documented increased mortality, adverse health effects, and reproductive failure in common bottlenose dolphins Tursiops truncatus following the Deepwater Horizon (DWH) oil spill. In order to determine the appropriate type and amount of restoration needed to compensate for losses, the overall extent of injuries to dolphins had to be quantified. Simply counting dead individuals does not consider long-term impacts to populations, such as the loss of future reproductive potential from mortality of females, or the chronic health effects that continue to compromise survival long after acute effects subside. Therefore, we constructed a sex-and agestructured model of population growth and included additional class structure to represent dolphins exposed and unexposed to DWH oil. The model was applied for multiple stocks to predict injured population trajectories using estimates of post-spill survival and reproductive rates. Injured trajectories were compared to baseline trajectories that were expected had the DWH incident not occurred. Two principal measures of injury were computed: (1) lost cetacean years (LCY); the difference between baseline and injured population size, summed over the modeled time period, and (2) time to recovery; the number of years for the stock to recover to within 95% of baseline. For the dolphin stock in Barataria Bay, Louisiana, the estimated LCY was substantial: 30 347 LCY (95% CI: 11 511 to 89 746). Estimated time to recovery was 39 yr (95% CI: 24 to 80). Similar recovery timelines were predicted for stocks in the Mississippi River Delta, Mississippi Sound, Mobile Bay and the Northern Coastal Stock.

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