Age and spatio-temporal variations in food resources modulate stress-immunity relationships in three populations of wild roe deer.

Living in variable and unpredictable environments, organisms face recurrent stressful situations. The endocrine stress response, which includes the secretion of glucocorticoids, helps organisms to cope with these perturbations. Although short-term elevations of glucocorticoid levels are often associated with immediate beneficial consequences for individuals, long-term glucocorticoid elevation can compromise key physiological functions such as immunity. While laboratory works highlighted the immunosuppressive effect of long-term elevated glucocorticoids, it remains largely unknown, especially in wild animals, whether this relationship is modulated by individual and environmental characteristics. In this study, we explored the co-variation between integrated cortisol levels, assessed non-invasively using faecal cortisol metabolites (FCMs), and 12 constitutive indices of innate, inflammatory, and adaptive immune functions, in wild roe deer living in three populations with previously known contrasting environmental conditions. Using longitudinal data on 564 individuals, we further investigated whether age and spatio-temporal variations in the quantity and quality of food resources modulate the relationship between FCMs and immunity. Negative covariation with glucocorticoids was evident only for innate and inflammatory markers of immunity, while adaptive immunity appeared to be positively or not linked to glucocorticoids. In addition, the negative covariations were generally stronger in individuals facing harsh environmental constraints and in old individuals. Therefore, our results highlight the importance of measuring multiple immune markers of immunity in individuals from contrasted environments to unravel the complex relationships between glucocorticoids and immunity in wild animals. Our results also help explain conflicting results found in the literature and could improve our understanding of the link between elevated glucocorticoid levels and disease spread, and its consequences on population dynamics.

Covariation between glucocorticoids, behaviour and immunity supports the pace-of-life syndrome hypothesis: an experimental approach.

The biomedical literature has consistently highlighted that long-term elevation of glucocorticoids might impair immune functions. However, patterns are less clear in wild animals. Here, we re-explored the stress-immunity relationship considering the potential effects of behavioural profiles. Thirteen captive roe deer (Capreolus capreolus) were monitored over an eight-week period encompassing two capture events. We assessed how changes in baseline faecal cortisol metabolite (FCM) concentrations following a standardized capture protocol and an immune challenge using anti-rabies vaccination affected changes in 13 immune parameters of innate and adaptive immunity, and whether these changes in baseline FCM levels and immune parameters related to behavioural profiles. We found that individuals with increased baseline FCM levels also exhibited increased immunity and were characterized by more reactive behavioural profiles (low activity levels, docility to manipulation and neophilia). Our results suggest that the immunity of large mammals may be influenced by glucocorticoids, but also behavioural profiles, as it is predicted by the pace-of-life syndrome hypothesis. Our results highlight the need to consider covariations between behaviour, immunity and glucocorticoids in order to improve our understanding of the among-individual variability in the stress-immunity relationships observed in wildlife, as they may be underpinned by different life-history strategies.

Decline in telomere length with increasing age across nonhuman vertebrates: A meta-analysis.

The prediction that telomere length (TL) shortens with increasing age is a major element in considering the role of telomeres as a key player in evolution. While telomere attrition is found in humans both in vitro and in vivo, the increasing number of studies reporting diverse age-specific patterns of TL challenges the hypothesis of a universal decline of TL with increasing age. Here, we performed a meta-analysis to estimate the relationship between TL and age across 175 estimates encompassing 98 species of vertebrates. We found that, on average, TL does decline with increasing age during adulthood. However, this decline was weak and variable across vertebrate classes, and we also found evidence for a publication bias that might weaken our current evidence of decreasing TL with increasing age. We found no evidence for a faster decline in TL with increasing age when considering the juvenile stage (from birth to age at first reproduction) compared to the adult stage. Heterogeneity in TL ageing rates was explained by the method used to measure telomeres: detectable TL declines with increasing age were found only among studies using TRF with in-gel hybridisation and qFISH methods, but not in studies using qPCR and Southern blot-based TRF methods. While we confirmed that TL declines with increasing age in most adult vertebrates, our results identify an influence of telomere measurement methodology, which highlights the need to examine more thoroughly the effect of the method of measurement on TL estimates.

Maternal effects shape offspring physiological condition but do not senesce in a wild mammal.

In vertebrates, offspring survival often decreases with increasing maternal age. While many studies have reported a decline in fitness-related traits of offspring with increasing maternal age, the study of senescence in maternal effect through age-specific changes in offspring physiological condition is still at its infancy. We assessed the influence of maternal age and body mass on offspring physiological condition in two populations of roe deer (Capreolus capreolus) subjected to markedly different environmental conditions. We measured seven markers to index body condition and characterize the immune profile in 86 fawns which became recently independent of their known-aged mothers. We did not find striking effects of maternal age on offspring physiological condition measured at 8 months of age. This absence of evidence for senescence in maternal effects is likely due to the strong viability selection observed in the very first months of life in this species. Offspring physiological condition was, on the other hand, positively influenced by maternal body mass. Between-population differences in environmental conditions experienced by fawns also influenced their average body condition and immune phenotype. Fawns facing food limitation displayed lower values in some markers of body condition (body mass and haemoglobin levels) than those living in good quality habitat. They also allocated preferentially to humoral immunity, contrary to those living in good conditions, which allocated more to cellular response. These results shed a new light on the eco-physiological pathways mediating the relationship between mother's mass and offspring condition.

Short-term telomere dynamics is associated with glucocorticoid levels in wild populations of roe deer.

While evidence that telomere length is associated with health and mortality in humans and birds is accumulating, a large body of research is currently seeking to identify factors that modulate telomere dynamics. We tested the hypothesis that high levels of glucocorticoids in individuals under environmental stress should accelerate telomere shortening in two wild populations of roe deer (Capreolus capreolus) living in different ecological contexts. From two consecutive annual sampling sessions, we found that individuals with faster rates of telomere shortening had higher concentrations of fecal glucocorticoid metabolites, suggesting a functional link between glucocorticoid levels and telomere attrition rate. This relationship was consistent for both sexes and populations. This finding paves the way for further studies of the fitness consequences of exposure to environmental stressors in wild vertebrates.

The influence of early-life allocation to antlers on male performance during adulthood: Evidence from contrasted populations of a large herbivore.

To secure mating opportunities, males often develop and maintain conspicuous traits that are involved in intrasexual and/or intersexual competition. While current models of sexual selection rely on the assumption that producing such traits is costly, quantifying the cost of allocating to secondary sexual traits remains challenging. According to the principle of allocation, high energy allocation to growth or sexual traits in males should lead to reduced energy allocation to the maintenance of cellular and physiological functions, potentially causing them to age faster, with impaired survival. We evaluated the short-term and delayed consequences of energy allocation to antlers early in life in two contrasted populations of roe deer, Capreolus capreolus. Although most males mate successfully for the first time in their fourth year, antlers are grown annually from the first year of life onwards. We tested the prediction that a high level of allocation to antler growth during the first two years of life should lead to lower body mass, antler size and survival during the early and late prime stages, as well as to reduced longevity overall. Growing and carrying long antlers during the first years of life was not associated with any detectable cost in the late prime stage. The positive association between antler growth in early life and adult body mass instead supports that fawn antler acts as an honest signal of phenotypic quality in roe deer. For a given body mass, yearling males growing longer antlers displayed impaired performance during their late prime. We also found a trend for a short-term survival cost of allocation to relative antler length during the second year of life. Yearling males that grow long antlers relative to their mass might display a fast life-history tactic. We argue that differential allocation to secondary sexual traits generates a diversity of individual trajectories that should impact population dynamics.

Drought-induced starvation of aardvarks in the Kalahari: an indirect effect of climate change.

Aardvarks (Orycteropus afer) are elusive burrowing mammals, predominantly nocturnal and distributed widely throughout Africa except for arid deserts. Their survival may be threatened by climate change via direct and indirect effects of increasing heat and aridity. To measure their current physiological plasticity, we implanted biologgers into six adult aardvarks resident in the semi-arid Kalahari. Following a particularly dry and hot summer, five of the study aardvarks and 11 other aardvarks at the study site died. Body temperature records revealed homeothermy (35.4-37.2°C) initially, but heterothermy increased progressively through the summer, with declining troughs in the nychthemeral rhythm of body temperature reaching as low as 25°C before death, likely due to starvation. Activity patterns shifted from the normal nocturnal to a diurnal mode. Our results do not bode well for the future of aardvarks facing climate change. Extirpation of aardvarks, which play a key role as ecosystem engineers, may disrupt stability of African ecosystems.

Age-dependent associations between telomere length and environmental conditions in roe deer.

Telomere length (TL) represents a promising biomarker of overall physiological state and of past environmental experiences, which could help us understand the drivers of life-history variation in natural populations. A growing number of studies in birds suggest that environmental stress or poor environmental conditions are associated with shortened TL, but studies of such relationships in wild mammals are lacking. Here, we compare leucocyte TL from cross-sectional samples collected from two French populations of roe deer which experience different environmental conditions. We found that, as predicted, TL was shorter in the population experiencing poor environmental conditions but that this difference was only significant in older individuals and was independent of sex and body mass. Unexpectedly, the difference was underpinned by a significant increase in TL with age in the population experiencing good environmental conditions, while there was no detectable relationship with age in poor conditions. These results demonstrate both the environmental sensitivity and complexity of telomere dynamics in natural mammal populations, and highlight the importance of longitudinal data to disentangle the within- and among-individual processes that generate them.

Uncoupling effect of palmitate is exacerbated in skeletal muscle mitochondria of sea-acclimatized king penguins (Aptenodytes patagonicus).

In king penguin juveniles, the environmental transition from a terrestrial to a marine habitat, occurring at fledging, drastically stimulates lipid catabolism and the remodelling of muscle mitochondria to sustain extensive swimming activity and thermoregulation in the cold circumpolar oceans. However, the exact nature of these mechanisms remains only partially resolved. Here we investigated, in vitro, the uncoupling effect of increasing doses of fatty acids in pectoralis muscle intermyofibrillar mitochondria isolated, either from terrestrial never-immersed or experimentally cold water immersed pre-fledging king penguins or from sea-acclimatized fledged penguins. Mitochondria exhibited much greater palmitate-induced uncoupling respiration and higher maximal oxidative capacity after acclimatization to marine life. Such effects were not reproduced experimentally after repeated immersions in cold water, suggesting that the plasticity of mitochondrial characteristics may not be primarily driven by cold exposure per se but by other aspects of sea acclimatization.

Microchip transponder thermometry for monitoring core body temperature of antelope during capture.

Hyperthermia is described as the major cause of morbidity and mortality associated with capture, immobilization and restraint of wild animals. Therefore, accurately determining the core body temperature of wild animals during capture is crucial for monitoring hyperthermia and the efficacy of cooling procedures. We investigated if microchip thermometry can accurately reflect core body temperature changes during capture and cooling interventions in the springbok (Antidorcas marsupialis), a medium-sized antelope. Subcutaneous temperature measured with a temperature-sensitive microchip was a weak predictor of core body temperature measured by temperature-sensitive data loggers in the abdominal cavity (R(2)=0.32, bias >2 °C). Temperature-sensitive microchips in the gluteus muscle, however, provided an accurate estimate of core body temperature (R(2)=0.76, bias=0.012 °C). Microchips inserted into muscle therefore provide a convenient and accurate method to measure body temperature continuously in captured antelope, allowing detection of hyperthermia and the efficacy of cooling procedures.

Variation in the link between oxygen consumption and ATP production, and its relevance for animal performance.

It is often assumed that an animal's metabolic rate can be estimated through measuring the whole-organism oxygen consumption rate. However, oxygen consumption alone is unlikely to be a sufficient marker of energy metabolism in many situations. This is due to the inherent variability in the link between oxidation and phosphorylation; that is, the amount of adenosine triphosphate (ATP) generated per molecule of oxygen consumed by mitochondria (P/O ratio). In this article, we describe how the P/O ratio can vary within and among individuals, and in response to a number of environmental parameters, including diet and temperature. As the P/O ratio affects the efficiency of cellular energy production, its variability may have significant consequences for animal performance, such as growth rate and reproductive output. We explore the adaptive significance of such variability and hypothesize that while a reduction in the P/O ratio is energetically costly, it may be associated with advantages in terms of somatic maintenance through reduced production of reactive oxygen species. Finally, we discuss how considering variation in mitochondrial efficiency, together with whole-organism oxygen consumption, can permit a better understanding of the relationship between energy metabolism and life history for studies in evolutionary ecology.

Oxidative phosphorylation efficiency, proton conductance and reactive oxygen species production of liver mitochondria correlates with body mass in frogs.

Body size is a central biological parameter affecting most biological processes (especially energetics) and the mitochondrion is a key organelle controlling metabolism and is also the cell's main source of chemical energy. However, the link between body size and mitochondrial function is still unclear, especially in ectotherms. In this study, we investigated several parameters of mitochondrial bioenergetics in the liver of three closely related species of frog (the common frog Rana temporaria, the marsh frog Pelophylax ridibundus and the bull frog Lithobates catesbeiana). These particular species were chosen because of their differences in adult body mass. We found that mitochondrial coupling efficiency was markedly increased with animal size, which led to a higher ATP production (+70%) in the larger frogs (L. catesbeiana) compared with the smaller frogs (R. temporaria). This was essentially driven by a strong negative dependence of mitochondrial proton conductance on body mass. Liver mitochondria from the larger frogs (L. catesbeiana) displayed 50% of the proton conductance of mitochondria from the smaller frogs (R. temporaria). Contrary to our prediction, the low mitochondrial proton conductance measured in L. catesbeiana was not associated with higher reactive oxygen species production. Instead, liver mitochondria from the larger individuals produced significantly lower levels of radical oxygen species than those from the smaller frogs. Collectively, the data show that key bioenergetics parameters of mitochondria (proton leak, ATP production efficiency and radical oxygen species production) are correlated with body mass in frogs. This research expands our understanding of the relationship between mitochondrial function and the evolution of allometric scaling in ectotherms.

Estimating resting metabolic rate by biologging core and subcutaneous temperature in a mammal.

Tri-axial accelerometry has been used to continuously and remotely assess field metabolic rates in free-living endotherms. However, in cold environments, the use of accelerometry may underestimate resting metabolic rate because cold-induced stimulation of metabolic rate causes no measurable acceleration. To overcome this problem, we investigated if logging the difference between core and subcutaneous temperatures (ΔTc-s) could reveal the metabolic costs associated with cold exposure. Using implanted temperature data loggers, we recorded core and subcutaneous temperatures continuously in eight captive rabbits (Oryctolagus cuniculus) and concurrently measured their resting metabolic rate by indirect calorimetry, at ambient temperatures ranging from -7 to +25°C. ΔTc-s showed no circadian fluctuations in warm (+23°C) or cold (+5°C) environments implying that the ΔTc-s was not affected by an endogenous circadian rhythm in our laboratory conditions. ΔTc-s correlated well with resting metabolic rate (R(2)=0.77) across all ambient temperatures except above the upper limit of the thermoneutral zone (+25°C). Determining ΔTc-s could therefore provide a complementary approach for better estimating resting metabolic rate of animals within and below their thermoneutral zone. Combining data from accelerometers with such measures of body temperature could improve estimates of the overall field metabolic rate of free-living endotherms.

Ontogeny of non-shivering thermogenesis in Muscovy ducklings (Cairina moschata).

In precocial birds, developing the capacity for early regulatory thermogenesis appears as a fundamental prerequisite for survival and growth in cold environments. However, the exact nature of these processes has not been thoroughly investigated. Several bird species, such as Muscovy ducks (Cairina moschata), develop muscular non-shivering thermogenesis when chronically exposed to cold. The aim of this study was to investigate the age-dependent development of non-shivering thermogenesis in ducklings reared either at thermoneutrality (25°C) or in the cold (4°C). Non-shivering thermogenesis was assessed weekly by simultaneously measuring whole body metabolic heat production and electromyographic activity during shivering at different temperatures ranging from 29°C to 0°C. We found that ducklings reared at thermoneutrality displayed a capacity for non-shivering thermogenesis during the first month of post-hatching life. This thermogenic mechanism increased further in ducklings chronically exposed to a cold environment, but it decreased over time when birds were kept in a thermoneutral environment.

Liver mitochondrial coupling efficiency and its relationship to oxidative capacity and adenine nucleotide translocase content: A comparative study among crocodiles, birds and mammals.

The primary objective of this study was to assess whether adenine nucleotide translocase (ANT) content could be associated with phylogenetic disparities in mitochondrial coupling efficiency, within liver mitochondria obtained from rats, crocodiles, and ducklings. Our measurements included mitochondrial membrane conductance, ANT content, and oxidative phosphorylation fluxes at various steady-state rates. We observed significant variations in liver mitochondrial coupling efficiency across the three species. These variations correlated with interspecific differences in mitochondrial oxidative capacity and, to a lesser extent, the ANT content of liver mitochondria. These findings expand upon previous research by highlighting the pivotal role of oxidative capacity and ANT in modulating mitochondrial efficiency on an interspecific scale.

Metabolic response to lipid infusion in fasting winter-acclimatized king penguin chicks (Aptenodytes patagonicus).

During the cold austral winter, king penguin chicks are infrequently fed by their parents and thus experience severe nutritional deprivation under harsh environmental conditions. These energetic constraints lead to a range of energy sparing mechanisms balanced by the maintenance of efficient thermogenic processes. The present work investigated whether the high thermogenic capacities exhibited by winter-acclimatized king penguin chicks could be related to an increase in lipid substrate supply and oxidation in skeletal muscle, the main site of thermogenesis in birds. To test this hypothesis, we examined i) the effect of an experimental rise in plasma triglyceride on the whole metabolic rate in winter-acclimatized (WA) and de-acclimatized king penguin chicks kept at thermoneutrality (TN), and ii) investigated the fuel preference of muscle mitochondria. In vivo, a perfusion of a lipid emulsion induced a small 10% increase of metabolic rate in WA chicks but not in TN group. In vitro, the oxidation rate of muscle mitochondria respiring on lipid-derived substrate was +40% higher in WA chicks than in TN, while no differences were found between groups when mitochondria oxidized carbohydrate-derived substrate or succinate. Despite an enhanced fuel selection towards lipid oxidation in skeletal muscle, a rise of circulating lipids per se was not sufficient to fully unravel the thermogenic capacity of winter-acclimatized king penguin chicks.

Validation of a field-friendly faeces drying and storage method for quantifying faecal glucocorticoid metabolites in African elephants (Loxodonta africana) opens up new perspectives for conservationists.

Faecal glucocorticoid metabolites (fGCMs) are a relevant means of non-invasively assessing adrenocortical activity and thus, a key physiological stress response in wildlife populations. However, the widespread use of fGCMs as a stress-related biomarker in conservation biology is often hampered by the logistical challenge of storing collected faecal material frozen until it reaches the laboratory for analysis. Although alternative approaches to minimize potential alteration of fGCM composition post-defecation have been recently identified, there is to our knowledge, no satisfactory alternative method established for the preservation of elephant dung. In this study, we validated a field-friendly protocol for dehydrating African elephant faeces samples using a food dehydrator with desiccant and investigated the stability of fGCM concentrations in the dehydrated faeces when stored at ambient temperature. We collected 40 faecal samples from African elephants and compared fGCM concentrations of freeze-dried and dehydrated sample sub-sets. Samples dried in the field showed a slight but significant overall -6% reduction in fGCM concentration compared with frozen control samples. However, fGCM concentrations following field dehydration protocol match those of control samples with high accuracy, as evidenced by the low bias and strong coefficient of determination between the two approaches (R2 = 0.88). In addition, over nearly 2 months, storage time at ambient temperature of the dehydrated samples had no effect on the fGCM concentrations compared with those measured in the control samples (F-statistic = 1.82; P = 0.18). Dehydrating the samples in the field thus provides an easy and cost-effective alternative to freezing, especially when working in remote areas with unstable electrical supply. Our results encourage the widespread use of fGCMs by conservationists as non-invasive means of steroid monitoring of African elephants in the current context of a general increase in wildlife welfare research. Future studies are needed to extend the use of this protocol to other species and to other steroid classes.

Instability of fecal glucocorticoid metabolites at 4°C: Time to freeze matters.

The use of fecal corticosteroid metabolites (FCMs) has proven to be well suited to evaluate adrenocortical activity, a major component of the stress response, particularly in wildlife. As with any tools, confounding factors and drawbacks must be carefully considered. Among them, sample preservation and storage are of particular importance, as they can affect stability of FCMs and lead to biased results and interpretations. Arguably, immediate freezing of fecal samples upon collection is the best practice to preserve FCM integrity, however, for logistical reasons, this condition is rarely feasible in the field. It is generally argued that temporary storage of samples at low above-zero temperature is an acceptable way of preserving samples in the field before freezing them for long-term storage. However, to our knowledge, there is no empirical study that demonstrates the stability of fecal metabolites in samples stored at +4°C. In this study, we collected a fresh fecal sample from 20 captive roe deer, each of which was homogenized and split into three subsamples (60 subsamples in total) to investigate the effects on FCMs levels of temporary storage at +4°C for 24 h and 48 h before freezing versus immediate freezing at -20°C after feces collection. Compared to immediate freezing, mean FCMs levels decreased by 25% every 24 h when feces were stored at +4°C before freezing. The variance of FCMs levels followed the same pattern, leading to a clear reduction in the ability to detect biological effects. Minimizing the storage time at +4°C before freezing should therefore be seriously considered when establishing sampling and storage protocols for feces in the field for adequate hormonal profiling.

Technical validation and a comparison of two methods to quantify individual levels of glucocorticoids in Alpine marmot hair.

Quantification of cortisol concentration in hair has become a promising conservation tool for non-invasive monitoring of "stress" in wild populations, yet this method needs to be carefully validated for each species. The goals of the study were:•Immunologically validate two methods (study 1 and 2 respectively) to extract and quantify cortisol in the hair of wild Alpine marmots.•Compare the amount of cortisol extracted from hair samples using two methods i.e. cut into fine pieces (study 1) and hair samples pulverized using a ball mill (study 2).•Determine the extent to which methods in study 2 could provide individual specific hair cortisol (HC) measures when samples were taken from the same body location. Within and between individual variations in HC levels were examined from multiple hair samples from 14 subjects in study 2. We evaluated if inter-individual variations in HC levels could be explained by sex and age.At least twice the amount of cortisol was obtained per g/hair when samples were pulverized in a ball mill prior to extraction compared to when cut into pieces. Our methods demonstrated intra-individual consistency in HC at a given time point: inter-individual variation in HC was three times larger than within individual variance. Sex and age did not impact HC levels.

Gait analysis after total hip arthroplasty by direct minimally invasive anterolateral approach: A controlled study.

INTRODUCTION: Clinical and functional improvement after minimally invasive total hip arthroplasty (THA) has become increasingly controversial. The minimally invasive anterolateral approach (MIALA) allows rapid recovery resulting in a reduced need for rehabilitation. Alterations in muscle and static balance have previously been demonstrated. Results in the context of quantified gait analysis (QGA) and MIALA compared to an asymptomatic population remain unknown beyond one year postoperatively. Thus, the main objective of this controlled study was to compare the spatiotemporal parameters of gait, obtained using a QGA, beyond one year postoperatively in subjects operated on for THA by MIALA, with a group of asymptomatic subjects of the same age. The secondary objectives of the study were to compare the other QGA and EMG data acquired in operated subjects with asymptomatic subjects. HYPOTHESIS: We hypothesized that QGA and EMG parameters would not normalize beyond one year postoperatively. PATIENTS AND METHODS: Thirty-one subjects were recruited, including 16 patients (68 years old; IQR: 65-70) who underwent MIALA, at 15.5 months postoperatively (IQR: 13-17) and 15 asymptomatic subjects (62 years old; IQR: 61-71). Subjects underwent QGA and maximal isometric muscle force tests on the gluteus medius, gluteus maximus, Tensor Fascia Lata (TFL) and Sartorius muscles. Spatiotemporal gait parameters were the primary endpoint. The other QGA parameters: kinetics (characteristic values of vertical ground reaction forces, peak hip moments) and kinematics (hip joint amplitudes and pelvic mobility in the frontal and sagittal plane) constituted the secondary criteria. RESULTS: Five subjects were excluded for unrestored offset. Walking speed was lower in operated patients (1.03m/s versus 1.18m/s, p=0.005). Maximal isometric muscle force moments were lower in patients operated on for the gluteus maximus and medius as well as the TFL (p<0.005). The vertical ground reaction forces were lower for the operated patients for the loading phase (FzFCmax, p=0.001), the single stance phase (FzSPmin, p=5.05.10-2) and the swing phase (FzTOmax, p=0.0002). The moments were lower in the sagittal plane for the operated patients (0.6N.m for the operated versus 1.1N.m for the asymptomatic, p=0.02). The pelvic amplitudes in the sagittal plane were lower for operated patients (3.3° versus 7.2°, p=0.05). DISCUSSION: Our hypothesis appears to be validated. Gait deficits persisted beyond one year postoperatively after THA with MIALA. A decrease in walking speed, maximal isometric muscle force of the gluteus medius and gluteus maximus and TFL was observed, as well as a decrease in propulsive force and peak hip moment. Functionally, these results could signify muscle damage following surgery, requiring rehabilitation for improved muscle function. LEVEL OF PROOF: III: Non-randomized controlled trial.