Locally applied heat stress during exercise training may promote adaptations to mitochondrial enzyme activities in skeletal muscle.

There is some evidence for temperature-dependent stimulation of mitochondrial biogenesis; however, the role of elevated muscle temperature during exercise in mitochondrial adaptation to training has not been studied in humans in vivo. The purpose of this study was to determine the role of elevating muscle temperature during exercise in temperate conditions through the application of mild, local heat stress on mitochondrial adaptations to endurance training. Eight endurance-trained males undertook 3 weeks of supervised cycling training, during which mild (~ 40 °C) heat stress was applied locally to the upper-leg musculature of one leg during all training sessions (HEAT), with the contralateral leg serving as the non-heated, exercising control (CON). Vastus lateralis microbiopsies were obtained from both legs before and after the training period. Training-induced increases in complex I (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) and II (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) activities were significantly larger in HEAT than CON. No significant effects of training, or interactions between local heat stress application and training, were observed for complex I-V or HSP70 protein expressions. Our data provides partial evidence to support the hypothesis that elevating local muscle temperature during exercise augments training-induced adaptations to mitochondrial enzyme activity.

Durability of the moderate-to-heavy-intensity transition is related to the effects of prolonged exercise on severe-intensity performance.

PURPOSE: Power output at the moderate-to-heavy-intensity transition decreases during prolonged exercise, and resilience to this has been termed 'durability'. The purpose of this study was to assess the relationship between durability and the effect of prolonged exercise on severe-intensity performance, and explore intramuscular correlates of durability. METHODS: On separate days, 13 well-trained cyclists and triathletes (V̇O2peak, 57.3 ± 4.8 mL kg-1 min-1; training volume, 12 ± 2.1 h week-1) undertook an incremental test and 5-min time trial (TT) to determine power output at the first ventilatory threshold (VT1) and severe-intensity performance, with and without 150-min of prior moderate-intensity cycling. A single resting vastus lateralis microbiopsy was obtained. RESULTS: Prolonged exercise reduced power output at VT1 (211 ± 40 vs. 198 ± 39 W, ∆ -13 ± 16 W, ∆ -6 ± 7%, P = 0.013) and 5-min TT performance (333 ± 75 vs. 302 ± 63 W, ∆ -31 ± 41 W, ∆ -9 ± 10%, P = 0.017). The reduction in 5-min TT performance was significantly associated with durability of VT1 (rs = 0.719, P = 0.007). Durability of VT1 was not related to vastus lateralis carnosine content, citrate synthase activity, or complex I activity (P > 0.05). CONCLUSION: These data provide the first direct support that durability of the moderate-to-heavy-intensity transition is an important performance parameter, as more durable athletes exhibited smaller reductions in 5-min TT performance following prolonged exercise. We did not find relationships between durability and vastus lateralis carnosine content, citrate synthase activity, or complex I activity.

Skeletal muscle proteins involved in fatty acid transport influence fatty acid oxidation rates observed during exercise.

Several proteins are implicated in transmembrane fatty acid transport. The purpose of this study was to quantify the variation in fatty acid oxidation rates during exercise explained by skeletal muscle proteins involved in fatty acid transport. Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to estimate peak whole-body fatty acid oxidation rate (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 2 h of fed-state, moderate-intensity cycling to estimate whole-body fatty acid oxidation during fed-state exercise (FO). Bivariate correlations and stepwise linear regression models of PFO and FO during 0-30 min (early FO) and 90-120 min (late FO) of continuous cycling were constructed using muscle data. To assess the causal role of transmembrane fatty acid transport in fatty acid oxidation rates during exercise, we measured fatty acid oxidation during in vivo exercise and ex vivo contractions in wild-type and CD36 knock-out mice. We observed a novel, positive association between vastus lateralis FATP1 and PFO and replicated work reporting a positive association between FABPpm and PFO. The stepwise linear regression model of PFO retained CD36, FATP1, FATP4, and FABPpm, explaining ~87% of the variation. Models of early and late FO explained ~61 and ~65% of the variation, respectively. FATP1 and FATP4 emerged as contributors to models of PFO and FO. Mice lacking CD36 had impaired whole-body and muscle fatty acid oxidation during exercise and muscle contractions, respectively. These data suggest that substantial variation in fatty acid oxidation rates during exercise can be explained by skeletal muscle proteins involved in fatty acid transport.

Peak fat oxidation is positively associated with vastus lateralis CD36 content, fed-state exercise fat oxidation, and endurance performance in trained males.

PURPOSE: Whole-body fat oxidation during exercise can be measured non-invasively during athlete profiling. Gaps in understanding exist in the relationships between fat oxidation during incremental fasted exercise and skeletal muscle parameters, endurance performance, and fat oxidation during prolonged fed-state exercise. METHODS: Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to assess peak whole-body fat oxidation (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 30-min maximal-effort cycling time-trial preceded by 2-h of fed-state moderate-intensity cycling to assess endurance performance and fed-state metabolism on separate occasions within one week. RESULTS: PFO (0.58 ± 0.28 g.min-1) was associated with vastus lateralis citrate synthase activity (69.2 ± 26.0 µmol.min-1.g-1 muscle protein, r = 0.84, 95% CI 0.58, 0.95, P < 0.001), CD36 abundance (16.8 ± 12.6 µg.g-1 muscle protein, rs = 0.68, 95% CI 0.31, 1.10, P = 0.01), pre-loaded 30-min time-trial performance (251 ± 51 W, r = 0.76, 95% CI 0.40, 0.91, P = 0.001; 3.2 ± 0.6 W.kg-1, r = 0.62, 95% CI 0.16, 0.86, P = 0.01), and fat oxidation during prolonged fed-state cycling (r = 0.83, 95% CI 0.57, 0.94, P < 0.001). Addition of PFO to a traditional model of endurance (peak oxygen uptake, power at 4 mmol.L-1 blood lactate concentration, and gross efficiency) explained an additional ~ 2.6% of variation in 30-min time-trial performance (adjusted R2 = 0.903 vs. 0.877). CONCLUSION: These associations suggest non-invasive measures of whole-body fat oxidation during exercise may be useful in the physiological profiling of endurance athletes.

Impact of smoking on pain and function in rotator cuff repair: a prospective 5-year cohort follow-up of 1383 patients.

BACKGROUND: This multicentre cohort study investigates the effect of smoking on the outcome of rotator cuff repair (RCR), with attention to age at presentation for surgery, pre-operative and post-operative pain and function and intra-operative findings. METHODS: Patient information was collected pre-operatively, including Flex Shoulder Function (Flex SF) and visual analogue scale pain, then at 6 months, 1, 2 and 5 years post-operatively. Intra-operative technical data were collected by the operating surgeon. Current smokers were classified by daily cigarette consumption. RESULTS: A total of 1383 RCRs in as many patients were included with an 84% 5-year follow-up. Smokers were on average 6.7 years younger than non-smokers (51.8 vs. 58.5, P < 0.001). There was no difference in intra-operatively assessed tear size both in anteroposterior dimension (P = 0.5) and retraction (P = 0.9). Pre-operative Flex SF score in smokers was below that of non-smokers (23.0 vs. 24.5, P = 0.002) and at 6 months (P = 0.02) but no different at 5 years (P = 0.7). Pain scores were higher in smokers than non-smokers both pre-operatively (5.34 vs. 4.67, P < 0.001) and up to 2 years (P < 0.001) but not at 5 years (P = 0.073). CONCLUSION: Smokers undergoing RCR were younger than non-smokers, and had worse pre-operative pain scores and shoulder function. Poorer post-operative function persisted to 6 months, and with higher reported pain to 2 years in smokers. However, at 5-year follow-up, patient-reported outcomes were not affected by smoking status.

Temperate performance and metabolic adaptations following endurance training performed under environmental heat stress.

Endurance athletes are frequently exposed to environmental heat stress during training. We investigated whether exposure to 33°C during training would improve endurance performance in temperate conditions and stimulate mitochondrial adaptations. Seventeen endurance-trained males were randomly assigned to perform a 3-week training intervention in 18°C (TEMP) or 33°C (HEAT). An incremental test and 30-min time-trial preceded by 2-h low-intensity cycling were performed in 18°C pre- and post-intervention, along with a resting vastus lateralis microbiopsy. Training was matched for relative cardiovascular demand using heart rates measured at the first and second ventilatory thresholds, along with a weekly "best-effort" interval session. Perceived training load was similar between-groups, despite lower power outputs during training in HEAT versus TEMP (p < .05). Time-trial performance improved to a greater extent in HEAT than TEMP (30 ± 13 vs. 16 ± 5 W, N = 7 vs. N = 6, p = .04), and citrate synthase activity increased in HEAT (fold-change, 1.25 ± 0.25, p = .03, N = 9) but not TEMP (1.10 ± 0.22, p = .22, N = 7). Training-induced changes in time-trial performance and citrate synthase activity were related (r = .51, p = .04). A group × time interaction for peak fat oxidation was observed (Δ 0.05 ± 0.14 vs. -0.09 ± 0.12 g·min-1 in TEMP and HEAT, N = 9 vs. N = 8, p = .05). Our data suggest exposure to moderate environmental heat stress during endurance training may be useful for inducing adaptations relevant to performance in temperate conditions.

Medium-term outcomes of a cohort of revision rotator cuff repairs.

BACKGROUND: There are limited medium- and long-term studies investigating clinical outcomes following revision rotator cuff surgery. The aim of the current study was to analyze the medium-term pain and functional outcomes of a cohort of revision rotator cuff repairs. METHODS: This was a multicenter, prospective cohort study of revision rotator cuff repairs undertaken between March 2009 and December 2010. Pain, function (Flex-SF), and postoperative data were collected at baseline; 6, 12, and 24 months; and 5 years. RESULTS: A total of 125 revision rotator cuff repairs were included in this study. Average improvement in Flex-SF and pain from baseline to 5 years was 8.5 (P < .001) and 2.1 points, respectively (P < .001). The improvement was not as pronounced as those who underwent primary repair. Significantly lower pain scores were seen in nonsmokers (P < .001) and in those who underwent tenotomy rather than tenodesis (2 vs. 3.5, P < .05) for a damaged long head of biceps. Significantly higher function scores were seen in those with only 1 tendon involved (P < .05). The patient-reported retear rate was 32.6%, and the reoperation rate was 34.7%. CONCLUSION: Revision rotator cuff repair provides significant improvement in both pain and function at 5 years postoperation, though not as good as primary repair. Superior clinical outcomes are seen in nonsmokers, those with only 1 tendon affected, and those who undergo tenotomy instead of tenodesis for a damaged long head of biceps tendon.

Arthroscopic, open and mini-open approach for rotator cuff repair: no difference in pain or function at 24 months.

BACKGROUND: The New Zealand Rotator Cuff Registry was established in 2009 to collect prospective functional, pain and outcome data on patients undergoing rotator cuff repair (RCR). METHODS: Information collected included an operation day technical questionnaire completed by the surgeon and Flex Shoulder Function (SF) functional and pain scores preoperatively, immediately post-operatively and at 6, 12 and 24 months. A multivariate analysis was performed analysing the three surgical approaches to determine if there was a difference in pain or functional outcome scores. RESULTS: A total of 2418 RCRs were included in this paper. There were 418 (17.3%) arthroscopic, 956 (39.5%) mini-open and 1044 (43.2%) open procedures. Twenty-four-month follow-up data were obtained for pain and Flex SF in 71% of patients. At 24 months, there was no difference in the average Flex SF score for the arthroscopic, mini-open and open groups. There was no difference in improvement in Flex SF score at 24 months. At 24 months, there was no difference in mean pain scores. There was no difference in improvement in pain score from preoperation to 24 months. Most patients returned to work within 3 months of surgery, with no difference between the three surgical approaches. CONCLUSION: RCR has good to excellent outcomes in terms of improvement in pain and function at 2-year follow-up. We found no difference in pain or functional outcome at 24 months between arthroscopic, open and mini-open approaches for RCR.

Comparison of Patellar Tendon and Hamstring Tendon Anterior Cruciate Ligament Reconstruction: A 15-Year Follow-up of a Randomized Controlled Trial.

BACKGROUND: Numerous studies have compared patellar tendon (PT) and hamstring tendon (HS) anterior cruciate ligament (ACL) reconstructions in the short to midterm, but fewer long-term results have been published. HYPOTHESIS: There will be no difference in functional outcome between ACL reconstruction performed with PT and HS grafts, but PT grafts will have more donor site morbidity. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Sixty-five patients undergoing ACL reconstruction were randomized to receive either a PT graft or a 4-strand HS graft. Early results were reported at 4, 8, 12, 24, and 36 months. Forty-seven patients (22 of 31 PT and 25 of 34 HS) were reviewed at a mean of 15.3 years. RESULTS: Four graft ruptures (1 PT, 3 HS) and 6 contralateral ACL injuries (4 PT, 2 HS) occurred in the group that was reviewed. There was no statistically significant difference between the groups for any of the variables measured. There was a similar incidence of anterior knee pain and kneeling pain in both groups. The previously observed increased extension deficit in the PT group at 3 years was not present at 15 years, and there was no significant between-group difference in knee laxity. A higher proportion of patients in the PT group were participating in sport on a weekly basis (73% PT, 48% HS; P = .05). There was no difference in the degree of osteoarthritis between the groups. CONCLUSION: This randomized controlled trial showed that HS and PT ACL reconstructions have comparable results at an average 15-year follow-up. Contrary to the study hypothesis, some of the graft differences seen at earlier review were not present at 15 years, and patients with PT grafts were more active in sport participation. Overall, both graft types provided good long-term subjective and objective outcomes.

Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction.

BACKGROUND: Graft rupture of the same knee or injury to the anterior cruciate ligament (ACL) in the contralateral knee is a devastating outcome after ACL reconstruction surgery. While a number of factors have been identified as potentially increasing the risk of subsequent ACL injury, the literature is far from definitive. PURPOSE: To determine the rates of graft rupture and contralateral ACL injury in a large cohort and to investigate patient characteristics that may be associated with these. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: A consecutive cohort of 750 patients who had undergone primary ACL reconstruction surgery with a minimum 3-year follow-up were questioned about the incidence of ACL graft rupture, contralateral ACL injury, family history of ACL injury, and current activity level. Patient databases provided details for age, sex, original injury mechanism, meniscus or articular surface injury, and graft diameter. RESULTS: Responses were received from 561 patients (75%) at a mean ± SD follow-up time of 4.8 ± 1.1 years. Anterior cruciate ligament graft ruptures occurred in 25 patients (4.5%), and contralateral ACL injuries occurred in 42 patients (7.5%). The highest incidence of further ACL injury occurred in patients younger than 20 years at the time of surgery. In this group, 29% sustained a subsequent ACL injury to either knee. The odds for sustaining an ACL graft rupture or contralateral injury increased 6- and 3-fold, respectively, for patients younger than 20 years. Returning to cutting/pivoting sports increased the odds of graft rupture by a factor of 3.9 and contralateral rupture by a factor of 5. A positive family history doubled the odds for both graft rupture and contralateral ACL injury. CONCLUSION: Patients younger than 20 years who undergo ACL reconstruction are at significantly increased risk for both graft rupture and contralateral ACL injury. Whether age per se is a risk factor or age represents a proxy for other factors remains to be determined.

Radial head reconstruction versus replacement in the treatment of terrible triad injuries of the elbow.

INTRODUCTION: Dislocation of the elbow with associated fractures of the radial head and the coronoid process of the ulna have been referred to as the terrible triad of the elbow because of the difficulties in treating this injury and the poor outcomes. MATERIALS AND METHODS: There were 23 patients (24 elbows) available for evaluation with this injury during a 7-year period at Auckland City Hospital. RESULTS: There were 11 women and 12 men with an average age of 43.5 years. The mean duration of follow-up was 41 months. The mean range of flexion was 135° (range, 110°-145°), extension was 8° (range, 0°-40°), supination was 75° (range, 15°-85°), and pronation was 80° (range, 20°-90°). No patients reported ongoing symptoms of instability. We compared the radial head repair group (13 patients) and the radial head replacement group (11 patients), which showed no significant difference between the variables of age, length of follow-up, American Shoulder and Elbow Surgeons score, satisfaction score, range of motion (flexion, extension, supination, pronation), and the associated arcs of motion. Only one significant difference was noted: the radial head replacement group scored higher values on the Disabilities of Arm, Shoulder, and Hand assessment. CONCLUSIONS: Elbow fracture-dislocations are difficult injuries to treat. Our study shows that with operative repair or replacement of the radial head to restore stability through radiocapitellar contact, coronoid, and lateral ligament repair, good range of movement and stability can be achieved at short-term follow-up.