Transfusion of non-red blood cell blood products does not reduce survival following cardiac surgery

OBJECTIVES

The literature supports the assertion that patients undergoing cardiac surgery who receive perioperative packed red blood cell (pRBC) transfusions have increased associated mortality. The aim of the current study is to assess whether there is an association between non-pRBC blood product transfusions and increased mortality.

METHODS

Data from our center's Society of Thoracic Surgeons database included patients who underwent cardiac surgery from 2010 to 2018. Patients with pRBC transfusions or circulatory arrest were excluded. Propensity matching was performed (1:1; caliper = 0.2 times the standard deviation of logit of propensity score). Kaplan-Meier estimates and Cox regression were used. Cardiac transplant, ventricular assist devices, transcatheter aortic valves, and patients who had experienced circulatory arrest were excluded from this analysis.

RESULTS

A total of 8042 patients met criteria for analysis. Following propensity matching (1:1), 395 patients requiring perioperative non-pRBC blood products (platelets, fresh-frozen plasma, and cryoprecipitate) were matched with 395 nontransfusion patients, yielding equitable patient cohorts. Median follow-up was 4.5 (3.0-6.4) years. Patients received platelets (327 [82.8%]), fresh-frozen plasma (141 [35.7%]), and cryoprecipitate (60 [15.2%]). There was no significant difference in the postoperative mortality (6 [1.5%] vs 4 [1.0%]; P = .52). Reoperation (20 [5.0%] vs 8 [2.0%]; P < .02) and prolonged ventilation (36 [9.1%] vs 19 [4.8%]; P < .02) were greater in the transfusion group. Emergent operation (odds ratio [OR] 2.86 [1.72-4.78]; P < .001), intra-aortic balloon pump (OR 3.24 [1.64-6.39]; P < .001), and multivalve operation (OR 4.34 [2.83-6.67]; P < .001) were significantly associated with blood product use. Blood product transfusion (hazard ratio; 1.15 [0.89-1.48]; P = .3) was not significantly associated with increased mortality risk. There was no significant long-term survival difference between cohorts.

CONCLUSIONS

Patients who undergo cardiac surgery requiring blood products alone, without pRBC transfusion, have similar postoperative and long-term survival compared with patients not requiring blood products. These data are based on a limited patient sample, and future studies will aid in improving the generalizability of these results.

Outcomes of reoperative aortic root surgery

OBJECTIVE

The study objective was to determine the impact of reoperative aortic root replacement on short-term outcomes and survival.

METHODS

This was a retrospective study of aortic root operations from 2010 to 2018. All patients with a complete aortic root replacement were included, and patients undergoing valve-sparing root replacements were excluded. Patients were dichotomized by first-time sternotomy versus redo sternotomy, which was defined as having had a prior sternotomy for whatever reason. Within the redo sternotomy group, reoperative aortic root replacements were identified, being defined as a complete aortic root replacement in patients with a prior aortic root replacement; 1:1 nearest neighbor propensity matching was used to compare outcomes across groups. Kaplan-Meier survival estimates were generated and compared using log-rank statistics.

RESULTS

A total of 893 patients undergoing complete ARR were identified, of whom 595 (67%) underwent first-time sternotomy and 298 (33%) underwent redo sternotomy. After matching, postoperative outcomes were similar for the first-time and redo sternotomy groups, including operative mortality. Redo sternotomy was not associated with reduced survival after aortic root replacement compared with first-time sternotomy (P = .084), with 5-year survival of 73.7% for first-time sternotomy and 72.9% for redo sternotomy. In the redo sternotomy group (n = 298), 69 (23%) were reoperative aortic root replacements and 229 (77%) were first-time aortic root replacements. After matching, postoperative outcomes were similar for the first-time and reoperative aortic root replacement groups, including operative mortality. Reoperative aortic root replacement was not associated with reduced survival, compared with first-time aortic root replacement (P = .870), with 5-year survival of 67.9% for first-time aortic root replacement and 72.1% for reoperative aortic root replacement.

CONCLUSIONS

Reoperative aortic root replacement can be performed safely and provides similar survival to first-time aortic root replacement.

The effect of receiving an award from the American Association for Thoracic Surgery Foundation

Objective

This study's objective was to evaluate the scholastic and career effects of receiving either the American Association for Thoracic Surgery (AATS) Foundation research scholarship or surgical investigator program.

Methods

AATS annual reports and recipient listings were used to generate the awardees. MEDLINE and SCOPUS were used to assess publications, citations, and H-Index for awardees. The National Institutes of Health (NIH) RePorter was used to collate NIH grant awarding to awardees. Publicly available institutional profiles were used to assess promotion status and leadership positions.

Results

Awardees of the research scholarship had a median of 4733 citations and a median H-Index of 33. The surgical investigator program recipients had a median of 1346 citations with a median H-Index of 17. Across both funding mechanisms, 45% secured subsequent NIH funding. Most awardees received an academic promotion, with 62% of the research scholarship awardees promoted to full professor and 37% of the surgical investigator program to associate professor. Approximately half (48%) of all awardees hold leadership positions, with most being a clinical director or division chief.

Conclusions

Receiving the AATS Foundation research scholarship or surgical investigator program positions early-career cardiothoracic surgeons for a promising future in academic surgery.

The Effect of COVID-19 on Cardiac Surgical Volume and its Associated Costs

The COVID-19 pandemic significantly affected health care and in particular surgical volume. However, no data surrounding lost hospital revenue due to decreased cardiac surgical volume have been reported. The National Inpatient Sample database was used with decreases in cardiac surgery at a single center to generate a national estimate of decreased cardiac operative volume. Hospital charges and provided charge to cost ratios were used to create estimates of lost hospital revenue, adjusted for 2020 dollars. The COVID period was defined as January to May of 2020. A Gompertz function was used to model cardiac volume growth to pre-COVID levels. Single center cardiac case demographics were internally compared during January to May for 2019 and 2020 to create an estimate of volume reduction due to COVID. The maximum decrease in cardiac surgical volume was 28.3%. Cumulative case volume and hospital revenue loss during the COVID months as well as the recovery period totaled over 35 thousand cases and 2.5 billion dollars. Institutionally, patients during COVID months were younger, more frequently undergoing a CABG procedure, and had a longer length of stay. The pandemic caused a significant decrease in cardiac surgical volume and a subsequent decrease in hospital revenue. This data can be used to address the accumulated surgical backlog and programmatic changes for future occurrences.

Midterm Outcomes of Stented Versus Stentless Bioprosthetic Valves After Aortic Root Replacement

To determine the impact of aortic root replacement (ARR) with a stentless bioprosthetic valve on midterm outcomes compared to a stented bioprosthetic valve-graft conduit. This was an observational study of aortic root operations from 2010 to 2018. All patients with a complete ARR for nonendocarditis reasons were included, while patients undergoing valve-sparing root replacements or primary aortic valve replacement or repair were excluded. Of the patients with a complete ARR, bioprosthetic valve implants were included, while mechanical valve implants were excluded. Patients were dichotomized into the stented ARR group and the stentless ARR group. A total of 1:1 nearest neighbor propensity matching was employed to assess the association of stentless valves with short-term and midterm outcomes. A total of 455 patients underwent a complete ARR with a bioprosthetic valve implant for nonendocarditis reasons, of which 212 (46.6%) received a stented valve, while 243 (53.4%) received a stentless valve. After matching, postoperative outcomes were similar across each group (P > 0.05), including operative mortality and adverse neurologic events. Median follow-up for the entire cohort was 4.41 years (95% CI: 4.01, 4.95). At 1 year follow-up, aortic regurgitation ≥ 2+ and ejection fraction were similar across each group (P > 0.05); however, the stentless valve group had lower aortic valve velocity and transvalvular pressure gradient. Finally, reoperations and survival were similar for each group over the study's follow-up (P > 0.05). Stentless valves may provide hemodynamic benefits after ARR; however, the clinical impact of those benefits for survival and reoperation may not yet be evident in the midterm.

Mild hypothermia versus normothermia in patients undergoing cardiac surgery

Objective

Temperature during cardiopulmonary bypass (CPB) for cardiac surgery has been controversial. The aim of the current study is to compare the outcomes for patients with mild hypothermia versus normothermic CPB temperatures.

Methods

All patients who underwent cardiac surgery with CPB and temperatures ≥32°C from 2011 to 2018 were included, which consisted of mild hypothermia (32°C-35°C) and normothermia (>35°C) cohorts. Propensity matching (1:1) was performed for risk adjustment. Primary outcomes included operative and long-term survival. Secondary outcomes included postoperative complications.

Results

A total of 6525 patients comprised 2 cohorts: mild hypothermia (32°C-35°C; n = 3148) versus normothermia (>35°C; n = 3377). Following adjustment for surgeon preference, there were 1601 propensity-matched patients who had similar baseline characteristics (standard mean difference, ≤0.10), including CPB time, crossclamp time, and intra-aortic balloon pump placement. Kaplan-Meier analysis showed no difference in long-term survival (82.6% vs 81.6%; P = .81). Over a median follow-up of 4.4 years, there were no differences in overall mortality (18.1% vs 18.1%; P = 1.1) or readmission (50.3% vs 48.3%; P = .2). Acute renal failure (3.7% vs 2.4%; P = .03) and intensive care unit hours (46.5 vs 45.1; P = .04) were significantly higher with hypothermia. There was no difference between cohorts for postoperative stroke (2.0% vs 2.0%; P = 1.0), reoperation (5.9% vs 6.0%; P = .9), or operative intra-aortic balloon pump placement (1.7% vs 1.8%; P = .9).

Conclusions

Patients with mild hypothermia during CPB had increased postoperative renal failure and length of intensive care unit stay. Although there was no difference in long-term survival, mild hypothermia does not appear to offer patients appreciable benefits, compared with normothermia.

Cardiac surgery in the afternoon is not associated with increased operative morbidity and mortality

BACKGROUND

Time of day for surgical procedures has been a topic of considerable controversy, with some suggesting that later operating times are associated with worse outcomes.

METHODS

All patients who underwent open cardiac surgery from 2011 to 2018 were included. Patients that had ventricular assist devices, heart transplant, transcatheter aortic valves, aortic dissections, and emergent operations were excluded. Primary outcomes included postoperative mortality and survival; secondary outcomes included postoperative complications and readmission.

RESULTS

The initial patient population consisted of 7883 patients who underwent index cardiac surgery. Following propensity matching (3:1), there were 2569 patients in the a.m. cohort (7-11 a.m.) and 860 patients in the p.m. cohort (3-11 p.m.). All baseline characteristics were matched to equivalent proportions. Total intensive care unit time following surgery was longer for the a.m. cohort (46.5 vs. 40.0 h; p<.001). Otherwise, there was no significant difference between cohorts including operative mortality (1.83% vs 2.21%; p= .48). On multivariable analysis, p.m. surgery was not significantly associated with 30 days mortality (hazard ratio [HR]: 0.96 [0.60, 1.53]; p= .86] or mortality over the study follow-up (HR: 0.87 [0.73, 1.03]; p= .10]. For propensity-matched cohorts, Kaplan-Meier survival at 30 days (97.9% vs. 97.4%; p= .44), 1 (93.4% vs  93.9%; p= .51), and 5 years (80.9% vs. 80.2%; p= .84) was not significantly different between cohorts.

CONCLUSION

Short- and long-term mortality, hospital readmission, and postoperative complications were not significantly different between patients that underwent cardiac surgery starting in the a.m. versus patients who had cases that started in the afternoon.

Complete revascularization during coronary artery bypass grafting is associated with reduced major adverse events

OBJECTIVE

Complete revascularization literature is limited by variance in patient cohorts and inconsistent definitions. The objective of the current study was to provide risk-adjusted outcomes for complete revascularization of significant nonmain-branch and main-branch vessel stenoses.

METHODS

All patients that underwent first-time isolated coronary artery bypass grafting procedures were included. Kaplan-Meier survival estimates, cumulative incidence function, and Cox regression were used to analyze outcomes.

RESULTS

The total population consisted of 3356 patients that underwent first-time isolated coronary artery bypass grafting. Eight hundred eighty-nine (26.5%) patients had incomplete and 2467 (73.5%) had complete revascularization. For main-branch vessels, 677 (20.2%) patients had incomplete revascularization and 2679 (79.8%) were completely revascularized. Following risk adjustment with inverse probability treatment weighting, all baseline characteristics were balanced (standardized mean difference, ≤ 0.10). On Kaplan-Meier estimates, survival at 1 year (94.6% vs 92.5%) and 5 years (86.5% vs 82.1%) (P = .05) was significantly better for patients who received complete revascularization. Freedom from major adverse cardiac and cerebrovascular events was significantly higher for the complete revascularization cohort at both 1 year (89.2% vs 84.2%) and 5 years (72.5% vs 66.7%) (P < .001). Complete revascularization (hazard ratio, 0.82; 95% confidence interval, 0.70-0.95; P = .01) was independently associated with a significant reduction in major adverse cardiac and cerebrovascular events. Incomplete revascularization of nonmain-branch vessels was not associated with mortality (hazard ratio, 1.14; 95% confidence interval, 0.74-1.8; P = .55) or major adverse cardiac and cerebrovascular events (hazard ratio, 0.90; 95% confidence interval, 0.66-1.24; P = .52).

CONCLUSIONS

Complete surgical revascularization of all angiographically stenotic vessels in patients with multivessel coronary artery disease is associated with fewer major adverse events. Incomplete revascularization of nonmain-branch vessels is not associated with survival or major adverse cardiac and cerebrovascular events.

Men and women trainers equally effective at promoting exercise adherence, self-efficacy, and fitness in women

BACKGROUND

This study examined the effect of a personal trainer's sex on self-efficacy and fitness in woman clients.

METHODS

Women (n: 28; mean ± SD; age, 41.6 ± 15.0 yrs.; height, 153.49 ± 28.11cm; BMI, 25.9 ± 6.4 kg•m-2) completed a perceptual scale of self-efficacy (BARSE) and fitness tests before and after a training program. Trainers (men and women) met one-on-one with the volunteers on a biweekly basis for 8 weeks. Univariate analyses of change scores and repeated measures analysis of variance with Fisher's LSD pairwise comparisons tested changes in dependent variables by trainer sex.

RESULTS

Significant increases were seen in (mean ± SE; change for men trainers; change for woman trainers): self-efficacy (7.3 ± 3.4; 7.3 ± 2.7%); leg press strength (18.2 ± 3.7; 16.4 ± 3.3 kg); seated row (6.1 ± 1.5; 5.3 ± 1.3 kg); muscular endurance in 60° flexion hold (20.5 ± 5.8; 24.8 ± 5.0 sec) and wall-sit (19.9 ± 6.4; 33.5 ± 5.8 sec); but not flexibility (V-sit, 7.11 ± 5.51; 4.23 ± 4.50 cm). Chest press strength significantly increased for women trainers only (2.7 ± 2.2; 5.3 ± 1.8 kg). Despite this, there were no significant differences for any variable in the change from pre-to-post based on the sex of the trainer.

CONCLUSIONS

Both men and woman-led training was effective for increasing markers of self-efficacy and fitness in woman clients.

Differences in brain structure and theta burst stimulation-induced plasticity implicate the corticomotor system in loss of function after musculoskeletal injury

Traumatic musculoskeletal injury (MSI) may involve changes in corticomotor structure and function, but direct evidence is needed. To determine the corticomotor basis of MSI, we examined interactions among skeletomotor function, corticospinal excitability, corticomotor structure (cortical thickness and white matter microstructure), and intermittent theta burst stimulation (iTBS)-induced plasticity. Nine women with unilateral anterior cruciate ligament rupture (ACL) 3.2 ± 1.1 yr prior to the study and 11 matched controls (CON) completed an MRI session followed by an offline plasticity-probing protocol using a randomized, sham-controlled, double-blind, cross-over study design. iTBS was applied to the injured (ACL) or nondominant (CON) motor cortex leg representation (M1_LEG) with plasticity assessed based on changes in skeletomotor function and corticospinal excitability compared with sham iTBS. The results showed persistent loss of function in the injured quadriceps, compensatory adaptations in the uninjured quadriceps and both hamstrings, and injury-specific increases in corticospinal excitability. Injury was associated with lateralized reductions in paracentral lobule thickness, greater centrality of nonleg corticomotor regions, and increased primary somatosensory cortex leg area inefficiency and eccentricity. Individual responses to iTBS were consistent with the principles of homeostatic metaplasticity; corresponded to injury-related differences in skeletomotor function, corticospinal excitability, and corticomotor structure; and suggested that corticomotor adaptations involve both hemispheres. Moreover, iTBS normalized skeletomotor function and corticospinal excitability in ACL. The results of this investigation directly confirm corticomotor involvement in chronic loss of function after traumatic MSI, emphasize the sensitivity of the corticomotor system to skeletomotor events and behaviors, and raise the possibility that brain-targeted therapies could improve recovery.NEW & NOTEWORTHY Traumatic musculoskeletal injuries may involve adaptive changes in the brain that contribute to loss of function. Our combination of neuroimaging and theta burst transcranial magnetic stimulation (iTBS) revealed distinct patterns of iTBS-induced plasticity that normalized differences in muscle and brain function evident years after unilateral knee ligament rupture. Individual responses to iTBS corresponded to injury-specific differences in brain structure and physiological activity, depended on skeletomotor deficit severity, and suggested that corticomotor adaptations involve both hemispheres.

Constitutive and Stress-Induced Psychomotor Cortical Responses to Compound K Supplementation

Isolated ginsenoside metabolites such as Compound K (CK) are of increasing interest to consumer and clinical populations as safe and non-pharmacological means to enhance psychomotor performance constitutively and in response to physical or cognitive stress. Nevertheless, the influence of CK on behavioral performance and EEG measures of cortical activity in humans is undetermined. In this double-blinded, placebo-controlled, counterbalanced within-group study, dose-dependent responses to CK (placebo, 160 and 960 mg) were assessed after 2 weeks of supplementation in nineteen healthy men and women (age: 39.9 ± 7.9 year, height 170.2 ± 8.6 cm, weight 79.7 ± 11.9 kg). Performance on upper- and lower-body choice reaction tests (CRTs) was tested before and after intense lower-body anaerobic exercise. Treatment- and stress-related changes in brain activity were measured with high-density EEG based on event-related potentials, oscillations, and source activity. Upper- (−12.3 ± 3.5 ms, p = 0.002) and lower-body (−12.3 ± 4.9 ms, p = 0.021) response times improved after exercise, with no difference between treatments (upper: p = 0.354; lower: p = 0.926). Analysis of cortical activity in sensor and source space revealed global increases in cortical arousal after exercise. CK increased activity in cortical regions responsible for sustained attention and mitigated exercise-induced increases in arousal. Responses to exercise varied depending on task, but CK appeared to reduce sensory interference from lower-body exercise during an upper-body CRT and improve the general maintenance of task-relevant sensory processes.

Prediction of exertional lower extremity musculoskeletal injury in tactical populations: protocol for a systematic review and planned meta-analysis of prospective studies from 1955 to 2018

BACKGROUND

Musculoskeletal injuries (MSI) represent more than half of all injuries in tactical populations (i.e., military service and public safety workers including police, firefighters, emergency medical services (EMS)). Most lower extremity MSIs result from physical exertion during training, occupational tasks, and recreation. Such exertional lower extremity injuries (ELEI) produce a significant human and financial cost. Accordingly, significant efforts have been made to identify sensitive, specific, and reliable predictors of ELEI. There is a need to synthesize and evaluate the predictive value of risk factors for ELEI while addressing the influence of occupation, sex, exposure, injury characteristics, and study quality. Therefore, the purpose of this systematic review and planned meta-analysis is to evaluate risk factors for ELEI in tactical populations.

METHODS

After the development of a search strategy, comprehensive searches will be conducted in MEDLINE, EMBASE, Cochrane, and CINAHL databases. Articles will be screened with a multi-user process and delimited to prospective comparative cohort studies that directly measure injury occurrence in the target population(s). Extracted data will be synthesized and assessed for reporting bias, meta-bias, and overall quality, with subgroup analyses to determine the influence of participant, injury, and exposure characteristics in addition to study quality.

DISCUSSION

This systematic review and planned meta-analysis will comprehensively evaluate ELEI risk factors. Information gained will inform injury prevention protocols, facilitate the use of improved measurements, and identify requirements for future research.

TRIAL REGISTRATION

The systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 3 Jan 2018 (registration number CRD42018056977 ).

Prevention of exertional lower body musculoskeletal injury in tactical populations: protocol for a systematic review and planned meta-analysis of prospective studies from 1955 to 2018

BACKGROUND

Exertional lower body musculoskeletal injuries (ELBI) cost billions of dollars and compromise the readiness and job performance of military service and public safety workers (i.e., tactical populations). The prevalence and burden of such injuries underscores the importance of prevention efforts during activities necessary to sustain core occupational competencies. Attempts to synthesize prevention techniques specific to tactical populations have provided limited insight on the comparative efficacy of interventions that do not modify physical training practices. There is also a need to assess the influence of sex, exposure, injury classification scheme, and study design. Thus, the primary purpose of the systematic review and planned meta-analysis detailed in this protocol is to evaluate the comparative efficacy of ELBI prevention strategies in tactical populations.

METHODS

A systematic search strategy will be implemented in MEDLINE, EMBASE, Cochrane, and CINAHL. A multi-tiered process will be used to capture randomized controlled trials and prospective cohort studies that directly assess the prevention of ELBI in tactical population(s). Extracted data will be used to compare prevention strategies and assess the influence of heterogeneity related to occupation, sex, exposure, injury characteristics, and study quality. In addition, individual risk of bias, meta-bias, and the quality of the body of evidence will be rigorously tested.

DISCUSSION

This systematic review and planned meta-analysis will comprehensively evaluate ELBI mitigation strategies in tactical populations, elucidate factors that influence responses to treatment, and assess the overall quality of the body of research. Results of this work will guide the prioritization of ELBI prevention strategies and direct future research efforts, with direct relevance to tactical, health and rehabilitation science, and human performance optimization stakeholders.

SYSTEMATIC REVIEW REGISTRATION

The systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 3 Jan 2018 (registration number CRD42018081799 ).

Developmental differences between boys and girls result in sex-specific physical fitness changes from fourth to fifth grade

To better understand how developmental differences impact performance on a broad selection of common physical fitness measures, we examined changes in boys and girls from fourth to fifth grade. Subjects included 273 boys (age, 9.5 ± 0.6 years; height, 139.86 ± 7.52 cm; mass, 38.00 ± 9.55 kg) and 295 girls (age, 9.6 ± 0.5 years; height, 139.30 ± 7.19 cm; weight, 37.44 ± 9.35 kg). We compared anthropometrics, cardiorespiratory and local muscular endurance, flexibility, power, and strength. A mixed-method analysis of variance was used to compare boys and girls at the 2 time points. Pearson correlation coefficients were used to examine relationships between anthropometric and fitness measurements. Significance was set at p ≤ 0.05. Weight increased significantly (>10%) in both sexes, and girls became significantly taller than boys after growing 4.9% by fifth grade (vs. 3.5%). Both groups improved cardiorespiratory endurance and power, although boys performed better than girls at both time points. Boys were stronger in fourth grade, but girls improved more, leading to similar fifth-grade values. Girls were more flexible in fourth grade, but their significant decreases (∼32.4%) coupled with large improvements in boys (∼105%) resulted in similar fifth-grade scores. Body mass index (BMI) was positively correlated with run time regardless of grade or sex. Power was negatively correlated with BMI and run time in fourth grade. In conclusion, sex-specific differences in physical fitness are apparent before pubescence. Furthermore, this selection of measures reveals sexually dimorphic changes, which likely reflect the onset of puberty in girls. Coaches and teachers should account these developmental differences and their effects on anthropometrics and fitness in boys and girls.

The relationship between muscle action and repetition maximum on the squat and bench press in men and women

The relationship between muscle action and fatigue is not well understood, especially in terms of potential sex-specific differences. The purpose of this investigation was to determine whether a different number of repetitions could be performed on the individual muscle actions of the bench press and squat in men and women. Ten resistance-trained men (n = 10; age, 25.2 ± 1.2 years; height, 178.6 ± 8.8 cm; weight, 91.4 ± 18.1 kg; body fat, 12.7 ± 3.6%) and women (n = 10; age, 25.4 ± 2.4 years; height, 164 ± 4.0 cm; weight, 58.45 ± 3.3 kg; body fat, 20.8 ± 1.5%) participated in this balanced and randomized within-group study. Using 85% of a 1 repetition maximum, over the course of 3 visits, subjects performed 1 eccentric (ECC), concentric (CON), or combined (COMB) set to failure on the squat and bench press. Differences in muscle action and sex-specific number of repetitions to failure were compared on the squat and bench press, where significance was p ≤ 0.05. Across both exercises and sex, we observed significant differences between each of the 3 muscle actions, where the number of repetitions decreased from ECC to COMB to CON. While no sex-specific differences were observed in the squat, women performed significantly more repetitions on the ECC and CON muscle actions of the bench press. Men performed more combined repetitions, however, indicating a greater reliance on the stretch-shortening cycle. Different muscle actions contribute uniquely to the successful performance of a lift and fatigue. These contributions appear to differ in men and women.

Acute resistance exercise stimulates sex-specific dimeric immunoreactive growth hormone responses

PURPOSE

We sought to determine if an acute heavy resistance exercise test (AHRET) would elicit sex-specific responses in circulating growth hormone (GH), with untreated serum and serum treated with a reducing agent to break disulfide-bindings between GH dimers.

METHODS

19 untrained participants (nine men and ten women) participated in an acute heavy resistance exercise test using the back squat. Blood samples were drawn before exercise (Pre), immediate post (IP), +15 min (+15), and +30 min (+30) afterwards. Serum samples were chemically reduced using glutathione (GSH). ELISAs were then used to compare immunoreactive GH concentrations in reduced (+GSH) and non-reduced (-GSH) samples. Data were analyzed using a three-way (2 sex × 2 treatment × 4 time) mixed methods ANOVA, with significance set at p ≤ 0.05.

RESULTS

GSH reduction resulted in increased immunoreactive GH concentrations when compared to non-reduced samples at Pre (1.68 ± 0.33 μg/L vs 1.25 ± 0.25 μg/L), IP (7.69 ± 1.08 μg/L vs 5.76 ± 0.80 μg/L), +15 min (4.39 ± 0.58 μg/L vs 3.24 ± 0.43 μg/L), and +30 min (2.35 ± 0.49 μg/L vs 1.45 ± 0.23 μg/L). Also, women demonstrated greater GH responses compared to men, and this was not affected by reduction.

CONCLUSIONS

Heavy resistance exercise increases immunoreactive GH dimer concentrations in men and women, with larger increases in women and more sustained response in men. The physiological significance of a sexually dimorphic GH response adds to the growing literature on aggregate GH and may be explained by differences in sex hormones and the structure of the GH cell network.

The addition of beta-hydroxy-beta-methylbutyrate and isomaltulose to whey protein improves recovery from highly demanding resistance exercise

OBJECTIVE

This study evaluated whether a combination of whey protein (WP), calcium beta-hydroxy-beta-methylbutyrate (HMB), and carbohydrate exert additive effects on recovery from highly demanding resistance exercise.

METHODS

Thirteen resistance-trained men (age: 22.6 ± 3.9 years; height: 175.3 ± 12.2 cm; weight: 86.2 ± 9.8 kg) completed a double-blinded, counterbalanced, within-group study. Subjects ingested EAS Recovery Protein (RP; EAS Sports Nutrition/Abbott Laboratories, Columbus, OH) or WP twice daily for 2 weeks prior to, during, and for 2 days following 3 consecutive days of intense resistance exercise. The workout sequence included heavy resistance exercise (day 1) and metabolic resistance exercise (days 2 and 3). The subjects performed no physical activity during day 4 (+24 hours) and day 5 (+48 hours), where recovery testing was performed. Before, during, and following the 3 workouts, treatment outcomes were evaluated using blood-based muscle damage markers and hormones, perceptual measures of muscle soreness, and countermovement jump performance.

RESULTS

Creatine kinase was lower for the RP treatment on day 2 (RP: 166.9 ± 56.4 vs WP: 307.1 ± 125.2 IU · L(-1), p ≤ 0.05), day 4 (RP: 232.5 ± 67.4 vs WP: 432.6 ± 223.3 IU · L(-1), p ≤ 0.05), and day 5 (RP: 176.1 ± 38.7 vs 264.5 ± 120.9 IU · L(-1), p ≤ 0.05). Interleukin-6 was lower for the RP treatment on day 4 (RP: 1.2 ± 0.2 vs WP: 1.6 ± 0.6 pg · ml(-1), p ≤ 0.05) and day 5 (RP: 1.1 ± 0.2 vs WP: 1.6 ± 0.4 pg · ml(-1), p ≤ 0.05). Muscle soreness was lower for RP treatment on day 4 (RP: 2.0 ± 0.7 vs WP: 2.8 ± 1.1 cm, p ≤ 0.05). Vertical jump power was higher for the RP treatment on day 4 (RP: 5983.2 ± 624 vs WP 5303.9 ± 641.7 W, p ≤ 0.05) and day 5 (RP: 5792.5 ± 595.4 vs WP: 5200.4 ± 501 W, p ≤ 0.05).

CONCLUSIONS

Our findings suggest that during times of intense conditioning, the recovery benefits of WP are enhanced with the addition of HMB and a slow-release carbohydrate. We observed reductions in markers of muscle damage and improved athletic performance.

The effects of resistance training prioritization in NCAA Division I Football summer training

Resistance training (RT) is an integral part of National Collegiate Athletic Association (NCAA) Division I Football performance programs. In the sport of football, there are several components that a strength and conditioning coach must be aware of. These include body mass, size, strength, power, speed, conditioning, and injury prevention, among others. The purpose of this study was to investigate if the RT component of a performance program could be prioritized for specific results using a nonlinear training model, grouping athletes by eligibility year. The NCAA Division I football student athletes were placed into 3 separate groups based on the playing year. All subjects participated in a 10-week, 4 days·week-1 off-season summer resistance training program. The training of group 1 (n = 20, age: 18.95 ± 0.76 years, height: 186.63 ± 7.21 cm, body mass: 97.66 ± 18.17 kg, playing year: 1.05 ± 0.22 years) prioritized hypertrophy-based RT to gain body mass. The training of group 2 (n = 20, age: 20.05 ± 1.05 years, height: 189.42 ± 5.49 cm, body mass: 106.99 ± 13.53 kg, and playing year: 2.35 ± 0.75 years) prioritized strength-based RT to gain strength. The training of group 3 (n = 20, age: 21.05 ± 1.10 years, height: 186.56 ± 6.73 cm, body mass: 109.8 ± 19.96 kg, playing year: 4.4 ± 0.50 years) prioritized power-based RT to gain power. Performance tests were evaluated during the first weeks of March (Spring) and August (Fall). The test measures included body mass (kilograms), 1-repetition maximum (1RM) bench press (kilograms), 1RM back squat (kilograms), 1RM power clean (kilograms), and countermovement vertical jump (CMVJ) height (centimeters). The primary findings of this investigation were as follows: group 1 saw significant increases in bench press maximum, back squat maximum, and power clean maximum (p ≤ 0.05). Group 2 saw significant increases in bench press maximum, back squat maximum, and power clean maximum (p ≤ 0.05). Group 3 saw a significant increase in power clean maximum (p ≤ 0.05). Group 1's significant increases were expected because of their low training age relatively shorter training history when compared with Groups 2 and 3. Group 1 did not see significant increases in body mass, with 7 out of 20 subjects being nonresponders. Group 2 and 3's significant increases were expected. Unexpectedly, no group saw significant increases in maximum CMVJ height. With so many factors that go into a football performance program contributing to football performance programing, it seems difficult to prioritize 1 RT goal over another without neglecting others during 10-week summer training program. Prioritization of strength appears to have the best overall affect on the RT portion of an off-season football performance program. Nonlinear periodization allows for the prioritization of 1 training goal without disregarding others with a smaller risk of neglecting other important components. This investigation showed that a performance program with a nonlinear model and prioritization on strength had produced the most desirable results.

Effects of acute resistance exercise on muscle damage and perceptual measures between men who are lean and obese

The purpose of this investigation was to assess indices of muscle damage and psychological stress between young, untrained, lean, and obese men. Using a between-subject design, 19 young men (9 lean men [age, 20.1 ± 2.1 years; body mass, 71.7 ± 5.8 kg; height, 177.8 ± 8.7 cm; body fat (BF), 14.7 ± 3.5%], 5 World Health Organization [WHO] class 1 obese men [age, 21.6 ± 2.5 years; body mass, 97.8 ± 8.6 kg; height, 176.3 ± 3.7 cm; BF, 34.7 ± 3.0%], and 5 WHO class 2 or 3 men [age, 20.0 ± 1.4 years; body mass, 120.8 ± 10.5 kg; height, 177.7 ± 5.2 cm; BF, 40.5 ± 5.8%]) volunteered and completed an acute resistance exercise (RE) protocol (6 exercises performed for 3 sets of 10 repetitions at an intensity of 85-95% of a 10 repetition maximum). Plasma myoglobin and serum creatine kinase were obtained before and immediately after exercise, and in recovery (at +110 minutes and +24 hours). Perceptual measures including rating of perceived exertion, pain and soreness, fatigue, and general soreness were assessed at different time points (during exercise for rating of perceived exertion, and for the fatigue and soreness measures before, immediately after, and at 24 hours of recovery from exercise). The primary findings of this investigation were that lean and obese, sedentary, young men do not significantly differ from each other in terms of indirect, humoral measures of muscle damage, or perceptual scales in response to a moderate-intensity acute RE bout, despite using significantly more exercise volume relative to fat mass (FM). We conclude that excess FM during daily activities of life provides a protective effect for muscle damage. When strength training individuals who are obese, practitioners should be aware of how excess FM affects muscle damage and total volume. But these considerations do not preclude individuals who are obese from using well-designed RE workouts which use free-weight, multijoint movements that stimulate all of the major muscle groups.

Obesity, growth hormone and exercise

Growth hormone (GH) is regulated, suppressed and stimulated by numerous physiological stimuli. However, it is believed that obesity disrupts the physiological and pathological factors that regulate, suppress or stimulate GH release. Pulsatile GH has been potently stimulated in healthy subjects by both aerobic and resistance exercise of the right intensity and duration. GH modulates fuel metabolism, reduces total fat mass and abdominal fat mass, and could be a potent stimulus of lipolysis when administered to obese individuals exogenously. Only pulsatile GH has been shown to augment adipose tissue lipolysis and, therefore, increasing pulsatile GH response may be a therapeutic target. This review discusses the factors that cause secretion of GH, how obesity may alter GH secretion and how both aerobic and resistance exercise stimulates GH, as well as how exercise of a specific intensity may be used as a stimulus for GH release in individuals who are obese. Only five prior studies have investigated exercise as a stimulus of endogenous GH in individuals who are obese. Based on prior literature, resistance exercise may provide a therapeutic target for releasing endogenous GH in individuals who are obese if specific exercise programme variables are utilized. Biological activity of GH indicates that this may be an important precursor to beneficial changes in body fat and lean tissue mass in obese individuals. However, additional research is needed including what molecular GH variants are acutely released and involved at target tissues as a result of different exercise stimuli and what specific exercise programme variables may serve to stimulate GH in individuals who are obese.

Positive effects of augmented verbal feedback on power production in NCAA Division I collegiate athletes

The purpose of this study was to determine how augmented verbal feedback, specifically knowledge of performance during a countermovement vertical jump (CMVJ) protocol, would affect acute power output. Each subject (N = 14 [9 men and 5 women], 21.4 ± 0.8 years, 179.6 ± 6.1 cm, 87.5 ± 14.8 kg) completed the CMVJ protocol twice in a balanced randomized order, one trial with feedback and one without feedback. At least 48 hours were allowed between sessions for resting. Student-athletes were used because of their trained state and their familiarity with plyometrics and receiving and processing feedback during training. Each testing session began with a 10-minute warm-up consisting of a combination of dynamic stretching and submaximal jumps (no proprioceptive neuromuscular facilitation or static stretching). After completion of the warm-up, the subjects then began the CMVJ protocol. The CMVJ protocol consisted of 3 sets of 5 jumps on a calibrated force plate set to read at 200 Hz (Accupower). Subjects were instructed at the start of the protocol to give maximal effort on each jump. The standard set and repetition scheme for this protocol was 3 sets of 5 maximal repetitions with 3 minutes rest between sets. This was used to mimic the practice of training for maximal power. Before each jump, the subject was told the jump number and given a verbal start cue before the jump's initiation. The verbal performance feedback given consisted of the full kinetic numerical value of the peak power output in watts of the last completed jump. Significance in this study was set at p ≤ 0.05. There was a significant difference between mean power outputs (4,335 ± 366 W to 4,108 ± 345 W, p = 0.003) and the peak power outputs (4,567 ± 381 W to 4,319 ± 371 W, p = 0.018) when comparing feedback to no feedback, respectively. There was a significant difference in peak power output between the feedback and no feedback trials during set 2 (mean difference 361 ± 161 W, p = 0.043) and set 3 (mean difference 283 ± 109 W, p = 0.022). Also, there was a significant difference in mean power output between feedback and no feedback trials during set 2 (mean difference 240 ± 66 W, p = 0.003) and set 3 (mean difference 299 ± 93 W, p = 0.007). When training for maximal power in a plyometric training protocol, verbal feedback can be used as both a simple and effective aid in producing optimal power outputs.

Relationships of physical performance tests to military-relevant tasks in women

PURPOSE

This investigation sought to determine the most predictive measures of performance on a repetitive box lifting task (RBLT) and load bearing task (LBT) among 123 women (aged ±4 years, height 165±7 cm, body mass 64±10 kg).

METHODS

To determine the relationship of various predictors to performance on the RBLT and LBT, multiple regression analysis was conducted on body mass, height, leg cross-sectional area, upper and lower body muscular strength, lower body explosive power, upper and lower body local muscular endurance, and aerobic capacity.

RESULTS

The mean±SD (range) number of repetitions for the RBLT was 86±23 (20-159). The mean±SD (range) time to complete the LBT was 2,054±340 seconds (1,307-3,447). The following equations were generated: RBLT (number of repetitions)=57.4+0.2(peak jump power)+0.4(number of pushups in 2 minutes)+0.15(number of repetitions during the squat endurance test)+1.39(one repetition maximal strength boxlift (kg))-0.04(2-mile run time (2MR) in seconds), R=0.81; standard error of the estimate (SEE)=14; LBT (in seconds)=1,831-4.28(number of repetitions during the squat endurance test)+0.95(2MR in seconds)-13.4(body mass), R=0.73; SEE=232.

CONCLUSIONS

We found that the 2MR and squat endurance test were significant predictive factors for performance on both load carriage tasks. These data also imply that women's performance in combat-related tasks can be improved with training that targets muscular strength, power, and local muscular endurance in addition to aerobic capacity.

Effects of resistance exercise on the HPA axis response to psychological stress during short-term smoking abstinence in men

PURPOSE

The purpose of this study was to examine the effects of resistance exercise on the hypothalamic-pituitary-adrenal axis (HPA) response to mental challenge, withdrawal symptoms, urge to smoke, and cognitive stress during 24-hour smoking abstinence.

METHODS

8 sedentary smokers (mean±SD age: 20.1±1.7y; height: 171.6±10.8cm; body mass: 70.4±12.0kg; smoking history: 2.9±0.8y) completed a 24-hour ad libitum smoking trial (SMO) followed by two 24-hour smoking abstinence trials. During abstinence trials, participants performed six whole body resistance exercises (EX) or a control condition (CON) in the morning, followed by mental challenge tasks in the afternoon. Plasma adrenocorticotropin hormone (ACTH), and salivary and serum cortisol were measured during each visit at rest (REST), and then before (PRE-EX), immediately after (IP-EX), and 30min after exercise (30-EX); and before (PRE-MC), immediately after (IP-MC), and 30min after mental challenge (30-MC).

RESULTS

Resistance exercise significantly (p≤0.05) elevated plasma ACTH and serum cortisol at IP-EX during EX compared with SMO and CON trials. Resting ACTH, salivary and serum cortisol concentrations at Pre-MC did not differ between EX and CON trials. The HPA axis response to mental challenge was similar after EX and CON trials. Finally, resistance exercise did not reduce withdrawal symptoms, urge to smoke, or stress.

CONCLUSION

Resistance exercise did not substantially alter resting HPA hormones or the HPA response to mental challenge tasks during 24h of smoking abstinence.

Epinephrine preworkout elevation may offset early morning melatonin concentrations to maintain maximal muscular force and power in track athletes

The optimal time of day for training has become an important question for many strength and conditioning specialists, and this study was designed to add some insights into this complex question. The primary purpose of this investigation was to examine physical performance within the temporal context of the relationship between physical performance, epinephrine, and melatonin concentrations in the early morning (0530 hours) and late (1500 hours) afternoon in elite collegiate male track and field athletes (jumpers and sprinters). Subjects had a mean (±SD) age, height, and body mass of 20.4 (±1.6) years, 185.8 (±9.4) cm, and 77.9 (±8.5) kg, respectively. Blood was obtained before each AM and PM testing session. Mean plasma melatonin concentrations were 34.9 ± 22.7 pg·ml and 4.8 ± 3.3 pg·ml for the AM vs. PM trials, respectively, demonstrating a significant (p ≤ 0.05) difference between time points. Mean resting plasma epinephrine concentrations for AM (171.7 ± 33.7 pmol·L) and PM (127.6 ± 47.8 pmol·L) also differed significantly between trails at the different times. In addition, significant differences were observed with respect to foot quickness in the AM (5.14 ± 1.06 seconds) and PM (4.39 ± 0.76 seconds). Mean peak power output for vertical jump power was 5,407.1 ± 1,272.9 W, 5,384.6 ± 888.3 W for AM vs. PM trials, respectively, which were not significantly different. The results of this investigation indicate that time of day did not negatively impact whole body physical performance in trained track athletes but did impact the quality of quickness. Thus in the morning, whole body power performances may be enhanced through adrenergic arousal when melatonin is elevated. However, this was not the case for movements requiring quickness and accuracy of movement. To compensate for the "sleepiness" associated with high concentrations of melatonin, being secreted from the pineal gland representing a continued "sleepiness" effect on the body, early morning practices may require greater adrenergic arousal to potentially offset melatonin's effects. The results of this study raise important questions on the use of early morning practices for more complex tasks that require high reaction speeds, even under conditions of adrenergic arousal.

Performance changes during a weeklong high-altitude alpine ski-racing training camp in lowlander young athletes

Thousands of youth athletes travel to high altitude to participate in lift-access alpine sports. The purpose of this study was to examine the impact of acute high-altitude exposure on balance, choice reaction time, power, quickness, flexibility, strength endurance, and V[Combining Dot Above]O2max in youth lowlander athletes during a weeklong preseason training camp in Summit County, CO, USA. Eleven youth ski racers (4 boys and 7 girls; age, 13.7 ± 0.5 years; height, 157.2 ± 12.6 cm; weight, 52.4 ± 6.8 kg) with 7.7 ± 2.2 skiing years of experience participated in baseline testing at 160 m one week before the camp and a set of daily tests in the morning and afternoon at 2,828 m and skied between 3,328 and 3,802 m during a 6-day camp. Balance and choice reaction time tests were stagnant or improved slightly during the first 3 days and then improved on days 4 and 6. Vertical jump, flexibility, T-agility test, and push-ups in 1 minute improved on day 6. The number of sit-ups in 1 minute did not improve, and scores on the multistage fitness test decreased 20.34%. There was no effect of Lake Louise acute mountain sickness (AMS) questionnaire scores on performance variables measured. Athletes sojourning to high altitude for ski camps can train on immediate ascent but should slowly increase training volume over the first 3 days. Athletes should expect improvements in balance and reaction time 3-6 days into acclimatization. Coaches and athletes should expect about 20% of youth lowlander athletes to have signs and symptoms of AMS during the first 3 days of altitude exposure for alpine lift access sports at altitudes of up to 3,800 m.

Resistance exercise induces region-specific adaptations in anterior pituitary gland structure and function in rats

The anterior pituitary gland (AP) increases growth hormone (GH) secretion in response to resistance exercise (RE), but the nature of AP adaptations to RE is unknown. To that end, we examined the effects of RE on regional AP somatotroph GH release, structure, and relative quantity. Thirty-six Sprague-Dawley rats were assigned to one of four groups: 1) no training or acute exercise (NT-NEX); 2) no training with acute exercise (NT-EX); 3) resistance training without acute exercise (RT-NEX); 4) resistance training with acute exercise (RT-EX). RE incorporated 10, 1 m-weighted ladder climbs at an 85° angle. RT groups trained 3 days/wk for 7 wk, progressively. After death, trunk blood was collected, and each AP was divided into quadrants (ventral-dorsal and left-right). We measured: 1) trunk plasma GH; 2) somatotroph GH release; 3) somatotroph size; 4) somatotroph secretory content; and 5) percent of AP cells identified as somatotrophs. Trunk GH differed by group (NT-NEX, 8.9 ± 2.4 μg/l; RT-NEX, 9.2 ± 3.5 μg/l; NT-EX, 15.6 ± 3.4 μg/l; RT-EX, 23.4 ± 4.6 μg/l). RT-EX demonstrated greater somatotroph GH release than all other groups, predominantly in ventral regions (P < 0.05-0.10). Ventral somatotrophs were larger in NT-EX and RT-NEX compared with RT-EX (P < 0.05-0.10). RT-NEX exhibited significantly greater secretory granule content than all other groups but in the ventral-right region only (P < 0.05-0.10). Our findings indicate reproducible patterns of spatially distinct, functionally different somatotroph subpopulations in the rat pituitary gland. RE training appears to induce dynamic adaptations in somatotroph structure and function.

Changes in creatine kinase and cortisol in National Collegiate Athletic Association Division I American football players during a season

The purpose of this study was to track creatine kinase (CK) and serum cortisol over an American college football season starting with the preseason practice. A secondary purpose was to observe changes in basic clinical chemistries. Twenty-two National Collegiate Athletic Association Division I football players (age: 20.4 ± 1.1 years, height: 188.27 ± 8.3 cm, weight: 115.8 ± 29.7 kg) volunteered to participate in this study. Each of the players had participated in the summer strength and conditioning supervised program. Resting blood samples were obtained just before the start of preseason practice (T-1), 2 weeks later (T-2), and the day after game 2 (T-3), game 4 (T-4), game 6 (T-5), and game 9 (T-6) of a 12-game season. Creatine kinase, a panel of clinical chemistries, cortisol, and testosterone were assayed at each time point. No significant changes in CK concentrations were observed over the season with peak values of each range ≤1,070.0 IU·L(-1), but the largest range was observed at T-6 after game 9 (119-2,834 IU·L(-1). The analysis of covariance analysis demonstrated that the number of plays in the ninth game (T-6) explained the magnitude of the changes in CK. No changes in serum cortisol concentrations were observed yet, again large variations existed with peak values of each range ≤465.0 nmol·L(-1). Clinical chemistries showed various significant changes from T-1, but none were considered clinically relevant changes for any player over the time course of the study. In conclusion, the strength and conditioning program before preseason camp or the structure of summer camp practices and the in-season strength and conditioning appeared to mute muscle damage and the stress response of cortisol. Such data demonstrate that changes in muscle damage and adrenal cortical stress over the season are minimal, yet large individual variations can be observed. Management of these variables appears to be related to optimal strength and conditioning and sports medicine programs. Thus, the greater concerns for student-athlete safety in the sport of American football are related to preventing sudden death, traumatic injury, and managing concussion syndromes.

Responses of proenkephalin Peptide F to aerobic exercise stress in the plasma and white blood cell biocompartments

Proenkephalin Peptide F [107-140] is an enkephalin-containing peptide found predominantly within the adrenal medulla, co-packaged with epinephrine within the chromaffin granules. In vivo studies indicate that Peptide F has classic opioid analgesia effects; in vitro studies suggest potential immune cell interactions. In this investigation we examined patterns of Peptide F concentrations in different bio-compartments of the blood at rest and following sub-maximal cycle exercise to determine if Peptide F interacts with the white blood cell (WBC) bio-compartment during aerobic exercise. Eight physically active men (n=8) performed sub-maximal (80-85% V˙O2peak) cycle ergometer exercise for 30 min. Plasma Peptide F and WBC Peptide F immunoreactivity were examined pre-exercise, mid-exercise and immediately post-, 5-min post-, 15-min post-, 30-min post- and 60-min post-exercise and at similar time-points during a control condition (30 min rest). Peptide F concentrations significantly (p<0.05) increased at 5 and 60 min post-exercise, compared to pre-exercise concentrations. No significant increases in Peptide F concentrations in the WBC fraction were observed during or after exercise. However, a significant decrease was observed at 30 min post-exercise. An ultradian pattern of Peptide F distribution was apparent during rest. Furthermore, concentrations of T cells, B cells, NK cells, and total WBCs demonstrated significant changes in response to aerobic exercise. Data indicated that Peptide F was bound in significant molar concentrations in the WBC fraction and that this biocompartment may be one of the tissue targets for binding interactions. These data indicate that Peptide F is involved with immune cell modulation in the white blood circulatory biocompartment of blood.

The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men

OBJECTIVE

For many resistance-trained men concerns exist regarding the production of estrogen with the consumption of soy protein when training for muscle strength and size. Thus, the purpose of this investigation was to examine the effects of soy and whey protein supplementation on sex hormones following an acute bout of heavy resistance exercise in resistance trained men.

METHODS

Ten resistance-trained men (age 21.7 ± 2.8 [SD] years; height 175.0 ± 5.4 cm; weight 84.2 ± 9.1 kg) volunteered to participate in an investigation. Utilizing a within subject randomized crossover balanced placebo design, all subjects completed 3 experimental treatment conditions supplementing with whey protein isolate (WPI), soy protein isolate (SPI), and maltodextrin placebo control for 14 days with participants ingesting 20 g of their assigned supplement each morning at approximately the same time each day. Following supplementation, subjects performed an acute heavy resistance exercise test consisting of 6 sets of 10 repetitions in the squat exercise at 80% of the subject's one repetition maximum.

RESULTS

This investigation observed lower testosterone responses following supplementation with soy protein in addition to a positive blunted cortisol response with the use of whey protein at some recovery time points. Although sex hormone binding globulin (SHBG) was proposed as a possible mechanism for understanding changes in androgen content, SHBG did not differ between experimental treatments. Importantly, there were no significant differences between groups in changes in estradiol concentrations.

CONCLUSION

Our main findings demonstrate that 14 days of supplementation with soy protein does appear to partially blunt serum testosterone. In addition, whey influences the response of cortisol following an acute bout of resistance exercise by blunting its increase during recovery. Protein supplementation alters the physiological responses to a commonly used exercise modality with some differences due to the type of protein utilized.