Thursday, March 15, 2012

Serum Sex Hormone–Binding Globulin and Cortisol Concentrations are Associated With Overreaching During Strenuous Military Training

Serum Sex Hormone–Binding Globulin and Cortisol Concentrations are Associated With Overreaching During Strenuous Military Training

Tanskanen, MM, Kyröläinen, H, Uusitalo, AL, Huovinen, J, Nissilä, J, Kinnunen, H, Atalay, M, and Häkkinen, K. Serum sex hormone-binding globulin and cortisol concentrations are associated with overreaching during strenuous military training. J Strength Cond Res 25(3): 787-797, 2011-

The purpose was (a) to study the effect of an 8-week Finnish military basic training period (BT) on physical fitness, body composition, mood state, and serum biochemical parameters among new conscripts; (b) to determine the incidence of overreaching (OR); and (c) to evaluate whether initial levels or training responses differ between OR and noOR subjects. Fifty-seven males (19.7 ± 0.3 years) were evaluated before and during BT. Overreaching subjects had to fulfill 3 of 5 criteria: decreased aerobic physical fitness (V̇O2max), increased rating of perceived exertion (RPE) in 45-minute submaximal test at 70% of V̇O2max or sick absence from these tests, increased somatic or emotional symptoms of OR, and high incidence of sick absence from daily service. 

V̇O2max improved during the first 4 weeks of BT. During the second half of BT, a stagnation of increase in V̇O2max was observed, basal serum sex hormone-binding globulin (SHBG) increased, and insulin-like growth factor-1 and cortisol decreased. Furthermore, submaximal exercise-induced increases in cortisol, maximum heart rate, and postexercise increase in blood lactate were blunted.

 Of 57 subjects, 33% were classified as OR. They had higher basal SHBG before and after 4 and 7 weeks of training and higher basal serum cortisol at the end of BT than noOR subjects. In addition, in contrast to noOR, OR subjects exhibited no increase in basal testosterone/cortisol ratio but a decrease in maximal La/RPE ratio during BT. As one-third of the conscripts were overreached, training after BT should involve recovery training to prevent overtraining syndrome from developing. The results confirm that serum SHBG, cortisol, and testosterone/cortisol and maximal La/RPE ratios could be useful tools to indicate whether training is too strenuous.


Wednesday, March 14, 2012

Topic:Short Term Effects of Antioxidants and Zinc Supplements on Oxidative Stress
Reference:"The Short-term Effects of Antioxidant and Zinc Supplements on Oxidative Stress Biomarker Levels in Plasma: A Pilot Investigation," Brantley MA Jr, Osborn MP, et al, Am J Ophthalmol, 2012 Feb 28; [Epub ahead of print]. (Address: Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee, USA).
Summary:In a prospective, interventional case series study involving 19 subjects, 12 of whom had intermediate or advanced age-related macular degeneration AND 7 who served as controls, dietary supplementation with 500 mg vitamin C, 400 IU vitamin E, 15 mg beta-carotene, 80 mg zinc oxide, and 2 mg cupric oxide, while adhering to a controlled diet, for a period of 7 days was found to be associated with significantly lower mean plasma levels of cystine (CySS).

Tuesday, March 13, 2012

Supraspinal fatigue impedes recovery from a low-intensity sustained contraction in old adults


This study determined the contribution of supraspinal fatigue and contractile properties to the age difference in neuromuscular fatigue during and recovery from a low-intensity sustained contraction.

Cortical stimulation was used to evoke measures of voluntary activation and muscle relaxation during and after a contraction sustained at 20% of maximal voluntary contraction (MVC) until task failure with elbow flexor muscles in 14 young adults (20.9 ± 3.6 yr, 7 men) and 14 old adults (71.6 ± 5.4 yr, 7 men). Old adults exhibited a longer time to task failure than the young adults (23.8 ± 9.0 vs. 11.5 ± 3.9 min, respectively, P < 0.001). The time to failure was associated with initial peak rates of relaxation of muscle fibers and pressor response (P < 0.05). Increments in torque (superimposed twitch; SIT) generated by transcranial magnetic stimulation (TMS) during brief MVCs, increased during the fatiguing contraction (P < 0.001) and then decreased during recovery (P = 0.02). The increase in the SIT was greater for the old adults than the young adults during the fatiguing contraction and recovery (P < 0.05). Recovery of MVC torque was less for old than young adults at 10 min post-fatiguing contraction (75.1 ± 8.7 vs. 83.6 ± 7.8% of control MVC, respectively, P = 0.01) and was associated with the recovery of the SIT (r = –0.59,r2 = 0.35, P < 0.001). Motor evoked potential (MEP) amplitude and the silent period elicited during the fatiguing contraction increased less for old adults than young adults (P < 0.05).

The greater fatigue resistance with age during a low-intensity sustained contraction was attributable to mechanisms located within the muscle.

Recovery of maximal strength after the low-intensity fatiguing contraction however, was impeded more for old adults than young because of greater supraspinal fatigue. Recovery of strength could be an important variable to consider in exercise prescription of old populations.


Monday, March 12, 2012

What Strains the Anterior Cruciate Ligament During a Pivot Landing?

What Strains the Anterior Cruciate Ligament During a Pivot Landing?

  1. Youkeun K. Oh, PhD*
  2. David B. Lipps, MS
  3. James A. Ashton-Miller, PhD*,§ and 
  4. Edward M. Wojtys, MD§
+Author Affiliations
  1. *Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan
  2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
  3. School of Kinesiology, University of Michigan, Ann Arbor, Michigan
  4. §Bone and Joint Injury Prevention and Rehabilitation Center, University of Michigan, Ann Arbor, Michigan
  5. Department of Orthopaedic Surgery and MedSport, University of Michigan, Ann Arbor, Michigan
  6. Investigation performed at the University of Michigan, Ann Arbor, Michigan
  1.  Edward M. Wojtys, MD, MedSport, University of Michigan, 24 Frank Lloyd Wright Drive, PO Box 391, Ann Arbor, MI 48106-0391 (
  1. Presented at the 37th annual meeting of the AOSSM, San Diego, California, July 2011.
Background: The relative contributions of an axial tibial torque and frontal plane moment to anterior cruciate ligament (ACL) strain during pivot landings are unknown.

Hypothesis: The peak normalized relative strain in the anteromedial (AM) bundle of the ACL is affected by the direction of the axial tibial torque but not by the direction of the frontal plane moment applied concurrently during a simulated jump landing.

Study Design: Controlled and descriptive laboratory studies.

Methods: Fifteen adult male knees with pretensioned knee muscle-tendon unit forces were loaded under a simulated pivot landing test. Compression, flexion moment, internal or external tibial torque, and knee varus or valgus moment were simultaneously applied to the distal tibia while recording the 3D knee loads and tibiofemoral kinematics. The AM-ACL relative strain was measured using a 3-mm differential variable reluctance transducer. The results were analyzed using nonparametric Wilcoxon signed–rank tests. A 3D dynamic biomechanical knee model was developed using ADAMS and validated to help interpret the experimental results.

Results: The mean (SD) peak AM-ACL relative strain was 192% greater (P < .001) under the internal tibial torque combined with a knee varus or valgus moment (7.0% [3.9%] and 7.0% [4.1%], respectively) than under external tibial torque with the same moments (2.4% [2.5%] and 2.4% [3.2%], respectively). The knee valgus moment augmented the AM-ACL strain due to the slope of the tibial plateau inducing mechanical coupling (ie, internal tibial rotation and knee valgus moment); this augmentation occurred before medial knee joint space opening.

Conclusion: An internal tibial torque combined with a knee valgus moment is the worst-case ACL loading condition. However, it is the internal tibial torque that primarily causes large ACL strain.

Clinical Relevance: Limiting the maximum coefficient of friction between the shoe and playing surface should limit the peak internal tibial torque that can be applied to the knee during jump landings, ther


Thursday, March 8, 2012

Retention of Movement Pattern Changes After a Lower Extremity Injury Prevention Program Is Affected by Program Duration

  1. Darin A. Padua, PhD, ATC*,
  2. Lindsay J. DiStefano, PhD, ATC,
  3. Stephen W. Marshall, PhD§
  4. Anthony I. Beutler, MD,
  5. Sarah J. de la Motte, PhD, ATC and 
  6. Michael J. DiStefano, MA, ATC
+Author Affiliations
  1. Department of Exercise and Sports Science, Sports Medicine Research Laboratory, University of North Carolina, Chapel Hill, North Carolina
  2. Department of Kinesiology, University of Connecticut, Storrs, Connecticut
  3. §Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina
  4. Uniformed Services University of the Health Sciences, Bethesda, Maryland
  5. Investigation performed at the University of North Carolina, Chapel Hill
  1. * Darin A. Padua, PhD, ATC, University of North Carolina at Chapel Hill, 216 Fetzer Gym CB#8700, Chapel Hill, NC 27599 (


Background: Changes in movement patterns have been repeatedly observed immediately after completing a lower extremity injury prevention program. However, it is not known if movement pattern changes are maintained after discontinuing the training program.
Hypothesis: The ability to maintain movement pattern changes after training has ceased may be influenced by the program’s duration. The authors hypothesized that among individuals who completed either a 3-month or 9-month training program and who demonstrated immediate movement pattern changes, only those who completed the 9-month training program would maintain movement pattern changes after a 3-month period of no longer performing the exercises.
Study Design: Cohort study; Level of evidence, 2.
Methods: A total of 140 youth soccer athletes from 15 separate teams volunteered to participate. Athletes’ movement patterns were assessed using the Landing Error Scoring System (LESS) at pretest, posttest, and 3 months after ceasing the program (retention test). Eighty-four of the original 140 participants demonstrated improvements in their LESS scores between pretest and posttest (change in LESS score >0) and were included in the final analyses for this study (n = 84; 20 boys and 64 girls; mean age, 14 ± 2 years; age range, 11-17 years). Teams performed 3-month (short-duration group) and 9-month (extended-duration group) injury prevention programs. The exercises performed were identical for both groups. Teams performed the programs as part of their normal warm-up routine.
Results: Although both groups improved their total LESS scores from pretest to posttest, only the extended-duration training group retained their improvements 3 months after ceasing the injury prevention program (F2,137 = 3.38; P = .04).
Conclusion: Results suggest that training duration may be an important factor to consider when designing injury prevention programs that facilitate long-term changes in movement control.