The effect of repeated periods of speed endurance training on performance,running economy,and muscle adaptations

The effect of repeated intense training interventions was investigated in eight trained male runners (maximum oxygen uptake [VO ₂‐max]: 59.3±3.2 mL/kg/min, mean±SD) who performed 10 speed endurance training (SET ; repeated 30‐seconds “all‐out” bouts) and 10 aerobic moderate‐intensity training sessions during two 40‐day periods (P1 and P2) separated by ~80 days of habitual training. Before and after both P1 and P2, subjects completed an incremental test to exhaustion to determine VO ₂‐max and a repeated running test at 90% vVO ₂‐max to exhaustion (RRT ) to determine short‐term endurance capacity. In addition, running economy (RE ) was measured at 60% vVO ₂‐max (11.9±0.5 km/h) and v10‐km (14.3±0.9 km/h), a 10‐km track‐running test was performed, and a biopsy from m. vastus lateralis was collected. 10‐km performance and VO ₂‐max (mL/min) were the same prior to P1 and P2, whereas RE was better (P <.05) before P2 than before P1. During P1 and P2, 10‐km performance (2.9% and 2.3%), VO ₂‐max (2.1% and 2.6%), and RE (1.9% and 1.8% at 60% vVO ₂‐max; 1.6% and 2.0% at v10‐km) improved (P <.05) to the same extent, respectively. Performance in RRT was 20% better (P <.05) after compared to before P2, with no change in P1. No changes in muscle expression of Na⁺,K⁺‐ATP ase α1, α2 and β1, NHE 1, SERCA 1 and SERCA 2, actin, and CaMKII were found during neither P1 nor P2. Thus, the present study demonstrates that a second period of intense training leads to improved short‐term performance and further improved RE , whereas 10‐km performance and VO ₂‐max improve to the same extent as during the first period.     

Effect of training load on OBLA determination

Fifteen male long-distance runners, 35.9 +/- 8.2 years of age, participated in the study. They had 5.7 +/- 2.3 years of running experience, marathon best time of 2,58:51 +/- 0,14:45 h, 10-km personal record of 37:18 +/- 2:50 min, and maximal aerobic power of 64.6 +/- 5.8 ml.kg-1.min-1. Their 4 mM.l-1 lactate threshold (OBLA) was tested twice in a randomized order: once following a week of light, pre-race-like training, and once after a week of heavy training load. The parameters measured during the OBLA tests were: rating of perceived exertion (RPE), running economy (E), heart rate (HR), respiratory exchange ratio (R), and running velocity at OBLA. Compared with the light load treatment, RPE following the heavy training week rose by 0.8 units, HR and E remained unchanged, and R decreased slightly (0.012). Running velocity at OBLA was raised 0.42 km.h-1 by the heavy training, but a negative correlation was found between this change and the baseline (light load) OBLA velocity (r = -0.57). It is suggested that in athletes the usefulness of OBLA testing, aimed at assessing current performance capacity, could be compromised by lack of control over the immediately preceding training schedules. However, it appears that the susceptibility to the lack of such standardization may be reduced or absent in higher level runners.     

No effect of seasonal variation in training load on immuno-endocrine responses to acute exhaustive exercise

This study was designed to examine the relationship between seasonal changes in training and competition load, and changes in leukocyte subsets, stress hormones, and interleukin-6 (IL-6) in response to a standardised bout of endurance exercise. In addition, changes in mood states were monitored. Ten male, international Nordic skiers, age 20-29, maximal oxygen uptake 70-82 ml x kg(-1) x min(-1) performed the same incremental treadmill tests to exhaustion at the same time of day (+/-1 h), during the competitive season (in-season HI test) and the recovery season (off-season LO test). The subject filled out a training and competition log (TC score) for three weeks prior to each test and a 65-item Profile of Mood State (POMS) test on arrival at the laboratory. Venous blood for haematological, hormonal, and IL-6 analysis was drawn before and at 0, 15, 30, 60, 120 and 240 min after the test. TC score was more than twice as high during the competitive season (16.0 +/- 3.9) compared to the off-season period (7.0 +/- 4.4). An ANOVA procedure for repeated measures showed no difference in exercise induced changes in concentrations of neutrocytes, lymphocytes, epinephrine, ACTH or cortisol between the in-season HI and off-season LO tests; however, norepinephrine and the IL-6 concentrations were elevated at the in-season HI test compared to the off-season LO test. There were no significant differences in POMS global mood score or sub-scores between the in-season HI and the off-season LO tests. Thus, in a group of elite Nordic skiers, we conclude that a doubling of the training and competition load during the winter season does not alter the leukocyte and stress hormone responses to an incremental exercise test to exhaustion.     

Resistance training for strength: effect of number of sets and contraction speed

PURPOSE: To compare effects on strength in the early phase of resistance training with one or three sets and fast or slow speeds. METHODS: A total of 115 healthy, untrained subjects were randomized to a control group or one of four training groups: one set fast (approximately 140 degrees.s(-1)), three sets fast, one set slow (approximately 50 degrees.s(-1)), or three sets slow. All subjects attended training 3 x wk(-1) for 6 wk. Subjects in the training groups performed unilateral elbow flexion contractions with a target six- to eight-repetition maximum load. Control subjects sat at the training bench but did not train. One repetition maximum strength, arm circumference, and biceps skinfold thickness were measured before and after training. RESULTS: One slow set increased strength by 25% (95% CI 13-36%, P < 0.001). Three sets of training produced greater increases in strength than one set (difference = 23% of initial strength, 95% CI 12-34%, P < 0.001) and fast training resulted in a greater increase in strength than slow training (difference = 11%, 95% CI 0.2-23%, P = 0.046). The interaction between sets and speed was negative (-15%) and of borderline significance (P = 0.052), suggesting there is a benefit of training with three sets or fast speeds, but there is not an additive benefit of training with both. CONCLUSIONS: Three sets of exercise produce twice the strength increase of one set in the early phase of resistance training. Training fast produces greater strength increases than training slow; however, there does not appear to be any additional benefit of training with both three sets and fast contractions.     

Movement profile influences systemic stress and biomechanical resilience to high training load exposure

Objectives

Determine the influence of movement profile on systemic stress and mechanical loading before and after high training load exposure.

The effect of a balance training program on the risk of ankle sprains in high school athletes

BACKGROUND: Ankle sprains are the most common musculoskeletal injuries that occur in athletes, and they have a profound impact on health care costs and resources. HYPOTHESIS: A balance training program can reduce the risk of ankle sprains in high school athletes. STUDY DESIGN: Randomized controlled clinical trial; Level of evidence, 1. METHODS: Seven hundred and sixty-five high school soccer and basketball players (523 girls and 242 boys) were randomly assigned to either an intervention group (27 teams, 373 subjects) that participated in a balance training program or to a control group (28 teams, 392 subjects) that performed only standard conditioning exercises. On-site athletic trainers recorded athlete exposures and sprains. RESULTS: The rate of ankle sprains was significantly lower for subjects in the intervention group (6.1%, 1.13 of 1000 exposures vs 9.9%, 1.87 of 1000 exposures; P = .04). Athletes with a history of an ankle sprain had a 2-fold increased risk of sustaining a sprain (risk ratio, 2.14), whereas athletes who performed the intervention program decreased their risk of a sprain by one half (risk ratio, 0.56). The ankle sprain rate for athletes without previous sprains was 4.3% in the intervention group and 7.7% in the control group, but this difference was not significant (P = .059). CONCLUSION: A balance training program will significantly reduce the risk of ankle sprains in high school soccer and basketball players.     

The effects of resisted sled-pulling sprint training on acceleration and maximum speed performance

AIM: The purpose of the present study was to examine the effects of resisted (RS) and un-resisted (US) sprint training programs on acceleration and maximum speed performance. METHODS: Twenty-two male students (age 20.1+/-1.9 y, height 1.78+/-7 cm, and weight 73+/-2 kg) completed RS (n=11) or US (n=11) sprint training programs. The RS group followed a sprint-training program with 5 kg sled pulling and the US group followed a similar sprint-training program without sled pulling. The training program consisted of 4x20 m and 4x50 m maximal runs, and was applied 3 times/week for 8 weeks. Before and after the training programs the subjects performed a 50 m run and the running velocity of 0(-1)0 m, 10(-2)0 m, 20-40 m and 40-50 m was measured. In addition, stride length and stride frequency were evaluated at the 3(rd) stride in acceleration phase and between 42-47 m in maximum speed phase. RESULTS: The RS improved running velocity in the run sections 0(-1)0 m and 0(-2)0 m, while in US group the running velocity in all run sections in acceleration phase remained unchanged (p>0.05). In contrast, RS training had no effect on running velocity in maximum speed phase, whereas US improved running velocity in 20-40 m, 40-50 m, and 20-50 m run sections (p<0.05). Stride rate increased only after RS in acceleration phase (+7.1+/-2.9%; p<0.05), whereas stride length increased only after US in maximum speed phase (+5.5+/-2.5%; p<0.05). CONCLUSION: Sprint training with 5 kg sled pulling for 8 weeks improves acceleration performance (0(-2)0), while un-resisted sprint training improves performance in maximum speed phase (20-40) in non-elite athletes. It appears that each phase of sprint run demands a specific training approach.     

The impact of bupropion on psychomotor performance

INTRODUCTION: The NDRI (noradrenalin-dopamine re-uptake inhibitor) bupropion SR (sustained-release) is marketed as Wellbutrin* for treatment of depression or Zyban as a smoking cessation aid. There has been considerable interest in the possibility of returning aircrew to restricted flying duties once stabilized on bupropion SR after resolution of depressive symptoms, or while taking bupropion SR for smoking cessation. This study was undertaken to determine whether bupropion SR affects psychomotor performance. METHOD: There were 24 subjects (18 men and 6 women) who were assessed for psychomotor performance during placebo and bupropion SR treatment in a double-blind cross-over in counter-balanced order. Each treatment arm lasted 5 wk. The daily bupropion SR dose was 150 mg during week 1, and 300 mg during weeks to 2 to 5. Subjects completed a drug side-effect questionnaire and were tested on two psychomotor test batteries once per week during each of the placebo and drug arms. RESULTS: There was no significant Impact of bupropion SR on serial reaction time, logical reasoning, serial subtraction, or multitask performance. With respect to drug side effects there was a main effect of drug on "number of awakenings" (p < 0.048), "difficulty returning to sleep" (p < 0.004), and "dry mouth" (p < 0.049). There was no impact of bupropion SR on dizziness. DISCUSSION: While we found some of the expected side effects due to bupropion SR, there was no effect on psychomotor performance. These findings support the possibility of returning aircrew to restricted flight duties (e.g., in non-fast jet aircraft) under close observation once stabilized on bupropion SR.     

The impact of sertraline on psychomotor performance

INTRODUCTION: Aircrew receiving treatment for depression are grounded during treatment and follow-up observation, generally amounting to at least 1 yr. Selective serotonin re-uptake inhibitors (SSRls) offer new treatment options for depression, of which sertraline (Zoloft) has the least imposing side-effect profile. There has been considerable interest in the possibility of returning aircrew to restricted flying duties once stablized on an SSRI with resolution of depression. This study was undertaken to determine whether or not sertraline effects psychomotor performance. METHOD: There were 19 volunteer non-depressed subjects (12 men and 7 women) who were assessed for psychomotor performance during placebo and sertraline treatment, in a double-blind cross-over protocol in counter-balanced order. Each treatment arm lasted 5 wk and involved ingesting one capsule each morning. The daily sertraline dose was 50 mg during week 1, 100 mg during week 2, and 150 mg during weeks 3, 4, and 5. Subjects completed a drug side-effect questionnaire and were tested on two psychomotor test batteries once per week, on the same weekday, at the same time of day throughout each 5-wk treatment period. RESULTS: There was no significant effect of sertraline on serial reaction time, logical reasoning, serial subtraction, or multitask performance. With respect to drug side effects, there was a main effect of drugs on "getting to sleep" (p < 0.002), "awakenings" (p < 0.007), "returning to sleep" (p < 0.001), "dry mouth" (p < 0.016), "nausea" (p < 0.001), "diarrhea" (p < 0.026), "tremors" (p < 0.005), and "sweating" (p < 0.016), as well as a drug x trials interaction for "drowsiness" (p < 0.012), "libido" (p < 0.039), and "difficulty with ejaculation" (p < 0.001). There was no effect of sertraline on dizziness. CONCLUSIONS: While we found some of the expected side effects due to sertraline, there was no effect on psychomotor performance. These findings support the possibility of selected use in aircrew and should be helpful in the ongoing aeromedical discussion about this evolving issue.     

The effect of reporting speed on plain film reporting errors

AIM: To determine whether reporting plain films at faster rates lead to a deterioration in accuracy. METHODS: Fourteen consultant radiologists were asked to report a total of 90 radiographs in three sets of 30. They reported the first set at the rate they would report normally and the subsequent two sets in two thirds and one half of the original time. The 90 radiographs were the same for each radiologist, however, the order was randomly generated for each. RESULTS: There was no significant difference in overall accuracy for each of the three film sets (p=0.74). Additionally no significant difference in the total number of false-negatives for each film set was detected (p=0.14). However, there was a significant decrease in the number of false-positive reports when the radiologists were asked to report at higher speeds (p=0.003). CONCLUSIONS: When reporting accident and emergency radiographs increasing reporting speed has no overall effect upon accuracy, however, it does lead to less false-positive reports.     

Effects of an eight week military training program on aerobic indices and psychomotor function

This study assessed the effects of eight weeks of military training on aerobic fitness indices, military skills and neuropsychological function. Thirty five (n = 35) male Irish Defence Forces personnel, divided into training (n = 20) and control (n = 15) subgroups, completed tests of military aptitude (Kim's games, judging distance, fire order, map reading, weapon assembly) and neuropsychological function (Symbol digit modalities test (SDMT), Trail making test, Stroop test and grooved pegboard test) pre- and post-intervention. The repeated measures study design sought to account for any learning effect. Participants also completed a 10km route march, a two mile run and three by 20m shuttle run tests at both time points to quantify changes in fitness variables. The training sub-group significantly (P < 0.001) improved mean 20m shuttle-run distance and consequently estimated VO2 max pre- to post-intervention (49.8 +/- 1.0 vs. 52.4 +/- 0.9 mL x kg x min(-1)). Two mile run time was not significantly improved. Mean %HRmax during the 10km route march was significantly higher in both training (P < 0.001) and control (P < 0.01) sub-groups post-intervention (71 +/- 1 and 83 +/- 1%) compared to pre-intervention (65 +/- 1 and 77 +/- 1%). However, the training sub-group conducted the route march at a significantly faster speed on the second occasion. Military training significantly improved performance in 3/18 neuropsychological test components and 2/12 military skills test components. Training significantly improved ability to estimate both short (error; 36 +/- 6 vs. 12 +/- 1%) and intermediate (error; 72 +/- 12 vs. 11 +/- 3%) distances post-intervention. The training sub-group significantly (P < 0.01) improved SDMT score and mean Trail 1 time pre- to post-intervention (58.0 +/- 2.8 vs. 69.5 +/- 3.4; 18.1 +/- 0.8 vs. 14.4 +/- 0.8s, respectively). In Part 3 of the Stroop test, time mediated a significant (P < 0.05) and selective improvement in the training sub-group (51.3 +/- 3.2 vs. 63.8 +/- 5.4). In conclusion, aerobic fitness and a minority of neuropsychological and military skills tests improved following 8 weeks of military training.     

The effect of two different speed endurance training protocols on a multiple shuttle run performance in young elite male soccer players

There is not enough evidence on the impact of different speed endurance training regimes on footballers’ ability to perform multiple shuttle run performance. This study examined the effect of 4 weeks of speed endurance maintenance (SEM) and speed endurance production (SEP) training on the 5-meter multiple shuttle run test (5-m MST) performance in young elite soccer players. A parallel two-groups, longitudinal design was used. Fifteen players were divided to either SEM (8 repetitions of 20-s all-out sprint interspersed with 40 s of recovery) or SEP (8 repetitions of 20-s all-out bout interspersed with 120 s of recovery) training group. SEM improved the ability to tolerate fatigue and maintained the performance development during the 5-m MST while SEP increased only the 1^st sprint showing, simultaneously, an increased fatigue index and performance decrement. The selection of which training regimes to prioritize should be based on the players’ characteristics and individual game requirements

Abbreviations: SEP: Speed Endurance Production; SEM: Speed Endurance Maintenance; PRE: Baseline; POST: End of experimental protocol; 5-m MST: 5-meters Multiple Shuttle Run Test; TD: Total Distance; FI: Fatigue Index; MSTdec: Percentage Decrement Score; BMI: Body Mass Index     

The effect of military load carriage on ground reaction forces

Load carriage is an inevitable part of military life both during training and operations. Loads carried are frequently as high as 60% bodyweight, and this increases injury risk. In the military, load is carried in a backpack (also referred to as a Bergen) and webbing, these combined form a load carriage system (LCS). A substantial body of literature exists recording the physiological effects of load carriage; less is available regarding the biomechanics. Previous biomechanical studies have generally been restricted to loads of 20% and 40% of bodyweight, usually carried in the backpack alone. The effect of rifle carriage on gait has also received little or no attention in the published literature. This is despite military personnel almost always carrying a rifle during load carriage. In this study, 15 male participants completed 8 conditions: military boot, rifle, webbing 8 and 16 kg, backpack 16 kg and LCS 24, 32 and 40 kg. Results showed that load added in 8 kg increments elicited a proportional increase in vertical and anteroposterior ground reaction force (GRF) parameters. Rifle carriage significantly increased the impact peak and mediolateral impulse compared to the boot condition. These effects may be the result of changes to the vertical and horizontal position of the body's centre of mass, caused by the restriction of natural arm swing patterns. Increased GRFs, particularly in the vertical axis, have been positively linked to overuse injuries. Therefore, the biomechanical analysis of load carriage is important in aiding our understanding of injuries associated with military load carriage.     

The effect of walking speed on muscle function and mechanical energetics

Modulating speed over a large range is important in walking, yet understanding how the neuromotor patterns adapt to the changing energetic demands of different speeds is not well understood. The purpose of this study was to identify functional and energetic adaptations in individual muscles in response to walking at faster steady-state speeds using muscle-actuated forward dynamics simulations. The simulation data were invariant with speed as to whether muscles contributed to trunk support, forward propulsion or leg swing. Trunk support (vertical acceleration) was provided primarily by the hip and knee extensors in early stance and the plantar flexors in late stance, while trunk propulsion (horizontal acceleration) was provided primarily by the soleus and rectus femoris in late stance, and these muscle contributions all systematically increased with speed. The results also highlighted the importance of initiating and controlling leg swing as there was a dramatic increase at the higher walking speeds in iliopsoas muscle work to accelerate the leg in pre- and early swing, and an increase in the biarticular hamstring muscle work to decelerate the leg in late swing. In addition, walking near self-selected speeds (1.2m/s) improves the utilization of elastic energy storage and recovery in the uniarticular ankle plantar flexors and reduces negative fiber work, when compared to faster or slower speeds. These results provide important insight into the neuromotor mechanisms underlying speed regulation in walking and provide the foundation on which to investigate the influence of walking speed on various neuromotor measures of interest in pathological populations.     

高性能战斗机飞行员颈肌拉力训练的效果评价

目的旨在探讨高性能战斗机飞行员颈肌训练的新方法及训练效果。方法采用自行设计研制的NMT-I型颈肌训练器,对来院疗养的98名高性能战斗机飞行员进行了颈肌训练,并对训练器材及训练效果进行了观察和评价。结果98名飞行员经系统的颈肌训练后,运动成绩较训练前明显提高,有非常显著性意义(P<0.01)。其中颈后拉训练平均提高2.74次/min,颈前拉提高2.59次/min,颈左右侧拉提高2.51次/min,颈左右侧屈拉提高2.62次/min;训练前不合格者37人经每周3次、共4周训练均达到了合格标准。结论该NMT-I型颈肌训练器结构合理,性能稳定,可进行前、后拉,左、右侧拉及左、右侧屈拉共6个方位的颈部肌肉训练,受训员可自行控制,安全可靠,可明显提高颈部肌肉力量及肌肉耐力。