Comparison between conventional and neuronavigated strategies to assess corticospinal responsiveness in unfatigued and fatigued knee-extensor muscles.

In studying neuromuscular fatigability, researchers commonly use functional criteria to position and hold the transcranial magnetic stimulation (TMS) coil during testing sessions. This could influence the magnitude of corticospinal excitability and inhibition responses due to imprecise and unsteady positions of the coil. To reduce coil position and orientation variability, neuronavigated TMS (nTMS) could be used. We evaluated the accuracy of nTMS and a standardized function-guided procedure for maintaining TMS coil position both in unfatigued and fatigued knee extensors. Eighteen participants (10F/8M) volunteered in two identical and randomized sessions. Maximal and submaximal neuromuscular evaluations were performed with TMS three times before (PRE_1) and three times after (PRE_2) a 2 min resting session and one time immediately after (POST) a 2-min sustained maximal voluntary isometric contraction (MVIC). The located "hotspot" [the location that evoked the largest motor-evoked potential (MEP) responses in the rectus femoris] was maintained either with or without nTMS. MEP, silent period (SP) and the distance between the "hotspot" and the actual coil position were recorded. A time × contraction intensity × testing session × muscle interaction was not observed for MEP, SP, and distance. Bland-Altman plots presented adequate agreements for MEP and SP. Spatial accuracy of TMS coil position over the motor cortex did not influence corticospinal excitability and inhibition in unfatigued and fatigued knee extensors. The variability in MEP and SP responses may be due to spontaneous fluctuations in corticospinal excitability and inhibition, and it is not altered by the spatial stability of the stimulation point.

Central and peripheral fatigue in knee and elbow extensor muscles after a long-distance cross-country ski race.

Although elbow extensors (EE) have a great role in cross-country skiing (XC) propulsion, previous studies on neuromuscular fatigue in long-distance XC have investigated only knee extensor (KE) muscles. In order to investigate the origin and effects of fatigue induced by long-distance XC race, 16 well-trained XC skiers were tested before and after a 56-km classical technique race. Maximal voluntary isometric contraction (MVC) and rate of force development (RFD) were measured for both KE and EE. Furthermore, electrically evoked double twitch during MVC and at rest were measured. MVC decreased more in KE (-13%) than in EE (-6%, P = 0.016), whereas the peak RFD decreased only in EE (-26%, P = 0.02) but not in KE. The two muscles showed similar decrease in voluntary activation (KE -5.0%, EE -4.8%, P = 0.61) and of double twitch amplitude (KE -5%, EE -6%, P = 0.44). A long-distance XC race differently affected the neuromuscular function of lower and upper limbs muscles. Specifically, although the strength loss was greater for lower limbs, the capacity to produce force in short time was more affected in the upper limbs. Nevertheless, both KE and EE showed central and peripheral fatigue, suggesting that the origins of the strength impairments were multifactorial for the two muscles.

Injury and Illness Rates During Ultratrail Running.

This study aimed to describe injury/illness rates in ultratrail runners competing in a 65-km race to build a foundation for injury prevention and help race organizers to plan medical provision for these events. Prospectively transcribed medical records were analysed for 77 athletes at the end of the race. Number of injuries/illnesses per 1 000 runners and per 1 000-h run, overall injury/illness rate and 90% confidence intervals and rates for major and minor illnesses, musculoskeletal injuries, and skin disorders were analysed. A total of 132 injuries/illnesses were encountered during the race. The overall injuries/illnesses were 1.9 per runner and 13.1 per 1 000-h run. Medical illnesses were the most prominent medical diagnoses encountered (50.3%), followed by musculoskeletal injuries (32.8%), and skin-related disorders (16.9%). Despite the ultra-long nature of the race, the majority of injuries/illnesses were minor in nature. Medical staff and runners should prepare to treat all types of injuries and illnesses, especially the fatigue arising throughout the course of an ultratrail run and injuries to the lower limbs. Future studies should attempt to systematically identify injury locations and mechanisms in order to better direct injury prevention strategies and plan more accurate medical care.

Gokyo Khumbu/Ama Dablam Trek 2012: effects of physical training and high-altitude exposure on oxidative metabolism, muscle composition, and metabolic cost of walking in women.

PURPOSE: We investigated the effects of moderate-intensity training at low and high altitude on VO2 and QaO2 kinetics and on myosin heavy-chain expression (MyHC) in seven women (36.3 yy ± 7.1; 65.8 kg ± 11.7; 165 cm ± 8) who participated in two 12- to 14-day trekking expeditions at low (598 m) and high altitude (4132 m) separated by 4 months of recovery. METHODS: Breath-by-breath VO2 and beat-by-beat QaO2 at the onset of moderate-intensity cycling exercise and energy cost of walking (Cw) were assessed before and after trekking. MyHC expression of vastus lateralis was evaluated before and after low-altitude and after high-altitude trekking; muscle fiber high-resolution respirography was performed at the beginning of the study and after high-altitude trekking. RESULTS: Mean response time of VO2 kinetics was faster (P = 0.002 and P = 0.001) and oxygen deficit was smaller (P = 0.001 and P = 0.0004) after low- and high-altitude trekking, whereas ˙ QaO2 kinetics and Cw did not change. Percentages of slow and fast isoforms of MyHC and mitochondrial mass were not affected by low- and high-altitude training. After training altitude, muscle fiber ADP-stimulated mitochondrial respiration was decreased as compared with the control condition (P = 0.016), whereas leak respiration was increased (P = 0.031), leading to a significant increase in the respiratory control ratio (P = 0.016). CONCLUSIONS: Although training did not significantly modify muscle phenotype, it induced beneficial adaptations of the oxygen transport-utilization systems witnessed by faster VO2 kinetics at exercise onset.

Changes in lung function during an extreme mountain ultramarathon.

This study aimed to assess the effects of an extreme mountain ultramarathon (MUM, 330 km, 24,000 D+) on lung function. Twenty-nine experienced male ultramarathon runners performed longitudinally [before (pre), during (mid), and immediately after (post) a MUM] a battery of pulmonary function tests. The tests included measurements of forced vital capacity, forced expiratory volume in 1 s, peak flow, inspiratory capacity, and maximum voluntary ventilation in 12 s (MVV12). A significant reduction in the running speed was observed (-43.0% between pre-mid and mid-post; P < 0.001). Expiratory function declined significantly at mid (P < 0.05) and at post (P < 0.05). A similar trend was observed for inspiratory function (P < 0.05). MVV12 declined at mid (P < 0.05) and further decreased at post (P < 0.05). Furthermore, there are significant negative correlations between performance time and MVV12 pre-race (R = -0.54, P = 0.02) as well as changes in MVV12 between pre- and post-race (R = -0.53, P = 0.009). It is concluded that during an extreme MUM, a continuous decline in pulmonary function was observed, likely attributable to the high levels of ventilation required during this MUM in a harsh mountainous environment.

Does the junior IAAF athletic world championship represent a springboard for the success in the throwing events? A retrospective study.

AIM: The aim of the present study was to analyze how many finalists of the IAAF World Junior Championships (WJC) in the throwing events were present in the senior IAAF ranking at the end of 2012. METHODS: The results of the 8 male and the 8 female finalists of all throwing events of the last 5 editions of the WJC from the 2002 edition were gathered. We analyzed how many athletes were missing from the IAAF ranking in 2012. For those athletes that did not drop out we monitored their progression in performance comparing their WJC and their 2012 performance. Moreover, we evaluated if the relative age effects (RAE) influenced drop out rate. RESULTS: Drop out rate was 58% in 2002, 59% in 2004, 39% in 2006, and 28% in 2008 and in 2010. The female javelin throwers showed the highest drop out rate (100%) in 2002, while the female hammer throwers showed the lowest drop out rate (0%) in 2008. Performance decreased for all male shot putters, discus and hammer throwers (P<0.001). For females and for male javelin throwers, performance increased (P<0.001). RAEs showed no significant influence on drop out rate CONCLUSION: Even if 8 of the finalists won a medal at the Olympic Games or at the World Championships, it is still not clear if participation at the WJC is a prerequisite to success at a senior level, given the elevated drop out rate observed in the present study.

Anthropometric characteristics of top-class Kenyan marathon runners.

AIM: This study aims to: 1) describe the current anthropometric profiles of Kenyan marathon runners and 2) establish a set of reference values useful for future investigations on athlete selection, talent identification, and training programme development. METHODS: The participants were 14 male top-class Kenyan marathon runners (mean [s] age 27.71 [3.75] yrs, height 171.21 [6.12] cm, body mass 57.71 [4.02] kg, marathon personal best 02h 07min 16s (01min 55s); training volume: 180-220 km·wk-1; high:low intensity training ratio: 1:2). The anthropometric profiles included the measurement of skinfolds, and segment lengths, breadths, and girths. To estimate body density (BD) multiple regression equations were calculated using the sum of 7-skinfolds method and then converted to percentage of body fat (%BF). The somatotype, somatotype dispersion mean (SDM), somatotype attitudinal mean (SAM), and height to weight ratio (HWR) as well as the skinfolds extremity to trunk ratio (E:T) were also calculated. RESULTS: The mean (s) of BD, %BF, SDM, SAM, HWR and E:T were 1.13 (0.02), 8.87 (0.07) %, 4.58 (3.62), 0.51 (0.09), 44.32 (1.06), and 0.36 (0.11), respectively. The mean (s) endomorphy, mesomorphy, and ectomorphy were 1.53 (0.32), 1.61 (1.81), and 3.86 (0.78), respectively. CONCLUSION: Top-class Kenyan marathon runners seem to have ectomorphy as dominant, with endomorphy and mesomorphy more than one-half unit lower. Despite population comparisons would be required to identify any connection between specific anthropometric dimensions, these reference data should be useful to practitioners and researchers, providing useful information for talent identification and development and for the assessment of training progression in marathon.

Cardiovascular responses during an indoor race walking competition.

AIM: This study aims to examine the cardiovascular responses during an indoor race walking competition over the distance of 3-km for female and 5-km for male athletes. METHODS: During the Italian indoor RW Championship heart rate was monitored on eleven well trained race walkers (five men and six women) and then refereed as percentages of individuals' theoretical maximum heart rate (206-0.7·age). To provide a measure of relative intensity, five HR zones were assessed. Alterations in % HRmax both for the five and three 1000-m split distances were determined. RESULTS: During the 5-km race the athletes spent 79.7% (15 min 45 s) at HR5 (i.e., 90-100% of HRmax). Specifically, % HRmax increased by 10% in the last compared to the first 1000-m sector (P=0.006, effect size = 2.47±0.83, very large), with the first 1000-m sector lower than the subsequent ones (P=0.01, effect size=2.17 to 2.47, very large). While, for the 3-km the athletes spent 86.9% (11 min 35 s) at HR5 (i.e., 90-100% of HRmax) with no differences observed in the % HRmax between the three 1000-m sectors (P>0.01). CONCLUSION: The dissemination of performance and physical attributes identified within the present study reveal that the exercise intensity of indoor race walking competitions has a high-intensity profile and will assist coaches and athletes in formulating appropriate training, competition and recovery.