Gymnastik- och idrottshögskolan, GIH

INTRODUCTION: The ability to carry heavy loads is an important and necessary task during numerous outdoor activities and especially in military operations. The aim of this study was to investigate factors associated with load-carrying ability in men and women with and without extensive load-carrying experience.

MATERIALS AND METHODS: The energy expenditure during carrying no load, 20, 35, and 50 kg at 2 walking speeds, 3 and 5 km h-1, was studied in 36 healthy participants, 19 men (30 ± 6 years, 82.5 ± 7.0 kg) and 17 women (29 ± 6 years, 66.1 ± 8.9 kg), experienced (>5 years) in carrying heavy loads (n = 16, 8 women) or with minor or no such experience (n = 20, 9 women). A standard backpack filled with weights to according carry load was used during the walks. Anthropometric data, leg muscle strength, as well as trunk muscle endurance and muscle fiber distribution of the thigh, were also obtained. Extra Load Index (ELI)-the oxygen uptake (VO2) during total load over unloaded walking-was used as a proxy for load-carrying ability at 20, 35, and 50 kg (ELI20, ELI35, and ELI50, respectively). In addition to analyzing factors of importance for the ELI values, we also conducted mediator analyses using sex and long-term carrying experience as causal variables for ELI as the outcome value. The study was approved by the Regional Ethics Committee in Stockholm, Sweden.

RESULTS: For the lowest load (20 kg), ELI20, was correlated with body mass but no other factors. Walking with 35 and 50 kg load at 5 km h-1 body mass, body height, leg muscle strength, and absolute VO2max were correlated, while relative VO2max, trunk muscle endurance, and leg muscle fiber distribution were not correlated to ELI35 and ELI50.ELI50 at 5 km h-1 differed between the sexes. This difference was only mediated by the difference in body mass. Neither muscle fiber distribution, leg muscle strength, trunk muscle endurance, and body height nor did absolute or relative VO2max explain the difference.Participants with long-term experience of heavy load carrying had significant lower ELI20 and ELI50 values than those with minor or no experience, but none of the above studied factors could explain this difference.

CONCLUSION: The study showed that body mass, without sex differences, and experience of carrying heavy loads are the dominant factors for the ability to carry heavy loads. Even though the effect of experience alludes to the need for extensive carrying training, no causality can be proven. Load carry training intervention studies is suggested for future investigations.

Effective practices to improve skeletal muscle fatigue resistance are crucial for athletes as well as patients with dysfunctional muscles. To this end, it is important to identify the cellular signaling pathway that triggers mitochondrial biogenesis and thereby increases oxidative capacity and fatigue resistance in skeletal muscle fibers. Here, we test the hypothesis that the stress induced in skeletal muscle fibers by endurance exercise causes a reduction in the association of FK506-binding protein 12 (FKBP12) with ryanodine receptor 1 (RYR1). This will result in a mild Ca²⁺ leak from the sarcoplasmic reticulum (SR), which could trigger mitochondrial biogenesis and improved fatigue resistance. After giving mice access to an in-cage running wheel for three weeks, we observed decreased FKBP12 association to RYR1, increased baseline [Ca²⁺]_i, and signaling associated with greater mitochondrial biogenesis in muscle, including PGC1α1. After six weeks of voluntary running, FKBP12 association is normalized, baseline [Ca²⁺]_i returned to values below that of nonrunning controls, and signaling for increased mitochondrial biogenesis was no longer present. The adaptations toward improved endurance exercise performance that were observed with training could be mimicked by pharmacological agents that destabilize RYR1 and thereby induce a modest Ca²⁺ leak. We conclude that a mild RYR1 SR Ca²⁺ leak is a key trigger for the signaling pathway that increases muscle fatigue resistance.

BACKGROUND: Strength and power development are abilities important for athletic performance in many sports. Generally, resistance training based on gravity is used to improve these qualities. Flywheel training instead utilizes kinetic energy transferred to a flywheel. This allows for eccentric overload and variable resistance throughout the movement. The aim of this review was to identify the effects of flywheel training on multiple strength-related variables affecting athletic performance. The meta-analysis investigates the effects on (1) muscle growth (cross-sectional area (CSA) and volume/mass), (2) maximum dynamic strength, (3) development of power, (4) development of horizontal movement, and (5) development of vertical movement.

METHODS: The meta-analysis includes 20 experimental studies that met the inclusion criteria. The quality of included studies was ranked according to the PEDro scale. Possible bias was identified in Funnel plot analyses. To enable the compilation of all results analyses, the random effect model was carried out using the software Review Manager Version 5.3 and presented with Forest plots.

RESULTS: Flywheel training for a period of 4-24 weeks shows statistically significant increases in all strength aspects. Effect sizes were for hypertrophy, CSA 0.59; volume/mass 0.59; maximum strength 1.33; power 1.19; horizontal 1.01 and vertical movement 0.85. The evidence is particularly strong for beneficial effects from flywheel training in the development of maximal strength and power in trained younger individuals, and utilization of this training modality in shorter more intensive blocks.

CONCLUSIONS: Flywheel training is an effective method for improving several aspects of strength and power with importance for sports performance.

Nonverbal behaviour has an important function in team sports, but research is limited. Adopting a psychological momentum (PM) framework, this study explores the relationship between a team’s history of events, nonverbal post-shot celebrations in the form of gestures and touch shown by the shooter after scoring, and subsequent team performance during handball matches. A naturalistic design with systematic observation was chosen for the present study. Based on an existing coding scheme, 616 post-shot periods from 18 high-stake matches of the highest league in Sweden were analysed. Results showed that the better a team’s prior performance, the more gestures were displayed after scoring in the following period. A high degree of touch when playing well, and a low degree of touch when playing poorly were related to positive subsequent team performance, while, showing much touch when playing poorly, or showing little touch when playing well were related to negative subsequent team performance. The amount of displayed gesture and touch alone was not significantly related to subsequent team performance. To conclude, nonverbal post-shot celebrations were related to subsequent team performance, but only when the ongoing history of events was taken into account, and only for touch. Based on these results, the history of events emerges as an important variable when the dynamics of ongoing team sport matches are investigated. Furthermore, touch, compared to gesture, seems to be of more importance for subsequent team performance. As expected when investigating complex phenomena in ongoing matches, the findings resulted in small effect sizes.

Background: The ability to measure activity and physiology through wrist-worn devices provides an opportunity for cardiovascular medicine. However, the accuracy of commercial devices is largely unknown. Objective: To assess the accuracy of seven commercially available wrist-worn devices in estimating heart rate (HR) and energy expenditure (EE) and to propose a wearable sensor evaluation framework. Methods: We evaluated the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2. Participants wore devices while being simultaneously assessed with continuous telemetry and indirect calorimetry while sitting, walking, running, and cycling. Sixty volunteers (29 male, 31 female, age 38 +/- 11 years) of diverse age, height, weight, skin tone, and fitness level were selected. Error in HR and EE was computed for each subject/device/activity combination. Results: Devices reported the lowest error for cycling and the highest for walking. Device error was higher for males, greater body mass index, darker skin tone, and walking. Six of the devices achieved a median error for HR below 5% during cycling. No device achieved an error in EE below 20 percent. The Apple Watch achieved the lowest overall error in both HR and EE, while the Samsung Gear S2 reported the highest. Conclusions: Most wrist-worn devices adequately measure HR in laboratory-based activities, but poorly estimate EE, suggesting caution in the use of EE measurements as part of health improvement programs. We propose reference standards for the validation of consumer health devices (http://precision.stanford.edu/).

Sjutton kvinnliga vältränade försökspersoner, åtta stycken med vana att bära tungt och nio stycken utan sådan vana, genomförde gång på löpband och mjukt underlag i hastigheterna 3 och 5 km/tim med bärvikter i ryggsäck på 20, 35 och 50 kg.Mjukt underlag i form av blå gymnastikmattor, indikerande gång i lätt terräng, ökade energiomsättningen under både hastigheterna mellan 10 och 15 %, jämfört med hårt underlag (löpband) med en grads lutning. Energiomsättningen ökade i genomsnitt lika mycket med ökad hastighet som med ökad bärvikt. Den individuella variationen vid en given bärvikt och hastighet är mycket stor. Beroende på bärvikt och hastighet kan energiomsättningen variera med 100 %. Dessa stora variationer i energiomsättning bör uppmärksammas vid beräkning av energitilldelning via kosten vid längre militära operationer.Energiomsättningen vid tyngsta belastningen – 50 kilo bärvikt och hastigheten 5 km/tim – belastade försökspersonerna på i genomsnitt 57 % av maximal syreupptagningsförmåga. I individuella fall var belastningen 72 % av maximal syreupptagningsförmåga. Dessa höga belastningar är oacceptabelt höga för transporter under längre tid och kan vara en orsak till belastningsskador.Förmågan att bära tungt sammanfaller med ökad kroppsvikt och benmuskelstyrka. Bärförmåga för mindre vikter, högst 35 kg, sammanfaller inte med någon av ovanstående faktorer. Således, för tyngre bärvikter vid förflyttningar bör selektion av soldater ske enligt de uppmätta parametrarna, medan vad gäller lättare vikter föreligger inte samma selektionskriterier.En slutsats från resultaten av denna undersökning är den ursprungliga uttagningen till tunga arbetsuppgifter inom försvaret bör genomföras med tunga arbetsbelastningar, motsvarande de i denna undersökning. I kommande rapport sammanfattas studierna på män och kvinnors bärförmåga, likheter och olikheter mellan könen, möjliga selektionskriterier samt rekommendationer med utgångspunkt från genomförda undersökningar och resultat från olika andra undersökningar.

Introduction

Unilateral (UL) training as an alternative method for developing athletic performance are not well studied (1, 2). The purpose is to examine the effects of bilateral (BL) versus UL complex training combined with high intensity interval training (HIIT) on bilateral deficit (BLD), power deficit, maximal strength, jumping ability, straight sprint, change of direction sprint (CODS), repeated sprint ability (RSA) and specific endurance in elite handball players.

Methods

18 male and 12 female elite handball players were assigned to a BL (n=10) or UL (n=20) complex training program. In addition both groups trained HIIT twice a week. Training volume, intensity and exercise motions were similar between the groups. Tests included 1RM UL and BL Smith machine squat, UL and BL counter movement jump (CMJ), squat jump (SJ), modified T-test, straight sprint (5, 10, 20 and 30 m), repeated shuttle sprint ability (RSSA) and Yo-Yo Intermittent Recovery test (YYIR) before and after 6 weeks of training.

Results

Pooled data from both groups showed significant (p <0.01) improvements in maximal UL and BL strength, UL CMJ dominant leg, CODS and YYIR test, and an unwanted increase in the BLD and power deficit.

There were no significant differences training groups in any of the tests. However, only the UL group significantly improved RSA_total pre- to post testing (p < 0.01).

Discussion

Results indicate that this type of training is a relevant model for pre-season training of maximal strength, power and functional endurance. Despite the lack of differences between groups, UL training can be safer than BL training because of less absolute load.

1) Jones MT, Ambeganokar JP, Nindl BC, Smith JA, Headley SA. (2012). J Strength Cond Res, 26(4), 1094-100

2) McCurdy K, Langford G, Doscher MW, Wiley LP, Mallard KG. (2005). J Strength Cond Res, 19(1), 9-15

Sammanfattning

Fysisk aktivitet är ett komplext beteende och definieras, rent fysiologiskt, som all kroppsrörelse som ökar energiförbrukningen utöver viloförbrukning.

Aerob fysisk aktivitet är den vanligaste formen och kan utföras på olika intensiteter, från låg till mycket hög. Aerob fysisk aktivitet som utförs i strukturerad form med syfte att öka eller bibehålla konditionen kan benämnas konditionsträning.

Muskelstärkande fysisk aktivitet är den form av fysisk aktivitet som belastar och ställer krav på muskelstyrkan. Muskelstärkande fysisk aktivitet som utförs i strukturerad form kan benämnas styrketräning.

Grundläggande principer för kroppens svar på träning, som ”overload”, progression, reversibilitet, specificitet och individuella skillnader presenteras.

Boken Idrott och hjärtat beskriver de positiva effekterna av träning och fysisk aktivitet men tar också upp risker förenade med högintensiv aktivitet. Boken ger en god inblick i de grundläggande förändringarna i hjärtats arbete vid träning, på motions- och elitnivå.


Idrott och hjärtat är uppbyggd i tre delar: ”Det (troligen) friska hjärtat”, ”Det sjuka hjärtat” samt den tredje delen ”Praktiska tillämpningar” vilken beskriver dels undersökningstekniker och utredningsgång, viktiga och vanliga differentialdiagnoser och symtom, allt relaterat till hjärta och idrott.


Idrott och hjärtat riktar sig till lagläkare och andra idrottsmedicinskt engagerade, till idrottsintresserade specialister inom kardiologi, internmedicin, klinisk fysiologi och allmänmedicin samt till specialintresserade sjuksköterskor och fysioterapeuter.