Gymnastik- och idrottshögskolan, GIH

This study investigates how different recovery periods after high-intensity interval training (HIIT) affects strength and explosive performance during a power training (PT) session. Fifteen female elite ice hockey players (22.5 ± 5.2 years) performed PT, including 6 sets of 2 repetitions (reps) of isometric leg press (ILP) and 6 sets of 3 reps of countermovement jump (CMJ), following a rested state and 10 minutes, 6 hours, or 24 hours after HIIT (3 sets of 8 × 20 seconds at 115% of power output at maximal oxygen consumption on a cycle ergometer). Peak force (PF) and peak rate of force development (pRFD) were measured during the ILP. Peak jump height (PJH), concentric phase duration (ConDur), eccentric phase duration, total duration, peak power (PP), velocity at peak power (V@PP), and force at peak power were measured during CMJ. The following variables were significantly reduced when only a 10-minute recovery period was allowed between HIIT and PT: PF was reduced by 7% (p < 0.001), pRFD by 17% (p < 0.001), PJH by 4% (p < 0.001), ConDur by 4% (p = 0.018), PP by 2% (p = 0.016), and V@PP by 2% (p = 0.007). None of the measured variables were reduced when PT was performed 6 and 24 hours after HIIT. We conclude that strength and explosive performance of elite female ice hockey players is reduced 10 minutes after HIIT but not negatively affected if a rest period of at least 6 hours is provided between HIIT and PT.

Spatiotemporal gait parameters such as step time and walking speed can be used to quantify gait performance and determine physical function. Inertial measurement units (IMUs) allow for the measurement of spatiotemporal gait parameters in unconstrained environments but must be validated against a gold standard.

While many IMU systems and algorithms have been validated during treadmill walking and overground walking in a straight line, fewer studies have validated algorithms during more complex walking conditions such as continuous turning in different directions.

This study explored the concurrent validity in a population of healthy adults (range 26–52 years) of three different algorithms using lumbar and foot mounted IMUs to calculate spatiotemporal gait parameters: two methods utilizing an inverted pendulum model, and one method based on strapdown integration. IMU data was compared to a Vicon twelve-camera optoelectronic system, using data collected from 9 participants performing straight walking and continuous walking trials at different speeds, resulting in 162 walking trials in total. Intraclass correlation coefficients ₍ICC_a,1) for absolute agreement were calculated between the algorithm outputs and Vicon output.

Temporal parameters were comparable in all methods and ranged from moderate to excellent, except double support time which was poor. Strapdown integration performed better for estimating spatial parameters than pendulum models during straight walking, but worse during turning. Selecting the most appropriate model should take into consideration both speed and walking condition.

New methods to screen for and identify early-stage dementia disorders are highly sought after. The purpose of this pilot study is to develop a study protocol for a dual-task test aimed at aiding the early detection of dementia disorders. We used the Timed Up-and-Go (TUG) test, which is a mobility task involving starting in a sitting position, standing up, walking three meters to cross a line on the floor, turning around, walking back and sitting down again. We combined TUG with the verbal task of naming different animals. Pilot study participants were 43 individuals with and without established dementia diagnoses who attended a clinic for memory assessment. Video-recorded test performances were systematically analysed. Deviant test performances concerning the interplay between test administration and participants' responses to the assessment instructions were revealed and led to refinements being made to the final study protocol. Exploration of the dual-task test outcome measures in a sub-sample of 22 persons, ten with and twelve without dementia, indicated that step-length and number of named animals after the turning point of the dual-task test might constitute appropriate measures for examining this kind of sample. We concluded that the refined study protocol is feasible for testing individuals undergoing initial memory assessments and healthy controls. Follow-up studies with larger samples are being carried out and will bring new knowledge to this area of research. It may also provide an opportunity for further studies exploring possibilities for broad clinical implementation.

The purpose of this study was to investigate the effect of ball temperature on impact ball speed and carry distance during golf drives in a blind randomized test design. The balls were exposed to a temperature-controlled environment (4?°C, 18?°C, 32?°C, and 46?°C) for 24?h prior to the test and each temperature group consisted of 30 balls. The 120 drives were performed by an elite male golfer (handicap: 0.0) in an indoor driving range. All drives were measured by a Doppler-radar system to determine the club-head speed, launch angle, spin rate, ball speed, and carry distance. Differences between the groups were investigated using a one-way analysis of variance. The results indicated that ball-speed and carry-distance differences occurred within the four groups (p?<?0.001 and p?<?0.01, respectively). The post hoc analyses showed that the ball temperatures of 18?°C and 32?°C had greater ball speeds and carry distances than balls at 4?°C and 46?°C (all p?<?0.05). The intervals for the between-group differences were 0.6?0.7?m?s?1 and 2.9?3.9?m for ball speed and carry distance, respectively. Hence, the results showed that ball temperature influences both the ball speed and the carry distance. Based on the findings in this study, standardization of ball temperature should be factored into governing body regulation tests for golf equipment.

THE EFFECT OF BALL TEMPERATURE ON BALL SPEED AND CARRY DISTANCE IN GOLF DRIVES Carlsson, T.1, Nilsson, J.1,2, Hellström, J.3, Tinmark, F.2, Carlsson, M.1. 1: Dalarna University (Falun, Sweden), 2: The Swedish School of Sport and Health Sciences (Stockholm, Sweden), 3: The Swedish Golf Federation (Stockholm, Sweden). 

Introduction

Previously it was reported that golf-ball temperature has influence on the golf balls’ coefficient of restitution, impact duration, and maximal deformation (Allen et al., 2012). They concluded that their research was the first step in a process for determining the effect of temperature on a golf drive. However, how large influence the golf-ball temperature has on golf drives remains to be investigated. The purpose was to investigate the effect of ball temperature on impact ball speed and carry distance during golf drives in a blind randomized test design. 

Methods

The balls were exposed to a temperature-controlled environment (4°C, 18°C, 32°C, and 46°C) for twenty-four hours prior to the test, and each of the four different ball-temperature groups consisted of 30 balls. The 120 drives were performed by an elite male golfer (handicap: 0.0) in an indoor driving range. All drives were measured by a Doppler-radar system to determine club-head speed, launch angle, spin rate, ball speed, and carry distance. Differences between the four ball-temperature groups were investigate using a one-way analysis of variance. 

Results

The results indicate that there are ball-speed and carry-distance differences within the four ball-temperature groups (P &lt; 0.001 and P &lt; 0.01, respectively). The post-hoc analyses showed that the ball temperatures 18°C and 32°C had both greater ball speeds and carry distances compared to the balls in the ball-temperature groups 4°C and 46°C (all P &lt; 0.05); the intervals for the between-group differences were 2.0 to 2.4 km/h and 2.9 to 3.9 m for ball speed and carry distance, respectively.

Conclusion

The novel results of the current study show that the ball’s temperature has a significant effect on the ball speed after club-head impact and carry distance for drives performed by an elite golfer. The ball temperatures 18°C and 32°C gave significantly increased ball speeds and carry distances compared to the ball-temperature groups 4°C and 46°C. This knowledge could be used to maximise the carry distance and/or to minimise the carry-distance variability related to ball temperature.

REFERENCES: Allen T, Bowley A, Wood P, Henrikson E, Morales E, James D. (2012) Procedia Eng, 34, 634-639.

The aim of this thesis was to gain insight into the control of complex bimanual movements that are both fast and accurate. For this, skilled golf ball striking was used as a model in two experimental studies (I and III). The thesis also includes two methodological studies (II and IV), intended to assist in present and future investigation on bimanual movement control. Study I shows a common kinematic proximal-to-distal sequencing (PDS) pattern and speed-summation effect in skilled golf players of both genders. Using a common PDS movement strategy in golf ball striking at various endpoint speeds appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy. In Study II a general expression for mobility was derived, which can be applied for extending the theory of mobility to double-handed grasping and manipulation. Study III found that kinematic contributions to endpoint velocity at slow, medium and fast test conditions were provided by the same subset of possible joint rotations. However, the specific subset differed between levels of expertise. The inertial behavior of the linkage arms-hands-club promoted movement parallel to and resisted movement orthogonal to the club path close to ball impact, at all endpoint speeds investigated. These findings extend previous knowledge regarding endpoint control in single-limb movements. Moreover, results regarding movement organization in Study I together with results in Study III regarding inertial behavior suggest the existence of limb configurations able to simultaneously exploit intersegmental dynamics and endpoint mobility in a proficient manner. To make the control of intersegmental dynamics in bimanual striking transparent, however, torques originating from segmental in teractions should be determined. However, when hands are placed next to each other or are overlapping it becomes challenging to find placements for standard force sensors which allow separation of right and left hand forces without altering normal behavior. As partially explored in Study IV, pressure mapping of the right hand together with inverse dynamics calculations for the golf club can potentially provide an adequate solution.

The concept of mobility describes an important property of the human body when performing manipulation tasks. It describes, in a sense, how easy it is to accelerate a link or a point on the manipulator. Most often it is calculated for the end-link or end-point of the manipulator, since these are important for the control objective of the manipulator. Mobility is the inverse of the inertia experienced by a force acting on the end-point, or a combined force and torque acting on the end-link. The concept has been used in studies of reaching tasks with one arm, but thus far not for bi-manual manipulation. We present here the concept for both single-handed and double-handed manipulation, in a general manner which includes any type of grip of the hands on the object. The use of the concept is illustrated with data on the left and right arm in a golf swing.

This study incorporated variations in speed and the horizontal resistance acting upon elite female skiers during double poling (DP) on a treadmill and specifically analyzed biomechanical adaptations to these variations. Whole body kinematics and pole force data were recorded and used to calculate the moment of force acting on the shoulder and elbow joints. Data were obtained with a 3D optoelectronic system using reflective markers at given anatomical landmarks. Forces along the long axis of the right pole were measured with a piezoelectric force transducer. Surface electrodes were used to record EMG activity in the rectus femoris, rectus abdominis, latissimus dorsi and triceps brachii muscles. In a first set of recordings, the participants double poled with zero elevation at five different speeds from 8 to 17 km h⁻¹. In a second set of recordings, horizontal resistance was added by weights (0.4–1.9 kg) attached to a pulley system pulling the skier posteriorly during DP at 14 km h⁻¹. Results showed increasing relative duration of the thrust phase with increasing resistance, but not with speed. Significant kinematic differences occurred with increase in both speed and resistance. The mean (±SD) horizontal force components ranged between 1.7 (±1.3) and 2.8 (±1.1) percent (%) bodyweight (BW) in the speed adaptation and 3.1 (±0.6) and 4.0 (±1.3) % BW in the adaptation to horizontal resistance. Peak muscle activity showed a central to peripheral (proximo-distal) activation sequence. The temporal cycle phase pattern in the adaptation to speed and horizontal resistance differed.

This study aimed to evaluate biomechanics during seated double-poling exercises in individuals with spinal cord injury (SCI) and to compare these with those of able-bodied persons (AB). 26 participants volunteered for the study; 13 with SCI (injury levels C7-T12), and 13 AB. A seated double-poling ergometer (SDPE) was developed. 3-dimensional kinematics was measured and piezoelectric force sensors were used to register force in both poles for calculation of power during incremental intensities. Significantly lower power outputs, (143.2 ± 51.1 vs. 198.3 ± 74.9 W) and pole forces (137.1 ± 43.1 vs. 238.2 ± 81.2 N) were observed during maximal effort in SCI compared to AB. Sagittal upper trunk range of motion increased with intensity and ranged from 6.1–34.8 ° for SCI, and 6.9–31.3 ° for AB, with larger peak amplitudes in flexion for AB (31.4 ± 12.9 °) compared to SCI (10.0 ± 8.0 °). All subjects with SCI were able to exercise on the SDPE. Upper body kinematics, power and force outputs increased with intensity in both groups, but were in general, lower in SCI. In conclusion, the SDPE could be successfully used at low to high work intensities enabling both endurance and strength training for individuals with SCI

The contribution of joint rotations to endpoint velocity was investigated in golf shots to submaximal and maximal shot distances using a 41degrees of freedom (DOF) kinematic model. A subset of 16 DOFs was found to explain 97%-99% of endpoint velocity regulation at club–ball contact. The largest contributors, for both groups at every shot condition, were pelvis and torso twist rotation among the most proximal DOFs, elbow pronation/supination and wrist flexion/extension among DOFs in the left arm, and shoulder internal/external rotation and wrist flexion/extension among DOFs in the right arm. The contributions from pelvis obliquity, left wrist flexion/extension, left wrist ulnar/radial deviation and right shoulder flexion/extension differed significantly between the advanced and intermediate group.

The aim of this study was to investigate whether kinematic proximal-to-distal sequencing (PDS) and speed-summation are common characteristics of both partial and full-swing shots in golf players of different skill levels and genders. A total of 45 golfers participated, 11 male tournament professionals, 21 male and 13 female elite amateurs. They performed partial shots with a wedge to targets at three submaximal distances, 40, 55 and 70 m, and full-swing shots with a 5 iron and a driver for maximal distance. Pelvis, upper torso and hand movements were recorded in 3D with an electromagnetic tracking system (Polhemus Liberty) at 240 Hz and the magnitude of the resultant angular velocity vector of each segment was computed. The results showed a significant proximal-to-distal temporal relationship and a concomitant successive increase in maximum (peak) segment angular speed in every shot condition for both genders and levels of expertise. A proximal-to-distal utilization of interaction torques is indicated. Using a common PDS movement strategy in partial and full-swing golf shots appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy.

The purpose was to study the validity of a recently proposed method [Forsell C, Halvorsen K. A method for determining minimal sets of markers for the estimation of center of mass, linear and angular momentum. Journal of Biomechanics 2009;42(3):361-5] for estimating the trajectory of the whole-body center of mass (CoM) in the case of running at velocities ranging from 10 to 22 kmh(-1). The method gives an approximation to the CoM using the position of fewer markers on the body than the standard method of tracking each segment of the body. Fourteen male athletes participated. A standard method for determining the CoM from a model of 13 segments and using the position of 36 markers was used as reference method. Leave-one-out cross-validation revealed errors that decreased with increasing number of markers used in the approximative method. Starting from four markers, the error in absolute position of the CoM decreased from 15mm to 3mm in each direction. For the velocity of the CoM the estimation bias was neglectable, and the random error decreased from 0.15 to 0.05 ms(-1). The inter-subject and intra-subject variability in the estimated model parameters increased with increasing number of markers. The method worked well also when applied to running at velocities outside the range of velocities in the data used to determine the model parameters. The results indicate that a model using 10 markers represents a good trade-off between simplicity and accuracy, but users must take into account requirements of their specific applications.

The aim was (1) to evaluate measurements of vertical displacements (V(disp)) of a single point on sacrum as an estimate of the whole body centre of mass (CoM) V(disp) during treadmill running and (2) to compare three methods for measuring this single point. These methods were based on a position transducer (PT), accelerometers (AMs) and an optoelectronic motion capture system. Criterion method was V(disp) of the whole body CoM measured with the motion capture system. Thirteen subjects ran at 10, 12, 14, 16, 18, 20 and 22kmh(-1) with synchronous recordings with the three methods. Four measurements of the (V(disp)) were derived: (1) V(disp) of CoM calculated from a segment model consisting of 13 segments tracked with 36 reflective markers, (2) V(disp) of the sacrum recorded with the PT, (3) V(disp) of the sacrum calculated from the AM, and (4) V(disp) of the sacrum calculated as the mid point of two reflective markers (sacrum marker, SM) attached at the level of the sacral bone. The systematic discrepancy between the measurements of sacrum V(disp) and CoM V(disp) varied between 0 and 1.5mm and decreased with increasing running velocity and decreasing step duration. PT and SM measurements showed strong correlation, whereas the AM showed a variability increasing with velocity. The random discrepancy within each subject was 7mm for all three methods. In conclusion single-point recordings of the sacrum V(disp) may be used to monitor changes in V(disp) of CoM during treadmill running.