The purpose of this thesis was to determine whether practice-induced adjustments and retention of a goal directed isometric motor accuracy task were similar between ipsilateral upper and lower limb and whether there is an ipsilateral transfer between upper and lower limbs. In addition, this thesis project aimed to determine whether motor output variability and the activity of the involved agonist and antagonist muscles could predict any of the above stated changes. Sixteen young adults (8 men, 8 women; 22.1 or - 2.1 years) performed 80 trials of goal directed isometric contractions that involved accurately matching a target force of 25% MVC in 200 ms, either with the upper limb or the lower limb followed by the other limb. After an interval of 48 hours, 10 trials similar to the practice trials were performed to examine retention. Feedback of performance was provided in the form of a force-time trajectory along with numerical error values for force and time on each trial. End-point error was quantified as the absolute deviation from the targeted force and time. Motor output variability was quantified as the SD of force, SD of time to peak force and SD of force trajectory. The practice-induced adjustments for force and time endpoint accuracy were similar for the two limbs, however, two days later, retention of the force accuracy was better with the upper limb compared with the lower limb. Practice-induced reduction and practice-to-retention increase in force and time endpoint error were predicted by respective changes in peak force and time to peak force trial-to-trial variability for both limbs. In addition, the changes in accuracy were predicted by the changes in the activity of the involved agonist and antagonist muscles. Nonetheless, the changes in muscle activity differed between the two limbs. The adjustments in muscle activity were also different during the practice session despite the fact that the rate of improvement was similar for the two limbs. Finally, there was an asymmetric transfer of force accuracy from the lower limb to the ipsilateral upper limb, which was associated with the changes in motor output variability. The upper limb, which is inherently less variable as compared to the lower limb, may have retained the task better due to the formation of a stronger muscle synergy (or stronger internal model) to perform the contractions with accuracy. The lower limb, on the other hand may have formed a weaker internal model due to the greater interference from amplified signal-dependent noise (motor output variability) or an alternative motor plan, which may have been concerned primarily with the minimization of motor output variability instead of formation of a muscle synergy to perform the contractions accurately.

The purpose of this present study was to assess the feasibility and determine the potential short-term efficacy of implementing a specific 9-week “Yoga for Rowers” (ROWGA) program on male varsity rowers during a competitive training season. Sixteen competitive male varsity rowers (20.6 ± 2.1 years) were recruited to participate, using a single group, pre-test-post-test, quasi-experimental research design. All participants performed two 60 min ROWGA sessions per week for 9 weeks during their fall competitive season. The primary objectives were to test the efficacy of a ROWGA program in a real-world context by evaluating: 1) the feasibility of implementing the program during the training and competitive season as measured by program adherence; 2) its potential effect on strength by evaluating hip muscle strength acting in the sagittal, frontal, and transverse planes as well as on hip muscle strength ratios between the agonist versus antagonist muscle groups; and 3) its potential effect on hip flexion range of motion (ROM). Two pre-test baseline measurements were performed on all participants over 1- week prior to initiating the ROWGA sessions while a single post-test was conducted following the ROWGA intervention. Intraclass correlation coefficients for ROM and strength were used to determine reliability of measurements by taking the two pre-intervention test scores. Outcome measures included hip flexion range of motion, peak isometric hip muscle forces normalized to body weight, including hip flexors, extensors, abductors, adductors, both internal and external rotators as well as peak isometric agonist-antagonist hip muscle strength ratios. Pre and post peak isometric hip strength measurements were calculated for agonist-antagonist muscle groups within each plane by dividing flexors by extensors, adductors by abductors, and internal by external rotators. Feasibility of the ROWGA program was determined from program attendance and adherence rates. The adherence rate was considered high with 89% attending all sessions, after adjusting for compulsory competitions. Significant improvements in peak isometric strength were demonstrated for hip flexors, extensors, abductors, and adductors, and external rotators, while a significant reduction for hip flexion ROM was observed. No significant changes in isometric hip muscle strength agonist-antagonist ratios were demonstrated. The results from this research support the feasibility of the ROWGA program in terms of rower’s acceptance, adherence, and the ability to accommodate the time requirements within their schedule as well as potential strength benefits gained. This research could help provide a platform for future large-scale research related to injury prevention in rowing. / Graduate / 2021-04-06

Ensidigt bedriven styrketräning och idrotter kan leda till en förändradstyrkekvot mellan olika muskelantagonister och anses i vissa fall kunna ökarisken för skador och besvär. Syftet med denna studie var att undersökastyrkekvoten mellan press- och dragstyrkan hos tränade personer samtundersöka om det fanns några styrkeskillnader hos deltagarna i bänkpressjämfört med bänkrodd. Femton tränade deltagare inkluderades i studien därdeltagarna var i snitt 26 år gamla, 177 cm långa och vägde 81 kg. Deltagarnautförde ett testprotokoll som inkluderade ett test i bänkpress respektivebänkrodd, där deltagaren skulle utföra maximalt antal repetitioner på den vikti bänkpress deltagaren själv ansåg sig klara omkring 5–10 repetitioner. Totaltantal kg (antal repetitioner x belastning) i respektive övning dokumenteradesoch angavs som en styrkekvot (press/drag-kvot). Resultatet avundersökningen var att deltagarnas press/drag-kvot var 2,4:1, vilket innebäratt deltagarna var 140% starkare i press- än i dragstyrkan. Det fanns ensignifikant styrkeskillnad (p=0,002) i bänkpress jämfört med bänkrodd hosmajoriteten av deltagarna. Det fanns en relativt stor variation i styrkekvot(press/drag-kvot) bland deltagarna. Faktorer som träningserfarenhet ochfamiljaritet med testprotokollets övningar kan vara faktorer som kan förklaraspridningen i styrkekvot. Att styrkekvoten befanns vara 2,4:1 kan därför inteanvändas som en utgångspunkt i ett träningsupplägg då det inte går att utgåfrån att personen som skall instrueras har den styrkekvoten. Vidare skulleresultaten kunna användas som referensmaterial i framtida studier som avseratt undersöka styrkekvoten mellan press- jämfört med dragstyrkan. / Previous literature considers that both strength training and many sports maylead to an increased risk of athletes incurring injury due to an unbalanced, orchanged, strength ratio. The purpose of this study was therefore to examinethe strength ratio between press- and pulling strength of trained individualsas well as investigate whether there was any difference in strength betweenthe two exercises tested. Fifteen participants with strength trainingexperience were included in the study where the participants mean were 26years old, 177 cm tall, and weighed 81 kg. They performed a protocol thatconsisted of a test of bench press and bench row, respectively. For bothexercises, the participants performed the maximum number of repetitions fora weight that was based on the participants’ self-assessed 5-10 repetitionmaximum bench press. Total weight lifted (weight x repetitions) for eachexercise was measured and converted to a push/pull strength ratio. Meanpush/pull strength ratio for the participants was 2,4: 1. The participants wereon average 140% stronger in pressing strength than in pulling strength(P=0,002) In the current study, the participants were stronger in bench presscompared to bench row. Factors such as training experience and familiaritywith the exercises in the could possibly have influenced the spread amongthe participants, but that cannot be determined. The variation in the strengthratio of the participants can therefore not be used as a starting point in atraining program as it is not possible to assume that the instructor's strengthratio is 2.4: 1. The results could be used as a comparison in future studiesthat aim to examine the strength ratio between press strength compared topulling strength.