Reliability and Validity of Different Lower-Limb Strength Tests to Determine 1RM in the Keiser A300 Leg Press.

Larsen, F, Loturco, I, Sigvaldsen, E, Strand, MF, Kalhovde, JM, and Haugen, T. Reliability and validity of different lower-limb strength tests to determine 1RM in the Keiser A300 leg press. J Strength Cond Res 37(10): 1963-1968, 2023-The aim of this study was to explore the reliability and validity of different lower-limb strength tests to determine the one-repetition maximum (1RM) value in the Keiser A300 leg press.

Validity and reliability of upper body push and pull tests to determine one-repetition maximum.

Objectives: The purpose of this study was to explore the validity and reliability of three different strength testing approaches to determine one-repetition maximum (1RM) in the bench press and prone bench pull.

Methods: Twenty-eight recreationally active subjects (25 ± 2 years, 178 ± 8 cm, 78 ± 9 kg) were assessed for load-velocity (L-V) relationship, 1RM, maximal isometric force (MIF), and maximal repetitions to failure (MRF) in a Smith Machine on three separated sessions. Linear regression was used for L-V relationship, MIF, and MRF to predict 1RM.

The validity and reliability of walking as exercise modality during VO2max testing.

Background: Although walking is the most common exercise modality in daily life for most humans, running and cycling are the most applied exercise modalities during maximal oxygen uptake (VO2max) testing. The aim of this study was to assess the reliability and validity of walking as exercise modality during VO2max testing.

Methods: Sixteen participants (25±3 years, 172±9 cm, 69±15 kg, and VO2max 50±4 mL/kg/min) performed four incremental running- and walking VO2max tests (two tests in each condition) within 2-3 weeks.

Maximal eccentric exercise induces a rapid accumulation of small heat shock proteins on myofibrils and a delayed HSP70 response in humans.

In this study the stress protein response to unaccustomed maximal eccentric exercise in humans was investigated. Eleven healthy males performed 300 maximal eccentric actions with the quadriceps muscle. Biopsies from vastus lateralis were collected at 30 min and 4, 8, 24, 96, and 168 h after exercise.

Gene expression and immune response kinetics using electroporation-mediated DNA delivery to muscle.

Background: Injection of DNA encoding exogenic proteins into muscle tissue combined with electroporation often results in a transient increase of the encoded protein concentration in the muscle and the blood. The reduction is normally due to an immune response against the exogenic protein but other factors may also be involved. How various electroporation parameters affect the concentration kinetics of syngenic and exogenic proteins is studied in relation to immune response and muscle damage after electroporation-mediated DNA transfer to muscle.

NFAT is a nerve activity sensor in skeletal muscle and controls activity-dependent myosin switching.

Calcineurin (Cn) signaling has been implicated in nerve activity-dependent fiber type specification in skeletal muscle, but the downstream effector pathway has not been established. We have investigated the role of the transcription factor nuclear factor of activated T cells (NFAT), a major target of Cn, by using an in vivo transfection approach in regenerating and adult rat muscles. NFAT transcriptional activity was monitored with two different NFAT-dependent reporters and was found to be higher in slow compared to fast muscles.

A protein kinase B-dependent and rapamycin-sensitive pathway controls skeletal muscle growth but not fiber type specification.

Nerve activity controls fiber size and fiber type in skeletal muscle, but the underlying molecular mechanisms remain largely unknown. We have previously shown that Ras-mitogen-activated protein kinase and calcineurin control fiber type but not fiber size in regenerating rat skeletal muscle. Here we report that constitutively active protein kinase B (PKB), also known as Akt, increases fiber size and prevents denervation atrophy in regenerating and adult rat muscles but does not affect fiber type profile.

Electrical muscle activity pattern and transcriptional and posttranscriptional mechanisms regulate PKA subunit expression in rat skeletal muscle.

We have examined protein kinase A (PKA) subunit expression in adult rat skeletal muscles. Northern blots identified PKA catalytic alpha and regulatory (R) I alpha and RII alpha subunits as the major subunits expressed in slowly contracting soleus (SOL) and rapidly contracting extensor digitorum longus (EDL) muscles. In addition, the steady-state RNA levels of PKA subunit mRNAs and activities of RI alpha and RII alpha promoters are similar in SOL and EDL.