Restarting FT after "years" of no training

[Scott Stevenson]

Thanks for the replies Scott, eating enough to fuel training and recovery is somthing i do need to work on.

Yes i am very familiar with Dudley & Pain's work, trying to understand the unique neural activation strategies of eccentric contractions, and its implications, has been a large undertaking.

At the moment i only have the one conference proceeding (European college of sport science congress 2020), unfortunately this has been postponed until the end of the year due to the current pandemic.We will most likely not be presenting this data now as the university is restricting international travel as well as having updated the data since.

Here is the accepted abstract that we submitted:

Determining Concentric and Eccentric Force-Velocity Profiles During Squatting Using A Novel Motorised Isovelocity Device
Armstrong R, Baltzopoulos V, Langan-Evans C, Clark D, Jarvis J, Stewart C, & O’Brien T
Research Institute of Sport & Exercise Science, Liverpool John Moores University

INTRODUCTION:
Understanding the relationship between force & velocity (FV) is an integral part of resistance training prescription to optimise neuromuscular adaptation. Typically, as concentric (CON) velocity decreases, force production increases, and the force of eccentric (ECC) contractions exceeds that of concentric contractions. However, the majority of FV research focuses on single-joint movements, or on the CON portion of a multi-joint movement. No previous study has investigated the CON & ECC FV relationships in the squat movement, due to the challenge of applying high ECC loads and velocities safely and accurately. This study used a motor driven cable training system (Kineo, GLOBUS) that allows isovelocity squatting to construct the CON & ECC portion of the FV profile during a squatting exercise.

METHODS:
Following 2 familiarisation sessions performed at least 4 days prior to testing, 13 resistance-trained males (23 ± 3 years old, 1.6 ± 0.3 x BW squat) performed 3 repetitions of maximal effort isovelocity squats at 3 CON (0.75, 0.5, & 0.25 m/s) & 3 ECC velocities (-0.25, -0.5, & -0.75 m/s). The isovelocity phase of each movement was identified from the cable velocity plateau, and confirmed by 3D motion capture (Qualysis, 200 Hz). Peak vertical ground reaction force in the isovelocity phase from each trial was collected using 2 force plates (Kistler, 2000 Hz). Force data were low-pass filtered (6 Hz) and normalised to an estimated isometric force to construct the FV profile. A One-way ANOVA between velocity and peak force was performed, whilst a paired sample T-Test, with limits of agreement (LOA), were used to assess differences between target & actual cable velocity.

RESULTS:
Measured cable velocity had a small fixed bias (0.02 m/s) greater than the prescribed velocity (P<0.001, LOA=0.002:0.037). There was a significant effect of velocity on peak force (P=0.001). Peak CON force increased as CON velocity decreased. Peak ECC force at -0.5 & -0.75 m/s was greater than isometric force (21 & 25% respectively), but not at -0.25 m/s. However, normalised ECC force at all velocities was highly variable between individuals (SD = 0.37).

CONCLUSION:
This is the first study to investigate the CON & ECC FV profile in a squatting movement, with the Kineo appearing to be a viable method for controlling squat velocity. The CON FV profiles of all participants conformed to well established patterns. However, ECC FV profiles varied between individuals. On average, the group produced a peak ECC force ~25% greater than the greatest CON peak force. Though this ranged from -24% to +87%. Therefore, practitioners should be cautious of using a ‘one-size fits all’ approach when prescribing ECC overloads during squat training. Performing CON & ECC FV profiling has the potential to inform barbell squat load prescription to optimise neuromuscular adaptation. Further research should identify why ECC force production varied between individuals and which eccentric overloads maximise strength and hypertrophy.



We will be submitting the full paper to journals within the next month. Some things to note, we have since increased our population to 15 and changed the data analysis techniques. Which has lowered the peak eccentric forces to 10% greater than isometric force.

If you have any questions, please feel free to ask

Hey Rich - Thanks for sharing that!

Had all your subjects been squatting on a regular basis?...

In testing the subjects, did you notice large variability in ability to maintain squatting form without back rounding or some breach of form compared to the concentric trials?...

(I'm imagining trying to produce maximal effort when squatting while the load is bearing down on me and can easily imagine sensing a form breach and an inhibitory "reflex" to just get out from under the load. I don't know that even highly trained powerlifters do negative only reps with loads >1RM.)

OTOH, the individual who produced nearly double isometric force during ECC contractions seems extraordinary. Was he an outlier?

[Did you run correlations on RT experience, squatting experience, relative CON squatting (F/kg body mass) strength and ECC strength?... Wondering if you can tease out some associations / explanations for the variability that could be of practical value, e.g., that those with lesser experience with squatting or not as well trained based on strength might be more prone to not produce greater forces, thus potentially negating the potential purpose of ECC training to create an overload... Heck, doing so could even mean "practicing" an ineffective activation strategy for force production during squatting and thus backfire as a training strategy to improve performance... Just shotgunning thoughts here...]

-S