See JAX Pipeline on the IMPC website for order of tasks for all mice tested

Project protocol: Grip strength test

• Introduction
• Study design
• Workflow
• Equipment, software and supplies
• Reagents and solutions
• Procedure
• Measurements

Introduction

The grip strength test is used to measure the neuromuscular function as maximal muscle strength of forelimbs and combined forelimbs and hindlimbs. These are assessed by the grasping applied by the mouse on a grid that is connected to a sensor. Three trials are carried out in succession measuring forelimb strength only, followed by three successive trials measuring the combined forelimb/hindlimb grip strength. Values are normalized against mouse body weight.

Study design

Paradigm: Baseline study

Panel: Collaborative Cross

Number of strains: 18

Sex: Both

Age: 7-9 wks

Sample size: Seven mice per sex from at least two litters

Number of cohorts: 1

Workflow

Step	Description	Equipment	Data collected
1	Grip strength: forelimb measures (3 trials)	Grip strength meter apparatus	Forelimb strength
2	Grip strength: forelimb and hindlimb measures (3 trials)	Grip strength meter apparatus	Combined forelimb and hindlimb strength
3	Weigh mice	Balance	Body weight

Equipment, software and supplies

• Grip strength meter: Columbus Instruments, Chatillon-Ametek Digital Force Gauge, DFE II
  • Grid size: 3 x 3" (HMGU plate)
• Balance

Reagents and solutions

• 70% Ethanol

 

Procedure

1. Set up and use of grip strength meter:
   • Check that the connection of the sensor to the grid is firmly in place to prevent the grid from turning around.
   • Turn the sensor on and select T peak mode, which will enable a measurement of the maximal strength exerted by the mouse. Do not apply loads greater than the nominal capacity of the force sensor at the risk of permanently damaging the strength gauge.
   • Reset the display sensor to zero.
2. Measuring grip strength force:
   • Remove a mouse from its home cage, gripping the base of the tail between the thumb and forefinger.
   • Forelimb measurement: Lower the mouse over the grid keeping the torso horizontal and allowing only its forepaws to attach to the grid before and measurements are taken. Gently pull the mouse back by its tail ensuring the mouse grips the top portion of the grid and the torso remains horizontal and record the maximal grip strength value of the mouse that is displayed on the screen. Repeat this procedure twice more to obtain 3 forelimb grip strength measurements.
   • Forelimb and hindlimb measurement: Lower the mouse over the grip keeping the torso parallel with the grid and allow both its forepaws and hindpaws to attach to the grid before any measurements are taken. Gently pull the mouse back by its tail ensuring the torso remains parallel with the grid and record the maximal grip strength value of the mouse that is displayed on the screen. Repeat this procedure twice more to obtain 3 forelimb-hindlimb grip strength measurements.
3. Place the mouse on the balance and record the weight.
4. Place mouse back in its home cage
5. Clean the grid with ethanol and allow time to dry before next test.

    

   Data QC: Calibrate the grip strength meter annually in accordance with the equipment guidelines. Force meter calibration 4-8 months with use of hanging weight.

   Formulas and derivations: Mean of 3 trials = sum of increments divided by the number of increments; strength normalized against body weight = mean divided by body weight

    

   
   

   Measurements

   LIMS field name	MPD variable name	Description	Units	Series	Primary measurement	Series order	MPD computed	Calculation	Method	Data type
   Forelimb strength t1	front_paws_1	forelimb grip strength, trial 1	g	Yes	frontpaws_1	1			grip strength test	Float
   Forelimb strength t2	front_paws_2	forelimb grip strength, trial 2	g	Yes	frontpaws_1	2			grip strength test	Float
   Forelimb strength t3	front_paws_3	forelimb grip strength, trial 3	g	Yes	frontpaws_1	3			grip strength test	Float
   Forelimb grip strength measurement mean	front_paws_mean	forelimb grip strength, average	g	Yes	front_paws_mean	1		sum of increments/number of increments	grip strength test	Float
   Forelimb grip strength normalized against body weight	front_paws_adj	forelimb grip strength, average normalized to bw	g	Yes	front_paws_mean	2		sum of increments/number of increments/body weight	grip strength test	Float
   Fore/hindlimb strength t1	all_paws1	forelimb and hindlimb grip strength, trial 1	g	Yes	all_paws1	1			grip strength test	Float
   Fore/hindlimb strength t2	all_paws2	forelimb and hindlimb grip strength, trial 2	g	Yes	all_paws1	2			grip strength test	Float
   Fore/hindlimb strength t3	all paws3	forelimb and hindlimb grip strength, trial 3	g	Yes	all_paws1	3			grip strength test	Float
   Forelimb and hindlimb grip strength measurement mean	all_paws_mean	forelimb and hindlimb grip strength average	g	Yes	all_paws_mean	1		sum of increments/number of increments	grip strength test	Float
   Forelimb and hindlimb grip strength normalized against body weight	all_paws_adj	forelimb and hindlimb grip strength, average normalized to bw	g	Yes	all_paws_mean	2		sum of increments/number of increments/body weight	grip strength test	Float
   Body weight	bw	body weight	g						body weight	Float